IHM Notes Site
- Dec 25, 2022
- 18 min read

Hotel Engineering | Solved Paper | 2016-17 | 1st Sem B.Sc HHA

Please note: The answers provided below, are just for reference. Always consult your college professor if you have any queries.

Q.1. (a) Draw an organisation chart of maintenance department of a 200 room hotel.

(b) Discuss in brief duties and responsibilities of maintenance department.

Duties or Functions of Maintenance Department:(A) Inspection:

(1) Inspection is concerned with the routine schedule checks of the plant facilities to examine their condition and to check for needed repairs.

(2) Inspections ensure the safe and efficient operation of equipment and machinery.

(3) Frequency of inspections depends upon the intensity of the use of the equipment. For example, belts in a machine may be checked every week; furnace equipment every month; an over-head bridge crane every four months and so on.

(4) Inspection section makes certain that every working equipment receives proper attention.

(5) Items removed during maintenance and overhaul operations are inspected to determine the feasibility of repairs.

(6) Maintenance items received from vendors are inspected for their fitness.

(B) Engineering:

(1) Engineering involves alterations and improvements in existing equipment and building to minimize breakdowns.

(2) Maintenance department also undertakes engineering and supervision of constructional projects that will eventually become part of the plant.

(3) Engineering and consulting services to production supervision are also the responsibilities of maintenance department.

(1) Maintenance of existing plant equipment.

(2) Maintenance of existing plant buildings, and other service facilities such as yards, central stores, roadways, sewers, etc.

(3) Engineering and execution of planned maintenance, minor installations of equipment, building and replacements.

(4) Preventive maintenance, i.e., preventing breakdown (before it occurs) by well-conceived plans of inspection, lubrication, adjustments, repair and overhaul.

(D) Repair:

(1) Maintenance department carries out corrective repairs to alleviate unsatisfactory conditions found during preventive maintenance inspection.

(2) Such a repair is an unscheduled work often of an emergency nature, and is necessary to correct breakdowns and it includes trouble calls.

(E) Overhaul:

(1) Overhaul is a planned, scheduled reconditioning of plant facilities such as machinery, etc.

(2) Overhaul involves replacement, reconditioning, reassembly, etc.

(F) Construction:

(1) In some organizations, maintenance department is provided with equipment and personnel and it takes up construction jobs also.

(2) Maintenance department handles construction of wood, brick and steel structures, cement and asphalt paving, electrical installations, etc.

(G) Salvage:

Maintenance department may also handle disposition of scrap or surplus materials.

This function involves:

i. Segregation, reclamation and disposition of production scrap, and

ii. The collection and disposition of surplus equipment, materials and supplies.

(H) Clerical Jobs:

Maintenance department keeps records:

i. Of costs,

ii. Of time progress on jobs,

iii. Pertaining to important features of buildings and production equipment; electrical installations; water, steam, air and oil lines ; transportation facilities (such as elevators, conveyors, powered trucks, cranes, etc.), etc.

(I) Generation and distribution of power and other utilities.

(J) Administration and supervision of labour force (of maintenance department).

(K) Providing plant protection, including fire protection.

(L) Insurance administration.

(M) Establishing and maintaining a suitable store of maintenance materials.

(N) Janitorial service.

(O) Housekeeping.

Good housekeeping involves upkeep and cleaning of equipment, building, toilets, wash-rooms, etc.

(P) Pollution and noise abatement.

Q.2. Define the term air-conditioning. State two scientific principles used in refrigeration. State the difference between refrigeration and air-conditioning.

Air conditioning is the process of creating and distributing air to control temperature, humidity, and air quality in selected areas. For temperature and humidity control, air is moved over chilled or heated coils and/or a spray of water at a controlled temperature. Direct water sprays also remove dust and odors. Other air cleaning systems may include mechanical separation, adhesion, screening, filtration, or static attraction, depending on the type of air contaminants encountered and the required air quality.

Refrigeration is the process of lowering the temperature of a substance below that of its surroundings and includes the production of chilled water for air conditioning or process applications. Chilled water for use in processes such as injection molding may be in the same temperature range as chilled water used for air conditioning. Refrigeration systems are also used to provide chilled antifreeze solutions (brines) at temperatures below the freezing point of water. Brines are used in icemaking and cold storage, in addition to a variety of chemical process applications.

Air Conditioning	Refrigeration
Thermal energy is taken away from the place to keep the air cooler	Thermal energy is transferred from one place to a place of higher temperature
It is a type of refrigeration used to cool a large area	Helps to flow thermal energy against the natural flow of heat
It deals with maintaining the temperature of a certain volume of air and also maintaining the purity and humidity	It deals only with regulating the temperature of air such as cooling and freezing of products
The compressor and condenser are a separate unit from the evaporator	The appliance has a condenser, compressor, and evaporator in one unit
The mechanism is supplied with gas from the tubes	Internal chemicals and even air is supplied from the environment
Cold air is pushed away from the unit	Cold air is kept inside the unit

OR Explain different types of fuses used in electrical circuit. Describe briefly safety precautions to be observed while working on electrical appliances.

The main category of Fuses are based on the type of circuit they are used in i.e. AC Fuses and DC Fuses. Again, AC Fuses are divided in to High Voltage (HV) Fuses and Low Voltage (LV) Fuses.

High Voltage (HV) AC Fuses are used for voltages above 1000V and Low Voltage (LV) AC Fuses are used for voltages less than 1000V. Low Voltage (LV) Fuses are again classified in to Cartridge Fuses (Totally Enclosed Type), Rewirable Fuses (Semi – Enclosed Type), Switch Fuses, Drop out Fuses and Striker Fuses.

High Voltage (HV) Fuses are further divided in to Cartridge Type HRC (High Rupturing Capacity) Fuses, Liquid Type HRC Fuses and Expulsion type Fuses.

Avoid water at all times when working with electricity. Never touch or try repairing any electrical equipment or circuits with wet hands. It increases the conductivity of the electric current.

2. Never use equipment with frayed cords, damaged insulation or broken plugs.

3. If you are working on any receptacle at your home then always turn off the mains. It is also a good idea to put up a sign on the service panel so that nobody turns the main switch ON by accident.

4. Always use insulated tools while working.

5. Electrical hazards include exposed energized parts and unguarded electrical equipment which may become energized unexpectedly. Such equipment always carries warning signs like “Shock Risk”. Always be observant of such signs and follow the safety rules established by the electrical code followed by the country you’re in.

6. Always use appropriate insulated rubber gloves and goggles while working on any branch circuit or any other electrical circuit.

7. Never try repairing energized equipment. Always check that it is de-energized first by using a tester. When an electric tester touches a live or hot wire, the bulb inside the tester lights up showing that an electrical current is flowing through the respective wire. Check all the wires, the outer metallic covering of the service panel and any other hanging wires with an electrical tester before proceeding with your work.

8. Never use an aluminum or steel ladder if you are working on any receptacle at height in your home. An electrical surge will ground you and the whole electric current will pass through your body. Use a bamboo, wooden or a fiberglass ladder instead.

9. Know the wire code of your country.

10. Always check all your GFCI’s once a month. A GFCI (Ground Fault Circuit Interrupter) is a RCD (Residual Current Device). They have become very common in modern homes, especially damp areas like the bathroom and kitchen, as they help avoid electrical shock hazards. It is designed to disconnect quickly enough to avoid any injury caused by over current or short circuit faults.

Q.3. Write short notes on any two of the following: (a) Methods of heat transfer

Convection: The process in which heat is transmitted from a hotter part of a body to a colder part by the actual movement of the material of the body is called convection.

Convection heat transfer occurs faster than conduction. Convection occurs by the movement of air, liquid, or steam around the food. Example: A convection oven can reduce the cooking time by 25 percent over standard ovens. It also increases browning of the food because of the concentrated heat on the surface of the food.

Conduction: The process in which heat is transmitted from a hotter part of a body to a colder part without any visible movement of the material of the body is called conduction.

Conduction transfers the heat using direct contact; food is heated directly in a metal pan, in a liquid, or surrounded by air. Example: Dropping an egg into a pan of boiling water , where the outside body of egg heats first , the heat then moves inward continuing to heat the egg to the desired temperature.

Radiation: the process by which heat is transmitted from one place to another without the help of any material medium or without heating the intervening medium is called radiation.

Radiation heat transfer occurs when microwave (light waves) or infrared energy (heat waves) are spread into the food. As the microwaves penetrate the food, they bump into molecules of water and fat, causing them to vibrate rapidly. This vibration creates friction, which creates heat that cooks the food.

(b) Types of wiring

Wiring is the process of laying the wires from the source of supply to the load points. Following are the different ways of wiring;

On the surface through cable trays.
Concealed through the walls inside metal pipes or PVC pipes
Underground cables or PVC pipes and cable trenches.

(c) Audio-visual equipment used in the hotel

Although hotels widely differ in the types and number of AV equipments, the following are mostly included in standard hotels.

Video Players and Recorders Follow Spot Lights Karaoke System Loudspeaker Microphone Overhead Projectors Portable Screens Fixed Projector Screens LCD/LED CCTV Desktop/Laptop Computers Wireless Keyboards

(d) Maintenance of swimming pool

To keep the pool water transparent, sparkling and free from dirt, filtered water must be used.
After a specified period of time, usually as recommended by a local public health authority, entire water content should be cycled through the filter.
To ensure proper functioning, the filtration equipment must be cleaned periodically according to o a maintenance schedule.
The process of cleaning the filters is known as backwashing.
Different types of nets are used to remove floating objects and also large objects that are settled at the bottom of the pool.
In some pools, the pool water is continuously kept in motion where it passes through the filter and all unwanted floating objects are trapped in the filter.
The swimming pool has an opening at the water surface level, leading to the drain at the outside. This opening is called WEIR and a strainer is placed at this opening which arrests the objects floating in the water, which is subsequently removed.
Chemicals are added to the pool water to maintain the proper hygienic conditions.
Disinfectants are added to make the water bacteria-free.
The dosing can be done manually or may be automated.
To maintain the correct pH level appropriate chemicals are added.
The pH is normally maintained between 7.2 to 7.6.
Algae which are water plants that grow in water, are also very difficult to eliminate. If their growth is not hampered by disinfectants, they are to be manually removed.
The initial, as well as the, make up water is supplied to the pool by the water treatment plant in the hotel.

Q.4. With a neat sketch, explain the functioning of a gas burner.

OR Write short notes on; (a) Contract maintenance

Contract Maintenance is defined as the contract between 2 parties which creates the agreement that one party will maintain an asset owned by another party, which is common across many industries.
Maintenance contracts can exist for equipment, a building, landscape, computers and other information technologies, and more.
The decision to perform a particular maintenance activity in – house or through contract is usually decided by the head of the Maintenance Department.

(b) Care and maintenance of Audio-Visual equipment used in a conference room

LCD/ VIDEO PROJECTORS – Care and Maintenance

Projector lens should be cleaned with isopropyl alcohol or a photographic lens cleaning solution. Apply the cleaning solution to cloth and wipe the lens. Never apply the cleaning solution to the lens directly. LCD projectors must be used at temperatures between 5 and 35 degrees Celsius. Dust should be regularly blown off from the lens by means of a blower but from a safe distance.

Care and Maintenance of Computers and its peripherals

Computers and their peripherals are quite robust and reliable. However, casual use of different components, may lead to serious problems ranging from faulty and unreliable operations to complete stoppage of operation. A few routine care and maintenance schedule can ensure trouble free operation for a reasonable period of time. But in case of serious problems, professional help should also be taken.

Care and Cleaning of LCD screens

Utmost care must be taken while dealing with LCD screens. THE DO’S

To remove stains on the screen, properly clean the display surface by gently wiping it with a lint free cloth and glass cleaning agent.
Avoid strong shocks and vibrations.
Be sure to use and store LCD monitors within the specified temperature and humidity range.
The screen should be turned off or brightness should be reduced to prevent ‘burn-in’, which is a permanent damage to certain pixels in the LCD due to overheating.

THE DONT’S

Do not place any heavy object on the laptop.
Do not scratch, twist or hit the surface of the LCD screen.
Do not spray cleaning liquid directly on to the screen.
Do not let moisture accumulate .
Never disassemble the LCD monitor, as the internal backlight assembly can retain a charge of 1000 V and may prove fatal.
LCD screens should not be subjected to sudden temperature change.

Care and Maintenance of Printers

The most common problems faced while using a printer are: poor print quality, streaking print, white lines through prints, no print etc. Most of these problems originate from ink drying up at the print head or nozzle and clogging them during printing operation.

Running the printer at least once a week helps avoid these problem.
Use the printer at least on a weekly basis with both black and white and colour text printing.
Always use printer switch rather than the UPS or Power switch to shut down the unit.
Refilling for colour cartridge must be done with proper ink in the proper chamber.
It is always better to refill an inkjet cartridge before it is empty as the ink of dried up cartridges, if left for too long will clog the print head.
Laser printers should be kept in a dust free area.

UPS – Maintenance and Care

A UPS (Uninterruptible Power Supply) provides instant emergency power to connected equipments by supplying power from a separate source (battery) in case of a failure of the main power supply. The battery is the most important part of the UPS. A periodic maintenance program extends the life of the battery. The following steps can help establish a good maintenance program for he UPS battery. UPS – Maintenance and Care (contd..) Inspection: Periodic inspection should be carried out . Periodic measurements: of the voltage, temperature, resistance etc. should be measured to ensure that the battery is operating to its optimum. Load testing: When the battery can no longer supply 80 % of its rated current, the aging process begins and the battery is considered for replacement. Individual cells of the battery should be monitored, so that only the weak or bad cells can be identified and scheduled for replacement. Record Keeping: All data collected through the above maintenance program should be documented to track the performance of the battery over time.

A Few Good Maintenance Practices for Reliable Operation of Computer Systems

Computer systems are now a part and parcel of modern organizations. Smooth and efficient functioning of the organization nowadays depend a lot on continuous and reliable functioning of the systems.

Switch off computers only after the operating system has properly shut down the computer.
Always use a UPS.
Keep the operating system software and other important utility software in a secured place.
Run scandisk and defragment the file system once a month.
Take regular data backup.
Keep at least 250 MB of C: drive free.
Do not let many programs load up in the computer memory or RAM when the computer starts.
Avoid storing files on the desktop.
Run system file checker twice a month.
Remove all unnecessary files and folders from ‘My Documents’ directory and empty ‘Recycle Bin’ once a month.
Get all critical windows update.
Scan the computer with antivirus at least once a week.
Install firewall protection for Internet access
Clean computer and its accessories on regular basis.

Q.5. Enumerate the differences and similarities between window and central airconditioning. Describe care and maintenance of deep freezer.

Window air conditioners are very different than central air conditioner. A central air conditioner involves many more parts. Typically, there is a condenser unit that sits outside of the building, whether it’s in the yard or up on a roof. The condenser uses a set of pipes to run coolant into the air handler. Central air conditioners also make use of the duct system within the building in order to distribute cool air throughout individual rooms.

A window air conditioner is a single unit that contains no other parts. The unit has a condenser, evaporator, thermostat and fan already built in. The unit is designed to be wedged into a window frame and is most effectively used to cool single rooms.

In Window A/C, all components are in one box, condensing unit in outer side interacting with outside air and evaporator in inside part interacting with room air.

Characteristics: Excessive sound, very economical, necessity of exposed wall for the room, limited capacity

In Central system, a common unit is producing cooling for many rooms or apartments. The central unit may be a package unit( which send cold air to different rooms), VRF unit (which send refrigerant liquid to the evaporator units in rooms) or a Water chiller which send chilled water to fan coil units( which is transferring cooling from water to room air) in each room.

Characteristics: No size or distance limitation, costly, expandable, no sound issues.

Care & Maintenance

Check the seal occasionally to ensure proper sealing. If the seal is not adequate, the door may require an adjustment or the seal may need to be replaced.
Defrost and clean the freezer regularly. Ice build-up will lower it’s efficiency.
Safeguard your small children by keeping freezers locked.
Vacuum any exposed condensor coils regularly to ensure proper air circulation.
Keep temperature constant to keep food from spoiling.
These tips are general in nature; consult your owner’s manual for specific care guidelines.

OR Write short notes on; (a) Preventive measures for slips and falls

cleaning all spills immediately
marking spills and wet areas
mopping or sweeping debris from floors
removing obstacles from walkways and always keeping walkways free of clutter
securing (tacking, taping, etc.) mats, rugs and carpets that do not lay flat
always closing file cabinet or storage drawers
covering cables that cross walkways
keeping working areas and walkways well lit
replacing used light bulbs and faulty switches

(b) Security equipment in hotels

1. Smoke Detectors:

Smoke or heat detection units are required by an increasing number of local jurisdictions. Regulations vary from those only requiring smoke and/or heat detectors in corridors, storerooms, and under stairways to those requiring full systems that provide protection in every guest room, guest bathroom, public area, and back-of-the-house location.

Smoke and heat detection units also vary in their characteristics; some have the ability to report a heat buildup prior to evidence of smoke or flame, while others respond only to smoke and other products of combustion.

Automated systems, which integrate all smoke detectors in each location with a master panel, permit staff to immediately determine where a smoke detector has activated and to respond accordingly.

Many local jurisdictions enacted regulations requiring fully automated smoke detector systems in all new construction and the retrofitting of smoke detectors for all lodging establishments.

2. Fire Extinguishers:

There are four classes of fires that a lodging property should be prepared for

1) Class A fires involve ordinary combustibles,

2) Class B fires involve flammable liquids,

3) Class C fires involve electrical equipment, and

4) Class K fires involve cooking oils and fats.

Tips: Although some jurisdictions will permit the elimination of fire extinguishers in a facility with a full sprinkler system, consideration should still be given to the use of extinguishers as they would permit the fighting of incipient fires rather than waiting for a fire to generate enough heat to activate an automatic sprinkler system.

3. Carbon Monoxide Detectors:

Carbon monoxide is a dangerous by-product of a malfunctioning water heater, kerosene heater, coal boiler, or any other wood, coal, or petroleum product unit. (It is also the most critical toxic gas generated in any structural fire).

There have been tragic incidents in which carbon monoxide from such units has resulted in the death of a guest or staff. Since carbon monoxide is invisible and has no smell, it cannot be detected by natural means.

4. Sprinkler Systems:

Sprinkler systems are now mandated in an establishment four stories or higher, adhering to the Hotel and Fire Safety laws on each country. This requires a system covering back-of-the-house, public, and all guestroom locations.

Most jurisdictions now require full sprinkler systems in the new construction of any commercial occupancy regardless of the height of the structure.

5. Accident Prevention Signs:

OSHA classifies accident prevention signs into three categories:

1) Danger signs.

2) Caution signs and,

3) Safety instruction signs.

Danger signs: which indicate immediate danger, should be posted to warn of specific dangers and to warn that special precautions may be necessary. Red should be the basic colour for identification of all danger signs, which include restricted area, in case of fire, do not enter, and emergency exit signs.

Caution signs: should only be used to warn against potential hazards or to caution against unsafe practices. The colour yellow has been used to advantage for marking physical hazards on stairs in both back-of-the-house stairways and fire stairwells. Areas of construction or remodelling should have caution signs. Floor stand signs could warn guests of wet floors and to watch their step.

Safety instruction signs: should be used only where there is a need for general instructions relative to safety measures. These signs are typically green with white lettering. Signs with green arrows, for example, could be used to note the path to follow between buildings or on trails.

Q.6. Describe in detail all the different types of fire extinguishers and their uses.

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.

Q.7. Describe briefly various types of pollution caused by the hospitality industry

Hotels and Water Pollution

Rampant discharge of wastewater and effluents into water bodies has played havoc with hygiene and ecology.
Wastewater disposal without proper treatment has severely affected marine life and living of downstream people using the water bodies for economic as well as day to day use of water.
Discharge of hot water also produces pollution in changing the aquatic environment of water bodies.
Hotels produce a lot of wastewater and many of them have now installed their own STP, which contributes greatly to reducing pollution as well as gaining economy by way of reuse of clear water.
This pollution can be minimized at the source by restricting chemicals that mix with water.

Hotels and Air Pollution

Hotels liberate gases and contaminated air from various utilities, such as kitchen gas and firewood ovens, fume from materials being cooked, boiler and diesel generating set exhausts, and release of refrigerant CFC, if there is any leakage.
If the boiler is fired with pulverized (powdered) coal, the exhaust gas will have a lot of dust particles leading to air pollution.
Diesel engines also produce pollutants such as carbon dioxide, carbon mono oxide and oxides of nitrogen.

Hotels and Soil Pollution

Hotels contribute to soil pollution by dumping their solid waste and sludge into the soil.
Excessive dumping of untreated or semi treated sewage and sludge may lead to contamination of soil and also produce a foul odor.

Hotels and Noise Pollution

Hotels have quite a few noises generating sources such as engines, pumps, motors, etc. And sound produced in banquet halls.

Liquid Waste (Sewage) its treatment and disposal

Hotels produce a lot of wastewater and usually, the wastewater is disposed of in water bodies such as river, sea, lake or as landfill.
But acc. to the norms of the PCB (Pollution Control Board), sewage needs to be properly treated before it is disposed of.

Q.8. Explain how hot water is supplied throughout a hotel using central indirect system.

Indirect Water Heating

In this system the water cylinder is replaced by a direct heat exchanger called the calorifier where hot water or steam from the boiler enters the calorifier through a coil of tubes and heats the cold water passing through the calorifier.
Two circulations are followed.
Primary Circulation – takes place between the boiler and the calorifier
Secondary Circulation – takes place between the calorifier and service taps.

Q.9. Define the following (any ten):

(a) Preventive maintenance :

Any activity which is carried out on the machinery or the equipment when any default is noticed and it seems that because of that fault the machine is not functioning well and may go out of order in the future is termed as a preventive maintenance.

(b) Class C fire :

Class C. Class C fires are fires involving energized electical equipment such as computers, servers, motors, transformers, and appliances.

A kilowatt hour (kWh) is a measure of energy. So a 1,000 watt drill needs 1,000 watts (1 kW) of power to make it work, and uses 1 kWh of energy in an hour.

(d) Open circuit :

an electrical circuit that is not complete.

(e) MCB :

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current from an overload or short circuit. Its basic function is to interrupt current flow after a fault is detected.

(f) Earthing :

The process of transferring the immediate discharge of the electrical energy directly to the earth by the help of the low resistance wire is known as the electrical earthing. … Mostly, the galvanised iron is used for the earthing.

(g) Energy Audit :

An energy audit is an inspection survey and an analysis of energy flows for energy conservation in a building. It may include a process or system to reduce the amount of energy input into the system without negatively affecting the output.

(h) Group replacement :

There are certain categories of equipment that normally do not require maintenance activities while in service.
During their lifetime, they operate and give service more or less to the design level and then fail suddenly.
Eg: Electric lamps, MCB’s, sensors, detectors, washers, valves, etc.

(i) Scale formation :

Boiler scale is caused by impurities being precipitated out of the water directly on heat transfer surfaces or by suspended matter in water settling out on the metal and becoming hard and adherent.

(j) BTU :

The British thermal unit is a unit of heat; it is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. It is also part of the United States customary units.

(k) Humidification :

The process of increasing the water vapour content of a gas.

(l) One of refrigeration :

Vapour compression refrigeration system

Q.10. A Fill in the blanks:

(i) Air is lighter than liquefied petroleum gas. (ii) Calorific value of LPG is higher than calorific value of coal. (iii) One calorie is equal to 3.96567 British Thermal Units. (iv) One ton of refrigeration means cooling by extracting heat at the rate of 3024 kilo calories per hour. (v) Lignite is an example of solid fuel.

B State True or False:

(i) Temporary hardness of water can be removed by boiling the water. True (ii) LPG consists of butane and hexane. False (iii) Lighting fan sub-circuits are meant to carry electric current not exceeding 6 amperes. False (iv) Soda acid fire extinguishers are used to extinguish oil fires. False (v) Refrigerators working on vapour absorption cycle require less maintenance. False

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