Notes of Hotel Engineering BHMCT-IV sem BHMCT-405

BHMCT- 405

Audio Visual Equipments for hotels                     

Laptop Computers, Modems, Printers: In hotels these electronic equipments are frequently used for various purposes for in-house data managing as well as a facility for the guests to use. In-house use may be for guest registration in front office, inventory management in housekeeping and kitchens and administrative staff related works with a LAN Network (Local Area Network)

Computer and Peripherals Maintenance:

Computer Usage Tips Þ Never, turn your computer off with the power switch until Windows has shut down. Þ It is recommend to use an UPS. Þ Take Backup data always. Þ Run Scandisk and De-fragment at least once a month Þ Never unplug peripherals from the computer when it is powered up. ÞDo keep at least 300 MBs of your C: drive free for Windows to use. Þ Do not let a lot of programs load up when you start your computer Þ Do use an anti-virus checker regularly (preferably in auto mode) Þ If you use a high speed Internet connection, you need a firewall program. Þ Keep track of the software disks you receive with your computer ÞMake sure Windows Update is set to Automatically      Update your computer. Þ Keep computer, modem, printer away from moisture and heat

Computer cleaning: Computer cleaning is the practice of physically cleaning the interior, and exterior, of a computer including the removal of dust and debris from cooling fans, power supplies, and hardware components.

Backup: Important data stored on computers may be copied and archived securely so that, in the event, of failure, the data and systems may be reconstructed. When major maintenance such as patching is performed, a backup is recommended as the first step in case the update fails and reversion is required.

Disk maintenance:  Disk storage, such as your hard drive, fills up with unwanted files over time. Disk cleanup may be performed as regular maintenance to remove these. Files may become fragmented and so slow the performance of the computer. Disk defragmentation may be performed to combine these fragments and so improve performance.

Dust and other cruft may accumulate as a result of air cooling. If filters are used to prevent this then they will need regular service and changes. If the cooling system is not filtered then regular Computer cleaning may be required to prevent short circuits and overheating.

Operating systems files such as the Windows registry may require maintenance. A utility such as a registry cleaner may be used for this.

Service intervals: Depending on your environment computers should be serviced at least once per quarter, though monthly service is optimal. This will ensure your computers run at their peak performance.

Software updates: Software packages and operating systems may require regular updates to correct software bugs and address security weaknesses. An automated or semi-automated program such as Windows update may be used for this.

Projection screens: In modern day environment, hotels provide facilities for corporate companies to hold business meetings, conferences, sales promotions and other functions. For this purpose the auditoriums are equipped with these modern equipments to facilitate the guests in their activities.

Overhead projector is a variant of slide projector that is used to display images to an audience. An overhead projector is a very basic but reliable form of projector. The overheadprojector displays images onto a screen or wall. It consists of a large box containing a cooling fan and an extremely bright light, with a long arm extended above it. At the end of the arm is a mirror that catches and redirects the light towards the screen.

LCD data/video projectors: An LCD projector is a type of video projector for displaying video, images or computer data on a screen or other flat surface. It is a modern analog of the slide projector or overhead projector. To display images, LCD (liquid crystal display) projectors typically send light from a Metal halide lamp through a prism or series of dichroic filters that separates light to three poly silicon panels – one each for the red, green, and blue components of the video signal. As polarized light passes through the panels (combination of polarizer, LCD panel and analyzer), individual pixels can be opened to allow light to pass or closed to block the light. The combination of open and closed pixels can produce a wide range of colors and shades in the projected image. Metal Halide lamps are used because they output an ideal colour temperature and a broad spectrum of colour. These lamps also have the ability to produce an extremely large amount of light within a small area: current projectors average about 2,000-15,000 ANSI lumens. Other technologies, such as DLP (Digital Light Processing) are also becoming more popular in modestly priced video projection.

Microphones, Amplifiers, Speakers: These are also essential equipment in conference halls, meeting rooms, auditoriums as well as for announcing arrival / departure of valet parking for guests.

VCR / DVD Players: These equipments are needed in hotels for the facility of guests and other in-house training purposes.

CCTV: Closed Circuit Television Cameras are used in hotels in various areas for security monitoring, surveillance and early information of emergency situations. These cameras are strategically located to capture images of sensitive areas and send them to a central control room for display on television screens and also for recording purposes.

Sensors:A sensor (also called detector) is a device that measures a physical quantity and converts it into a signal that can be read by an observer or by an instrument. Sensors may be used for sensing heat, smoke, light interference, touch, vibration, temperature, water flow, over-current etc.  For example, a mercury-in-glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated glass tube. A thermocouple converts temperature to an output voltage which can be read by a voltmeter. For accuracy, most sensors are calibrated against known standards. Sensors are used in everyday objects such as touch-sensitive elevator buttons (tactile sensor) and lamps which dim or brighten by touching the base. There are also innumerable applications for sensors of which most people are never aware. Applications include cars, machines, aerospace, medicine, manufacturing and robotics.

FIRE

Fuel  + Oxygen + Heat = Fire

Fire is a chemical reaction initiated by presence of heat energy in which a substance combines with oxygen (from air). The process involves giving out heat energy (exothermic reaction), light and sometimes sound.

FIRE TRIANGLE

The following are essential for fire:

(i)                 A combustible substance – fuel

(ii)               Oxygen, Nitrogen (e.g. Magnesium burns in Nitrogen)

(iii)             Heat source, spark or flame

(iv)             Process of chain reaction.

Flash Point: It is the lowest temperature at which the fuel gives off enough vapours that ignite for a moment when a small flame is brought near to it.

Fire Point: It is the lowest temperature at which the vapours of the fuel burn continuously for at least 5 secs. When a tiny flame is brought near it.

Types of Combustion:

a)      Rapid: Gas is ignited, producing heat and light

b)      Spontaneous: Without the application of external heat.

c)      Explosion: Combustion in confined space under pressure. Heat, light and sound is produced.

Stages of Fire:

i)                    Incipient stage: Preheating and gasification (slow pyrolysis) is in progress. Invisible pyrolysis produces gas.

ii)                  Submicron size: Aerosols (tiny particles) are found in the vicinity of fire.

iii)                Smouldering stage: Lasting for 4 hours – gas and smoke.

iv)                Radiation stage: Convective heat

v)                  Heat stage: Heat, flame, smoke, toxic gas – for few seconds.

Development of a Fire
A fire develops typically in four stages, and fire detectors are designed to detect some characteristic effect of one or more of these stages:
* Incipient stage. No visible smoke, no flame and very little heat. A significant amount of invisible (but sometimes smell able) combustion particles may be created. This stage usually develops slowly.
* Smouldering stage. Smoke, but no flame and little heat.
* Flame stage. Visible flame, more heat, often less or no smoke, particularly with flammable liquids and gas fires.
* Heat stage. Large amounts of heat, flame, smoke and toxic gases are produced. The transition from the previous stage can be very fast.

Classes of fire:           To make it easier to select the appropriate extinguishing media according to the nature of the material undergoing combustion, fires are arranged in 'Classes'.

Class A	Wood, paper, textile, rubbish, grass etc.	Water is the best extinguishing medium for Class A. Some Dry Chemical Powder (DCP) is also used.
Class B	Flammable liquids. (Oils, petrol, varnishes, paints, solvents, grease.)	Foam is the best extinguishing medium for Class B fires. Its reactivity should be ensured in case of Chemical fires.
Class C	Flammable gases	Dry Chemical Powder is widely used for extinguishing gaseous fires. Its ability to cut the chain reaction in the combustion process makes it suitable for the purpose.
Class D	Burning metal viz. Magnesium, Aluminium, Zinc,	Steam, Dry Chemical Powder be used against metal fires.
Class E	Fires of electrical origin involving transformers, circuit breakers, switchgears	Dry sand may be used. CO2 type extinguisher to be used. DO NOT USE WATER.
Class F	Cooking oil, fats (animal and vegetable)	Wet Chemicals to cool and emulsify.

EXTINGUISHING A FIRE a) Starving: By removal of the fuel material b) Smothering: Removing the air (oxygen) supply c) Cooling: Turning of the source of heat.

Fire Extinguishers: The following is a quick guide to help choose the right type of extinguisher.

Class A extinguishers are for ordinary combustible materials such as paper, wood, cardboard, and most plastics. The numerical rating on these types of extinguishers indicates the amount of water it

 holds and the amount of fire it can extinguish. Geometric symbol (green triangle)

Class B fires involve flammable or combustible liquids such as gasoline, kerosene, grease. The numerical rating for class B extinguishers indicates the approximate number of square feet of fire it can extinguish. Geometric symbol (red square)

Class C for fires of gaseous origin, using dry chemical powder.

Class D fire extinguishers are commonly found in a chemical laboratory. They are for fires that involve combustible metals, such as magnesium, titanium, potassium and sodium. These types of extinguishers also have no numerical rating, nor are they given a multi-purpose rating - they are designed for class D fires only. Geometric symbol (Yellow Decagon)

Class E fires involve electrical equipment, such as appliances, wiring, circuit breakers and outlets. Never use water to extinguish class E fires - the risk of electrical shock is far too great! Class E extinguishers do not have a numerical rating. The E classification means the extinguishing agent is non-conductive. Geometric symbol (blue circle)

Class F fire extinguishers are for fires that involve cooking oils, trans-fats, or fats in cooking appliances and are typically found in restaurant and cafeteria kitchens. Geometric symbol (black hexagon)

Types of Portable Fire extinguishers:

(A) Water Type Fire extinguisher: This type is used for prevention and control of fire in ordinary combustible materials such as wood and paper. Water has better cooling properties than most other agents and is suitable for fires that may start up again if not cooled properly. Water type extinguishers should never be used with flammable liquid fires or electrical fires. Water is a conductor of electricity and may inflict an electrical shock to the operator.

(B)  Spray Foam (Cream) type extinguishers: Here a chemical foam is made to form over the fire so that oxygen supply is cut off and fire dies down.

(C)  Dry Chemical Powder type extinguisher: Here the fire is controlled by the inhibiting action of the dry chemical powder which breaks the chain reaction.

Fire Detection Systems:

Detection systems are based on smoke, heat, flame, gas leakage, combustion, water flow.

Conduction/Convection Heat detection: Housing of detector has a fusible element that melts at a specified temperature causing electrical contact to activate a fire alarm.

Smoke detector: These are used to detect fires in the incipient stages.

Heat detectors: They respond to high temperatures caused by fire.

Flame detector: Detects light from flames where rapid development of flame occurs.

Electromagnetic detectors: They employ photocells sensitive to infrared and ultraviolet light emitted by the fire.

Water flow detector: It indicates because the other detector types (smoke, flame or heat) is activated and starts the water sprinkler system.

Tips on Kitchen Fire Safety

Extra care should be taken when working in the kitchen in order to avoid the onset of a fire. Here are some safety tips:

Wear appropriate clothing, not long, flowing sleeves or open, loose-fitting shirts that can come in contact with hot burners.

Wear your long hair up and do not leave any strands hanging.

Never take your eyes off hot oil because it can ignite in an instant. If it catches fire, immediately place a cover on the pan.

Always unplug electrical cords from all ancillary appliances. A plug can ignite even though the equipment is turned off. Any power surge or unforeseen problem with electricity can cause a fire.

Do not use electrical appliances near water and keep cords away from all heat sources.

Turn pot handles inward on the hot stove so as to avoid bumping into them accidentally and spilling their contents.

Do not place potholders, boxes, towels, cutting boards, or plastic utensils and containers near cooking areas.

Keep the kitchen work area clean, free from grease and burnt food.

Keep a box of baking soda on the kitchen counter while cooking as it can quickly put out a small fire at its onset.

Make sure all appliances are in good working condition. At the first sign of a problem, have it fixed or get rid of it.

Fire Extinguishers:

Fire extinguishers contain different chemicals, depending on the application. Handheld extinguishers, which are commonly sold at hardware stores for use in the kitchen or garage, are pressurized with nitrogen or carbon dioxide (CO₂) to propel a stream of fire-squelching agent to the fire. The active material may be a powder such as potassium bicarbonate (KHCO₃), liquid water, an evaporating fluorocarbon or the propelling agent itself. The most effective and common fluorocarbon used until recently for this application had been bromochlorodifluoromethane (CF₂ClBr), referred to as halon 1211. By international agreement, however, production of all types of halons ceased in 1994 because the bromine and chlorine atoms in the chemical were found to migrate over time to the stratosphere, where they react to deplete ozone in a very efficient catalytic cycle.

Many fire extinguishing systems are built into the building or other structure being protected. Water sprinklers are by far the most common type of fixed system because they are inexpensive, highly reliable and safe for people. But water damage cannot always be tolerated (say, in a computer room or electrical fire); it is sometimes ineffective (a fuel storage system); and it is impractical where weight and space are limited (in an airplane). In these situations, fire extinguishers use different materials--ones that flood a protected compartment with a fire-fighting gas. CO₂ works well, but is fatal at the concentrations necessary to extinguish a fire, and so cannot be used where people will be present. Bromotrifluoromethane (CF₃Br, or halon 1301) is a close cousin to halon 1211, but has a much lower boiling point and toxic level--properties that have made halon 1301 the firefighting chemical of choice for applications where sprinklers cannot be used. Manufacturers have introduced new families of chemicals containing no chlorine or bromine, called hydrofluorocarbons (HFCs),that have physical properties similar to the halons and no ozone depletion potential. But lacking Br or Cl atoms, the HFCs cannot disrupt the combustion reaction to the same degree. HFCs extinguish fires in a manner similar to CO₂ or N₂--by absorbing heat and reducing the concentration of oxygen. Even so, several different companies are marketing such HFCs as CHF₃, C₂HF₅, and C₃HF₇ for a variety of applications.

Most often, simple fire extinguishers use sodium carbonate and dilute sulfuric acid to produce carbon dioxide, that extinguishes fire. small pouch carries the acid within a matrix of sodium carbonate. The pouch prevents the acid to come in contact with sodium carbonate outside. When the bottle is shaken, the two chemicals come in contact with each other, liberating carbon dioxide and water droplets that extinguishers.
Another type of fire extinguisher contains compressed Carbon Tetrachloride in it. When the nozzle is pushed, an aerosol of carbon tetrachloride is liberated that suppresses and extinguishes fire.

 This type has a major advantage that it can extinguish fires of oils, electric circuits, etc.
Other forms of fire extinguishers use forced water to extinguish fire.

Types of extinguishers:

Multi-Purpose Dry Chemical (A, B, C)

A dry chemical agent called mono ammonium phosphate. The chemical is non-conductive and can be mildly corrosive if moisture is present. In order to avoid corrosion, it is necessary to scrub and thoroughly cleanup the contacted area once the fire is out. A dry chemical fire extinguisher is usually used in schools, general offices, hospitals, homes.

Regular Dry Chemical (B, C)

 A dry chemical agent called sodium bicarbonate. It is non-toxic, non-conductive and non-corrosive. It is easy to cleanup, requiring only vacuuming, sweeping or flushing with water. Extinguishers with sodium bicarbonate are usually used in residential kitchens, laboratories, garages.

Carbon Dioxide (B, C)

 Carbon dioxide removes oxygen to stop a fire but has limited range. It is environmentally friendly and leaves no residue, so cleanup is unnecessary. Extinguishers with carbon dioxide are usually used in contamination-sensitive places such as computer rooms, labs, food storage areas, processing plants, etc.

Halotron (A, B, C)

 A vaporizing liquid that is ozone friendly and leaves no residue. Because it requires no cleanup, fire extinguishers with halotron are ideal for computer rooms, telecommunication areas, theaters, etc.

Foam (A, B)

 Foam floats on flammable liquids to tame the fire and helps prevent reflashes. To cleanup the affected area, it must be washed away and left to evaporate. Fire extinguishers with foam are usually used in garages, homes, vehicles, workshops.

Purple K Dry Chemical (B, C)

 A dry chemical called potassium bicarbonate. It is non-conductive and non-corrosive. Clean up requires vacuuming, sweeping or flushing with water. Extinguishers with potassium bicarbonate are usually used in military facilities, oil companies, vehicles, etc.

Water (A)

The most common agent is water; however, it cannot be used for class B or C fires because it is conductive. Water-based fire extinguishers are usually used in stockrooms, schools, offices, etc.

Wet Chemical fire extinguishers (F)

The potassium acetate based agent discharges as a fine mist which forms a soapy foam that suppresses any vapors and steam or the risk of fire reflash as it extinguishes the fire. Class K fire extinguishers can usually be found in commercial cooking areas such as restaurants and cafeterias.

Fuel Source	Class of Fire	Type of Extinguisher (Extinguishing Agent)
Ordinary combustibles (e.g. trash, wood, paper, cloth)	A	Water; chemical foam; dry chemical
Flammable liquids (e.g. oils, grease, tar, gasoline, paints, thinners)	B	Carbon dioxide (CO2); halon**; dry chemical; aqueous film forming foam (AFFF)
Flammable gases	C	Dry chemicals powder
Combustible metals (e.g. magnesium, titanium)	D	Dry powder (suitable for the specific combustible metal involved)
Electricity (e.g. live electrical equipment)	E	CO2; halon; dry chemical
Combustible Cooking (e.g. cooking oils; animal fats, vegetable fats)	F	Wet chemical (Potassium acetate based)

 

	Some Examples Ordinary Combustibles - the most common type of fire caused when organic solids such as wood, paper or cloth ignite. It's ok to use water extinguishers for this type of fire. Flammable Gasses or Liquids - this is any fire where liquid or gas fuels ignite. These should be extinguished using dry chemical or halon extinguishers Combustible Metals - metals such as titanium, magnesium and uranium are flammable. Dry powder extinguishers should be used to fight such fires Electrical Appliances - this covers any appliance that could potentially be electrically energised. Water, foam and other agents which might conduct electricity should not be used to fight electrical fires. Cooking Fats and Oils - common in household kitchens, saponification (a process that produces soap from fats) or fire blankets can be used to extinguish these fires. Water extinguishers should never be used on fat or oil fires.
	Using fire extinguishers You are not required to fight a fire. Ever. If you have the slightest doubt about your control of the situation DO NOT FIGHT THE FIRE. Please see the Disclaimer below. The building is being evacuated (fire alarm is pulled) The fire department is being called The fire is small, contained and not spreading beyond its starting point. The exit is clear, there is no imminent peril and you can fight the fire with your back to the exit. You can stay low and avoid smoke. The proper extinguisher is immediately at hand. You have read the instructions and know how to use the extinguisher. IF ANY OF THESE CONDITIONS HAVE NOT BEEN MET, DON'T FIGHT THE FIRE YOURSELF. CALL FOR HELP, PULL THE FIRE ALARM AND LEAVE THE AREA.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Flammability limits, also called flammable limits, give the proportion of combustible gases in a mixture, between which limits this mixture is flammable. Gas mixtures consisting of combustible, oxidizing, and inert gases are only flammable under certain conditions. The lower flammable limit (LFL) describes the leanest mixture that still sustains a flame, i.e. the mixture with the smallest fraction of combustible gas, while the upper flammable limit (UFL) gives the richest flammable mixture.

There is a quantitative difference between flammability limits and explosive limits. In an explosive mixture the fuel oxidizer mixture is closer to stoichiometric proportion. This difference has no practical application in safety engineering as the flammable vapor cloud is turbulent and the exact mixture of fuel and oxidizer varies greatly. Therefore, many references use the term flammability limit(LFL, UFL) and explosive lim

HOTEL ENGINEERING SOLUTIONS

Q1:      Organisation chart of maintenance department:

Typical Organisation Chart of Maintenance Department

 

Q2:      Duties of Chief Engineer (Maintenance)

Duties and responsibilities of Chief Engineer of Maintenance Department

(Changing from a FAIL and FIX Approach to a PREDICT and PREVENT Approach)

The care and operation of the physical assets (plant/equipment/machines) is largely the responsibility of the head of maintenance dept i.e. the Chief Engineer. This would include Inspection, Maintenance, Engineering, Repair, Overhaul, Construction and Salvage of the complete plant system. The duties are:

a.                   To keep plant and machinery in proper working condition and reduce breakdown.

b.                  To make sure that the services from plant and machinery are smooth and uninterrupted.

c.                   All customers’ requirements are properly taken care of.

d.                  To obtain maximum return on the investments incurred upon plant and machinery.

e.                   The safety of hotel guests / employees is assured.

f.                   The normal working life of equipment is extended

g.                  The total system is ready to meet any emergent conditions.

h.                  The throughput /output of the entire system is enhanced thus increasing efficiency.

i.                    Wasteful expenditure incurred during breakdown is reduced.

j.                    Customer satisfaction is achieved by providing continuous services.

Q3:      What are the types of fuses?

Fuse—An over-current protective device with a circuit-opening fusible part that is heated and severed by the passage of over-current through it. A fuse interrupts excessive current (blows) so that further damage by overheating or fire is prevented. Overcurrent protection devices are essential in electrical systems to limit threats to human life and property damage. Fuses are selected to allow passage of normal current and of excessive current only for short periods.

The types of fuses are:

Kit-Kat or Porcelain re-wireable fuse	A fuse (Kit-Kat fuse)consists of a metal strip or wire fuse element, of small cross-section compared to the circuit conductors, mounted between a pair of electrical terminals, and (usually) enclosed by a non-conducting and non-combustible porcelain housing.
HRC fuse	A High Rupturing Capacity (HRC) fuse is a fuse that has a high breaking capacity (higher kA Rating). The minimum fault value for an HRC fuse is 80kA.
Round type fuse	This is made of porcelain or bakelite having two separated wire terminals for holding the fuse wire between them
Cartridge type fuse	In this type the fuse wire is enclosed in a bulb or case of insulating material. In case the fuse blows, the cartridge has to be replaced with a fresh one.

SAFETY CHECKLIST Always use correct size of fuse. Always keep earth connection in satisfactory condition. Check that the switch is in off position before replacing lamp or handling fans etc. Make portable equipment earthing in sound condition. Discharge all inductive circuits before commencing any work on them. Never touch an overhead line. Never energise any circuit without proper authorization. Never bring a naked light near a battery; smoking is prohibited in the battery room. Place proper rubber mats in front of switch boards and electric panels. Use insulated tools for repairing electric fixtures. Wear rubber boots / shoes while working with electric circuits. Check for wear and tear of electric cords in appliances. Check all breakers and fuse boxes are clearly &  completely labeled. Each switch should be positively identified as to which outlet or appliance it is for. All space heaters, microwave ovens, and other high-current devices are plugged directly into wall receptacles and not into extension cords. All hotel equipment should have grounded plugs (three-prong plugs) used in accordance with the manufacturer's instructions. Never remove the third (grounding) prong from any three-prong piece of equipment.

Q4: Safety precautions while dealing with electricity.

Electrical safety depends on three levels:

1. The electrical system, including the connection, the switchboard with electrical protections, and the cables, switches and sockets.

2. The electrical appliances that used in the hotel.

3. The awareness of electrical safety among staff.

1. A safe electrical installation

A high quality hotel electrical system can: a) protect the guests and staff against the risks of using unsafe appliances; for example by including an over current protection, a residual current device, and a correct earthing system. b) Stimulate the employees to make use of the installation in a correct way; e.g. by providing enough sockets so that they don’t feel the need to use adapters. The electrical installation should be designed in such a way that it is safe in itself, no matter how it is used. E.g. it should include separate circuits for higher power appliances, sufficient cable diameters, and an over-voltage protection.

2. A safe design of electrical appliances

By imposing certain standards of safety to the design and manufacturing of appliances. Those standards can for instance describe correct ways of earthing, the use of high quality materials, a shock- and water-proof design, etc.

3. The human factor

Bad habits like hiding extension cables under carpets, the multiple usages of adapters, or the usage of unsuitable electrical equipment in the bathroom, have been causes of electrocution or fire. Information campaigns can raise awareness among hotel staff and change their behaviour.

Q5:      Methods of heat transfer:

Conduction: (Mainly seen in solid materials)Regions with greater molecular kinetic energy will pass their thermal energy to regions with less molecular energy through physical contact, a process known as conduction. Heat conduction is the transfer of thermal energy between regions of matter due to a temperature gradient. It is a property of the matter and greater is heat conducted when greater is the Thermal Coductivity. Heat spontaneously flows from a region of higher temperature to a region of lower temperature, till thermal equilibrium is reached. To distinguish conduction specifically, it should be stated that the heat flows through the region of matter itself, as opposed to requiring bulk motion of the matter as in convection. Conduction takes place in all forms of matter, viz. solids, liquids, gases and plasmas, but does not require any bulk motion of matter. In solids, it is due to the combination of vibrations of the molecules with the energy transported by free electrons. In gases and liquids, conduction is due to the collisions and diffusion of the molecules during their random motion.

Convection: (Mainly seen in liquids and gases) When heat conducts into a static fluid it leads to a local volumetric expansion. As a result of gravity-induced pressure gradients, the expanded fluid parcel becomes buoyant and displaces, thereby transporting heat by fluid motion (i.e. convection) in addition to conduction. Such heat-induced fluid motion in initially static fluids is known as free convection.

Convection is the movement of molecules within fluids (i.e. liquids, gases) . It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids.

Radiation: (All materials radiate thermal energy in amounts determined by their temperature, where the energy is carried by photons of light in the infrared and visible portions of the electromagnetic spectrum. When temperatures are uniform, the radiative flux between objects is in equilibrium and no net thermal energy is exchanged. The balance is upset when temperatures are not uniform, and thermal energy is transported from surfaces of higher to surfaces of lower temperature. Thermal radiation is the emission of electromagnetic waves from all matter that has a temperature greater than absolute zero It represents a conversion of thermal energy into electromagnetic energy. Thermal energy is the collective mean kinetic energy of the random movements of atoms and molecules in matter.

Q6:      Gas burner diagram:

 

Q7:      Precautions while using gas:

COMPRESSED AND LIQUEFIED GAS USE

The general “good practice” guidelines to follow when using gas cylinders and compressed gases are:

General Requirements:

Ensure that regulator pressure control valve is relieved (i.e. closed) before attaching to gas tanks.

Close valves on gas cylinders when a system is not in use.

Remove all pressure from regulators not currently used (by opening valves downstream after the regulators are closed).

Shut-off valves must not be placed between pressure relief devices and the equipment they are to protect.

Use pressure relief valves in downstream lines to prevent high-pressure buildup in the event that a regulator valve does not seat properly and a tank valve is left on.

Relief valves should be vented to prevent potential buildup of explosive or toxic gases.

Never allow flames or concentrated heat sources to come in contact with a gas cylinder.

Never allow a gas cylinder to become part of an electrical circuit.

Never partially open a tank valve to remove dust or debris from the cylinder inlet.

Never use cylinder gas as compressed air.

Pressurize regulators slowly and ensure that valve outlets and regulators are pointed away from all personnel when cylinder valves are opened.

Cylinders that require a wrench to open the main valve shall have the wrench left in place on the cylinder valve while it is open. Never apply excessive force when trying to open valves. Cylinders with “stuck” valves should be returned to suppliers to have valves repaired.

Do not attempt to open a corroded valve; it may be impossible to reseal.

Valves should only be opened to the point where gas can flow into the system at the necessary pressure. This will allow for quicker shutoff in the event of a failure or emergency.

Use a cylinder cap hook to loosen tight cylinder caps. Never apply excessive force or pry off caps. Return to supplier to remove “stuck” caps.

Keep piping, regulators and other apparatus gas tight to prevent gas leakage.

Confirm gas tightness by using leak test solutions (e.g., soap and water) or leak test instruments.

Release the pressure from systems before connections are tightened or loosened and before any repairs.

Do not use Teflon tape on compressed gas fittings where the seal is made by metal-to-metal contact. Use of Teflon tape causes the threads to spread and weaken, increasing the likelihood of leaks.

Never use adapters or exchange fittings between tanks and regulators.

Fluorescent light can be used to check for grease or oil in regulators and valves.

Storage Requirements

All gas cylinders:

§ Shall not be stored in exits or egress routes.

§ Shall be stored within a well-ventilated area.

§ Shall not be stored in damp areas, near salt or corrosive chemicals, fumes, heat or exposed to the weather.

§ Shall be stored in an upright position.

§ Shall be secured with a chain or appropriate belt above the midpoint, but below the shoulder.

§ Shall be capped when not in use or attached to a system (if the cylinder will accept a cap).

§ Shall be kept at least 20 ft. away from all flammable, combustible or incompatible substances. Storage areas that have a noncombustible wall at least 5 ft. in height and with a fire resistance rating of at least 30 minutes may be used to segregate gases of different hazard classes in close proximity to each other.

§ Shall be stored so that cylinders are used in the order in which they are received.

§ Shall be stored so that gases with the same hazard class are stored in the same area. Inert gases are compatible with all other gases and may be stored together.

§ Shall not be stored longer than one year without use.

§ Shall be stored so that full cylinders remain separate from empty cylinders.

Q8: Define Preventive Maintenance and Breakdown Maintenance:

Preventive maintenance (PM) has the following meanings: (Preventive Maintenance is done on running plant/machinery)

The care and servicing by personnel for the purpose of maintaining equipment and facilities in satisfactory operating condition by providing for systematic inspection, detection, and correction of incipient failures either before they occur or before they develop into major defects.

All Maintenance, including tests, measurements, adjustments, and parts replacement, performed specifically to prevent faults from occurring.

Preventive Maintenance is a combination of those actions as a result of which equipment will be expected to continue to perform the operation it is intended to do. It includes:   Regular maintenance, oiling, cleaning, and dusting.

                        Periodic Inspection (Identification of faults, wear and tear)

                        Preventive replacement before the equipment life.

                        Overhaul of equipment.

Breakdown Maintenance: (Breakdown Maintenance is done on plant/machinery under breakdown). This comes into play when there is a failure of equipment to perform and deliver to its expected capacity. The function involves the disassembling of the equipment, to locate fault, repair / replace the part, re-assembly, checking and testing for required performance.

Breakdown maintenance needs heavy level of operator involvement. Thus the availability of skilled, trained and experienced operator / staff is to be ensured. They should be aware of the complexities of breakdown maintenance.

The cost of breakdown maintenance is very high, because it incurs direct cost of equipment part repair / replacement and also incurs indirect loss of output of plant / machinery.

Q9:      Define Contract Maintenance:

Contract Maintenance vs. Departmental Maintenance (In-House)

Maintenance may be done by your own maintenance personnel, or else the job may be off-loaded to an outside agency on contract basis. This will depend largely on facilities available in-house, trained staff, overall cost, availability of spares etc.

Contract Maintenance

Departmental Maintenance

No need to recruit trained personnel / staff Reduces labour cost Reduces cost of tools, spares, material. Uses latest techniques. Saves administrative time Flexibility of meeting emergencies. Disadvantages: -     Management laziness during negotiating contract price, resulting in higher cost. Loss of involvement and ownership of in- house staff Predictive maintenance mind-set is absent or very low.

Involvement and ownership of staff Multi- tasking, multi-skilled operation Can focus more on Predictive Maintenance Optimum utilization of man-power and machines

Contract maintenance may be awarded for the following areas:

Routine maintenance of overall ground area, Preventive maintenance of plant and equipment like water treatment plant, heating plant, AC plant, elevators etc., Civil maintenance of Building and other infra-structure, Fire and safety equipments, Kitchen appliances, Overall cleaning, plumbing and laundry.

All contracts must have:      a) Insurance of maintenance employees,   b) Inspection facility of work done, c) Safe practices should be followed,  d) Local codes and statutory regulations must be followed.

What is a Valid Contract?

According to Sec. 10 of the Indian Contracts Act, 1872, "All agreements are contracts, if they are made by the free consent of the parties, competent to contract, for a lawful consideration with a lawful object, and not hereby expressly to be void."

Q10:    Give circumstances under which equipments are replaced:

All equipments are designed to give a certain life-cycle of normal operation. After this, due to wear and tear the parts of the equipment start failing / breaking down. Thus the MTBF (Mean Time Between Failures) increases and the operational efficiency of the equipment goes down resulting in heavy maintenance costs. Then the equipments need replacement part by part or in whole. To reduce the repair time and to carry out the maintenance effectively, parts needing replacement should be planned.

-                      Fast wearing parts whose service life does not exceed the period between two consecutive planned repairs.

-                      Large complicated and labour consuming parts

-                      Standard spares, assemblies and apparatus.

-                      Spares of major assemblies, minor assemblies.

The reasons for replacement of equipment are: a) Inadequacy of equipment capacity, b) Obsolescence (i.e. outdated) of equipment, c) Declining effeciency with wear and tear, d) Low reliability, e) Producing more noise and vibrations, f) Unsatisfactory work output.

The financial cost of repair and maintenance, increasing labour cost are to be considered for replacement of equipment

Present Equipment	New equipment
Operating expenses Direct and indirect labour cost. Power, repair and maintenance cost. Downtime cost and cost of replacing parts. Insurance, interest on capital, salvage value at the end of useful life. Rebuilding cost	Initial cost of new equipment Operating expenses Direct and indirect labour cost. Power, repair and maintenance cost. Cost advantage of improved product Interest on capital, salvage value at the end of useful life.

Q11:    What are the different types of fuels? Give Merits and demerits.

What are fuels?  They are the source of heat used to cook food.

Examples? Firewood, charcoal, kerosene, liquefied petroleum gas (LPG) and electricity.

Solid Fuels	Liquid Fuels	Gaseous Fuels	Electricity (as heat source)
Wood, coal, peat, lignite, coke, anthracite	Petrol, Diesel, Kerosene, Spirit, Oil	Coal gas, methane, LPG,producer gas, coke oven gas	Sources: Thermal, Hydel, Nuclear, Non-conventional energy
Advantages: Easy transport & storage, low cost, moderate ignition temp. Disadvantages:High ash content, high clinker,  low burning effeciency, not easy to control combustion, high handling cost, low calorific value, high chimney for emission gases.	Advantages: Low ash content, easy to control combustion, small storage space, easy transport, high calorific value, high efficiency Disadvantages: High cost, special storage, high fire hazard, burner choking,	Advantages: High calorific value, easy combustion, easy transport through pipes, no smoke/ash/soot, clean to use. Disadvantages: Large storage tanks needed, high fire hazard. Hgh cost, less natural resources.	Advantages:Ease of operation, easy control, no smoke/ash/soot, clean to use, high effeciency Disadvantages: High cost, Power cut disruptions

Naturally occuring fuels	Secondary / Prepared / Derived fuels
Wood, coal, lignite, anthracite, oils, shale, petroleum	Charcoal, coke, coal tar, spirit, kerosene, diesel, water gas, butane, electricity

 

Q12:    Conservation of energy in 5 star hotels:

Energy Conservation Measures in the Hotel

1. Due to competition and aggressive marketing strategies, hotels have to gear up with new activities and additions, latest illumination, new technology, and to meet demands by guests.

2. New demands increase the energy consumption, compared to earlier periods. Also energy cost has increased considerably. This has necessitated various energy conservation steps to reduce the energy bill, to be a profitable business.

Deployment of Energy efficient machines.

Auto – controls for A/c systems

Efficient chilled water distribution system

Changing cooling tower blades– metallic to FRP.

Room automation – key card system, (Key switches)

1) 

2) 

3) 

Utilization of cool atmospheric air

Use energy wheel recovery of cooling effect.

Offline dedicated filter for cooling tower

Efficient lighting system, use of energy saving  bulbs/CFL Use of Dimmers

Electronic Ballast / energy efficient tube lights

Voltage reducer for lighting circuits.

Lighting circuits On /Auto Controller

Energy efficient motors.

Timers for remote lighting/Security lighting
Boiler insulation – Front/Back covers.
Burner modulation.
Fuel additives.
Reclaiming heat from boiler flue.
Waste heat from condensate – waste heat recovery

Q13:    Calculate the amount of electricity

Q14: Give properties of Refrigerants:

Non-poisonous, non-toxic, non-corrosive, non-explosive, non-inflammable, low boiling point, condensing pressure low, High latent heat of vaporization, Low specific heat, inert to oil, easy availability.

Q15:  Compare Vapour Compression and Vapour Absorption system of refrigeration.

Absorption system	Compression System
Uses low grade energy like heat. Therefore, may be worked on exhaust systems from I.C. engines etc.	Using high-grade energy like mechanical work.
Moving parts are only in the pump, which is a small element of the system. Hence operation is smooth.	Moving parts are in the compressor. Therefore, more wear, tear and noise.
The system can work on lower evaporator pressures also without affecting the COP.	The COP decreases considerably with decrease in evaporator pressure.
No effect of reducing the load on performance.	Performance is adversely affected at partial loads.
Liquid traces of refrigerant present in piping at the exit of evaporator constitute no danger.	Liquid traces in suction line may damage the compressor.
Automatic operation for controlling the capacity is easy.	It is difficult.

Q16: List the security systems / equipment in hotels:

Security systems:       

1. External Access Control: Limiting Access / Entry Points to the hotel premises (provision of CCTV cameras),

2. Perimeter Security:  Road barriers, Checking cars  and boot space with mirrors, CCTV installation, Patrolling

3. Material Access Control: Guest baggage check, Material Supply checks

4. People Access Control: Walk in guests check, Guest profiling, Employee Verification, Visitor Management.

5. Internal Access Control: Restriction on movement in prohibited parts of hotel, Use of proximity cards and

    magnetic interlocks, Entrance to boiler room, Computer room, Control room, Switch board room, Lift usage to

    be monitored.

Security equipments: Security equipment can be roughly divided into two types: equipments that prevents (or attempts to

prevent) unauthorized access to an area and equipment that detects the presence of unauthorized people. The first classification refers to locks or locking systems. Rather than depend on permanent, unchangeable, metal keys, many hospitality facilities now use either computer-coded plastic cards or push button devices encoded with different combinations whenever a new guest checks in. The combination may be set at random or by the guest himself. The second classification refers to sensors of various types that identify an event and transmit a signal for appropriate action to be taken. These can be photo-beam sensors, proximity sensors, heat sensors, RFID chips etc.

Q17: What are the Audio-Visual equipments used in hotel industry:

The Audio Visual equipments used are Computers (Laptop / Desk / Main Frame), Projectors (Slide / Screen, LCD), Video Casette Recorders, DVD players, Tape Recorders, Television sets, CCTV cameras, Microphones (Stand / Wireless), Amplifiers, Speakers, Home Theatre system.

Q18: Importance of water in the hotel industry.

Water requirement in hotels is 180ltrs/bed/day approx. Water for restaurants is 70 ltrs/seat/day approx. Water for gardening is 17000-35000 ltrs/day/hectare.

For the existence and survival of human life, water is an essential commodity, next only to air. It is essential for life, health and sanitation. It is the principal raw material for food production. It is needed for drinking, bathing, washing body and clothes, washing floors, flushing of WC, gardening, vehicles and road washing,

fountains, air-conditioning, swimming pools, air coolers, brewing, cleaning, fire fighting etc.

Q19: Give factors that affect water quality.

When toxic substances enter lakes, streams, rivers, oceans, and other water bodies, they get dissolved or lie suspended in water or get deposited on the bed. This results in the pollution of water whereby the quality of the water deteriorates, affecting aquatic ecosystems. Pollutants can also seep down and affect the groundwater deposits.

Raw water obtained from lakes etc.  is not potable and has many defects. These can be:

>>        Volatile and oxidizable impurities

>>        High salt content

>>        Corrosivity and scale formation

>>        Acidic content

>>        Hardness

>>        Bacterial contamination

>>        Odour and foul taste

>>        Suspended impurities

>>        Dissolved impurities

Q20: Give water hardness removal details:

Water SOFTENING GENERAL:
Water may be generally classified as "soft" or "hard" water. Hard water is characterized by the elevated concentration of polyvalent metal ions (cations). Soft water is characterized by a low concentration of these metal ions. The most common hard water metal ions are those of calcium and magnesium, which are divalent metal ions expressed as: Ca+2 and Mg+2 respectively.

While there are no hard and fast definitions of what soft water and hard water entail, we generally define soft water as having less than 75 mg/L calcium carbonate (CaCO3) and hard water as having greater than 150 mg/L calcium carbonate (CaCO3). Typically, groundwater is harder than surface waters, due to water dissolving and then carrying calcium and magnesium from the surrounding rocks. Hard water, when it dries, creates water spots (white scale) on vehicle windows and finishes, household windows, shower doors, tile, etc. It also creates scale on the insides of water distribution pipes, boilers, and water heaters. Elevated water temperatures create the scale much faster than cold water temperatures, thus creating a problem for water heaters or boilers. The scale creates a barrier to the efficient transfer of heat, which requires a greater quantity of fuel to heat to the same temperature. Premature failure of boilers and hot water heaters is most often contributed to this scaling. Hardness may be Temporary or Permanent hardness. Temporary hardness is due to bicarbonates of calcium or magnesium. It can be removed by boiling or adding lime to the water. Permanent hardness is due to presence of sulphates, chlorides and nitrates of calcium and magnesium.

Treatment Process:   There are three basic treatment processes to treat hard water:
1) Ion Exchange:  This process involves the use of a high ion exchange resin. An example of this resin is a polystyrene type. Zeolite (Trade name) is a compound of aluminium, silica and soda. The resin is specifically designed to hold sodium ions on its ion exchange sites. As the hard water passes through the beads of resin, the calcium and magnesium ions replace the sodium ions that are attached to the resin. This process removes the calcium and magnesium from water being treated and releases the sodium to the treated water. The sodium does not form this scale, nor cause water spots. At some point in time, all of the sodium has been replaced with calcium magnesium and the resin can therefore no longer remove it from the raw water. The resin is regenerated by stopping the flow water through the resin bed, and then backwashing the resin bed with a highly concentrated solution of rock salt (a sodium chloride brine). This concentrated brine solution removes the calcium and magnesium ions from resin and replaces it with sodium ions. The resin bed is then rinsed gently with soft water, for re-use. In many communities utilizing groundwater sources, the well sites possess ion exchange treatment units to soften groundwater prior to the addition of a disinfectant or fluoridation. The ion exchange process is more cost-effective when treating groundwater, as they are typically a non-carbonate form of water hardness i.e. the hardness is specifically a predominance of the calcium and magnesium ions by themselves, not attached to their anionic components of carbonates, etc. Surface waters are typically the carbonate form of water hardness, which is more cost effectively treated by utilizing a lime or lime soda ash treatment process.
Advantages & Disadvantages:

a) An advantage of the ion exchange treatment process is that it does not change the pH or alkalinity of the water. Other advantages include excellent process reliability, process stability, and chemical safety.
b)Disadvantages of the ion exchange process include:
      i) First is the increase of total dissolved solids (TDS) in the treated water due to the release of sodium.
      ii) Second is the cost of disposing of the regeneration cycle’s salt brine. This regeneration backwash water contains

           sodium chloride, calcium chloride, and magnesium chloride in a concentrated solution that ranges from 30,000 to

           50,000 mg/L TDS. The quantity water may vary from 1.7 % to 7.5% of the softened water total depending upon the

           raw water source, the type of hardness being removed, and the quantity of water being treated. Proper disposal of

           this regeneration backwash water is obviously difficult due to these parameters.
      iii) Depending on the pH of the treated water, most waters treated by the ion exchange process, are corrosive waters due

            to loss of the calcium and magnesium. Blended water or the addition of stabilizing chemicals will correct this.
      iv) Resin problems:

            a) Iron in the ferrous state must not be allowed to enter the ion exchange process, as it will oxidize to the iron oxide

             state on the resin and become a permanent resident on the resin. If the iron oxide state is achieved prior to entering

             the ion exchange process, it will be removed from the process water during treatment and is able to be removed

             from the resin during the normal backwash cycle. Best practice is to remove all iron prior to the ion exchange

             process.
            b) Modern ion exchange resins are very resilient, with the life expectancy in excess of 15 years, when the process is

             properly operated. Excessive chlorine residuals will break down the resins, and must therefore not be applied to the

              resin beds. Surface waters, with accompanying biological growths, higher turbidities, and color values must be

              treated prior to the ion exchange process in order to prevent these materials coating the resin beads and interfering

              with the softening process.

2) Membrane Filtration: this is a physical process whereby either reverse osmosis or nano-filtration are utilized to physically remove the calcium and magnesium ions from the raw water source. The type of membrane will determine the degree of treatment.
Advantages and Disadvantages
a) Advantages include: hardness removal without large quantities of chemicals involved such as lime and sodium chloride (rock salt), simplicity of operation, increased operator safety due to lack of potentially hazardous chemicals.
b) Disadvantages include: high cost of membranes, (which are experiencing a trend of decreasing cost over the past several years), proper disposal of concentrated rejection water, and a potential requirement for pre-treatment of surface waters prior to membrane filtration.

3) Chemical Precipitation: this process is characteristically both chemical and physical in nature. This type of softening process does not completely remove all hardness from the treated water (such as an ion exchange process), and therefore requires less of a requirement for a downstream water stabilization process. Approximately 45 to 90 mg/L of hardness, expressed as calcium carbonate (CaCO3 ), will exist in the treated water which will provide an adequate corrosion protection value for the water distribution system and consumer plumbing fixtures. This may be accomplished by either of two manners:
a) Sodium hydroxide (NaOH)(caustic soda) may be utilized for chemical precipitation. Advantages: produces less sludge than lime, or lime-soda ash processes. Disadvantage: higher total chemical cost.
b) Utilizing lime, or lime and soda-ash. This is the preferred method of most facilities, and therefore the one we will detail.
Lime-soda ash Treatment Process.
The raw water is brought to a rapid mixer where calcium hydroxide Ca(OH)2 is added to it. In the majority of cases soda ash is also added to it, for what is termed a "lime-soda ash" softening process. (On a side stream, dry lime (CaO) is "slaked" by adding water to it to create the Ca(OH)2.) This slurry is added to the water being treated to increase the pH to 10 for calcium removal or to a pH of 11 for magnesium removal. The addition of the lime and soda ash to the hard water creates a precipitate consisting of calcium carbonate and magnesium hydroxide. The water then flows into flocculation basins for a detention time for approximately 15 to 20 minutes. The lime utilized in the slaking process generates approximately 8 to 10% silica grit by weight. Much of this grit is removed in the lime slaker, but a fair quantity usually finds its way into the rapid mix and flocculation basins. The grit must be removed periodically from the flocculation basins to minimize damage to the flocculation equipment. The water then flows into sedimentation basins specifically designed for capture of the calcium and magnesium precipitates. Up-flow or solids contact clarifiers are usually utilized for combining the flocculation and sedimentation process into one unit. We discussed these clarifiers in the sedimentation chapter previously. Solids contact clarifiers are especially suited for this type of treatment. Rectangular sedimentation basins are usually avoided due to the excessive wear that can occur on the chains and flights due to the abrasive qualities of the grit and precipitates.

After the sedimentation process, the pH of the water must be properly adjusted prior to further treatment. This is usually accomplished by the addition of an acid or carbon dioxide (CO2 ). "Recarbonation" is the term utilized to describe the addition of carbon dioxide to the water being treated. For smaller facilities, carbon dioxide is usually purchased and delivered in liquid or gas cylinders, or in dry ice containers. Larger facilities have found it more cost-effective to produce carbon dioxide onsite in submerged combustion burners where natural gas is burned to create the carbon dioxide or by utilizing cleaned and scrubbed exhaust gases from furnaces, lime regeneration or carbon regeneration equipment process units. Generally speaking re-carbonation by itself can only reduce the pH to approximately 8.3. Additional reductions in the pH value will require the addition of an acid.

Advantages and Disadvantages:
Advantages of this type of process include: the ability to soften water yet maintain an adequate water stability for corrosion protection; and it’s cost-effectiveness in treating large quantities of surface water.
Disadvantages include: proper disposal of the large quantity of high pH sludge; constant removal of the calcium carbonate scale on slaking equipment, rapid mixers, and flocculation basin equipment; safety issues regarding dosing sodium hydroxide or soda ash, and the slaking and feeding of lime. Extreme care must be taken when working around dry lime (CaO). The addition of water generates a lot of heat. One must never apply water from a hose directly to a dry lime spill or accumulation in a slaker, as there exists the potential of explosion resulting from escaping gases in heat from the interior of the lime pile.

Q21: What are methods of solid waste disposal:

1.      Controlled land filling

2.      Disposal into sea

3.      Filling of low lying areas

4.      Mechanical composting

5.      Pulverising

6.      Compaction

7.      Incineration

8.      Pulping

Q22:    Define the following / write in short notes:

Kilo Calorie:  1 calorie is the heat required to raise the temperature of 1g of water through 1°C  (e.g. 25°C to 26°C)

[1 kilocalorie = 1000 calories]

Specific Heat: The amount of heat required to raise the temperature of a unit mass of substance by 1°C, compared with the amount of heat required to raise the temperature of the same weight of water by 1°C. The Sp. Ht. of water is 1cal/gram°C = 4.186 joule/gram°C and is higher than any other common substance.

BTU: (British Thermal Heat Unit): Qty. of heat required to raise the temperature of 1 lb (pound) of water through 1°F

 [1BTU = 252.16cal]

CHU: (Centigrade Heat Unit): Quantity of heat required to raise the temperature of 1 pound (lb) of water through 1°C. [1CHU = 453.6cal.]

Ignition temperature: or Ignition Point Temperature: The temperature to which a fuel must be raised to cause a chemical union with oxygen and start burning. (For Coal -150°C, Methane-700°C, Hydrogen-595°C, Petrol-343°C)

Flash point: It is the lowest temperature at which the fuel gives off enough vapours that ignite for a moment when a small flame is brought near to it.

Fire point: It is the lowest temperature at which the vapours of the fuel burn continuously for at least 5 secs. When a tiny flame is brought near to it. In most cases the fire points are 5°C to 40°C higher than the flash point.

Watt:   It is the rate of doing work. The electric unit of power is Watt, defined as the power expended when one Joule of work is done in one second. (1 watt = 1 Joule / sec. = 1 Nm/sec.)

Potential Difference: (P.D.) The voltage at any point is known as the potential of the point. The difference of the electrical voltage between any two points is called the Potential Difference. The electrical potential difference is work done in moving a unit charge. Potential difference is measured in Volts.

Ampere:         The rate of flow of electric charge is current. The unit of current is Ampere. Flow of one coulomb charge in one second is one ampere. (1Amp = 1coulomb/sec)

Energy KWh: Energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems. Since work is defined as a force acting through a distance (a length of space), the total work done in a given time is called Energy. Its unit is watt-sec. In general terms, energy is stated in kilowatt-hours (kwh). (1 unit of electrical energy  = 1 kwh.)

Conductor:     A conductor or wire  is a material which contains movable electric charges, enabling electric current to flow through it. It offers low resistance to the passage of current.

 

Fuses: An over-current protective device with a circuit-opening fusible part that is heated and severed by the passage of over-current through it. A fuse interrupts excessive current (blows) so that further damage by overheating or fire is prevented. Overcurrent protection devices are essential in electrical systems to limit threats to human life and property damage. Fuses are selected to allow passage of normal current and of excessive current only for short periods. A fuse (Kit-Kat fuse)consists of a metal strip or wire fuse element, of small cross-section compared to the circuit conductors, mounted between a pair of electrical terminals, and (usually) enclosed by a non-conducting and non-combustible housing. The fuse is arranged in series to carry all the current passing through the protected circuit. The resistance of the element generates heat due to the  current flow. If too high a current flows, the element rises to a higher temperature and either directly melts, or else melts a soldered joint within the fuse, opening the circuit. Fuses act as a weak link in a circuit. They reliably rupture and isolate the faulty circuit so that equipment and personnel are protected. Following fault clearance they must be manually replaced before that circuit may be put back into operation.

MCB: (Miniature Circuit Breaker) A device designed to open and close a circuit by non-automatic means and to open the circuit automatically on a predetermined over-current without damage to itself when properly applied within its rating. Miniature circuit breakers (MCBs) or Moulded Case Circuit Breakers (MCCBs) are also over-current protection devices often with thermal and magnetic elements for overload and short circuit fault protection. As a switch they allow isolation of the supply from the load. Normally the MCB requires manual resetting after a trip situation but solenoid or motor driven closing is also possible for remote control. The MCB is an automatic, electrically operated switching device that was designed to automatically protect an electric circuit from overload currents and short circuit currents. It is a complicated construction made up of almost 100 individual parts. It has the ability to respond within milliseconds when a fault has been detected. Westinghouse Electric introduced the world’s first MCB and it initially had a porcelain base and cover mounted in a metal housing.

Good Earthing The qualities of a good earthing system are : 1) Must be of low electrical resistance 2) Must be of  good corrosion resistance 3) Must be able to dissipate high fault current repeatedly

Earthing: This is made up of material that is electrically conductive. A fault current will flow to 'earth' through the live conductor, provided it is earthed. This is to prevent a potentially live conductor from rising above the safe level.  All exposed metal parts of an electrical appliance must be earthed . The main objectives of the earthing are to :

1) Provide an alternative path for the fault current to flow so that it will not endanger the user

2) Ensure that all exposed conductive parts do not reach a dangerous potential

3) Maintain the voltage at any part of an electrical system at a known value so as to prevent over current or excessive voltage on the  appliances or equipment . 

Open Circuit, Closed Circuit, Short Circuit:         

OPEN CIRCUIT: When there is a break in the electrical circuit it is called open circuit.

CLOSE CIRCUIT: When the path of the current flow is complete, it is called close circuit.

SHORT CIRCUIT: When the path of the current flow is completed through not the intended path but through some leakage / damaged path to earth, it is called short circuit.

PVC:   Polyvinyl chloride, commonly abbreviated PVC, is a thermoplastic polymer,is commonly used as the insulation on electric wires

SWG:  Standard Wire Gauge; a notation for the diameters of metal wires or thickness of metal sheet ranging from 16 mm to 0.02 mm or from 0.5 inch to 0.001 inch.

HP:      The horsepower used for electrical machines is defined as exactly 746 W.

Foot-candle (abbreviated fc, lm/ft², or sometimes ft-c) is a non-SI unit of illuminance or light intensity widely used in photography, film, television and lighting industry.  It can be defined as the illuminance on a 1-square foot surface of which there is a uniformly distributed flux of one lumen. This can be thought of as the amount of light that actually falls on a given surface. The foot-candle is equal to one lumen per square foot. One footcandle is equal to approximately 10.764 lux.

Relative Humidity:    It is a term used to describe the amount of water vapor in a mixture of air and water vapor. It is defined as the partial pressure of water vapor in the air-water mixture, given as a percentage of the saturated vapor pressure under those conditions. The relative humidity of air thus changes not only with respect to the absolute humidity (moisture content) but also temperature and pressure, upon which the saturated vapor pressure depends. Relative humidity is often used instead of absolute humidity in situations where the rate of water evaporation is important, as it takes into account the variation in saturated vapor pressure. Humans are sensitive to humid air because the human body uses evaporative cooling as the primary mechanism to regulate temperature. Under humid conditions, the rate at which perspiration evaporates on the skin is lower than it would be under dry arid conditions. Because humans perceive the rate of heat transfer from the body rather than temperature itself, we feel warmer when the relative humidity is high than when it is low.

Dry Bulb Temperature: The Dry Bulb temperature, usually referred to as air temperature, is the air property that is most commonly used. When people refer to the temperature of the air, they are normally referring to its dry bulb temperature.

The Dry Bulb Temperature refers basically to the ambient air temperature. It is called "Dry Bulb" because the air temperature is indicated by a thermometer not affected by the moisture of the air. Dry-bulb temperature can be measured using a normal thermometer freely exposed to the air but shielded from radiation and moisture. The temperature is usually given in degrees Celsius (^oC) or degrees Fahrenheit (^oF). The SI unit is Kelvin (K). (Zero Kelvin equals to -273^oC).

Wet Bulb Temperature: The Wet Bulb temperature is the temperature of adiabatic saturation. This is the temperature indicated by a moistened thermometer bulb exposed to the air flow. Wet Bulb temperature can be measured by using a thermometer with the bulb wrapped in wet muslin cloth. The adiabatic evaporation of water from the thermometer and the cooling effect is indicated by a "wet bulb temperature" lower than the "dry bulb temperature" in the air. The rate of evaporation from the wet bandage on the bulb, and the temperature difference between the dry bulb and wet bulb, depends on the humidity of the air. The evaporation is reduced when the air contains more water vapor. The wet bulb temperature is always lower than the dry bulb temperature but will be identical at 100% relative humidity (the air is at the saturation line).

Dew Point Temperature: The Dew Point is the temperature at which water vapour starts to condense out of the air (the temperature at which air becomes completely saturated). Above this temperature the moisture will stay in the air.

If the dew-point temperature is close to the dry air temperature -  the relative humidity is high

If the dew point is well below the dry air temperature - the relative humidity is low

If moisture condensates on a cold bottle taken from the refrigerator, the dew-point temperature of the air is above the temperature in the refrigerator.

The Dew Point temperature can be measured by filling a metal can with water and some ice cubes. Stir by a thermometer and watch the outside of the can. When the vapor in the air starts to condensate on the outside of the can, the temperature on the thermometer is pretty close to the dew point of the actual air.

Thermostat:   A thermostat is the component of a control system which regulates the temperature of a system so that the system's temperature is maintained near a desired setpoint temperature. The thermostat does this by switching heating or cooling devices on or off, or regulating the flow of a heat transfer fluid as needed, to maintain the correct temperature. Domestic water and steam based central heating systems have traditionally been controlled by bi-metallic strip thermostats.

Refrigerant: A refrigerant is a substance used in a heat cycle usually including, for enhanced efficiency, a reversible phase change from a gas to a liquid. Traditionally, fluorocarbons, especially chlorofluorocarbons, were used as refrigerants, but they are being phased out because of their ozone depletion effects. Other common refrigerants used in are ammonia, sulfur dioxide, and non-halogenated hydrocarbons such as methane. Common refrigerants are: Carbon tetrachloride- CCl_4,  Trichlorofluoromethane- CCl₃F, Tetrafluoromethane- CF_4, Trichloromethane- CHCl_3, Ethane- C₂H_6.

Ton of refrigeration: It is approximately equal to the cooling power of one short ton (2000 pounds or 907 kilograms) of ice melting in a 24-hour period. The value is defined as 3024 Kcal/hr or 12,000 BTU per hour, or 3517 watts. Residential central air systems are usually from 1 to 5 tons (3 to 20 kilowatts (kW)) in capacity.

Defrosting (or thawing) is a procedure, performed periodically on refrigerators and freezers to maintain their operating efficiency. Over time, as the door is opened and closed, letting in new air, water vapour from the air condenses on the cooling elements within the cabinet. It also refers to leaving frozen food at a higher temperature prior to cooking.

Chilled water air conditioning applications temperature: Chilled water systems are commonly designed to provide full cooling load with a chilled water temperature of about 42°F (i.e. 5.5°C).

Pollution: It is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light. Pollutants, the elements of pollution, can be foreign substances or energies or naturally occurring. The major forms of pollution are as below along with the particular pollutants relevant to each of them:

a) Air pollution:- the release of chemicals and particulates into the atmosphere. Common gaseous pollutants include carbon monoxide, sulfur dioxide:- chlorofluorocarbons (CFCs) and nitrogen oxides produced by industry and motor vehicles. Photochemical ozone and smog are created as nitrogen oxides and hydrocarbons react to sunlight

b) Light pollution:- includes light trespass, over-illumination and astronomical interference.

c) Littering:- the criminal throwing of inappropriate man-made objects, unremoved, onto public and private properties.

d) Noise pollution:- which encompasses roadway noise, aircraft noise, industrial noise as well as high-intensity sonar.

e) Soil contamination:- occurs when chemicals are released intentionally, by spill or underground leakage. Among the most significant soil contaminants are hydrocarbons, heavy metals, herbicides, pesticides and chlorinated hydrocarbons.

f) Radioactive contamination:- resulting from 20th century activities in atomic physics, such as nuclear power generation and nuclear weapons research, manufacture and deployment.

g) Thermal pollution:- is a temperature change in natural water bodies caused by human influence, such as use of water as coolant in a power plant.

h) Visual pollution:- This affects the aesthetic looks. They can refer to the presence of overhead power lines, motorway billboards, scarred landforms (as from strip mining), open storage of trash or municipal solid waste.

i) Water pollution:- by the discharge of wastewater from commercial and industrial waste (intentionally or through spills) into surface waters; discharges of untreated domestic sewage, and chemical contaminants, such as chlorine, from treated sewage; release of waste and contaminants into surface runoff flowing (including urban runoff and agricultural runoff, which may contain chemical fertilizers and pesticides); waste disposal and leaching into groundwater; and littering.

Elevator: (or lift in British English) is a type of vertical transport equipment that efficiently moves people or goods between floors (levels, decks)of a building, vessel or other structure. Elevators are generally powered by electric motors that either drive traction cables or counterweight systems like a hoist, or pump hydraulic fluid to raise a cylindrical piston like a jack.

Tap (also called Spigot or Faucet in the U.S.) is a valve controlling release of liquids or gas. The word Tap is used for any everyday type of valve, particularly the fittings that control water supply to bathtubs and sinks. In the U.S., the term "tap" is more often used for beer taps. "Spigot" or "faucet" are more often used to refer to water valves, although this sense of "tap" is not uncommon, and the term "tap water" is the standard name for water from the faucet.

The physical characteristic which differentiates a spigot from other valves is the lack of any type of a mechanical thread or fastener on the outlet. Water for baths, sinks and basins can be provided by separate hot and cold taps; this arrangement is common in older installations, particularly in public washrooms/lavatories and utility rooms/laundries. In kitchens and bathrooms mixer taps are commonly used. In this case, hot and cold water from the two valves is mixed together before reaching the outlet, allowing the water to emerge at any temperature between that of the hot and cold water supplies. Mixer taps were invented by Thomas Campbell of Saint John, New Brunswick and patented in 1880.

Trap: Trap is a downward looped section of pipe of U-shape, in the lower part of which remains a quantity of water, acting as a seal for foul smelling gas. Because of its shape, the trap retains a small amount of water after the fixture's use. This water in the trap creates a seal that prevents sewer gas from passing from the drain pipes back into the occupied space of the building. Essentially all plumbing fixtures including sinks, bathtubs, and toilets must be equipped with either an internal or external trap. Requirements of a good trap are a) It should not allow passage of foul gases, b) It should have sufficient depth of water always, c) It shoul be easily cleared. On the basis of shape the traps may be P-Trap, Q-Trap, S-Trap or U-trap. On the basis of use the traps may be a) WC trap, b) Floor trap, c) Gully trap d) Intersecting trap.

Rain water harvesting: The areas which have a fair amount of natural rainfall, but do not have geographical conditions to absorb and impound the rain water, should have rain water harvesting system. Here the natural rain water is channelised into the sub-soil near the bore-wells / tube-wells, so that the ground water level rises and these wells do not dry up in summer season.

SAFETY

Some causes of accidents Overexertion — 27 percent of time-loss claims. These are injuries resulting from the application of force to an object or person — such as lifting, pushing, pulling, and carrying. Being struck by an object — 16 percent. With this type of accident, the worker is injured by a moving object such as equipment and tools. Falls on the same level — 14 percent (e.g., slips). Falls from elevations or heights — 10 percent.

In the fast-paced environment of hotels and

restaurants, a common attitude is that accidents are inevitable and a part of doing business. But injuries mean losses. Lost money, lost time, and lost productivity. And more importantly, they mean that workers and their families suffer pain and have their lives disrupted. If accidents are prevented, the savings can be significant — less overtime, less retraining, and less time spent investigating accidents, to name a few. The other benefits are also rewarding — morale improves and workers feel valued.

Safety tips for preventing common accidents

Following are some safety tips for preventing accidents that commonly occur in the hotel and restaurant industries. Safety tips are included on:

• Cuts • Knives • Slips and falls • Floors • Stairways • Storage areas • Burns and scalds • Ladders

 

Cuts: These can occur from: • Knives • Furniture • Equipment • Counters • Utensils • Glassware • Preparation areas • Dishes • Cleaning equipment

Do

Do not

• Throw away broken or chipped glassware. • Use a cutting board for safe cutting and chopping. • Lock out or disconnect the power source before cleaning equipment such as meat slicers. • Make sure that you receive proper training in operating equipment and safe job procedures. • Consult the manufacturer’s instruction manual for operating, cleaning, and maintaining the equipment. • Make sure that cutting blades are sharp. • After cleaning, make sure that all guards and safety devices are put back in place. • Place a warning tag on defective and unsafe equipment and do not re-start the equipment. Inform your supervisor.

• Do not operate equipment if you feel unwell or drowsy. (Remember, some cold remedies can make people feel sleepy.) • Do not place hands near the edge of cutting blades. Make sure you can always see both hands (and all fingers) and the cutting blades. • Do not try to catch falling objects. • Do not try to clean or "just brush something off" a moving part such as cutting blades or beaters in mixers. • Do not push or place your hand in feed hoppers or delivery chutes. Use food pushers. • Do not try to cut anything in a slicer that becomes too thin. Use a knife to finish cutting. • Do not wear loose or frayed clothing, gloves, or jewellery that can be caught in a moving machine.

Knives:   Potential injuries: cuts and amputation.

Do

Do not

• Use the right knife for the job. • Always use a proper chopping board or block. • Make sure the knife is sharp. • Carry only one knife at a time, tip pointed down at your side. • Store knives securely in proper racks in a visible place. • Hold the knife with your stronger hand. • Cut away from your body when cutting, trimming, or boning. • When not using knives, place them at the back, with the sharp edge away from you. • After using a knife, clean it immediately or place it in a dishwasher. • Use protective clothing such as mesh gloves.

• Do not leave a knife in dishwater. • Do not use a knife as a can opener. • Do not try to catch a falling knife. Let it fall and then pick it up. • Do not engage in horseplay with a knife in your hand. • Do not carry knives while carrying other objects. • Do not carry a knife in your pocket. • Do not leave knives where they could be accidentally covered. • Do not talk to your co-workers while you are using a knife — you could become distracted.

Slips and falls: Slips and falls can occur from: • Slippery and cluttered floors and stairs • Loose or bumpy carpets and floor mats • Defective ladders and footstools • Poor visibility

Do

Do not

• Keep floors and stairs clean, dry, and non-slippery. • Keep floors and stairs clear of debris and obstruction. • Use slip-resistant waxes to polish and treat floors. • Make sure that carpeting, rugs, and mats are free of holes, loose threads, loose edges, and bumps that may cause tripping. • Use adequate warning signs for wet floors and other hazards. • Make sure that wooden duckboards and railings are in good repair and free of splinters. • Make sure that ladders and footstools are in good repair and have non-skid feet. • If possible, immediately remove or clean up any tripping or slipping hazard you notice. If it’s not possible to take care of the hazard yourself, report it immediately to your supervisor.

• Do not use defective ladders or footstools. • Do not use chairs, stools, or boxes as substitutes for ladders. • Do not leave oven, dishwasher, or cupboard doors open. These may present a tripping hazard for you or your co-workers.

Floors:  Potential accidents: slips and falls.

Do

Do not

• Make sure that walking surfaces are uncluttered, non-slippery, clean, and adequately lighted. • If you drop or spill something, clean it up immediately. • Mop floors with the recommended amount of cleaning product in the water, or cleaning fluid, to ensure grease and other slippery substances are removed. • Make sure floors are free from trip hazards such as raised or broken sections. • Treat floors with slip-resistant products if the floors must be waxed. • Place wet floor warning signs to prevent people from slipping. • Use non-slip mats and floor finishes. • Replace doormats regularly. • Walk — don’t run. • Mark swinging doors with in and out signs.

• Do not leave carts, boxes, trash cans, or other objects on the floors and in the aisles.

Proper footwear prevents injuries • Wear footwear that is closed at the toe and without a pattern of holes. • Wear shoes that protect against spilled liquids, including hot ones. • Wear slip-resistant shoes. For wet surfaces, the sole should have a well-defined pattern as more edges will provide a better grip. • Don’t wear shoes that are dirty or worn out as this affects their slip-resistance. To preserve your shoes, leave them at work and wear other shoes to and from work. • Wear shoes with low or no heels. • Wear shoes or boots with internal steel toe caps if you lift and carry heavy objects

 

Stairways:  Potential accidents: slips and falls.

Do	Do not
• Ensure that stairways are well lit. • Keep stairs clear of obstructions. • Use handrails. • When carrying a load up and down stairs, make sure that the load does not block your vision. • Report tripping hazards to your supervisor and place warning signs.	• Do not store boxes and supplies on the stairs. • Do not throw things up or down stairways. • Do not switch off lights in the stairways.

Storage Areas:  Potential hazards: collapse of stored goods; slipping and tripping.

Do

Do not

• Make sure the shelves are firmly secured in place against walls and on the floor. • Ensure adequate lighting. • Store chemicals, detergents, and pesticides in a separate area away from foodstuff. • Ensure that chemicals that are notcompatible with each other are not stored together. (Check the material safety data sheet.) • Store heavy items on lower shelves, particularly when cartons contain fluids. • Use bins and racks as much as possible. • Leave adequate clearance space between the top of the stored goods and the ceiling in areas protected by a sprinkler

• Do not block passages in the storage area. • Do not stack loose items on the top shelves. • Do not overload shelving units. • Do not store cardboard cartons in damp areas. • Do not overstock.

Ladders:  Potential accidents: falls from portable ladders; splinters; slipping.

Do

Do not

• Inspect a ladder before and after each use. • Reject a ladder if it has loose, broken, or missing rungs; loose hinges; or loose or missing screws or bolts. • Reject and tag defective ladders. Have defective ladders repaired or thrown out. • Use a ladder designed for your task. Consider its strength and type. (eg. insulated ladder for electrical work) • Set up barricades and warning signs when using a ladder in a doorway or passageway. • Clean muddy or slippery footwear before mounting a ladder. • Face the ladder when going up or down and when working from it. • Keep the centre of your body within the side rails. • Place ladder feet 30 cm (1 ft.) from the wall for every 1 m (3 ft.) of height. • Extend the ladder at least 1 m (3 ft.) above the landing platform. • Locate the ladder on a firm footing using slip-resistant feet or secure blocking, or have someone hold the ladder. • Rest both side rails on a top support, and secure the ladder to prevent slipping. • Use a three-point stance, keeping both feet and at least one hand on the ladder at all times.

• Do not use ladder in a horizontal position as a scaffold plank or runway. • Do not carry objects in your hands while on a ladder. Hoist materials or attach tools to a belt. • Do not work from the top two rungs. The higher you go on a ladder, the greater the possibility that the ladder will slip out at the base. • Do not use makeshift items such as a chair, barrel, milk crate, or boxes as ladders.

Burns and scalds:  Burns and scalds can occur from: • Stoves • Toasters • Ovens • Boiling hot liquid • Hot utensils

• Pressure cookers • Cooking pots • Hot dishwashers

Do

Do not

• Assume that all pots and pans and metal handles are hot. Touch them only when you are sure that they are not hot or when you are using proper gloves. • Organize your work area to prevent contact with hot objects and flames. • Keep pot handles away from hot burners. • Make sure that handles of pots and pans do not stick out from the counter or cooking stove. • Use oven mitts appropriate for handling hot objects. Use long gloves for deep ovens. • Follow electric and fire safety guidelines. • Follow the manufacturer’s operating instructions. • Use only recommended temperature settings for each type of cooking. • Open hot water and hot liquid faucets slowly to avoid splashes. • Lift lids by opening away from you. • Wear long-sleeved cotton shirts and cotton pants. • Report problems to your supervisor.

• Do not overfill pots and pans. • Do not leave metal spoons in pots and pans while cooking. • Do not spill water in hot oil. • Do not overstretch over a stove, grill, or other hot area in order to reach an uncomfortable distance. • Do not use a wet cloth to lift lids from hot pots. • Do not open cookers and steam ovens that are under pressure. • Do not lean over pots of boiling liquids. • Do not leave a hot electric element or gas flame of stove "on" all the time.

Preventing overexertion accidents:  Risk factors

The key to preventing injuries is to reduce or eliminate the risk factors contributing to the injuries. Workplace factors associated with overexertion accidents to the back include:

• Awkward back posture held for a period of time or repeated due to poor working heights and reaches. Examples include

reaching for linen or supplies located on high shelves.

• Heavy or frequent lifting, pushing, pulling, and carrying. For example, lifting and carrying bulk food containers.

• Prolonged sitting or standing. Examples include:

- Sitting — front office staff working on computers

- Standing — a restaurant worker whose duties consist of greeting customers and working the cash•

- Whole body vibration. For example, delivery truck drivers.

The time to complete a task, how often it is repeated, and the worker’s perception about time pressures can also influence workplace risk factors.

How to reduce overexertion accidents:

Reducing risks need not be a complicated process. Following are examples of solutions in hotel and restaurant industries:

• Store heavier or frequently used items at a height between workers’ hips and chest to reduce awkward postures when

handling these items.

• Place smaller loads in laundry washing machines to reduce tangling and the subsequent heavy pulling needed to remove the laundry from the washer.

• Use laundry carts with spring-loaded bottoms that rise as the cart is unloaded. This reduces repetitive, awkward bending.

• Install platforms at the base of laundry chutes to eliminate repetitive bending and lifting from the floor while sorting laundry.

• Use long-handled tools to reach the walls and tub when cleaning showers to decrease reaching and stooping.

• Ask a co-worker for help when moving heavy furniture. Employers should set a policy to give guidance in these situations.

• Ensure cleaning products and equipment are efficient and do not require extra force to use. For example, use a window

cleaner that doesn’t streak to reduce the number of wiping motions, or use a cleanser that removes dirt and grime with one swipe.

• Use smaller banquet trays to lighten loads and to make them easier to handle.

• Store clean plates on spring-loaded dollies to reduce repetitive bending.

• Use carts to move heavy products from storage coolers and freezers.

• Don’t store heavy items in small, confined areas where the worker may not be able to use safe lifting techniques.

• Design or alter “pass through” windows in restaurants to reduce the risk of back injury. If they are too high or too deep, workers are forced to use long reaches and awkward postures to pick up orders.

• Lower storage racks at dishwasher stations to minimize awkward lifting and reaching. Lowering the racks or using a sturdy step stool can help to reduce the height of the lift.

• Add a footrest or matting to a hostess counter to give some relief from prolonged standing.

• Reduce risks through organizing work differently. For example, room attendants could unload laundry from their carts more often to lighten the loads they handle and to reduce the amount of pushing needed to move the cart.

• Train and supervise workers in safe work practices that have been developed to reduce their exposure to risk factors.

BAD WORKING HABITS: Some common working habits that can be identified in catering situations as safety hazards are as below:

#- Habit of lighting cooking gas ranges without placing anything on the burner for cooking.

#- Habit of keeping electric switches “ON” while dismantling an equipment for cleaning or repair.

#- Placing knives and other sharp kitchen tools in the sink for washing, along with other equipment can cause cuts.

#- Not wiping the spillages immediately can result in slips and falls

#- The tendency to dispose of broken glass pieces along with other wastes can cause cuts.

#- Inserting loose wires into electric sockets, especially with moist hands can result in fatal shock.

#- Replacing hot electric bulbs immediately upon fusing, can cause burns on the hand.

#- Lifting lids off hot pans suddenly poses threat of getting burns through hot steam.

      

Preventing exposure to HIV/AIDS, and Hepatitis ‘’B and ‘C’ at work:

Hotel and restaurant workers sometimes find used needles between bedsheets, under beds, in garbage containers, and hidden in washrooms. Sometimes cleaning staff come into contact with condoms when they try to unclog toilets. These items could be contaminated with blood and body fluids infected with tiny organisms that can cause disease in humans. These micro-organisms are known as bloodborne pathogens. The bloodborne pathogens of most concern are the human immunodeficiency virus (HIV) and the Hepatitis B and C viruses. HIV causes the disease AIDS (acquired immune deficiency syndrome), and the hepatitis B and hepatitis C viruses cause diseases with the same names. Since exposure to blood and certain body fluids may spread these viruses, these diseases are also called bloodborne diseases. Most hotel and restaurant workers won’t ever contact, at work, blood and certain body fluids that can spread HIV and the hepatitis B and C viruses. But even employers and workers in settings where contact with blood and these body fluids is not expected should be aware of some basic precautions because it is possible to become infected with a single exposure incident — that is, harmful contact to infected blood and body fluids. Hepatitis B and C should not be confused with hepatitis A — a food / water borne illness. That means that you can become infected with the hepatitis A virus if you eat food that has been prepared by someone who is infected with the virus. Hepatitis A is primarily a public health concern. Hotel and restaurant owners who would like more information on how to prevent the spread of hepatitis A should contact their local health units.

 

Contract Maintenance

Maintenance Policy:  The policy adopted by the hotel management for maintenance purposes would depend on the following parameters:

-                      Type of organization structure

-                      Availability of trained staff

-                      Overall budget for maintenance staff, tools, spares etc.

-                      Contract vs. In-House maintenance

-                      Position of stand-by equipment

-                      Safety standards

Contract Maintenance vs. Departmental Maintenance (In- House)

Maintenance may be done by your own maintenance personnel, or else the job may be off-loaded to an outside agency on contract basis. This will depend largely on facilities available in-house, trained staff, overall cost, availability of spares etc.

Contract Maintenance

Departmental Maintenance

No need to recruit trained personnel / staff Reduces labour cost Reduces cost of tools, spares, material. Uses latest techniques. Saves administrative time Flexibility of meeting emergencies. Disadvantages: -                 Management laziness during negotiating contract price,             resulting in higher cost.             Loss of involvement and ownership of in- house staff             Predictive maintenance mind-set is absent or very low.

Involvement and ownership of staff Multi- tasking, multi-skilled operation Can focus more on Predictive Maintenance Optimum utilization of man-power and machines

Contract maintenance may be awarded for the following areas:

-                      Routine maintenance of overall ground area

-                      Preventive maintenance of plant and equipment like water treatment plant, heating plant, AC plant, elevators etc.

-                      Civil maintenance of Building and other infra-structure

-                      Fire and safety equipments

-                      Kitchen appliances

-                      Overall cleaning, plumbing and laundry.

All contracts must have:      a) Insurance of maintenance employees,   b) Inspection facility of work done, c) Safe practices should be followed,  d) Local codes and statutory regulations must be followed.

What is a Valid Contract?

According to Section 10 of the Indian Contracts Act, 1872, "All agreements are contracts, if they are made by the free consent of the parties, competent to contract, for a lawful consideration with a lawful object, and not hereby expressly to be void."

Essential Elements of a Valid Contract are:

1.Proper offer and proper acceptance. There must be an agreement based on a lawful offer made by person to another and lawful acceptance of that offer made by the latter. Section 3 to 9 of the contract act, 1872 lay down the rules for making valid acceptance.

2. Lawful consideration: An agreement to form a valid contract should be supported by consideration. Consideration means “something in return” (quid pro quo). It can be cash, kind, an act or abstinence. It can be past, present or future. However, consideration should be real and lawful.

3. Competent to contract or capacity: In order to make a valid contract the parties to it must be competent to be contracted. According to section 11 of the Contract Act, a person is considered to be competent to contract if he satisfies the following criterion:

a. The person has reached the age of maturity.

b.The person is of sound mind.

c. The person is not disqualified from contracting by any law.

4. Free Consent: To constitute a valid contract there must be free and genuine consent of the parties to the contract. It should not be obtained by misrepresentation, fraud, coercion, undue influence or mistake.

5. Lawful Object and Agreement: The object of the agreement must not be illegal or unlawful.

6. Agreement not declared void or illegal: Agreements which have been expressly declared void or illegal by law are not enforceable at law; hence does not constitute a valid contract.

7. Intention To Create Legal Relationships

8. Certainty, Possibility Of Performance

9. Legal Formalities

Types of   Contracts

Lump-sum contract: This contract requires the contractor to undertake complete services including providing labour, material, spares, tools etc. for proper maintenance under his scope.

Advantages:    Early completion of work as no waiting time, low cost, definite amount.

Disadvantages:            Conflicting interests if scope is ambiguous, high cost of uncertainty due to extra work.

Unit price contract: (Contracts given for individual works item) This contract is made where plans and specifications may not be possible to foresee, work quantity and quality is difficult to predict. Thus every department decides its own works schedules and rates. The nature of work should be simple.

Advantages: Starting of work is easy, flexibility in accomplishing work, economic cost is easy to arrive at.

Disadvantages: Classification of material is not clear, final cost is difficult to arrive at in case of changes.

Cost plus a fixed percentage contract: In this type of contract, the contractor agrees to supply all labour, material etc. at actual costs plus a fixed percentage of this cost, which may be termed as his service charges. It works well when specifications are not complete and prices not stable. Final cost may be lower because contractor does not have to control the cost of material etc. Quality of work will be good.

Cost plus contract with upper limit: Advantages: Non-conflicting interest, extra work, early completion of where starting of work is easy.

Disadvantages: Final cost not clear, checking of contract account difficult.

Procedures for tenders

 There are four types of tendering procedures that can be used by commissioning bodies to buy services or products.

Open Tender: One of the most common procedures used is called an ‘open’ procedure. This is where an opportunity (including all tender documents) is advertised inviting providers to bid directly for a contract. All interest parties then submit a tender. Scoring takes place and the successful organisation is awarded the contract. Sometimes there is a selection stage first, which is then followed by the award stage.

Limited tender or restricted procedure. This involves the opportunity being advertised in the relevant places and media. Organisations will then submit an expression of interest and fill in a pre qualification questionnaire. Only successful organisations will go onto select list and be given an invitation to tender with the tender documents. Tender documents are completed and submitted. From the submitted tender documents scoring takes place and the successful organisation is awarded the contract. There must be a minimum of three bidders. This procedure works best when a commissioning body is clear at the start of the process what it wants to buy in terms of pricing and other award criteria

Negotiated tender can only be used in a limited number of carefully defined cases (e.g. large capital projects where a range of solutions to deliver are possible). The cases where using this procedure is prescribed is featured in the Public Contract Regulations 2006. An opportunity is advertised (the specification is not established at the start of the process) and organisations can submit an expression of interest and fill in a pre qualification questionnaire. Successful bidders are invited to negotiate with the procuring body, which is called the dialogue phase. Once dialogue has generated solutions to the agreed requirements, final tenders are submitted based on each bidders individual solution. Scoring then takes place and the successful organisation is awarded the contract. There must be a minimum of three bidders

Competitive dialogue is another procedure only used in the case of particularly complex contracts. An opportunity is advertised and organisations can submit an expression of interest and fill in a pre qualification questionnaire (the specification is not established at the start of the process). Successful bidders discuss the form of the contract and technical specifications with the bidders before the tender documents are issued. The discussion ends when the procuring body can identify a solution to meet its needs. Bidders then submit a tender based on the solution resulting from the discussion. Scoring then takes place and the successful organisation is awarded the contract. There must be a minimum of three bidders.

Negotiations of tender bids:

Negotiations may be done with the bidders with a view to obtain clarity, competitive price. However, the lowest bidder shall be given preference unless otherwise ruled out on technical grounds. In a Two-part tender bid, the bidders are invited to submit their offers in two parts viz. i) Technical Part ii) Price part. Negotiations may be done on the technical part and then only the price bid shall be opened for finalisation of the contract.

Electric Current: The flow of charge (i.e. the ordered directional motion of charged particles) constitutes electric current. Atoms of all substances are built up of positive charged particles called protons and negative charged particles called electrons. If particles interact with one another through forces that decrease slowly with increase in distance and exceed the forces of universal gravitation many times, they are said to have an electric charge and are called charged particles. There can be particles without any electric charge, but an electric charge does not exist without a particle. In metals the carriers of charge are electrons. An atom consists of a central nucleus made up of protons and neutrons. Neutrons are particles that have no electrical state, neither positive nor negative. Around this

Hydrogen atom Electron (- ive)                            Atomic No.1                                        Nucleus          (+ ive Proton &  neutral Neutron)

nucleus there are a number of electrons revolving in different orbits. In the normal state, the number of electrons in an atom equals the number of protons, thus balancing the positive and negative charges, and hence the atom is electrically neutral. The number of protons in an atom is called the Atomic Number. (E.g. Atomic number of hydrogen is 1, oxygen is 8, copper is 29). The revolving electrons are held to the nucleus by an attractive force. In conductors they are easily displaced and can move from one atom to another. A conductor[2005] or wire  is a material which contains movable electric charges, enabling electric current to flow. SWG [2005]  Standard Wire Gauge; a notation for the diameters of metal wires or thickness of metal sheet ranging from 16 mm to 0.02 mm or from 0.5 inch to 0.001 inch. When a potential difference is applied between the ends of a conductor, the haphazard

movement of charges causes a steady flow along the conductor and it is this moving stream of electrons that constitutes the electric current. The electron movement is impeded by collision with the molecules giving rise to a certain opposition to the flow of current. This is called resistance. The flow of current is from positive to negative while the electrons flow from negative to positive. In insulators the electrons are firmly held and hence if a potential difference is applied, little or no electrons flow and hence no current flows.

Effects of electric current: We cannot observe directly the motion of particles in the conductor. However, the presence of electric current is manifested in effects and phenomenon accompanying the current. First, a current carrying conductor gets heated. Second, the current can change the chemical composition of substance (e.g. in electrolysis, copper gets separated from copper sulphate solution). Third, the current exerts a force on neighbouring conductors and magnetized bodies. This is called the magnetic effect of current.

Types of charges: 1.When atom loses one electron it becomes a positive charge. 2. Electron has a negative charge.

Quantitatively, electric current is defined as the rate of flow of charge. (I = q/t, where ‘I’ is the current and ‘q’ is the charge that has passed through a given area in time ‘t’)

Charge: The quantity of electricity residing on an electrostatically charged body. The unit of charge is ‘Coulomb’. (1 coulomb = 6.29 x 10¹⁸ electrons)

Current: The rate of flow of electric charge is current. The unit of current is Ampere.[2009,2006]  Flow of one coulomb charge in one second is one ampere. (1Amp = 1coulomb/sec)

Voltage: Electromotive force is the force that starts and maintains flow of electrons in a conductor. Volt is the unit of electromotive force i.e. a measure of the electrical pressure. Volt is the pressure of electricity, Ampere (amp for short) is the flow of electricity. The voltage at any point is known as the potential of the point. The difference of the electrical voltage between any two points is called the Potential Difference.[2009,2006] The electrical P.D. is 1 Volt if 1 Joule of work is done in moving a unit charge (i.e.1 coulomb) from one point to another.

Temperature dependence of resistance Resistance increases with temperature: Rt = R0(1 + at) R0 is resistance of conductor at 0oC Rt is resistance of conductor at temp. t oC a is Temperature Coefficient of resistance

Resistance: Is the property of material by which it opposes the flow of current through it. The electron movement i.e. the current, is impeded by collision with the molecules giving rise to a certain opposition to the flow of current. It can be seen that the resistance depends on the length of the conductor viz. more the length, more the resistance. Similarly if the cross-section of the conductor is more, the less will be its

 resistance to current.  Thus resistance R = r(L/A), L is length of wire, A is area of cross-section, r (row) is the resistivity or specific resistance, which is constant depending on the material of conductor. The resistance is measured in Ohms.[2005]  The ohm is defined as a resistance between two points of a conductor when a constant potential difference of 1 volt, applied to these points, produces in the conductor a current of 1 ampere, The resistance of a conductor varies with temperature.

Ohm’sLaw: The ratio of the potential difference V between any two points in a conductor and the current I flowing through it is constant and it equals the resistance R between the two points. R = V/I. (resistance R is expressed in ohms, voltage V in volts, current I in amps.)(Temperature of the conductor being constant)

Resistors: These are devices used in electric circuits and offer resistance to current flow. They are of various types like Carbon Resistor, Metal Film resistor, Carbon film resistor, Wire wound resistor, Variable resistor etc.

Insulating Materials
Solids	Gases
Paper and press board	Air
Fibrous material	Nitrogen
Resins and polymers	Hydrogen
Natural and synthetic rubbers	Argon
Glass	Helium
Mica	Methane
Asbestos	Propane
Ceramics	Carbon dioxide

Insulators: Very high resistance materials. When the resistance offered to flow of current is very high, it almost totally impedes the flow of current. These materials are called insulators. A good insulation material should have high resistance, good thermal conductivity, high di-electric strength, high mechanical strength, low dissipation factor. The insulating materials generally used are solid or gases (including vacuum). Air is the most important of all di-electric gases because it occurs free in nature. Air is a reliable insulating material when voltages are not very high. Leakage currents are very low in air as compared to other insulating materials. Insulating materials can withstand temperatures depending upon their thermal properties. The classification of insulating materials as per their thermal properties is as follows:

Class	Limiting temp.	Material
Y	900C	Cotton, silk, paper
A	1050C	Impregnated paper, resins
E	120	Mica, fibre glass
B	1300C	Impregnated Mica, Fibre glass,
F	1550C	Polyester epoxy
H	1800C	Composite materials mica, fibre
C	Above 1800C	Mica, Teflon, glass, ceramics

PVC:[2005]   Polyvinyl chloride, commonly abbreviated PVC, is a thermoplastic polymer,is commonly used as the insulation on electric wires

Force, Work, Power, Energy:

Force: When you push or pull some object you exert a force on it. Thus force is an agent that produces or tends to produce, destroys or tends to destroy, motion. A force is any influence that causes a free body to undergo a change in speed, a change in direction, or a change in shape. The SI unit of force is Newton, which is the force required to give a mass of 1kg an acceleration of one meter per sec². (In CGS the unit is Dyne)

For electrical purposes: Work = (Potential diff.) x (current )x time = VxIxt Nm For mechanical purposes: Work = (Force x Distance moved) J

Work: It is the amount of energy transferred by a force acting through a distance in the direction of the force. The SI unit of work is the joule (J), which is defined as the work done by a force of one newton acting over a distance of one meter (1Newtom meter)

Power:.[2005,2006]  It is the rate of doing work. The electric unit of power is Watt,[2009,2005]  defined as the power expended when one Joule of work is done in one second. (1 Watt = 1 Joule / sec. = 1 Nm/sec.) (4.186J=1cal.)

So, Power P = Work / time = V x I x t /t = V x I Watts. From Ohm’s Law V = I x R, hence P = I x I x R = I²R Watt.

Energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems. Since work is defined as a force acting through a distance (a length of space), the total work done in a given time is called Energy. Its unit is watt-sec. In general terms, energy is stated in kilowatt-hours (kWh). (1 unit of electrical energy  = 1 kWh.) .[2009,2004]  (1 kWh = 3.6 x 10⁶ Joules = 860 k cal.)

Question

Solution

In a house, the consumption is as below: 2 nos. 20 W CFL are lighted for 8 hours per day. 2 – 60 W bulbs are lighted for 5 hours per day. Calculate the energy consumed in 30 days.

2-20 W CFL consume (2x20x8x30)W in 30 days                                       = 9600 W-hour = 9.6 kWh 2-60 W bulbs consume (2x60x5x30)W in 30 days                                       = 18000 W-hour = 18.0 kWh                 Total energy  = (9.6 + 18.0) = 27.6 kWh

A kitchen heater draws 100A at 220V supply. Find cost of using heater for 6 hours every day for 30 days. The cost of 1 unit (i.e.1 kwh) is Rs.4.00

Power = V x I watts = 220 x 100 = 22000 W = 22 kw Total usage hours = 6 x 30 = 180 hours Total consumption = 22 kw x 180 hrs. = 3960 kwh Hence cost = 3960 x 4 = Rs.15840/-

An electric kettle of 500 W, 230 V takes 15min. to bring 1 kg of water from 15 oC to boiling at 100 oC. Find the heat efficiency of the kettle. (Given Sp. Heat of water = 1 in MKS units i.e.1 kcal / kg) and 1kcal = 4.2 x 103 Joule

Heat reqd. by water = Mass x Sp.Heat x Rise in temp.                                  = 1 x 1 x (100-15) = 85 kcal. Heat generated by electricity = W x t watt-sec = 500x15x60 watt-sec. or Joule (1watt-sec= 1 Joule) = (500 x 15 x 60)/4.2 x 103  kcal. (1kcal = 4.2 x 103 Joule Thermal efficiency = (Heat reqd.)/(Heat Generated) = (85 x 4.2 x 103 )/(500x15x60) x 100 = 79.33%

[2005]

Direct Current: In case of direct current (DC) it is seen that the voltage or current remains constant throughout the time of flow. There will be two wires, one of them will be positive and the other will be negative that can be earthed. The voltage obtained by Dry cell battery and DC generator is DC type.

Direct and Alternating Current Horizontal axis shows Time Vertical Axis shows Voltage or Current

Alternating Current (AC): In case of Alternating Current, the voltage or current becomes positive and negative alternatively. One positive and one negative loop form a complete cycle. The number of cycles per second is called frequency. The unit of frequency is Hz (Hertz) or cycles per second (cps). In India the electric supply frequency is 50 Hz i.e. the alternating quantity goes through 50 complete cycles in 1 sec. This wave shape of the AC is called a sine wave.

One way to express the intensity, or magnitude (also called the amplitude), of an AC quantity is to measure its peak height on a waveform graph. This is known as the peak or crest value of an AC waveform:

INSTANTANEOUS value of an alternating voltage or current is the value of voltage or current at one particularinstant. The

Average Value of current             = (i1 +  i2 + i3 + . . . . . in)/ n                 where i1 ,  i2 , i3 …. are instantaneous                 values at various times

value may be zero if the particular instant is the time in the cycle at which the polarity of the voltage is changing. It may also be the same as the peak value, if the selected instant is the time in the cycle at which the voltage or current stops increasing and starts decreasing. There are actually an infinite number of instantaneous values between zero and the peak value.

AVERAGE VALUE: of an alternating current or voltage is the average of all the INSTANTANEOUS values during ONE alternation. Since the voltage increases from zero to peak value and decreases back to zero during one alternation, the

average value must be some value between those two limits. You could add series of instantaneous values of the alternation (between 0° and 180°), and then divide the sum by the number of instantaneous values used.

 

 

The computation would show that one alternation of a sine wave has an average value equal to 0.637 times the peak value. The formula for average voltage is  Eavg = 0.637 x Emax, where Eavg is average voltage of one alternation, and Emax is the maximum or peak voltage. Similarly, the formula for average current is Iavg = 0.637 x Imax where Iavg is the average current in one alternation, and Imax is the maximum or peak current. Do not confuse the above definition of an average value with that of the average value of a complete cycle. Because the voltage is positive during one alternation and negative during the other alternation, the average value of the voltage values occurring during the complete cycle is zero. The average value is the value that usually determines the voltage or current indicated on a test meter. There are some meters that will read the Root Mean Square RMS value, these are called "True RMS meters".

Six of the most important characteristics of a sine wave: The PEAK TO PEAK value. The AMPLITUDE. The PEAK value. The PERIODIC TIME The AVERAGE value. The RMS value.

The PEAK TO PEAK value is the vertical distance between the top and bottom of the wave. It will be measured in volts on a voltage waveform, and may be labelled V_PP or V_PK−PK. In a current waveform it would be labelled I_PP or I_PK−PK as I (not C) is used to represent current.

The AMPLITUDE of a sine wave is the maximum vertical distance reached, in either direction from the centre line of the wave. As a sine wave is symmetrical about its centre line, the amplitude of the wave is half the peak to peak value, as shown in Fig above.

The PEAK value of the wave is the highest value the wave reaches above a reference value. The reference value normally used is zero. In a voltage waveform the peak value may be labelled V_PK or V_MAX (I_PK or I_MAX in a current waveform).

(If the sine wave being measured is symmetrical either side of zero volts (or zero amperes), meaning that the dc level or dc component of the wave is zero volts, then the peak value must be the same as the amplitude, that is half of the peak to peak value.)

The PERIODIC TIME (symbol T) is the time, in seconds taken for one complete cycle of the wave. It can be used to find the FREQUENCY of the wave ƒ using the formula T =1/ƒ.

Thus if the periodic time of a wave is 20ms (or 1/50^th. of a second) then there must be 50 complete cycles of the wave in one second. A frequency of 50 Hz. Note, if the periodic time is in seconds then the frequency will be in Hz.

Form factor = (RMS value)/(Avg. value) For a sine wave Form Factor = 1.11

The RMS or ROOT MEAN SQUARED value is the value of the equivalent direct (non varying) voltage or current which would provide the same energy to a circuit as the sine wave measured. That is, if an AC sine wave has a RMS value of 240 volts, it will provide the same energy to a circuit as a DC supply of 240 volts. It can be shown that the RMS value of a sine wave is 0.707 (i.e. 1/Ö2) of the peak value.

V_RMS = V_PK x 0.707 and I_RMS = I_PK x 0.707. (Peak value of a sine wave is equal to 1.414 x the RMS value.)

 

                                                                                  

                                                              

  

Phase difference is the difference, expressed in electrical degrees or time, between two waves having the same frequency and referenced to the same point in time. (See fig. above)

(Phase in waves is the fraction of a wave cycle which has elapsed relative to an arbitrary point.)

AC Phases: Phases in AC circuits are of 3 types: Single-phase (1f), Two-phase (2f) & Three-phase (3f).

A DC circuit has two wires through which the current in the circuit flows from a source of electricity through a load and back to the source. A single-phase AC circuit also has two wires connected to the source of electricity. However, unlike the DC circuit in which the direction of the electric current does not change, the direction of the current changes many times per second in the AC circuit. The 230volt electricity supplied to our homes is single-phase AC electricity and has two wires - an "active / live" and a "neutral / earth".

Electrical phase is measured in degrees, with 360° corresponding to a complete cycle. A sinusoidal voltage is proportional to the cosine or sine of the phase.

Three-phase, abbreviated 3φ, refers to three voltages or currents that that differ by a third of a cycle, or 120 electrical degrees, from each other. They go through their maxima in a regular order, called the phase sequence.

In India, the standard supply for domestic consumption is Single-phase (1-f), 230V, 50 Hz, AC while for commercial applications the supply is Three-phase (3-f), 440V, 50 Hz, AC.

 

 

 

 

Concept of Phase

Advantages of polyphase (i.e. more than one phase)	Comparison of AC and DC
In 1-f if fault is in one line, power becomes zero which is undesirable. In 1-f motor, torque is pulsating, but in 3-f the torque is rotating and uniform A 3-f transmission requires less conductor copper or aluminium. It is easy to synchronise 3-f alternator. 3-f motors occupy less space, take less current, are light in weight and cheaper. From 3-f supply we can use 1-f, 2-f or 6-f supply.	AC	DC
	Cannot be used for electrolysis or electroplating	Only DC can be used for electrolysis or electroplating
	It cannot be used directly for battery charging	Only DC can be used for battery charging
	AC can be easily transformed to high or low voltage	DC voltage cannot be easily transformed to high or low
	Normally DC appliance will not be damaged if used on AC	Appliance marked for use on AC will be damaged if used on DC
	Inductor offers opposition to current flow	Inductor offers little opposition to current flow
	Capacitor does not prevent current flow	Capacitor prevents current flow.

Connection arrangement of three-phase system:

There are two connection arrangements of the three-phase system. 1. Star connection 2. Delta connection

     

REFRIGERATION AND AIR-CONDITIONING

Temperature / Humidity Ranges for Comfort
Conditions	Relative Humidity	Acceptable Operating Temperatures
		°C	°F
Summer light clothing	If 30%, then If 60%, then	24.5 - 28 23 - 25.5	76 - 82 74 - 78
Winter warm clothing	If 30%, then If 60%, then	20.5 - 25.5 20 - 24	69 - 78 68 - 75

Ventilation: Ventilation is the process by which 

‘Clean’ air (normally outdoor air) is intentionally provided to a space and stale air is removed. This may be accomplished by either natural or mechanical means. Ventilation is needed to provide oxygen for metabolism and to dilute metabolic pollutants (carbon dioxide and odour). It is also used to assist in maintaining good indoor air quality by diluting and removing other pollutants emitted within a space but should not be used as a substitute for proper source control of pollutants. Good ventilation is a major contributor to the health and comfort of building occupants.

Product	Recommended Relative Humidity – RH - (%)
Sugar Storage	20 - 35%
Breweries	35 - 45%
Coffee Powder	30 - 40%
Milk Powder Storage	20 - 35%
Seed Storage	35 - 45%

Air infiltration and exfiltration: In addition to intentional ventilation, air inevitably enters a building by the process of ‘air infiltration’. This is the uncontrolled flow of air into a space through adventitious or unintentional gaps and cracks

in the building envelope. The corresponding loss of air from

an enclosed space is termed ‘exfiltration’.

Air re-circulation: Air re-circulation is frequently used in commercial buildings to provide for thermal conditioning.

 Re-circulated air is usually filtered for dust removal but, since oxygen is not replenished and metabolic pollutants are not removed, re-circulation should not usually be considered as contributing towards ventilation needs.

Advantages of Air conditioning Better quality of work environment Controlled humidity Reduces corrosive atmosphere Better psychological impact Better comfort level Improves efficiency and activity Cleanliness Low noise level

Air conditioning is the removal of heat from indoor air for thermal comfort. In another sense, the term can refer to any form of cooling, heating, ventilation, or disinfection that modifies the condition of air. An air conditioner (often referred to as AC or air con.) is an appliance, system, or machine designed to stabilize the air temperature and humidity within an area (used for cooling as well as heating depending on the air properties at a given time), typically using a refrigeration cycle but sometimes using evaporation, commonly for comfort cooling in buildings and motor vehicles.

A room air conditioner most commonly fits into a window is a unitary system as opposed to a Central system, though there are models that can be installed into an exterior wall. Whether mounted in a window or wall, this type of air conditioner plugs into a standard electrical outlet and doesn't need special wiring.

 

A room air conditioner pulls hot air in from the outside and cools it with a fairly complicated process that involves a refrigerant gas, compression, heat absorption, condensation, coils and a fan that blows the cooled air into the room. It's essential to determine the size of the area you want to cool: If you buy too small a unit, it will keep running, increasing your electricity bills without making you feel much cooler. If the unit is too large for the space, it will cool but very inefficiently with humidity build-up, leaving you feeling cold and clammy.

A central air conditioner cools your entire house at once using a condenser (usually located outside) and a fan-and-coil system and ductwork that brings the cooled air to each room and returns the air for cooling again. It usually works in tandem with a forced-air furnace and its related ducting; for lack of that type of furnace, the cooling coils and fan will be in the attic, with ductwork coming from it to deliver the cooled air.

Dry Bulb Temperature	It is the temperature recorded by a thermometer which is not affected by moisture.
Dew Point Temperature	It is the temperature of air at which water vapour in air starts condensing.
Specific Humidity or Humidity Ratio	It is the mass in kg. of water vapour contained in the air-water mixture per kg. of dry air. It is the ratio of mass of water vapour to the mass of dry air in a certain volume of mixture.
Wet Bulb Temperature	The bulb is covered with muslin wick wetted with water is moved past unsaturated air at velocity of 300 m/min. The temperature reading obtained is wet bulb temperature.
Actual Humidity	Actual quantity of water in a given amount of air.
Load on air-conditioner	Amount of heat that must be removed from air of a given space.

Refrigeration may be defined as lowering the temperature of an enclosed space by removing heat from that space and transferring it elsewhere.A device that performs this function may also be called a heat pump. This is the removal of heat from a body to make it colder than its surroundings.

Laws of refrigeration: (i) Fluids absorb heat while changing from liquid to a vapour state and vice-versa (called evaporation and condensation respectively). (ii) The temperature at which the change of state occurs is constant if pressure remains constant.

Unit of Refrigeration: This is generally given in tons of refrigeration (TR). One ton of refrigeration means one ton of water at 0^oC converted to one ton of ice at 0^oC. (1 TR = 3024 kcal/hr= 50.4 kcal/min = 12600kj/hr= 3.517kW.)

(1cal = 4.1868 J). A ton of refrigeration is approximately equal to the cooling power of one short ton (2000 pounds or 907 kilograms) of ice melting in a 24-hour period. The value is defined as 12,000 BTU per hour, or 3517 watts. Residential central air systems are usually from 1 to 5 tons (3 to 20 kilowatts (kW)) in capacity.

Coefficient of Performance: Cop= (Heat removed in kcal per unit time) / (Work supplied in kcal per unit time)

Refrigeration in catering Preservation of food/ice-cream, Cooling of food to a temperature suitable for serving, Cooling of drink, Ice-water, Cooling of food and drink for sale, Ice-making, Bakery, Fish Storage, Vegetables cold storage.

Methods of refrigeration: (a) Ice Refrigeration: Ice is put around the object which is to be cooled. In this the heat is taken from the object by the ice and it gets converted to water.

(b) Evaporative System: Volatile liquids absorb its latent heat of vaporization from the object that is to be cooled and gives this heat to the coolant in the condenser and again becomes liquid.

(c) Gas / Air expansion system: First, compress a gas adiabatically (i.e. a process in which no heat is transferred from the system) and then cool this high pressure gas keeping pressure constant. Then cool this high pressure low initial temperature gas to atmospheric pressure. It is found that the temperature of the gas is less than 0^oC.

 

Vapour-compression refrigeration system

Components of Vapour Compression System Compressor: Rotary, Centrifugal or Condenser: Shell or Tube type Air Cooler: Natural, Forced or Water Spray Type Expansion Valve: Automatic, Thermostatic Evaporator: Shell and Tube, Double pipe type

The vapour-compression uses a circulating liquid refrigerant as the medium which absorbs and removes heat from the space to be cooled and subsequently rejects that heat elsewhere. All such systems have four components: a compressor, a condenser, a Thermal expansion valve (also called a throttle valve), and an evaporator. Circulating refrigerant enters the compressor in the thermodynamic state known as a saturated vapor and is compressed to a higher pressure, resulting in a higher temperature as well. The hot, compressed vapor is then in the thermodynamic state known as a superheated vapor and it is at a temperature and pressure at which it can be condensed with typically available cooling water or cooling air. That hot vapor is routed through a condenser where it is cooled and condensed into a liquid by flowing through a coil or tubes with cool water or cool air flowing across the coil or tubes. This is where the circulating refrigerant rejects heat from the system and the rejected heat is carried away by either the water or the air (whichever may be the case).

The condensed liquid refrigerant, in the thermodynamic state known as a saturated liquid, is next routed through an expansion valve where it undergoes an abrupt reduction in pressure. That pressure reduction results in the adiabatic flash evaporation of a part of the liquid refrigerant. The auto-refrigeration effect of the adiabatic flash evaporation lowers the temperature of the liquid and vapor refrigerant mixture to where it is colder than the

temperature of the enclosed space to be refrigerated. The cold

mixture is then routed through the coil or tubes in the evaporator. A fan circulates the warm air in the enclosed space across the coil or tubes carrying the cold refrigerant liquid and vapor mixture. That warm air evaporates the liquid part of the cold refrigerant mixture. At the same time, the circulating air is cooled and thus lowers the temperature of the enclosed space to the desired temperature. The evaporator is where the circulating refrigerant absorbs and removes heat which is subsequently rejected in the condenser and transferred elsewhere by the water or air used in the condenser.

To complete the refrigeration cycle, the refrigerant vapour from the evaporator is again a saturated vapor and is routed back into the compressor.

Vapour Absorption Refrigeration Systems: (VARS) belong to the class of vapour cycles similar to vapour compression refrigeration systems. However, unlike vapour compression refrigeration systems, the required input to absorption systems is in the form of heat. Hence these systems are also called heat operated or thermal energy driven systems. Since conventional absorption systems use liquids for absorption of refrigerant, these are also called as wet absorption systems. Since these systems run on low-grade thermal energy, they are preferred when low-grade energy such as waste heat or solar energy is available. As absorption systems use natural refrigerants such as water or ammonia they are environment friendly. In the absorption refrigeration system, refrigeration effect is produced mainly by the use of energy as heat. In such a

 system, the refrigerant is usually dissolved in a liquid. A concentrated solution of ammonia is boiled in a vapour generator producing ammonia vapour at high pressure. The high pressure ammonia vapour is fed to a condenser where it is condensed to liquid ammonia by rejecting energy as heat to the surroundings. Then, the liquid ammonia is throttled through a valve to a low pressure. During throttling, ammonia is partially vaporized and its temperature decreases.

This low temperature ammonia is fed to an evaporator where it is vaporized removing energy from the evaporator. Then this low-pressure ammonia vapour is absorbed in the weak solution of ammonia. The resulting strong ammonia solution is pumped back to the vapour generator and the cycle is completed. The COP of the absorption system can be evaluated by considering it as a combination of a heat pump and a heat engine

Comparison between Vapor Compression and Absorption system:

Absorption system	Compression System
Uses low grade energy like heat. Therefore, may be worked on exhaust systems from I.C engines,etc.	Using high-grade energy like mechanical work.
Moving parts are only in the pump, which is a small element of the system. Hence operation is smooth.	Moving parts are in the compressor. Therefore, more wear, tear and noise.
The system can work on lower evaporator pressures also without affecting the COP.	The COP decreases considerably with decrease in evaporator pressure.
No effect of reducing the load on performance.	Performance is adversely affected at partial loads.
Liquid traces of refrigerant present in piping at the exit of evaporator constitute no danger.	Liquid traces in suction line may damage the compressor.
Automatic operation for controlling the capacity is easy.	It is difficult.

Properties of Refrigerants: The refrigerants should be,

Non-poisonous, Non-toxic, Non-corrosive, Non-explosive, Non-inflammable, Low boiling point, Condensing pressure low, High latent heat of vaporization, Low specific heat, Inert to oil, Easy availability.

Temperatures recommended for storage of perishables

Type of Food	Optimum Temperature
Fruits and vegetables (except bananas)	1.1oC to 7.2oC
Dairy products	3.3 oC to 7.8 oC
Meat and poultry	0.6 oC to 3.3 oC
Fish and shell fish	5.0 oC to 1.1 oC
Frozen foods	1.8 oC to 6.7 oC

Precautions in refrigeration systems: Keep the refrigerator well away from boilers and cooking appliances. b) Keep the air condenser cooled by keeping the system away from walls for better circulation of air. c) The goods while keeping inside the refrigerator should not be hot, they should be at room temperature (i.e. about 17 ^oC to 23 ^oC) c) Keep the fins of the condenser clean and free of lint  & dust accumulation d) Keep the door gaskets clean and dent free.

Air Conditioning: Air-conditioning is achieved by a cycle of expansion and compression of a refrigerant, where the compression converts cold gas to high pressure hot gas and the expansion converts liquid refrigerant to cold gas which in turn cools the desired area. This cycle continues until your thermostat reaches the desired temperature. An air conditioner is basically a refrigerator without the insulated box. It uses the evaporation of a refrigerant, like Freon, to provide cooling. The mechanics of the Freon evaporation cycle are the same in a refrigerator as in an air conditioner. The term Freon is generically "used for any of various nonflammable fluorocarbons used as refrigerants and as propellants for aerosols."

This is how the evaporation cycle in an air conditioner works:

The compressor compresses cool Freon gas, causing it to become hot, high-pressure Freon gas (shown in the diagram).

This hot gas runs through a set of coils so it can dissipate its heat, and it condenses into a liquid.

The Freon liquid runs through an expansion valve, and in the process it evaporates to become cold, low-pressure Freon gas (shown in the diagram).

This cold gas runs through a set of coils that allow the gas to absorb heat and cool down the air inside the building.

Mixed in with the Freon is a small amount of lightweight oil. This oil lubricates the compressor.

Air conditioners help clean your home's air as well. Most indoor units have filters that catch dust, pollen, mold spores and other allergens as well as smoke and everyday dirt found in the air. Most air conditioners also function as dehumidifiers. They take excess water from the air and use it to help cool the unit before getting rid of the water through a hose to the outside.

 

Central chilled water air conditioning systems - All Air Systems

 An all-air system provides complete sensible and latent cooling capacity in the cold air supplied by the system.  Heating can be accomplished by the same air stream, either in the central system or at a particular zone.  All-air systems can be classified into 2 categories:-

-Single duct systems

-Dual duct systems

 System Advantages

 1. The central plant is located in unoccupied areas, hence facilitating operating and maintenance, noise control and choice of suitable equipment.

 2. No piping, electrical wiring and filters are located inside the conditioned space.

 3. Allows the use of the greatest numbers of potential cooling seasons house with outside air in place of mechanical refrigeration.

 4. Seasonal changeover is simple and readily adaptable to climatic control.

 5. Gives a wide choice of zonability, flexibility, and humidity control under all operating conditions.

 6. Heat recovery system may be readily incorporated.

 7. Allows good design flexibility for optimum air distribution, draft control, and local requirements.

 8. Well suited to applications requiring unusual exhaust makeup.

 9. Infringes least on perimeter floor space.

 10. Adapts to winter humidification.

 System Disadvantages

 1. Requires additional duct clearance which can reduce the usable floor space.

 2. Air-balancing is difficult and requires great care.

 3. Accessibility to terminals demands close cooperation between architectural, mechanical and structural engineers.

Central chilled water air conditioning systems - All-water Systems

 All-water systems are those with fan-coil, unit ventilator, or valance type room terminals with unconditioned ventilation air supplied by an opening through the wall or by infiltration.  Cooling and dehumidification is provided by circulating chilled water through a finned coil in the unit.  Heating is provided by supplying hot water through the same or a separate coil.

 System Advantages:

 1. Flexible and readily adaptable to many building module requirements.

 2. Provides individual room control.

 System Disadvantages

 1. No positive ventilation is provided unless wall openings are used.

 2. No humidification is provided.

 3. Seasonal change over is required.

 4. Maintenance and service work has to be done in the occupied areas.

In air conditioning systems, chilled water is typically distributed to heat exchangers, or coils, in air handling units, or other type of terminal devices which cool the air in its respective space(s), and then the chilled water is re-circulated back to the chiller to be cooled again. These cooling coils transfer sensible heat and latent heat from the air to the chilled water, thus cooling and usually dehumidifying the air stream. A typical chiller for air conditioning applications is rated between 15 to 1500 tons (180,000 to 18,000,000 BTU/h or 53 to 5,300 kW) in cooling capacity, and at least one company has a 2,700 ton chiller for special uses. Chilled water temperatures can range from 35 to 45 degrees Fahrenheit (1.5 to 7 degrees Celsius), depending upon application requirements.

The Potential for Raising Chilled Water Temperature: Chilled water systems are commonly designed to provide full cooling load with a chilled water temperature of about 42°F (i.e. 5.5°C). Plant operators typically leave the chilled water temperature fixed at this value or some other. This is inefficient for most applications, such as air conditioning, where the load is well below its maximum most of the time. Typically, you can raise the chilled water temperature by 5°F to 10°F for much of the time. Even at full load, the typical oversizing of airside components (air handling units, fan-coil units, etc.) usually allows some increase in chilled water temperature.