civil engineering services

A monograph on basic engineering services for buildings.

.

Olayinka OkeolaDepartment of Civil Engineering

Faculty of Engineering & TechnologyUniversity of Ilorin

Ilorin. Nigeria

2 Olayinka Okeola Civil Engineering Services (CVE 582)

Course: CVE 582 –Civil Engineering Services

(2 Credit/Compulsory)

Lecturer: Olayinka Okeola

Ph.D. (Ilorin), MNSE, MASCE, MIWA, MAISC, R. Eng.

Email: [email protected], [email protected]

Office Location: Block 8, G28, University of Ilorin. Ilorin

Consultation Hours: 9am – 10 am. (Wednesdays)

1pm – 4pm (Thursdays)

Department of Civil EngineeringFaculty of Engineering & Technology

University of IlorinIlorin. Nigeria

www.unilorin.edu.ng

mailto:[email protected]

mailto:[email protected]


Table of Contents

Chapter Title Page

1 Water Supply and Installation 3

2 Solid Waste Management 15

3 Electrical Supply 18

4 Emergency and Standby Power Systems 25

5 Ventilation, Refrigeration and Air-Conditioning 30

6 Fire Services 43

7 Lift, Escalators, Stairs and Vacuum Cleaners 45

PREFACE

Civil Engineering Services (CVE 582)This is a monograph for Civil Engineering Services in residential, commercial and industrial buildings with focus on residential buildings. The course is designed to fulfill the requirement of CVE 582 by providing 30 hours of continuing education on building services and practices. The monograph has been deliberately planned to serve as a basic introduction in to all major aspect of mechanical, electrical, water supply, solid waste management, fire services,lifts, escalators, & vacuum cleaner services requirement for any building to be safe and comfortable to the occupants for all intended purposes.

The students are urged to refer to listed books at end of the chapters for further readings. Suggestions, corrections are welcomed from students for improvement on the monograph. The monograph is not intended to serve as a reference manual for servicing and maintenance of any of the services installation covered most especially electrical installations.

February 2012


CHAPTER ONE

WATER SUPPLY AND INSTALLATION

1.1 Introduction

1.1.1 Hydrology cycle Hydrology cycle is the water transfer cycle which occurs continuously in nature through three important phases: (a) evaporation and evapotranspiration (b) precipitation and (c) runoff. Ocean is considered as starting point of the hydrology cycle. Of the total estimated world water, the contribution of ocean is 96.5%. The total available fresh water on the earth is 2.5% of the total estimated world water. Engineers are concerned about the runoff phase since it is the source of water reservoirs for purposes of municipal water supply, irrigation and hydroelectric power.

1.1.2 Water treatmentThe elements that made up a modern water supply system include the source of supply, storage facilities, transmission (to treatment) facilities, treatment facilities, transmission (from treatment) and intermediate storage facilities, and distribution facilities. Most treatment plant incorporates unit operations and processes such as aeration, coagulation/flocculation, sedimentation, filtration, and disinfection. Treated water is pumped to various distribution reservoirs for further distribution networks serving the benefitting communities.

1.1.3 Water qualityThe definition of water quality depends on the intended use of water. Many parameters have evolved that qualitatively define water quality and the impact on intended water usage. These parameters are used to assess the physical, chemical and biological characteristics of water. Physical parameters define those characteristics of water that respond to the senses of sight, touch, taste or smell. Turbidity, suspended solids, odour, colour, and taste fall into this category. Chemical parameters are related to the solvent capabilities of water since water is a universal solvent. Total dissolved solids, alkalinity, hardness, metals and organic matters are chemical parameters of concern in water-quality management. For bacteriological parameters, these are biological organism in water that are pathogens. The world health organization (WHO) has established minimum criteria for drinking water that all nations are urged to meet.

1.2 Distribution of WaterWater distribution systems are designed to adequately satisfy the water requirements for a combination of domestic, commercial, industrial and fire fighting purposes. The distribution system consists of a network of pipes with appurtenances, for transporting water from the treatment plant to the final consumer categories. Water distribution system is essentially a composite of four basic constituents: Pipe network,Storage, pump performance and pumping station as well as valves, all integrated into functioning system for various schedules of demand. A thorough analysis of each system must be made to ensure that it will operate satisfactory under all anticipated combinations of demand and hydraulic components characteristics.


A water distribution system also includes the design and operation of storage, service or balancing reservoirs. The design should prevent total services disruption during breakdown period or disruption to traffic flow during major repair work.

1.3 Method of DistributionThe three common methods of distribution depend largely upon the topography of the area: (1) Gravity system, (2) Combined gravity and pumping system, and (3) Pumping system. It is important that there is adequate pressure in the distribution mains at all points. 1.3.1 Gravity systemThe source of water supply is located with respect to the area of distribution such that water is available with sufficient pressure at various points of the servicing areas without the need for pumping. The treated water then flows entirely under gravity. This is a reliable and economical distribution method. Figure 1.1shows the system with the desired effective head, He.

Figure 1.1 Water distributions by method of gravity

1.3.2. Combined gravity and pumping systemThis is the most commonly adopted system in Nigeria. The Asa and Oyun water treatment plants in Ilorin and Offa respectively employ this method. In this method, the water treatment plants are located almost at the same level as the raw water source river. In order to obtain sufficient distribution pressure, the filtered water is pumped into clear water tank from where it is pumped to the elevated reservoir. The water from at the elevated reservoir then flows under gravity to the servicing communities, as illustrated in figure 1.2.

1.3.3 Pumping systemIn this approach, treated water is pumped directly into the distribution system to achieve the requiredpressure, as shown in figure 1.3. Such an approach is not desirable. Generally double pumping is required first to the treatment works and then pump purified water direct into the distribution mains. The pumps have to be run at varying speeds according to the variations in the consumption. In case of the power failure, the entire water distribution system of the locality is disrupted.


Figure 1.2 Water Distributions By Method Of Combined Gravity And Pumping System

Figure 1.3 Water distributions by method of pumping system (Figures 1.1, 1.2 & 1.3 are adapted from Punmia et al., 2002)

1.4 Storage and Distribution ReservoirsStorage and distribution reservoirs are important components in a modern distribution system network. Clear water storage reservoirs are required for storage of filtered water until it is pumped into the services reservoirs or distribution reservoirs. The pumps generally work for 7-10 hours daily. The clear water reservoirs are designed to have a capacity to store filtered water corresponding to 14 to 16 hours average flow for storage when pumps are idle.


Distribution reservoir provides service storage to meet the widely fluctuating demands often imposed on a distribution system to provide storage for fire fighting and emergencies and to equalize operating pressure.

Distribution reservoirs are located strategically for maximum benefits. Normally, they are positioned near the centre of use, but in large metropolitan areas, a number of distributions reservoirs may be located at key points. Reservoirs providing services storage must be high enough to develop adequate pressures in the system they serve. They are classified as either surface reservoirs or elevated reservoir according to their position on the ground, or classified according to the materials of which they are made such as steel, reinforced concrete and masonry. Distribution reservoirs are mostly of elevated types.

The key purposes they serve are in enabling pumping at uniform rate and maintain the desired pressure in the mains constantly. There are elevated distribution reservoirs located in Ijagbo, Omupo, Ipee and surface reservoir located at Offa as part of Oyun water treatment scheme. The storage capacities of the distribution reservoir are based on the following three requirements: (i) balancing or equalizing reserve, (ii) breakdown reserve and, (iii) fire reserve. When a storage or distribution reservoirs is to be designed for the purpose of balancing or equalizing the flow, its storage capacity can determined by two methods: (1) Hydrograph method and (2) Mass curve method.

Interactive Session:Treatment processes in Asa, Sobi, and Agba Water Works in IlorinDistribution reservoir types and locations in Ilorin, the capital of Kwara state of Nigeria.

1.5 Appurtenances in Distribution SystemThese are the various devices installed along the distribution system to serve the following purposes: (1) control flow rate, (2) prevent leakages (3) enable efficiency of distribution system and (4) to release or admit air into the network as appropriate. They are categorized into three within the distribution system: (a) valves (b) water meters and (3) fire hydrants.

1.5.1 ValvesThese are devices incorporated in pipelines to control flow into, through, and from them. They are usually made of cast iron, brass or bronze and now of PVC. The types of valves commonly used in residential water supply are gate, ball, and angle valves. Ball valves are quick-closing valves. Water hammer is caused by pressure that is developed during sudden stoppage of flow. This result in a banging sound and thephenomena can be prevented by installing air chambers on pipelines or other types of water hammer arrestors, which act as a cushion to dissipate the pressures. Valves are of different types according to the function they perform such as enumerated below:

1. Sluice valve: This is also known as gate- or stop- valve and essentially employed to control flow of water in a pipeline at appropriate points in the network. A pipe is a circular conduit for conveying water from one place to another under gravity or pressure. Closing a sluice valve shuts off flow of water in a pipeline. Gate valves are usually used in locations where it can be left completely open or closed for long period of time.


2. Non-return valve: This device automatically allows flow of water in one direction only. When water flow in the opposite direction, the valve closes thus prevent backflow.3. Scour valve: This valve is installed at dead ends of mains for the purpose of washing out deposited sand in the pipeline.4. Air-relief valve: Water in a pipeline does contain some quantity of air which may result in air lock thus reducing the discharge in the pipe. This device automatically allows air to escape through it. It also allows air in case a vacuum is created. They are normally installed at summit points in the alignment of the pipe.5. Pressure relief valve: These valves are normally installed at points along the pipelines where pressure is likely to exceed the permissible limit and thus may likely burst the pipe. As the name indicates, the relief valves relieve the pressure in pipe automatically when it exceeds a designed permissible limit.

1.5.2 Fire hydrantsThis device is used for drawing water in case of fire breakout. Fire hydrants are provided in the distribution system depending on serving population, building types and probability of occurrence. Fire hydrants are strategically located within the entire buildup area. There are many fire hydrants located at appropriatestrategic and conspicuous locations on the University of Ilorin campus.

1.5.3 Water metersThis is a device used for measuring the volumetric amount of water flowing through. They are installed on service pipelines leading to residential, industrial and public buildings to measure the quantity of water consumed and subsequently levied by municipal water supply authority.

Interactive Session:1. Ever sighted water meter ?2. Any municipal installed water meter in Ilorin?3. The water supply for a city is pumped from wells to a distribution

reservoir. The estimated hourly water requirements for the maximum day are as follows. If the pumps are to operate at a uniform rate, what distribution reservoir capacity is required?Hour Demand Hour DemandEnding m/h Ending m/h0100 273 1300 7590200 206 1400 7640300 256 1500 7290400 237 1600 6710500 257 1700 6700600 312 1800 6570700 438 1900 6120800 627 2000 6250900 875 2100 4231000 820 2200 3651100 820 2300 3281200 773 2400 309


EXERCISES

1. Briefly describe with the aid of clear labeled diagram three methods of water distribution for a

township.

2. Briefly explain 4 factors that affect water consumption.

3. List five important considerations in planning water supply for a city.

4. With the aid of clear and well labeled diagram only show the three methods of water distribution

for a city.

5. State the use of service reservoirs and describe mains water distribution methods.

6. The distribution storage capacity needed for both equalizing demand and fire reserve based on the

following hourly demands on the day of maximum water consumption is as listed in the table below.

Fire flow requirements are 6000gpm for duration of 6hour for the high value district, with 4000gpm

from storage.

i. Calculate the gallons of water consumed each of the day and the cumulative consumption

ii. Plot the cumulative water consumption (gpm) against time and determine the pumping rate for

constant 24 hours pumping (midnight to midnight).

iii. Calculate the distribution storage needed using Mass Diagram method.

iv. What is the total storage capacity including the fire reserve.

v. Determine the pumping rate and the required storage capacity for 8 hours pumping (6am to 2 pm)

Time Hourly Consumption Time Hourly Consumption

12 0 1pm 21301am 866 2pm 21702am 866 3pm 23303am 600 4pm 23004am 634 5pm 27405am 1000 6pm 30706am 1330 7pm 33307am 1830 8pm 26708am 2570 9pm 20009am 2500 10pm 133010am 2140 11pm 117011am 2080 12 93312am 2170


1.6 Residential Plumbing Fixtures and EquipmentThe pipes, fixtures and appurtenances inside a building for bringing in water are called plumbing and all installations are also referred to as plumbing. The water supply system in a building distributes water to plumbing fixtures at points of use. These include but not limited to urinals, bathtubs, showers, water closets, laundry trays and kitchen sinks. The plumbing fixtures are at the terminals of the water supply system and the start of the waste water system. Water closets (WC) consists of a bowl and integral trap which always contain water and a tank which supplies water for flushing the bowl.

Separate traps are required for most fixtures not fitted with integral trap. The cleansing action of water flow in a bowl may be achieved through the following methods: siphon jet, reverse trap and Siphon vortex. Floor drains are provided in all areas that are vulnerable to water spillage such as kitchen, shower and laundry. Most building codes in developed countries have rigid requirements for fixtures in order to ensure maximum sanitation and health protection. Pipes for water distribution in residential building have adopted the use of polyvinyl chloride (PVC) in the last decade.

1.7 Cold-Water ServiceMains water from public utility such as Kwara State Water Corporation is used in two ways: direct from mains and as low-pressure supplies from cold-water cisterns (storage tanks). Cold water services are taken to taps, WC ball valves, showers, hot-water storage cylinder and equipment needing low-pressure supplies. In tall buildings the pressure required to reach the upper floors can be greater than the available head, or pressures in the mains. Subsequently, a pneumatic water-pressure-boosting system is used.

Cold water storage tank (cistern) is made of steel, plastic or concrete. Its purpose is to provide storage against interruption of the supply from municipal water supply agency. The water supply into the cistern is usually controlled by a ball valve. It is a hollow copper or plastic ball which floats on the water which activates it to fall as water is drawn and rises to close the valve as water flow in. A gate valve is also fitted to the distribution pipe supply in the cistern. This is to isolate the cistern from the system in event of repair or renewals. One of the advantages of provision of cold water storage is that it helps reduce the effects of a mains failure. Other merits include; (i) reduces the demand on the water main, (ii) reduces the pressure fluctuation on the mains and, (iii) reduces the pressure on distributing pipes that supply WC, basins, baths, showers, etc.

1.8 Hot-Water ServicesHot water can either be generated by the central boiler plant and stored or produced close to the point of use by electricity or gas. There are two hot water services namely, the central and the local systems. For central water system, water is heated and stored centrally for general distribution while in the local system water is heated and stored locally for local usage. The water is heated and stored or heated instantaneously as it flows through the heater. The central system is used in hotels, dormitories and hospital.

1.9 Sanitary AppliancesSanitary appliances also known as sanitary fittings include all fixed appliances in which water is used either for flushing foul matter away or in which water is used for cleaning, culinary and drinking purposes. The former is termed soil appliances and include water closets (WC) and urinals, the discharge from which is


described as soil water and the latter, termed waste appliances, include wash-basins, baths, showers, sinks, and bidets the discharge from which is described as wastewater.

1.9.1 Soil appliances1. WC suiteThis comprises of W.C made of ceramic, seat and flushing appliances. WC is to take solid and liquid excrement, with an inlet for flushing appliances in a cistern designed to discharge water rapidly into the pan through a flush pipe for cleansing and disposal of the contents.2. UrinalThe three types of urinals in general use are the slab urinal, stall urinal and bowl urinal. The bowl urinal consists of individual bowls mounted on the wall and this type was installed in the recently commissionedFBSS building on campus. Slab and bowl urinals are made of vitreous China. The former can be found in Faculty of Art toilet.

1.9.2 Waste appliances1. Wash basinsThe basins are designed for washing the upper part of the body and are supported by wall brackets or on a pedestal secured to the floor. Traps are designed to contain a water seal against odours rising from sanitary pipe work and drains. WC pans have an integral trap to contain a water seal. All other sanitary appliances are fitted with a trap that is connected to the outlet of the appliances and to which the branch discharge pipe is connected.

1.10 Cold and Hot Water Pipe Sizing

The assessment and subsequent design of cold and hot –water installation is based on the concept of probable maximum water flow (or termed demand unit DU). The justification for the approach is due to the fact that it is very rare for all total installation appliances in a building to be used simultaneously. Therefore, for economic reasons, the installations are designed for a peak usage which is less than possible max usage. The probable demand will depend on type and number of sanitary appliances, the building type and frequency of usage. Howick, H.A. devised a method of assessing the probable maximum demand based on upon probability theory leading to application of “loading unit” rating for each of the sanitary appliances. Table 1.1 gives the loading unit rating for various appliances.

Interactive Session:A cold water storage is 60m vertically above a centrifugalpump which is to be used for raising 6000litres of water

from a low-level break cistern every 3 hours. Allowing 30% of the height for pipe friction, calculate the rating of the electric motor if the efficiency of the pumping equipment is 65%


Table 1.1 Loading Unit Rating for Various Appliances

Loading unit rating

Dwelling and flatsWC flushing cistern 2Wash basin 1.5Bath 10Sink 3-5

OfficesW.C. flushing cistern 2Wash basin (distributed use) 1.5Wash basin (concentrated use) 3

Schools and industrial buildingsWC flushing cistern 2Wash basin 3Shower (with nozzle) 3

Public bath 22

WORKED EXAMPLES

Que. 1

Determine the design flow rate for a hot or cold water distributing pipe supporting 8 WCs and 12 wash basin in an office.8WCs x 2 = 16 loading units

12 wash basins x 1.5 = 18 loading unitsTotal = 34 loading units

From Fig 1.1 the flow rate required for 34 loading units would be 0.6litres/s

Que. 2Provision of storageThe capacities of cold-water storage cistern are normally estimated using standard figures from reputable sources such as in for example Calculate the capacity of coldwater storage cisterns for a five-storey office block which will have a canteen. The populations will be 80 persons on each floor and a 10-hour storage of water in case of interruption of supply has been decided.

SolutionStorage capacity for 24-hr interruption of supply = 5 x 80 x 45 + 18,000 litresStorage capacity for 10-hr interruption of supply = 18000 x (10/24) = 7500 litres.


It is not always possible at the early stage to know the number of people that will occupy a building, but number and types of sanitary fittings will be known.

Que. 3Determine the design flow rate for a cold water distributing pipe supplying 20 WCs, 24 Wash basins, 10 urinals, 6 showers, and 4 cleaner’s sinks in a factory where there is high peak demand for the use of showers.

Solution:20 WCs x 2 = 40 loading units24 wash basins x 3 = 72 loading units 4 sinks x 4 = 16 loading unitsTotal = 128 loading units

From Fig 1.1, the flow rate for 128 loading units would be 1.6l/s and this must be added to the water required for urinal flushing and continuous use of showers. The urinals would require flushing every 20mins, and each urinal would require 4.5 litre flush.

10 x 4.5 = 45 litres every 20minutes45/ (20 x 60) = 0.0375L/sThe 6 showers would require 6 x 0.12 = 0.72l/s.The total flow rate required would be 1.6 + 0.0375 + 0.72 = 2.357l/s. Approx. 2.4 L/s

Que. 4

Determine the diameter of a copper cold-water rising main capable of discharging 2L/s through a 20mm orifice, when the pressure on the main is 500KPa (Kilopascal) (51m head), the height of the ball valve above the main is 10m and the actual length from the main to the ball valve is 40m with 4 elbows and 2 stopvalves in the run.

Solution:Assuming a 28mm o.d. copper pipe, then the effective length is:

40 + (4 x 1) = 44mFrom Fig 1.3 at a flow rate of 2L/s, the loss of head through a ball valve with a 20mm orifice is about 3m and ref Fig 1.4 the loss of head through a 25mm stop valve would be approx. 4.5m

The available head is 51 – (10 + 3 + 4.5) = 33.5m

The permissible loss of head per metre run of effective length of pipe is :Head/length = 33.5/44 = 0.76m/m run.By Ref Fig. 1.2, a 28mm o.d. copper pipe under these conditions would convey about 2.4 L/s so that this size of pipe would be satisfactory.


References

1. Clark, J.W., Viessman, W(Jr)., and Hammer, M.J. (1978) Water supply and pollution control. Harper and Row Publisher Inc., New York.

2. Duggal, K. N.(2004) Element of Environmental Engineering. S. Chand & Company Ltd. Ram Nagar. New Delhi.

3. Engelman, R. and LeRoy, P. (1995). Sustaining water: An update. Revised data for the Population Action International. Sustaining water: population and the future of renewable water supply.Washington, D.C., U.S.A.

4. Gladfelter, G.P. and Olsen, B.L (2002) Plumbing- Water supply, sprinkler, and wastewater syatem. In: Wise, A.F.E. and Swaffield, J.A.S. (2002) Water, Sanitary, and Waste Services for Buildings. 5th Edition. Butterworth Heinemann. UK.

5. Hall, F. (1994) Building Services and Equipment. Vol. 2. & Vol. 3.6. Kamala, A. and Kanth-Rao, D. L. (1988) Environmental Engineering:Water Supply, Sanitary Engineering

and Pollution. Tata McGraw-Hill Publishing Company Ltd. New Delhi.7. Linsley, R.K., Franzini, J.B., Freybberg, D.L., and Tchobanoglous, G. (1992)Water-Resources Engineering.

4th Edition8. Okeola, O.G. (2000). Evaluation of the effectiveness of Oyun Regional Water Supply Scheme, Kwara

State. M.Eng Thesis. Dept. of Civil Engineering. University of Ilorin. Ilorin. Nigeria9. Punmia, B.C., Jain, A and Jain, A. (2002) Water Supply Engineering. Laxmi Publications (P) Ltd. Daryaganj,

New Delhi10.Raghunath, H.M. (1986) Hydrology: Principles, Analysis, and Design. Wiley Eastern Limited. New Delhi.11.Suresh, R. (2005) Watershed Hydrology. Standard Publishers Distributors. 1705-B Nai Sarak, Delhi. India

EXERCISES

1. Define Plumbing.2. What is a trap and floor drain in a plumbing installation.3. Differentiate between Gate valve and Ball valve within the context of cold water cistern.5. Differentiate between local and central hot water system.6. What is the essence of probable maximum water flow in the design of cold water supply installation in a

residential building plumbing design?7. Explain the meaning and use of “demand Unit”8. A cold-water storage tank in a house with five occupants is to have a capacity of 100l/per person and be

fed from a water main able to pass 0.25l/s. How long will it take to fill the tank?9. Determine the diameter of a galvanized steel (G.S) cold-water rising main capable of discharging

2litres/s through a 25mm orifice, when the pressure on the main is equivalent of 60m head. The height of the ball valve above the main is 10m and the actual length from the main to ball valve is 42m with 4 bends and 2Nos 25mm stop valves in the run. The frictional resistance of fittings expressed in equivalent pipe length for G.S is 0.6m. Assume a 28mm o.d G.S to start with.


CHAPTER TWO

SOLID WASTE MANAGEMENT

2.1 Definition of TermsSolid waste management involves generation, storage, collection and disposal of refuse. Other important terms in solid waste management are as follows:Refuse: This is all the putrescible and non-putrescible solid wastes except body wastes and includes all such materials as rubbish and garbage.Rubbish: refers to that portion of the refuse which is non-putrescible solid waste constituents and includes such items as paper, glass, wood, etc.Garbage: This refers to that portion of the refuse which is the waste or rejected food constituents resulting from food preparation, cooking or storage of meat, fruits, vegetables, etc.

2.2 Classification of Solid WastesResidential waste consisting of leaves, food wastes, paper, glass, etc.Commercial wastes due to activity of offices, markets, hotels, etcIndustrial wastes including food-processing residue, ash, plastic, packaging wastes, etcBuilding construction wastes such as bricks, sand, stones, etc.Hospital wastes composed of blood, limbs parts of human body, etc.Bulky waste including trees, furniture, telephone poles, etc.Hazardous wastes comprising of explosives, radioactive materials, toxic materials, etc.These wastes have to be collected, transported and disposed off.

2.3 Quantity and Characteristics of RefuseThis is an aspect of solid waste management that is very important in determining appropriate methods for disposal. The quantity of refuse generated by a community is commonly calculated on average basis and expressed in Kg/capital/day. The characteristics and composition of refuse depends on the following factors: social and economic, weather, geographic location. Refuse is usually stored temporarily till the time it could be conveniently removed and hauled for disposal purposes.

2.4 DisposalThe solid waste is collected, transported and disposed off in one of the following ways; open dumping,sanitary landfill, incineration and composting.

2.4.1. Open dumping: In this method, the solid waste collected from the town is deposited in low-lying land, usually on the outskirts of the town. Since the ‘open dump’ are uncovered, these attract flies, insects and rodent and odors are produced. This method is unscientific and causes nuisance to the public and is vulnerable to the fire hazard. At the same time it causes health and pollution hazards and is not suitable aesthetically. This method is adopted in many Nigerian towns. Studies1 have revealed impairment of groundwater quality through leachates outflow and infiltration from landfill.


2.4.2. Sanitary land fillingThis is a modified form of open dumping. Waste is deposited in 0.9-4.5m thick layers in depression and then compacted and covered at least once a day by earth with bulldozers. The covering prevents breeding of flies, rats, etc. While selecting site for land filling, it is necessary to examine if any underground potable water source in the vicinity will be polluted and if the neighboring habitation will be affected by odor or fire. Sanitary land filling is the cheapest method of refuse disposal.

Advantages:1. The process is completely sanitary.2. It doesn’t require highly skilled personnel.3. Converts low-lying, marshy wasteland into useful area.

Disadvantages;1. A large area is required.2. Transportation cost is also high since in most cases land is available away from town.3. Can cause fire hazard due to formation of methane in wet weather.

2.4.3. IncinerationIn this method, the refuse is burnt in a controlled manner. Incinerators are built with lined furnaces, grate area for burning, air blowers for aiding combustion and oil burners to provide additional heat to burn wet garbage. The primary products of combustion are carbon dioxide, water vapour and Nitrogen and a solid residue of glass, ceramics, mineral ash, e.t.c. 90% of the volume of refuse is done away and 10% ash is left. Air has to be supplied to carry away the gaseous products and smoke treatment is necessary to keep pollution hazards under control. Incineration method is commonly adopted for disposing hazardous toxic wastes.

Advantages1. The residue is only 20-25% original weight and the clinker can be used after treatments.2. It requires very little spaces.3. Cost of transportations is not high as incinerators are located within city limits.4. Safest from hygiene point of view.

Disadvantages1. Its capital and operating cost is high.2. Needs skilled personnel.3. Air pollution may be caused.

1Yerima, F.A.K., Daura, M.M. and Gambo, B.A. (2008) Assessment of groundwater quality of Bama town, Nigeria.J. of Sustainable Development in Agriculture and Environment. 3(2): 128-1371Longe, E.O and Balogun, M.R. (2010) Groundwater quality assessment near a municipal landfill, Lagos, Nigeria. Research Journal of Applied Sciences, Engineering and Technology. (2)1 : 39-44


2.4.4. CompostingComposting is the biological decomposition of organic substances available in the waste, under controlled conditions. Rotting, putrefaction, etc., are natural processes that take place in a controlled manner. The compost thus formed under controlled conditions is a brown peaty material. There are two systems by which compost can be produced: anaerobic and aerobic.

In the anaerobic system, anaerobic bacteria perform the work in the absence of oxygen. The disadvantages of anaerobic system are:

1. Process is slow, extending over a period of 4-12 months2. It is a low-temperature process3. It produces offensive odour.

In the aerobic process, the compost is produced by aerobic bacteria. High temperature is produced, but bad odours are absent and the compost is formed rapidly. There are two methods by which compost is prepared in the aerobic process: Non-mechanical and Mechanical methods. In both methods of compostingthe following steps are involved:

1. Sorting2. Grinding or shredding3. Windrow making4. Turning5. Aerating

References1. Howard S. P., Rowe, R.R. and Tchobanoglous, G. (2000) Environmental Engineering. McGraw-Hill

International Editions. Singapore.2. Duggal, K. N.(2004) Element of Environmental Engineering. S. Chand & Company Ltd. Ram Nagar. New

Delhi.3. Kamala, A. and Kanth-Rao, D. L. (1988) Environmental Engineering: Water Supply, Sanitary Engineering

and Pollution. Tata McGraw-Hill Publishing Company Ltd. New Delhi.

EXERCISES 1. What is solid waste management?2. Assess what is being done on the campus to reduce the quantities of solid wastes collected for disposal.

Has these efforts reduced the quantity of solid wastes generated?3. Assess and discuss what is being done in your own or a nearby community to encourage the reuse of

materials.4. Explain the disposal of solid wastes by the following methods: (1) Open dumping

(2) Sanitary landfill (3) Incineration.5. Briefly explain the following term: (1) Refuse (2) Rubbish (3) Garbage.

ROUND TABLE TECHNICAL PRESENTATIONAn appraisal of University of Ilorin solid waste management.An appraisal of Ilorin municipality solid waste management.


CHAPTER THREE

ELECTRICITY SUPPLY

3.1 Electrical WiringElectrical wiring in general refers to insulated conductors used to carry electricity and associated devices. Wiring safety codes are intended to protect people and property from electrical shock and fire hazards. In order to enable wires to be easily and safely identified, all common wiring safety codes mandate a colour scheme for the insulation on power conductors. In a typical electrical code, some colour coding is mandatory, while some may be optional. Many electrical codes recognize (or even require) the use of wire covered with green insulation, additionally marked with a prominent yellow stripe, for safety grounding connections. The international standard was adopted for its distinctive appearance, and thus reduces the likelihood of dangerous confusion of safety grounding wires with other electrical functions, especially by persons affected by red-green colour blindness.

Heavy industries have more demanding wiring requirements, such as very large currents and higher voltages, frequent changes of equipment layout, corrosive, or wet or explosive atmospheres. In facilities that handle flammable gases or liquids, special rules may govern the installation and wiring of electrical equipment in hazardous areas. Materials for wiring interior electrical systems in buildings vary depending on:

Intended use and amount of power demand on the circuit Type of occupancy and size of the building National and local regulations Environment in which the wiring must operate.

Wiring systems in a single family home or duplex, for example, are simple, with relatively low power requirements. Electricity enters residential home through a service head from a series of outdoor Power Holding Company of Nigeria (PHCN) power lines or an equivalent underground connection. A typical service head consists of two 120-volt wires and one neutral wire that deliver power to lights and appliances in the house. The electric meter is usually mounted outdoors within the vicinity where electricity enters the house. This device is used to measure the amount of electricity that is consumed in the household. The meter tampering is illegal and notes that it is even extremely dangerous. Also there is service panel provision. It is the central distribution point for delivering electricity to switches, outlets, and appliances throughout the house. Located near the electric meter, the service panel is equipped with a breaker that shuts off power to the circuits if an electrical system failure occurs.

Interactive Session:Students to identify Service panel, Switches, Electric meter, Circuit breaker, conduits, trunking, socket etc

WARNING: Students are strongly warned not to tamper with electrical installation.

http://en.wikipedia.org/wiki/Conductor_%28material%29

http://en.wikipedia.org/wiki/Electricity

http://en.wikipedia.org/wiki/Electrical_code

http://en.wikipedia.org/wiki/Red-green_colour_blindness

http://en.wikipedia.org/wiki/Electrical_equipment_in_hazardous_areas

http://en.wikipedia.org/wiki/Electrical_equipment_in_hazardous_areas


3.2 Cable and CircuitsWires and cables are rated by the circuit voltage, temperature rating, and environmental conditions (moisture, sunlight, oil, chemicals) in which they can be used. The amount of current a cable or wire can safely carry depends on the installation conditions. The two circuits’ method adopted for buildings are radial circuit and ring circuit. A circuit that runs from the fuse way to the outlets it supplies is a radial circuit, and a circuit that runs from the fuse way to the outlet it serves and back to the fuse way is a ring circuit.

Electricity is conducted along wires of copper which have to be insulated and also protected against mechanical damage. Insulated wire or wires are commonly termed cable to distinguish them from bare wire. The wire in a cable is often stranded, each wire being made from a number of small wires twisted to form one conductor. The cable size is described by the cross-sectional area of the wire for example 1.5mm2.

The majority of cables use for electrical wiring in building today are insulated and sheathed in PVC which is a tough, incombustible, chemically inert plastic that does not deteriorate with age. PVC softens at temperatures above 800c and therefore should not be used where ambient temperatures are above 700c. The insulation and sheath to cable such as PVC provides some protection against damage during building operations. In many situations the sheath does not provide sufficient protection and it is usual to run cable inside metal or plastic conduct which provides protection and facilitates withdrawing and renewing cable if necessary.

3.2.1 Metal conduitsThis consist of steel tubes, couplings and bends which are either coated with black enamel or galvanized, the latter coating specifically for use where conduit is exposed.

3.2.2 PVC conduitsThis conduit is commonly used in Nigeria, perhaps due to its affordability and ease of workmanship. The conduit is of round section joined together with couplers that are solvent cemented to the conduit. High impact grade PVC conduit is used for its resistance to mechanical damage. PVC is not a conductor; hencethe cable along with an earth wire is used with it. Cable is run in conduit in the structure of buildings where it is buried in floors, walls and finishes such as screeds. Where several cables are run together it is important to protect them inside metal or plastic trunking. Various elbows and gussets tees are made for angles. Trunking is generally too bulky to bury in the structure of buildings and therefore are accommodated in the ducts and false ceilings.

3.3 Supply and DistributionThe Power Holding Company of Nigeria distribution network is 415V three phase or 240V single phase is run to all residential buildings while commercial and industrial complexes employ 240V and 415V. There is aseparate 3 phase supply to motors over 3hp for lifts, ventilating plant and other heavy equipment. In order to spread the load over the three phases of its supply the PHCN brings in a single phase cable from each of its three phase supply for adjacent buildings or group of buildings in an estate for example.

A 240V supply is considered high enough to be dangerous in some countries, for example U.S.A. suppliesare 110V for safety reasons while Nigeria takes after Britain and adopt 240V. The PHCN runs a single phase


supply into the building to a service cut out box and then through a meter to a distribution board. For domestic uses the distribution board is called a consumer control unit which incorporates an isolating switch and fuse board with up to twelve fuse ways. Each fuse ways is connected to a separate lighting or power circuits.

In large buildings, for e.g. blocks of flats, it is often convenient to bring the service main inside the building to distribution boards on each or alternate floors from which the flats on each floor are served. A distribution board is usually in the form of a metal box containing a busbar or conductor to which the service main is connected and from which the supply to each of the flats is run through a fuse to the consumer control unit in each flat.

3.4 Fuses and Circuit BreakersA fuse acts as a safety device against overload of a circuit so that the fuse wire heats, melts, and break the circuit. The wire in a fuse is selected to heat, fuse and break the circuit at predetermined current to prevent overheating and damage to the circuit. The common types of fuses are the rewireable and cartridge. The former consists of a thin wire, the fuse wire, run between the terminals of a porcelain holder the terminals of which make contact when the holder is pushed into a place in the fuse carrier. A rewireable fuse has a limited breaking capacity and if large current flows, the fuse wire melts, and a large amount of energy are released which is sufficient to damage the fuse carriers. While in the later, the fuse wire in a cartridge fuse is mounted inside a plastic case with a metal end cap.

Miniature circuit breakers (MCB) have been developed from the large circuit breakers used in large power distribution systems. When overloading occurs, the internal mechanism trips off the circuit breakers. MCB are more expensive than either rewireable or cartridge fuses. It is advisable that homes are protected by circuit breakers. Unlike a fuse that must be replaced when it blows, a circuit breaker that has “tripped” can be mechanically reset to resume operations once the problem has been resolved.

Figure 3.1 Modern Circuit Breaker Figure 3.2 Portable Installation Tester equipment


3.5 EarthingFuses and MCB in distributions boards and fuses in ring circuit plugs are designed to break a circuit at predetermined current rating to protect the circuit cable and appliance from damage by overheating. If a live electric wire or conductor touches or is close to exposed metal such as water pipe, the pipe will acts as a conductor and become live. The current that flows along the wire and into the pipe will be greater than the designed maximum and circuit fuse or MCB will break the circuit. The operating time of the fuse or MCB may well be long enough for a spark from the live wire to the pipe or from the now live pipe to nearby metal sufficient to cause damage or a fire. To prevent this possibility it is practice to bond all metal pipework, such water pipes, to the earth supply to the incoming services mains as near as possible to the point where the pipes enter the building.

3.6 Grounding Grounding is the method used to connect an electrical system to the earth with a wire. Grounding adds critical protection against electric shock and electrocution by using a grounding rod to provide a third path for conducting electricity in the event of a short circuit or an overload. Grounding will help protect the person working on the system, the system itself, and any appliances and equipment that are connected to the system. Every home has a service panel that distributes electricity to switches, outlets, and appliances. Service panels are equipped with fuses or circuit breakers that protect the wires in each circuit from overheating and causing fire outbreak. Older service panels use fuses, while more modern systems utilize circuit breakers. A tripped breaker is likely the result of too many appliances overloading the circuit and should be fixed immediately.

Electricity always seeks to return to its source and complete a continuous circuit. A typical circuit in house’s wiring system has two conductors -one that flows from the service panel to appliances in the house, and another that returns the current to the main service panel. In a grounded electrical system, a third or “grounding” wire is connected to all outlets and metal boxes and is then connected directly to the earth using a metal grounding rod or a cold water pipe. In contrast, an ungrounded system does not prevent electricity from taking the path of least resistance – even if that path is through an unsuspecting person who comes into contact with an appliance that has a short circuit. Grounding is a critical safety feature that safeguard against shock or electrocution.

3.7 Electrical Installation TestingThe purpose of electrical installation testing is primarily to ensure that people and goods are kept safe and are protected in the event of a fault. It also facilitates preventive maintenance of installations, preventing serious faults which might prove expensive for instance if it result in production shutdown. The risks linked to incorrect use of electricity may include:

life-threatening danger for people, threat of damage to electrical installations and property, harmful effects on systems operation and equipment life spans.

To guarantee people's safety with regard to these installations and the electrical equipment connected to them, standards have naturally been developed and updated to take changes into account. The IEC 60364 standard and its various national equivalents published in each European country, such as NF C 15-100 in


France or VDE 100 in Germany, specify the requirements concerning electrical installations in buildings. Chapter 6 of this standard describes the requirements for testing the compliance of an installation. Here in Nigeria, there is no Standard Code, but work is going on toward establishing it by the Nigeria Society of Engineers (NSE)while Nigeria Institute of Builders have produce Building Standard Code which is with the National Assembly for passage. However, NSE views their code as inadequate and more so codes are refer to from Regulations. It is the regulations that are supposed to be taken to Federal House of Assembly for passage and not code. The practice so far for tests on electrical installations has kept to the compliance with standard obtainable in regulations by Nigeria Society of Engineers, Nigeria Institutes of Builders, Power Holding Company requirement for substation and distribution and Federal Ministries of Mines and Power and Labour & Productivity.

The effectiveness of the safety measures implemented can only be guaranteed if regular tests prove they are operating correctly. This is why the standards cover not only the initial verifications when installations are commissioned, but also periodic testing whose frequency depends on the type of installation and equipment, its use and the legislation in the country involved. In addition, the tests must be carried out with measurement instruments that comply with the IEC 61-557 European standard ensuring user safety and reliable measurements. The electrical testing is divided into 2 parts: (1) Visual inspection to guarantee that the installation complies with the safety requirements (presence of an earth electrode, protective devices, etc.) and does not show any visible evidence of damage and (2) Measurements.

There are 4 main measurements required: (1) Earth (2) Insulation (3) Continuity and (4) Tests of protective devices

3.7.1. EarthIn order to guarantee safety on residential or industrial electrical installations, there must be an earth electrode. If there is no earth electrode, it may endanger people's lives and damage electrical installations and property. When a large enough area is available to set up stakes, it is imperative to measure the earth with the traditional 3-pole method, also known as the 62 % method. When the 62 % method is not applicable, other methods can be used. There are many methods for measuring the earth; some are more suitable than others, depending on the neutral system, the type of installation (residential, industrial, urban, rural, etc.), the possibility of cutting off the power, the area available for planting stakes, etc.

3.7.2. ContinuityThe purpose of continuity measurement is to check the continuity of the protective conductors and the main and supplementary equipotential bonds. The test is carried out using a measurement instrument capable of generating a low-load voltage of 4 to 24 V (DC or AC) with a minimal current of 200 mA. The resistance measured must be lower than a threshold specified by the standard applicable to the installation tested, which is usually 2 Ω. As the resistance value is low, the resistance of the measurement leads must be compensated, particularly if very long leads are used.

3.7.3. InsulationGood insulation is essential to prevent electric shocks. This measurement is usually carried out between active conductors and the earth. This involves injecting a DC voltage, measuring the current and thendetermining the insulation resistance value. The power must be switched off and the installation must be


disconnected before performing this test to ensure that the test voltage will not be applied to other equipment electrically connected to the circuit to be tested, particularly devices sensitive to voltage surges.

3.7.4. Tests of Protective Devices

1. Fuses / Circuit-breakersTo check the specifications of the protective devices such as fuses or circuit breakers, a fault loop impedance measurement is carried out to calculate the corresponding short-circuit current. A visual inspection can then be used to check that the sizing is correct.

2. Residual current devices (RCDs)RCDs can detect earth leakage currents. The test can be carried out using two methods:

1. the basic test, also called a pulse test, which determines the trip time (in milliseconds)2. the step test, which determines the trip time and trip current, thus detecting any RCD ageing.

3.8 Energy Efficient LightingToday, lighting accounts for nearly 20 percent of a typical home’s energy bill. Fortunately, there is a way to dramatically cut down household energy costs and at same time improve upon safety. Compact fluorescent light bulbs (CFLs) uses 75 percent less energy than a standard incandescent light bulb and last up to ten times longer. In addition, CFLs also produces 75 percent less heat and thus make them a much safer option for homes. CFLs contain an extremely small amount of mercury. Also CFLs offer a net environmental benefit. Standard incandescent light bulbs will soon be phased out.

3.8.1 Compact fluorescent light bulbs (CFLs)The National Centre for Hydropower Research and Development (NACHRED), University of Ilorin is actively involved in the Federal Government of Nigeria energy saving programme. The centre has retrofitted energy consuming incandescent lamps with CFLs provided by Energy Commission of Nigeria (ECN) in a number oforganized residential estates in Ilorin metropolis, the Lower Niger River Basin Development Authority staff quarters and University of Ilorin community.

3.9 Electricity Regulatory BodyThere are statutory bodies that regulate and monitor electricity supply installation works and other auxiliaries attach to it. The following Federal Government institutions are vested with authority to regulate different categories of electrical work installation in Nigeria:

Nigeria Electricity Regulation Commission (NERC) Federal Ministry of Mines and Power(FMMP) Power Holding Company of Nigeria (PHCN) Federal Ministry of Energy Federal Ministry of Works

It is only duly licensed electrical contractors are allowed to operate in electrical installation works and services business. The Federal Ministry of Works grant license to four electrical contractor categories based on educational qualification and requisite experience from category 1 (highest) to category 4(lowest).


References

1. Alim and Associates. Electrical & Mechnical Engineers. Kaduna. Nigeria. Personnel Communication

2. Barr, R. (1980).The Construction of Buildings. Volume 5. The English Language Book Society and Granada

Publishing Limited, UK.

3. Electrical Safety Foundation International (www.eletrical-safety.org)

4. Chadderton, D.V. (2004) Building Services Engineering. Spon Press . London

5. Hall, F. (1994) Building Services and Equipment. Vol. 3. 3rd Edition

6. Ibironke Technologies Limited. Electrical & Mechnical Engineers. No 50, Basin Road, Ilorin. Nigeria.

Personnel Communication

7. Knight, J. and Jones, P. (2004) Building Services Pocket Book. Elsevier Ltd. UK

8. Professional Measurement Instrument. Chauvi Arnoux Group. Paris. (www. chauvi-arnoux.com/ptm)

EXERCISES

1. What is electricity wiring?

2. What is the essence of electrical wiring safety colour codes?

3. How are wires and cables rated?

4. What is the need for trunking in a residential building or industrial complexes?

5. Who is the Nigeria electricity service provider and how is the service been supplied to residential homes

6. Differentiate between fuses and circuit breakers

7. What are the risks from wrongfully usage of electricity?

8. What is the reason for testing electrical installations?

9. Briefly describe methods of testing electrical installations.

10.What do you understand by “Grounding”?

http://www.eletrical-safety.org/


CHAPTER FOUR

EMERGENCY AND STANDBY POWER SYSTEMS

4.1 Household Electrical GeneratorThe poor performance of public utility services in Nigeria has been a subject of considerable discussion particularly the electricity1. The poor state of electricity supply imposed huge costs on business sector.Presently Nigeria is generating about 3,000Mw, which is a far cry from the estimated national demand of about 40 000Mw. Electric generators are selling like hot cake in Africa most populous and greatest country, NIGERIA. Sales of Generators are on the increase because they have become essential commodities in Nigeria due to deterioration of one of the critical infrastructure1, ie electricity.

Nigerians have been looking for alternatives source of power which in most cases are electricity generators. This alternative has become popular because of the proliferation of cheap electricity generators from China. The Tiger generator seems to be in most houses and is a very popular low power electric power generator. Elemax, Honda, Tec, Sumec Firman, and Hyundai brands of generators are also popular in Nigeria for low power applications for homes and small businesses. However, for medium and high power applications required by industries and large commercial enterprises, generators like Cummins and Perkins are commonly employed.

4.2 Emergency and Standby Power SystemsThe nature of electrical power failure, interruptions, and the duration ranges in time from seconds to days. In the face of possible failures of normal electrical utility power sources, a reliable alternate supply of electric power must be provided for facilities and systems that cannot go without power e.g. health care facilities, data processing, life safety systems, etc. This provision is usually from emergency and standby power system. A typical emergency and standby power system component includes the following:

1. engine-generator set2. transfer switch3. battery system4. engine/ generator control5. fuel system/ storage6. exhaust and inlet/outlet air

4.2.1 EngineGenerator set which consists of an engine coupled with a generator that it drives.

4.2.2 Transfer switchThe transfer switch is the component in the emergency and standby power system that transfers power from the “normal” Power source to the alternate power source when the “normal” source of power fails.The design and installation of transfer switches must meet several standards. Transfer switches are offered in different configurations and operating schemes.

1Okeola, O. G. and A.W. Salami (2012). A Pragmatic Approach to the Nigeria’s Engineering Infrastructure Dilemma. Epistemic in

Science, Engineering and Technology.(2):1 pp 55-61

http://naijatechguide.blogspot.com/2007/09/generator-series-buying-generator.html

http://www.naijatechguide.com/2007/09/as-we-wait-for-constant-power-supply.html

http://naijatechguide.blogspot.com/2008/03/tiger-generators-nigeria.html

http://naijatechguide.blogspot.com/2008/03/elemax-generator-nigeria.html

http://naijatechguide.blogspot.com/2008/10/honda-generator-dealers-motorcycles.html

http://naijatechguide.blogspot.com/2010/05/sumec-firman-spg-3000-e2-generators.html


4.2.3 Battery SystemThe reliability is paramount in emergency and standby power applications. A common cause of engine generator sets failure to start is a battery failure.

1. Gen set startingEngines are typically started by using battery powered electric motor starters. In rare cases, engines may be started by compressed air operated motors depending on the type of engine and the availability of compressed air. The starting batteries must have sufficient capacity for 60 seconds of continuous cranking. The engine manufacturers define required battery capacity in terms of cold cranking amperes.

2. Battery typesBoth lead acid and nickel cadmium batteries are commonly used. The most common voltage for diesel gen set battery systems is 24 volts DC.

3. ChargerA properly specified battery charger offers accurate and automated battery charging that automatically adjusts to changing input voltage, load, battery and ambient temperature conditions. This can prevent battery overcharging and the consequent loss of battery electrolyte.

4. Controls Both engines and the generator require panels for displaying operating conditions and for mounting the controls, providing protection and displaying alarms.

4.2.4 Fuel storage and pumping systemA typical system of a day tank and bulk storage tank are also common.

4.2.5 Air supply and exhaustsA means of providing an unimpeded flow of fresh outside air into the generator is necessary and serves two purposes: (a) Cooling air for the generator and to keep the generator room comfortable and, (b) To provide clean air available to the engine for combustion.

4.3 System Component Features and OptionsEngine driven generators are work horses that fulfill the need for reliable emergency and standby power. They are available from 1 kVA units up to several thousand kVA. When properly maintained and kept warm, they dependably come on line within 8-15 seconds. Engine-generator sets are just- an engine coupled with and driving an electrical generator. There are several types of gen sets that are classified by the energy source (fuel) of their prime mover (in the case of the engine): (1) Gasoline Engine (2) Diesels Engine (3) Gas Turbine.

4.3.1 Gasoline engine sets They are available from several hundred watts to about 100 KW. Smaller sets use two-and four-cycle high speed, lightweight engines. Larger sets use multiple cylindrical engines built for automobiles and trucks.


4.3.2 Diesel Engine sets They are available for just under 100KW to 10,000 KW. Diesel gen are rugged, dependable and most suitable for continuous duty. The fire and explosion hazard is considerably lower than for gasoline engines

4.4 GovernorThe governor regulates or governs the amount of fuel delivered to the engine at various loads to keep the speed or frequency of the generator relatively constant. Governor are of two typical types: droop and isochronous. With a droop type governor, the engine speed is slightly higher at a light loads and at heavy loads, while a isochronous governor maintains a steady speed at any loads up to full load.

4.5 Transfer SwitchesTransfer switches are offered in different configuration and operating schemes including: automatic , non automatic (manual), bypass- isolation, open transition, closed transition and closed transition- soft load.

4.5.1 AutomaticThe automatic transfer switch transfer power between two power sources without requiring the intervention of an operator. The switch monitors the electrical conditions of both power sources (normal and alternates) i.e voltage, frequency, phase rotation and load. When one of the system characteristic deviates from the specified allowed range, the transfer switch transfers to the other system if it has more suitable power available. Some automatic transfer switches also include provisions for none automatic operation in the deviant of failure of the switches automatic features.

4.5.2 Non automatic switches Non automatic switches require the manual action of an operator and cannot be used for emergency power applications.

4.6 Uninterruptible Power Source (UPS)

The Emergency Standby Power System (ESPS) is designed to provide electricity when normal utility power fails and subsequently, lights, office equipment, and home appliances can all be powered with the ESPS. However, due to the sensitive nature of some equipment such as computers it requires additional protection of an uninterruptible power source. There are two basic types of UPS systems: standby power systems (SPSs) and on-line UPS systems.

SPS monitors the power line and switches to battery power as soon as it detects a problem. The switch to battery, however, can require several milliseconds, during which time the computer is not receiving any power. Standby Power Systems are sometimes called Line-interactive UPSs. An on-line UPS avoids these momentary power lapses by constantly providing power from its own inverter, even when the power line is functioning properly. In general, on-line UPSs are much more expensive than SPSs.

The components for the ESPS are a special combination inverter and charger, a battery bank, and related safety equipment. Under normal circumstances, utility power is connected to the inverter/charger to charge the batteries and also to power the loads. When the utility power fails, the inverter/charger automatically takes stored power from the batteries, converts it to 120 volts AC, and supplies it to the

http://www.webopedia.com/TERM/S/system.html

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loads. In this way the loads continue to operate at all times. The inverter changes DC (direct current) into AC (alternating current), while the charger changes AC to DC.

The size of the inverter/charger and battery bank is determined by the loads to be run and the duration that the loads will be expected to operate in the event of an outage. The total connected load to be powered (expressed in watts) determines the size of the inverter/charger that is required. The amount of time that backup power is expected to be needed determines the capacity of the batteries. The larger the battery set, the longer the loads will operate during an outage. The overall size of an ESPS system is limited only by budgetary constraints. Other components necessary to install the ESPS are the proper size cables to connect the batteries; cables to connect the batteries to the inverter/charger, DC rated circuit breakerfor the battery to inverter/charger cables, and a box for the batteries. 120 volt AC wiring is required to connect the inverter/charger into the existing home or office wiring system.

4.7 Solar Energy

Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar energy technologies include solar heating, solar photovoltaics, solar thermal electricity and solar architecture, which can make considerable contributions to solving some of the most urgent problems of electricity generations and usage in residential buildings.

Solar technologies are broadly characterized as either passive solar or active solar depending on the way they capture, convert and distribute solar energy. Active solar techniques include the use of photovoltaic panels and solar thermal collectors to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air. Solar energy is used to provide:

1. Comfort heating through architectural design in a ‘passive’ system;2. Comfort heating using collectors, with air as the heat transfer fluid, in an ‘active’system;3. Comfort heating and hot-water using collectors, with water as the heat transfer fluid, in

an active system.

http://en.wikipedia.org/wiki/Light

http://en.wikipedia.org/wiki/Heat

http://en.wikipedia.org/wiki/Sun

http://en.wikipedia.org/wiki/Ancient_history

http://en.wikipedia.org/wiki/Solar_heating

http://en.wikipedia.org/wiki/Solar_photovoltaics

http://en.wikipedia.org/wiki/Solar_thermal_electricity

http://en.wikipedia.org/wiki/Solar_architecture

http://en.wikipedia.org/wiki/Passive_solar

http://en.wikipedia.org/wiki/Active_solar

http://en.wikipedia.org/wiki/Solar_thermal_energy

http://en.wikipedia.org/wiki/Thermal_mass

http://en.wikipedia.org/wiki/Ventilation_%28architecture%29


References


2. Gnan, J.W. (2010) Standby Power Systems. Engineer Educators Inc. Tallashass. USA.

(www.engineereducator.com)

EXERCISES

1. What is the need for emergency and standby power system in most residential and commercial

buildings?

2. Name 5 brands of emergency power system for residential buildings and 2 for industrial enterprises.

3. Differentiate between standby power system and uninterruptible power source (UPS)

4. Discuss inverter and charger within the context of emergency Standby power system. What is and why

the need for emergency Standby power system (ESPS)

5. Name and differentiate between 2 basic types of UPS under ESPS group.

6. Itemize the components of ESPS

7. Itemize the component of standby power generator engine system.


CHAPTER FIVE

VENTILATION, REFRIGERATION AND AIR CONDITIONING

5.1 The Built EnvironmentA building is an enclosure for the comfort of human habitation, work, recreation and also be for industrial need. The human ability to extract enormous amount of natural energy from the earth has enabled the keeping of habitable structures cool or warm as required. Buildings are thus maintained with varied standard of comfort but with energy cost implication. The building services engineering is concerned with every part of the interface between building and its occupant. Heat transfer between the human body and its surrounding are by three processes namely conduction, convection and radiation.

5.2 Air CompositionThe atmospheric air is considered to compose the following elements: Nitrogen (78.1%), Oxygen (20.9 %), Carbon dioxide (0.04%) and Water vapour (0.96%). The percentages proportions are by volume. Both the temperature and humidity are very important in the principles and explanation of ventilation.

5.2.1 TemperatureHeat is being generated by body metabolism. The body maintains a particular temperature and any excess must be dissipated. Physiologically, the body heat loss is cutaneous. A difference of temperature between the body and air is necessary in order to cause the heat flow.

5.2.2 HumidityThis is the moisture content of the air. The amount of moisture which the air can hold varies with temperature. Relative humidity is the percentage of the moisture which the air at any temperature contains when compared with the amount which it can hold. Relative humidity is an index of the capacity of air to evaporate water. At 100% relative humidity, air will not evaporate any water. It is measured through a comparison of the wet-bulb and dry-bulb.

5.3 VentilationVentilation is the process of replacing used or vitiated air by fresh air in a dwelling. This involves either supply or removing air to or from the occupancy through natural or artificial means. The crucial need for ventilation in a building has lead to understanding of the necessary combination of natural and mechanical systems. Air conditioning is a total mechanical control of air movement through the building. Therefore, air-conditioning is the process of tampering or conditioning air so as to control simultaneously various factors affecting the physical and chemical conditions of the atmosphere within the occupancy. These factors are humidity, temperature, air movement as well


as its cleanliness, volume and distribution. The four possible combinations of natural and mechanical ventilation are:

5.3.1 Natural inlet and outletThis employs the usage of openable windows, lovres, doorways and chimneys. The effectiveness is a function of the prevailing wind direction and strength.

5.3.2 Natural inlet, mechanical outletThis employs the use of mechanical extract fans in windows or roofs, and ducted system where the air is to be discharged away from the occupied space due to its contaminations with fumes, smokes, heat or odour. Because there are no filtration of incoming impurities, this system is particularly used for toilet, kitchen extraction, smoke removal from the public rooms and heat removal from industrial premises.

5.3.3 Mechanical inlet, natural outlet In this method, air is blown into the building through a fan convector or ducted system to pressurize the internal atmosphere slightly with a heated air supply. The air is subsequently leaks out of the building through openings and permanent air bricks or lovres. This system can be used for offices, factories, large public halls.

5.3.4 Mechanical inlet and outletIn a situation where natural ventilation opening can not cope with large air flow rates without disturbing the architecture or causing uncontrollable draughts, then full mechanical control of air movement is required. This may augment natural ventilation during peak occupancy. Note that when a building is to be sealed from the external environment a full air- conditioning system is used.

WORKED EXAMPLES

Que 1.A room 15m by 7m by 2.8m high is to have a ventilation rate of 11 air changes per hour. Air enters from a duct at a velocity of 8.5m/s. Find the air volume flow rate to the room and the dimensions of the squareduct.

Solution:The air flow rate is given as

Q = hour

changesairN X

changeair

mV 3

X s

h

3600

1

Where room volume Vm3 = 1 air change

Q = 3600

NVm/s = 0.9m3 /s.


Also Q = AVQm3/s = duct cross – sectional area Am2 X air velocity Vm/s.

A = V

Q=

5.8

9.0m2 = 0.106m2

Assume the duct side is Ym then A = Y2 m2

Y = Am

= m106.0 = 0.325m

Que 2:A lecture theatre has dimensions 25m × 22m × 6m high and has 110 occupants; 8 l/s of fresh air and 25 l/s of recirculated air are supplied to the theatre for each person. A single-duct ventilation system is used. If 10% of the supply volume leaks out of the theatre, calculate the room air change rate and the air volumeflow rate in each duct.

Solution:Quantity of supplied air = (8 + 25)1/s x (1m3/103l) = 0.033 m3/sTherefore: Q = 0.033 x 110 m3/s = 3.63 m3/sQ = NV/3600 Therefore, N = (3600Q)/VN = (3600 x 3.63)/(25 x 22 x 6) = 3.96 air changes per hour

The leakage from the theatre is:Q1 = 10% x Q = 0.1 x 3.63 m3/s = 0.36 m3/s

The quantity of air extracted from the theatre is :

Qe = 3.63 – 0.36 m3/s = 3.27 m3/s

The quantity of fresh air entering the ductwork is :Qf = (8 x 110)/103 m3/s

The quantity of recirculated air is :Qr = Q – Qf = 3.63 – 0.88m3/s = 2.75m3/s

The exhaust air quantity is :Qex = Qe – Qr = 3.27 – 2.75 m3/s = 0.52 m3/s


Que 3:There are 35 people in a gymnasium, each producing CO2 at a rate of 10 × 10−6 m3/s. If the maximum CO2

level is not to exceed 0.4%, find the air supply rate necessary. The outdoor air CO2 concentration is 0.03%. Explain what this means to the ventilation designer.

Solution:

smCC

PQ

sr

/3

sm /1003.040.0

101035 3

2

6

sm /095.0 3

This result shows that the air flow is very small of outdoor air through a gymnasium where it is expected to have strenuous activity by 35 people. The outdoor air of 91 l/s may be provided by natural ventilation through controlled low and high level vents to the outside.

5.4 Removal of Heat GainsThe excess heat gains from buildings are removed by ventilation air. Two types of heat gain are involved: sensible and latent. Sensible heat gains result from solar radiation, conduction from outside to inside during hot weather, warm ventilation air, lighting, electrical machinery and equipment, people and industrial processes. Such heat gains affect the temperature of the air and the building construction.

Latent heat gains result from exhaled and evaporated moisture from people, moisture given out from industrial processes and humidifiers. These heat gains do not directly affect the temperature of the surroundings but take the form of transfer of moisture. They are measured in weight of water vapour transferred or its latent heat equivalent in watts. The latent heat of evaporation of water into air at a temperature of 200C and a barometric pressure of 1013.25mb is 2453.61 kJ/kg. Thus the latent heat (LH) required to evaporate 60 g of water in still air is:

LH = 60g x (1Kg/103g) x 2453.61(KJ/Kg) = 147.22KJAssuming the evaporation takes place over for example 1 hour, the rate of latent heat transfer will be:LH = 147.22 (KJ/h) x (1h/3600s) x (103J/KJ) x Ws/J = 40.9 W. This is the moisture output from a sedentary adult.

Rooms that are isolated from exterior building surfaces have internal heat gains from people and electrical equipment, producing a net heat gain throughout the year.The heat balance is as follows:Net sensible heat flow into room = sensible heat absorbed by ventilation air


Therefore,SH = air mass flowrate × specific heat capacity × temperature risewhere SH is the sensible heat. The specific heat capacity of humid air is 1.012 kJ/kgK.The volume flow rate of air is normally expressed as follow:

smt

tt

SHkWQ s

sr

/357

273 3

Note that:1. the density of air at 200C d.b. and 1013.25mb is ρ = 1.205 kg/m3.2. the supply air temperature ts, can have any value, and as density is inversely proportional to the

absolute temperature.3. For summer cooling, tr is greater than ts during a net heat gain. For winter heating, tr is less than ts as

there is a net heat loss, and so the temperature difference (ts −tr) must be used in the equation. It is more convenient to rewrite the equation in the form,

WORKED EXAMPLES

Que 1.An office 20m × 15m × 3.2m high has 30 occupants, 35m2 of windows, twenty five (2 × 30)W fluorescent tube light fittings, a photocopier with a power consumption of 1500W and conduction heat gains during summer amounting to 2 kW. Solar heat gains are 600W/m2 of window area. The sensible heat output from each person is 110 W. The room air temperature is not to exceed 240C when the supply air is at 130C.Calculate the supply air flow rate required and the room air change rate. State whether the answers are likely to be acceptable.

Solution:The sensible heat gains are computed thus:

Source Quantity (W/m2 x m2) SH (W)

Windows 600 x 35 21 000Occupants 110 x 30 3300Lights 25 x 2 x 30 1500Photocopier 1500Conduction 2000

SH gains 29 300 (29.3 KW)

Q = (29.3)/(24 – 13) x (273 + 13)/357 m3/s= 2.13 m3/s

Q = (NV)/(3600)N = (3600 x Q)/V

= (3600 x 2.13)/(20 x 15 x 3.2) air changes per hour= 8 air changes per hour.


Between 4 and 20 air changes per hour are likely to create fresh air circulation through an office without causing draughts and it is expected to be suitable for this application.

Que 2.A room has a heat loss in winter of 32kW and a supply air flow rate of 3.5m3/s. The room air temperature is to be maintained at 220C. Calculate the supply air temperature to be used.

Solution:

From smt

tt

SHkWQ s

sr

/357

273 3

Rearranging the equation to find the supply of air temperature ts required:

sss

srs

srs

tQSHtSHtQ

tSHSHtQtQ

tSHttQ

357273357

273357357

273357

That is

CSHQ

QtSHt

tQSHSHQt

rs

rs

0

357

357273

357273357

For this example,

Ct

t

s

s

075.29

325.3257

225.335732273

5.5 Refrigeration and Air Conditioning

Refrigeration and air conditioning is used to cool products or a building environment. Air conditioners and refrigerators work the same way. The refrigeration or air conditioning system transfer heat from a cooler low-energy reservoir to a warmer high-energy reservoir as shown in figure 5.1. Instead of cooling just the small, insulated space inside of a refrigerator, an air conditioner cools a room, a whole house, or an entire business. Air conditioners use chemicals that easily convert from a gas to a liquid and back again. This chemical is used to transfer heat from the air inside of a home to the outside air. The machine has three main parts. They are a compressor, a condenser and an evaporator. The compressor and condenser are usually located on the outside air portion of the air conditioner. The evaporator is located inside the house, sometimes as part of a furnace. That's the part that heats the house or building.


Figure 5.1. Schematic Representation of Refrigeration SystemSource: UNEP, 2004

The working fluid arrives at the compressor as a cool, low-pressure gas. The compressor squeezes the fluid. This packs the molecule of the fluid closer together. The closer the molecules are together, the higher its energy and its temperature. The working fluid leaves the compressor as a hot, high pressure gas and flows into the condenser. Students are urged to look at the air conditioner part outside a house or an office and identify the part with metal fins all around. The fins act just like a radiator in a car and help the heat go away or dissipate more quickly.

When the working fluid leaves the condenser, its temperature is much cooler and it has changed from a gas to a liquid under high pressure. The liquid goes into the evaporator through a very tiny, narrow hole. On the other side, the liquid's pressure drops. When it does it begins to evaporate into a gas. As the liquid changes to gas and evaporates, it extracts heat from the air around it. The heat in the air is needed to separate the molecules of the fluid from a liquid to a gas. The evaporator also has metal fins to help in exchange the thermal energy with the surrounding air.

By the time the working fluid leaves the evaporator, it is a cool, low pressure gas. It then returns to the compressor to begin its trip all over again. Connected to the evaporator is a fan that circulates the air inside the house to blow across the evaporator fins. Hot air is lighter than cold air, so the hot air in the room rises to the top of a room. There is a vent where air is sucked into the air conditioner and goes down ducts. The hot air is used to cool the gas in the evaporator. As the heat is removed from the air, the air is cooled. It is then blown into the house through other ducts usually at the floor level. This continues over and over and over until the room reaches the desire cooled temperature. The thermostat senses that the temperature has reached the right setting and turns off the air conditioner. As the room warms up, the thermostat turns the air conditioner back on until the room reaches the temperature.


Figure 5.2 Central Air-Conditioning and Heating SystemAdapted from Air-conditioning & Refrigeration Institute

5.6 Refrigeration Heat Transfer System

There are several heat transfer loops in a refrigeration system as shown in Figure 5.3. Thermal energy moves from left to right as it is extracted from the space and expelled into the outdoors through five loops of heat transfer:

Indoor air loop. In the left loop, indoor air is driven by the supply air fan through a cooling coil, where it transfers its heat to chilled water. The cool air then cools the building space.Chilled water loop. Driven by the chilled water pump, water returns from the cooling coil to the chiller’s evaporator to be re-cooled.Refrigerant loop. Using a phase-change refrigerant, the chiller’s compressor pumps heat from the chilled water to the condenser water.Condenser water loop. Water absorbs heat from the chiller’s condenser, and the condenser water pump sends it to the cooling tower.Cooling tower loop. The cooling tower’s fan drives air across an open flow of the hot condenser water, transferring the heat to the outdoors.


Figure 5.3. Typical Heat Transfer Loop in Refrigeration System

(Adapted from Bureau of Energy Efficiency, 2004)

5.7 Air-Conditioning Systems

5.7.1 Single ductThe single-duct system is used for a large room such as an atrium, a banking hall, a swimming pool, or a lecture, entertainment or operating theatre. It can be applied to groups of rooms with a similar demand for air conditioning, such as offices facing the same side of the building. A terminal heater battery under the control of a temperature sensor within the room can be employed to provide individual room conditions.

A variable air volume (VAV) system has either an air volume control damper or a centrifugal fan in the terminal unit to control the quantity of air flowing into the room in response to signals from a room air temperature sensor. Air is sent to the terminal units at a constant temperature by the single-duct central plant, according to external weather conditions. A reducing demand for heating or cooling detected by the room sensor causes the damper to throttle the air supply or the fan to reduce speed until either the room temperature stabilizes or the minimum air flow setting is reached.

5.7.2 Dual ductIn order to provide for wide-ranging demands for heating and cooling in multi-room buildings, the dual-duct system is used. Air flow in the two supply ducts may, of necessity, be at a high velocity (10–20m/s) to fit into service ducts of limited size. Air turbulence and fan noise are prevented from entering the conditioned room by an acoustic silencer.

In summer, the hot duct will be for mixed fresh and recirculated air, while the cold duct is for cooled and dehumidified air. The two streams are mixed in variable proportions by dampers controlled from a room air


temperature detector. During winter, the cold duct will contain the untreated mixed air and the air in the hot duct will be raised in temperature in the plant room. The system is used for comfort air conditioning as it does not provide close humidity control. It reacts quickly to changes in demand for heating or cooling when, for example, there is a large influx of people or a rapid increase in solar gain.

5.7.3 Packaged unitA packaged unit is a self-contained air-conditioning unit comprising a hermetically sealed refrigeration compressor, a refrigerant evaporator coil to cool room air, a hot-water or electric resistance heater battery, a filter, a water-or air-cooled refrigerant condenser and automatic controls. Packaged units can either be completely self-contained, needing only a supply of electricity, or piped to central heating and condenser cooling-water plant. Small units are fitted into an external wall and have a change-over valve to reverse the refrigerant flow direction. This enables the unit to cool the internal air in summer and the external air in winter.

Split system units have a separate condenser installed outside the building. Two refrigerant pipes of small diameter connect the internal and external equipment boxes. This allows greater flexibility in siting the noise-producing compressor.

5.8 Type of Refrigeration and Air conditioning

Two principle types of refrigeration plants found in industry: Vapour Compression Refrigeration (VCR) and Vapour Absorption Refrigeration (VAR). VCR uses mechanical energy as the driving force for refrigeration, while VAR uses thermal energy as the driving force for refrigeration. The electrically driven VCR system is the principal type commonly used. The VAR burns gas to produce cooling in the absorption cycle with a coefficient of performance of around 1. However the VCR has a coefficient of performance in the range 2-5, and it is cheaper to operate.

5.9 Assessment of Refrigeration and Air Conditioning5.9.1 Assessment of refrigeration1. TRTR is the cooling effect produced and is normally quantified as tons of refrigeration, also referred to as“chiller tonnage”.

3024

oip TTCQTR

Where: Q is mass flow rate of coolant in kg/hr Cp is coolant specific heat in kCal /kg deg C Ti is inlet, temperature of coolant to evaporator (chiller) in 0C

To is outlet temperature of coolant from evaporator (chiller) in 0C. 1 TR of refrigeration = 3024 kCal/hr heat rejected


2. Specific Power ConsumptionThe specific power consumption kW/TR is a useful indicator of the performance of a refrigeration system. By measuring the refrigeration duty performed in TR and the kW inputs, kW/TR is used as an energy performance indicator. In a centralized chilled water system, apart from the compressor unit, power is alsoconsumed by the chilled water (secondary) coolant pump, the condenser water pump (for heat rejection to cooling tower) and the fan in the cooling tower. Effectively, the overall energy consumption would be the sum of:

1. Compressor kW2. Chilled water pump kW3. Condenser water pump kW4. Cooling tower fan kW, for induced / forced draft towers

The kW/TR, or the specific power consumption for a certain TR output is the sum of:1. Compressor kW/TR2. Chilled water pump kW/TR3. Condenser water pump kW/TR4. Cooling tower fan kW/TR

3. Coefficient of PerformanceThe theoretical Coefficient of Performance (Carnot), (COPCarnot, a standard measure of refrigeration efficiency of an ideal refrigeration system) depends on two key system temperatures: evaporator temperature Te and condenser temperature Tc. COP is given as:COPCarnot = Te/(Tc – Te)The above expression indicates that higher COPCarnot is achieved with higher evaporator temperatures and lower condenser temperatures. But COP Carnot, is only a ratio of temperatures, and thus not takes into account the type of compressor. Therefore the COP normally used in industry is calculated from the following equation where the cooling effect is the difference in enthalpy across the evaporator and expressed as KW:

)(

)(

kWcompressortoinputPower

kWeffectCoolingCOP

5.9.2 Assessment of air conditioningFor air conditioning units, the airflow at the Fan Coil Units (FCU) or the Air Handling Units (AHU) can be measured with an anemometer. Dry bulb and wet bulb temperatures are measured at the inlet and outlet of the AHU or the FCU and the refrigeration load in TR is assessed as:

3024

outin hhQTR


WhereQ is the air flow in m3/hΡ is density of air kg/m3

Hin is enthalpy of inlet air kCal/kgHout is enthalpy of outlet air kCal/kg

Psychometric charts are normally employ to ease the calculation of hin and hout from dry bulb and wet bulbtemperature values which are measured during trials by a whirling psychrometer. Power measurements at compressor, pumps, AHU fans, cooling tower fans can be taken with a portable load analyzer.

5.10 Estimation of the Air Conditioning LoadThis is possible by calculating various heat loads, sensible and latent, based on inlet and outlet air parameters, air ingress factors, air flow, number of people and type of materials stored. An indicative TR load profile for air conditioning is presented as follows:

1. Small office cabins = 0.1 TR/m2

2. Medium size office i.e., 10 – 30 people occupancywith central A/C = 0.06 TR/m2

3. Large multistoried officecomplexes with central A/C = 0.04 TR/m2

References

1. Barr, R. (1980).The Construction of Buildings. Volume 3. The English Language Book Society and Granada

Publishing Limited, UK.

2. Chadderton, D.V. (2004) Building Services Engineering. Spon Press. London

3. Clements-Croome, D. (2003) Ventilated Buildings. E & FN Spon. London.

4. Duggal, K. N. (2004) Element of Environmental Engineering. S. Chand & Company Ltd. Ram Nagar. New

Delhi.

5. Energy Efficiency Guide for Industry in Asia. (www.energyefficiecyasia.org)

6. Air-conditioning, Heating, and Refrigeration Institute (www.ahrinet.org)


http://www.energyefficiecyasia.org/

http://www.ahrinet.org/


EXERCISES

1. Distinguish between the vacuum ventilation system and the plenum ventilation system and bring out

their relative advantages and disadvantages.

2. Comment on the statement: “Humidification is the heart of the air-conditioning system”

3. What are the general requirements of good system ventilation? How can these be ensured in the

natural system of ventilation.

4. Air enters an office through a 250mm × 200mm duct at a velocity of 5m/s. The room dimensions are

5m × 3m × 3m. Calculate the room air change rate.

5. State, with reasons, the appropriate combinations of natural and mechanical ventilation for the

following: (a) residence;(b) city office block;(c) basement boiler room;(d) industrial kitchen;(e) internal

toilet accommodation;(f) hospital operating theatre;(g) entertainment theatre.

6. A gymnasium of dimensions 20m × 12m × 4m is to be mechanically ventilated. The maximum occupancy

will be 100 people. The supply air for each person is to comprise 20 l/s of fresh air and 20 l/s of

recirculated air. Allowing 10% natural exfiltration, calculate the room air change rate, the air flowrate in

each duct and the dimensions of the square supply duct if the limiting air velocity is 8m/s.


CHAPTER SIX

FIRE SERVICES

6.1 Fire ServicesThe goals of firefighting are (in order of priority): personal safety, saving victims' lives, saving property, and protecting the environment. As such, the skills required for safe operations are regularly practiced during training evaluations throughout a firefighter's career. Prevention attempts to ensure that no place simultaneously has sufficient heat, fuel and air to allow ignition and combustion. Most prevention programs are directed at controlling the energy of activation (heat). In addition, a major duty of fire services is the regular inspection of buildings to ensure they are up to the current building fire codes, which are enforced so that a building can sufficiently resist fire spread, potential hazards are located and to ensure that occupants can be safely evacuated.

It is instructive to note that the Nigeria fire services cannot effectively and adequately provide the basic primary fire services enumerated above due to the deterioration of the country critical infrastructure1. In developed countries firefighters are essentially rescuers. They in addition to putting out hazardous fires that threaten civilian populations and property, they also rescue people from car incidents, collapsed and burning buildings and other such situations. The increasing complexity of modern industrialized life with anincrease in the scale of hazards has created an increase in the skills needed in firefighting technology and a broadening of the firefighter-rescuer's remit. They sometimes even provide emergency medical services. The fire services are known in some countries as the fire brigade or fire department. Firefighting and firefighters have become ubiquitous around the world, wildland areas to urban areas and on board ships.

6.2 Fire Classification

A building’s fire risk is classified according to its occupancy and usage. A fire is supported by three essential ingredients: fuel, heat and oxygen. The absence of any one of these causes an established fire to be extinguished. The fire-fighting system must be appropriate to the location of the fire and preferably limited to that area in order to minimize damage to materials, plant and the building structure. Radiation from a fire may provoke damage or combustion of materials at a distance. Structural fire protection can include water sprays onto steelwork to avoid collapse as used in the Concorde aircraft production hangar for example.

The system of fire-fighting employed depends upon the total combustible content of the building (fire load), the type of fire risk classification and the degree of involvement by the occupants. Fire escape design where children, the elderly or infirm are present needs particular care so that sufficient time is provided in the fire resistance of doors and partitions for the slower evacuation encountered. Fires are classified as shown in Table 6.1.

1Okeola, O. G. and A.W. Salami (2012). A Pragmatic Approach to the Nigeria’s Engineering Infrastructure Dilemma. Epistemic in

Science, Engineering and Technology.(2):1 pp 55-61

http://en.wikipedia.org/wiki/Fire_code

http://en.wikipedia.org/wiki/Emergency_medical_services

http://en.wikipedia.org/wiki/Fire_brigade

http://en.wikipedia.org/wiki/Fire_department

http://en.wikipedia.org/wiki/Wildfire


Table 6.1 Fire classifications

Classification Fire type Fire-fighting system

A Wood and textiles Water, coolsB Petroleum Exclude oxygenC Gases Exclude oxygenD Flammable metals Exclude oxygenE Electrical Exclude oxygen, non-conducting

Source: Chadderton (2004)

6.3 Fire Safety Engineering

Fire safety engineering can be defined as the application of scientific and engineering principles to the effects of fire in order to reduce the loss of life and damage to property by quantifying the risks and hazards involved and to provide an optimal solution to the application of preventive or protective measures. The components of this discipline that are related both to life safety and property safety and also non-mutually exclusive actions are identified as follow:

Control of ignition Control of means of escape Detection Control of spread of fire Prevention of structure collapse

Fire safety engineering is basically provision of both active and passive measures for effective protection from fire outbreak. Fire fighting system devices can be grouped it to two: manual and automatic and also as fixed or non-fixed in position of activation to extinguish fire or curtail spread.

6.3.1 Active measuresProvision of alarm systemsProvision of smoke control systemProvision of in-built fire-fighting or fire control systems Control of hazardous contents Provision of access for external fire-fighting Provision of a fire safety management system

6.3.2 Passive measuresAdequate compartmentationControl of flammability of the structure fabricProvision of fixed escape routesProvision of adequate structural performance.


6.4 Fire-Fighting Equipment

Fire-Fighting Equipments are categorized into five types for building. They are listed as follows:

1. Portable extinguishers2. Sprinklers and other fixed water sprays.3. Fixed wet or dry risers4. Fixed foam, carbon dioxide and dry powder extinguishers5. Fire doors, dampers and fire-resisting forms of construction.

6.5 Non Fixed Fire Extinguishers

6.5.1 Portable fire extinguishersPortable fire extinguishers are manually operated first-aid appliances from where extinguishing agents are expelled under pressure to stop or limit the propagation of small fires at early stages. They can be incorporated in a building having sprinkler and hose reel. However, they cannot be employed successfully for large fires. Fire blankets are provided in kitchens where burning pans of oil or fat need to be covered or personnel need to be wrapped to smother ignited clothing.

6.5.1.1 Water typeWater is used on Class A fires. Because of its cooling properties, it is preferable for use in fires with tendency to reignite if it is not adequately cooled. Water must not be used on petroleum or on live electrical equipment because water is a conductor of electricity.

6.5.1.2 Dry powder typeDry powder extinguishers contain from 1 to 11 kg of treated bicarbonate of soda powder pressurized with CO2, nitrogen or dried air. It is generally suitable for all classes of fire risks and most especially for fires in inflammable liquids. The powder interrupts the chemical reactions within the flame and produce rapidlyflame knockdown. The powder is non-conducting and does little damage to electric motors or appliances. A deposit of powder is left on the equipment.

6.5.1.3 Foam typePortable foam extinguishers may contain foaming chemicals that react upon mixing or a CO2 pressure-driven foam. They cool the combustion, exclude oxygen and can be applied to wood, paper, textile or liquid fires. It can be used on Class B fires involving liquids or liquefied solids such as oil or grease.

6.5.1.4 Carbon dioxide typePressurized CO2 extinguishers is suitable for use on Class B and E fires involving inflammable liquids and those complicated with the pressure of live electricity respectively . They leave no deposit and are used on small fires involving solids, liquids or electricity. They are recommended for use on delicate equipment suchas electronic components and computers. The CO2 vapour displaces air around the fire and combustion ceases. There is minimal cooling effect and the fire may restart if high temperatures have become established. Water-cooling backup is used where appropriate. Table 6.2 summarizes their types and applications.


Table 6.2 Type of portable fire extinguisher

Group Extinguishing agent Fire type Action Colour

1 Water Class A Cools Red

2 Dry powder All Flame interference Blue

3 Foam Class B Excludes oxygen Cream

4 Carbon dioxide (CO2) Classes B,E Excludes oxygen Black

5 Vaporizing liquid Small fires, Flame interference GreenMotor vehicles, Class E

Source: Chadderton (2004)

6.6 Fixed Fire-Fighting InstallationVarious fire-fighting systems are employed in a building so that an appropriate response will minimizedamage from the fire and the fire-fighting system itself. Backup support for portable extinguishers may be provided by a hose reel installation and this can be used by staff while the fire brigade is called.

Some public buildings, shops and factories in developed countries are protected by a sprinkler system, which only operates directly over the source of fire. This localizes the fire to allow evacuation. Where petroleum products are present, a mixture of foam and water is used. The type of fire fighting installation for multistorey buildings can take the form of a wet or dry riser which is a function of the building type andgovernment regulation.

6.6.1 Dry riserThe dry riser normally does not contain water until charged with water by fire brigade during fire outbreak. The fire brigade connects the suction side of their pump to the fire hydrant normally located close to thebuilding. Students are urged to have a look at the fire hydrant meant for this purpose for University Senate building. Thereafter, the pump forces water into the riser. The firemen can then enter the building and connect their hose reels to the landing valve fitted to the riser. It is instructive to note that dry riser is functionally an extension of firemen’s hose. The risers are for effectiveness installed near the lobby approach staircase and this is exactly the location of dry riser in the senate building. It is recommended that dry risers be electrically earthed.

6.6.2 Wet riserThe wet riser is always charged with water under pressure and hydrants are connected to the riser on each floor. Wet risers are required on buildings more than twenty storeys or 60m in height above the ground level dedicated for fire-fighting purposes. This is also available at the University senate building.


6.6.3 Hose reelsHose reels are a rapid and easy to use first-aid method, complementary to other systems and used by the building’s occupants. They are located in clearly visible recesses in corridors so that no part of the floor is further than 6m from a nozzle when the 25mm bore flexible hose is fully extended. The protected floor area is an arc 18–30m from the reel depending on the length of hose. A minimum water pressure of 200 kPa is available with the 6mm diameter nozzle.

This produces a jet 8m horizontally or 5m vertically. Minimum water flow rate at each nozzle is 0.4 l/s, and the installation should be designed to provide not less than three hose reels in simultaneous use: a flowrate of 1.2 l/s. The local water supply authority might allow direct connection to the water main and there may be sufficient main pressure to eliminate the need for pressure boosting. Pump flow capacity must be at least 2.5 l/s. The stand-by pump can be diesel-driven. Flow switches detect the operation of a hose and switch on the pump. This type of installation is not available on the campus and neither in Ilorin metropolis.

6.6.4 Automatic sprinklerHigh-fire-risk public and manufacturing buildings are protected by automatic sprinklers. In some developed countries this is a statutory requirement if the building exceeds a volume of 7000m3. Loss of life is very unlikely in a sprinkler-protected building. Sprinkler water outlets are located at about 3m centres usually at ceiling level and spray water in a circular pattern. A deflector plate directs the water jet over the hazard or onto walls or the structure.

6.6.5 Carbon dioxideCarbon dioxide is used in fixed installations protecting electrical equipment such as computer rooms, transformers and switchgear. Heat or smoke detectors sound alarms and CO2 gas floods the room from high-pressure storage cylinders. Pipe work transfers the CO2 to ceiling and under floor distributors. System initiation can be manual or automatic but complete personnel evacuation is essential before CO2 flooding is allowed.

6.6.6 Fire detectors and alarmsDetection of a potentially dangerous rise in air temperature or pressure or the presence of smoke is required at the earliest possible moment to start an alarm. Fire detectors and alarms are not fire-fighting equipment. However, their installation provides warning of fire thus reducing the time taken for the fire to be brought under control and subsequently extinguished. Means of detection can be combined with security surveillance. Fire detection takes the following forms:

Hazard detectors Ionization smoke detector Visible smoke detector Laser beam Close-circuits television Smoke ventilation


6.7 Hazards caused by fire

The primary risk to people in a fire are not the flames themselves but the smoke inhalation and it is the most common cause of death in a fire. The risks of smoke include:

suffocation due to the fire consuming or displacing all of the oxygen from the air poisonous gases produced by the fire as products of combustion aspirating heated smoke that can burn the inside of the lungs and damage their ability to exchange

gases during respiration

Additional risks of fire include the following:

smoke can obscure vision, potentially causing a fall, disorientation, or becoming trapped in the fire; structural collapse.

To combat these potential effects, firefighters carry self-contained breathing apparatus (SCBA; an open-circuit positive pressure compressed air system) to prevent smoke inhalation. These are not oxygen tanks; they carry compressed air. SCBA usually hold 30 to 45 minutes of air, depending upon the size of the tank and the rate of consumption during strenuous activities.

Obvious risks are associated with the immense heat. Even without direct contact with the flames conductive heat can create serious burns from a great distance. There are a number of comparably serious heat-related risks: burns from radiated heat, contact with a hot object, hot gases (e.g., air), steam and hot and/or toxic smoke. Firefighters are equipped with personal protective equipment (PPE) that includes fire-resistant clothing (Nomex or polybenzimidazole fiber (PBI)) and helmets that limit the transmission of heat towards the body. However, there is no PPE that can completely protect the user from the effects of all fire conditions.

Heat can make flammable liquid tanks violently explode producing what is called a BLEVE (boiling liquid expanding vapor explosion). Some chemical products such as ammonium nitrate fertilizers can also explode. Explosions can cause physical trauma or potentially serious blast or shrapnel injuries.

http://en.wikipedia.org/wiki/Smoke_inhalation

http://en.wikipedia.org/wiki/Asphyxia

http://en.wikipedia.org/wiki/Oxygen

http://en.wikipedia.org/wiki/Atmosphere_of_Earth

http://en.wikipedia.org/wiki/Lung

http://en.wikipedia.org/wiki/Gas_exchange

http://en.wikipedia.org/wiki/Gas_exchange

http://en.wikipedia.org/wiki/Falling_%28accident%29

http://en.wikipedia.org/wiki/Disorientation

http://en.wikipedia.org/wiki/Structural_collapse

http://en.wikipedia.org/wiki/Self-contained_breathing_apparatus

http://en.wikipedia.org/wiki/Conduction_%28heat%29

http://en.wikipedia.org/wiki/Burn

http://en.wikipedia.org/wiki/Smoke

http://en.wikipedia.org/wiki/Personal_protective_equipment

http://en.wikipedia.org/wiki/Nomex

http://en.wikipedia.org/wiki/Polybenzimidazole_fiber

http://en.wikipedia.org/wiki/Explosion

http://en.wikipedia.org/wiki/BLEVE

http://en.wikipedia.org/wiki/Ammonium_nitrate

http://en.wikipedia.org/wiki/Fertilizer

http://en.wikipedia.org/wiki/Physical_trauma

http://en.wikipedia.org/wiki/Shrapnel_shell


References1. Clements-Croome, D.(2003)Naturally Ventilated Buildings. E & FN Spon. London.2. Purkiss, J. A. (1996) Fire Safety engineering of structures. Butterworth Heinemann. UK3. Chadderton, D.V. (2004) Building Services Engineering. Spon Press . London4. Fire Fighter. (www.wikkipedia.org)

EXERCISES1. Itemize the goals of firefighting in order of priority.2. List the sources of fire within a building and describe how they may develop into a major conflagration.

State how the spread of fire is expected to be limited by good building and services practice.3. List the ways in which fire and smoke are detected and fire-fighting systems are brought into action.4. Describe the methods and equipment used to fight fires within buildings in their likely order of use.5. State the principal hazards faced by the occupants of a building during a fire outbreak. How are these

hazards overcome? Give examples for housing, shops, cinemas, office blocks, single-storey factories and local government buildings.

6. How are water and foam systems used to protect building structures from fire damage?7. Compare a fixed sprinkler installation with other methods of fire-fighting. Give three applications for

sprinklers.8. Explain how sprinkler systems function, giving details of the alternative operating modes available. State

the suitable sources of water for sprinklers.8. Tabulate the combinations of fire classification and types of extinguisher to show the correct application

for each. State the most appropriate fire-fighting system for each fire classification and show which combinations are not to be used.


CHAPTER SEVEN

LIFTS, ESCALATORS, STAIRS, and VACUUM CLEANERS

7.1 Lifts, Escalators, Stairs and Vacuum Cleaners

Lifts, Escalators and stairs belong to Vertical Transportation System.

7.1.1 LiftThe three common types of Lifts are: (1) Electric Traction (Cable) Lift (2) Hydraulic Lift and (3) Rack and Pinion Lift. In order for a lift to deliver efficient service the type and number of lifts must take into consideration some important factors such as type of building and nature of its occupancy. The many details and dimensions of lifts are contained in the manufacturer’s catalogues which can serve as a guide during the design stage of a particular building and subsequently at implementation.

7.1.2 EscalatorAn escalator is a moving staircase. It is a conveyor transport device for carrying people between floors of a building. The device consists of a motor-driven chain of individual, linked steps that move up or down on tracks, allowing the step treads to remain horizontal. Escalators are used around the world to move pedestrian traffic in places where elevators would be impractical. Principal areas of usage include department stores, shopping malls, airports, transit systems, convention centers, hotels, arenas, stadiumsand public buildings. The benefits of escalators are many. They have the capacity to move large numbers of people, and they can be placed in the same physical space as one might install a staircase. They have no waiting interval (except during very heavy traffic), they can be used to guide people toward main exits or special exhibits, and they may be weatherproofed for outdoor use.

Escalators in a Copenhagen Metro station, Denmark

http://en.wikipedia.org/wiki/Conveyor_transport_%28disambiguation%29

http://en.wikipedia.org/wiki/Electric_motor

http://en.wikipedia.org/wiki/Pedestrian

http://en.wikipedia.org/wiki/Elevator

http://en.wikipedia.org/wiki/Department_store

http://en.wikipedia.org/wiki/Shopping_mall

http://en.wikipedia.org/wiki/Airport

http://en.wikipedia.org/wiki/List_of_transit_systems

http://en.wikipedia.org/wiki/Convention_center

http://en.wikipedia.org/wiki/Hotel

http://en.wikipedia.org/wiki/Arena

http://en.wikipedia.org/wiki/Stadium


7.1.3 Stairs

Stairs (staircase, stairwell, or stairway) are designed and constructed to bridge a large vertical distance by dividing it into smaller vertical distances, called steps. Stairs may be straight, round, spiral or helical. Stairs may consist of two or more straight pieces connected at angles. The stairs consist of the following components: steps, tread, and riser. The step is composed of the tread and riser. Tread are the part of the stairway that is stepped on. It is constructed to the same thickness as any other flooring. The riser are the vertical portion between each tread on the stair. All staircases are normally provided with the balustrade. This is the system of railings and balusters that prevents people from falling over the edge.

7.1.4 Vacuum cleaner

A vacuum cleaner is a device that uses an air pump to create a partial vacuum to suck up dust and dirt, usually from floors, and optionally from other surfaces. The dirt is collected by either a dustbag or a cyclonefor later disposal. Vacuum cleaners which are used in homes as well as in industry exist in a variety of sizes and models— small battery-operated hand-held devices, domestic central vacuum cleaners, huge stationary industrial appliances that can handle several hundred litres of dust before being emptied and self-propelled vacuum trucks for recovery of large spills or removal of contaminated soil.

A conventional vacuum cleaner is actually made up of only six essential components as listed below:

An intake port (may include a variety of cleaning accessories) An exhaust port An electric motor A fan A porous bag A housing that contains all the other components

http://en.wikipedia.org/wiki/Vertical_direction

http://en.wikipedia.org/wiki/Stair_riser

http://en.wikipedia.org/wiki/Balustrade

http://en.wikipedia.org/wiki/Pump

http://en.wikipedia.org/wiki/Vacuum

http://en.wikipedia.org/wiki/Suction

http://en.wikipedia.org/wiki/Dust

http://en.wikipedia.org/wiki/Cyclonic_separation

http://en.wikipedia.org/wiki/Central_vacuum_cleaner

http://en.wikipedia.org/wiki/Vacuum_truck


When the vacuum cleaner is connected to the electricity it triggers the following operations:

1. The electric current operates the motor which is attached to the fan.2. As the fan blades turn, they force air forward, toward the exhaust port.3. When air particles are driven forward, the density of particles (and therefore the air pressure)

increases in front of the fan and decreases behind the fan.

As long as the fan is running and the passageway through the vacuum cleaner remains open, there is a constant stream of air moving through the intake port and out the exhaust port. The key principle behind the flowing stream of air collecting dirt’s and debris from surfaces/beneath rug, carpet etc is friction.

References

Vacuum Cleaner. (http://home.howstuffworks.com/vacuum-cleaner.htm)

Escalator. (http://en.wikipedia.org/wiki/Escalator)

http://electronics.howstuffworks.com/motor.htm

http://en.wikipedia.org/wiki/Escalator


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