chapter 3 4 5

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Dr Satesh Namasivayam

3.0 Air Handling Equipment

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The following components can be found in air handling units.

Fan sections for supply air and return air/relief air fans.

Cooling section for chilled water or refrigerant cooling coils.

Heating section for hot water or steam coils a gas heat exchanger or an electricalcoil.

Humidification section for extra humidity if required.

F ilter sections for prefiltering, filtering and post filtering.

Air mixing sections for outdoor air to mix with recirculated air.

Discharge air plenum.

Other components for electrical power controls operating a motor, drainage etc.

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Heat transfer occurs at the heat exchange section of the air hauling unit. Severalheating and cooling media are common including water, steam, refrigerant andelectric.

Water coils are the most common components for transferring heat withcirculating air. Coils are normally constructed of copper tubes and aluminium fins.A special coating and special materials such as stainless steel may be appropriatefor corrosive environments including salt spray and industrial pollution.

The performance of a water coil depends on the arrangement of the fin tubeswhich can either be staggered or stacked. F in tubes are great for increasing heattransfer through the addition of fins onto tubes, which increase heat transfersurface area.

The number or rows of fin tubes can also increase the performance of the watercoil.

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Steam coils are similar to water coils but their design is to ensure easy drainage of condensate.

Electrical coils may be designed as part of the air handling unit. The heatingelements are usually made from a nickel chromium alloy. Electrical coils have verylow resistance to airflow so higher velocities can be used than water or steamcoils.

When the cooling medium is a refrigerant, the cooling coil is designed to allowrefrigerant to vaporize in the coil, thus absorbing heat from the air. These types of systems are normally called Direct Expansion (DX) Coils.

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Air in urban environments contain impurities in the form of gas, liquid and solidparticulates. Many of these particulates are classified as pollutants such as smog,smoke and pollen. In addition the air may contain bacteria and viruses which areall detrimental to health.

Air can be cleaned by passing it through a liquid curtain or a spray (a chemicalsolution to remove particulates but these solutions usually serve other functionsas well such as cooling or humidification) or through a dry filter medium.

There are 3 major operating characteristics of air filters.

1.Efficiency2.Resistance to airflow3.Dust holding capacity.

To rate the efficiency of air filters, four types of tests are performed.

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Dust weight arrestance test. The particles of synthetic dust of various sizes are fedinto the air cleaner (filter) and the fraction of weight of the dust removed isdetermined.

Dust spot efficiency test. Atmospheric dust is passed into the air cleaner and thediscoloration is observed.

Fractional efficiency or penetration test. Uniform sized particles are fed into the air

cleaner and the percentage removed by the cleaner is determined.

Particle size efficiency test. Atmospheric dust is fed into the air cleaner and airsamples taken upstream and downstream are counted to determine the efficiencyof removal of each size particle.

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Typical types of air filters.

F ilters are normally classified according to the following criteria.

1.F iltration principle filtration by medium or by electrostatic precipitation.2.Impingement dry medium or viscous impingement3.Configuration F lat or extended surfaces4.Service life one time disposal or renewable

5.Performance low to medium efficiency, high efficiency particulate air (HEPA) orultra high efficiency (UEPA)6.Special features odor absorption, disposal of radioactive material.

Air filters are normally used for the following applications.

1.For residential and commercial buildings low efficiency to medium efficiency.2.For health care and labs HEPA

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3. For hazardous materials4. For odor removal adsorption type filters are used to remove gaseous

contaminants from the airstream (HEPA).

Air mixing is an important component where the outside air required forventilation of a building is usually ducted to the inlet of an air handling unit bymixing with return air. The 2 airstreams must be balanced with dampers tointroduce sufficient outside air for ventilation but not so much as to require

excessive condition during extreme weather.

The mixing box section of the air-handling unit must be carefully designed toprevent stratification of cold outside air in winter which can freeze the tubesof coils. Low airflow into mixing boxes in cold weather results in low velocitythrough the mixing sections, stratification of cold air and the risk of freezingthe coils.

Large airflow can over pressurise a building unless relieving of this air can occur.

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To channel the air from the air handling unit, ductwork forms part of the airhandling system and includes the supply, return, outside air, relief air and exhaustair ducts. Ducts are usually fabricated from sheet metal such as galvanised steelaluminium or stainless steel, thus ductwork is also called sheet metal workalthough some can be made from plastics.

Duct systems for supplying air may be classified as low pressure /velocity, mediumpressure/velocity and high pressure/velocity. For a given airflow, lower velocities

reduce friction in the duct and power for distribution. In addition lower velocitiesreduce air noise.

Low velocity ductwork is used for small airflow requirements generally at finalbranches of a system. It can also be used for large air quantities where space isavailable for larger ductwork and the initial cost for the extra duct material iswarranted.

Higher velocity flow is generally used for conserving space and duct materials.

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4 .0 Plumbing Equipment and Systems

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4.1 Domestic Water Distribution Systems

Domestic water system loads can be grouped into:

1.Plumbing facilities2.Food service preparation, refrigeration, washing, dining, etc.3.Laundry4.Heating and cooling systems

5.Exterior lawn and plant irrigation, reflecting pools, fountains, hoses, etc.6.Pools7.Research and Process lab equipment, commercial and industrial processes,computer equipment8.F ire protection (if combined with a domestic system)9.Others

The required water capacity of a building depends on the coincidental peak loaddemand (CPLD) of all load categories based on an assumed time of day in theheavy demand season.

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For example the highest CPLD for an office building would be noontime in thesummer when the building is fully occupied, plumbing facilities are in heavy useand air conditioning is near its peak.

For an apartment building it would be around dinnertime in the summer whenmost people are home taking showers, washing or preparing meals.

Water demand for plumbing facilities depends on the number and type of fixturesactually involved. Each plumbing fixture is assigned a water supply fixture unit(wsfu) rating representing the relative water demand for its intended operatingfunctions.

For example a lavatory that does not demand a heavy flow of water is given a wsfyof 1 and a flush valve operated water closet that demands a heavy flow of water isgiven a wsfu of 10.

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Example 4.1

If an office building is installed with 10 water closets, 4 urinals and 8 lavatorieswhat is the total wsfu installed? You may assume that the building is usingpredominantly flush valves.

You may use the following information.

Load value for water closet (flushometer) wsfu = 10Urinals (flushometer) wsfu = 5Lavatories wsfu = 8

Example 4.2

For the office building in the example above, what is the estimated demand forcold water in GPM?

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You may use the following information

For office buildings using F lush Valves

@wsfu 100 Demand GPM = 68 GPM@wsfu 160 Demand GPM = 83 GPM

Water demand for food services varies considerably between residential andcommercial equipment. In general, food preparation and cooking does not requiremuch water. The major demand for water is for washing in sinks or dishwashers.

Water demand for laundry also varies between residential and commercialequipment.

Heating and cooling systems are closed circuit systems that do not requireconstant water replacement

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Example 4.3

IF the office building in example 4.1 has a gross floor area of 25000 sq ft and a100-ton chiller is installed, what are the water demands for the cooling system andthe annual water consumption if the system operates 12 hours a day for 200 days?

You may assume that the circulating rate of the condensing water is 3 GPM/tonwith 4% of water makeup

Water usage for exteriors depends on the size of the lot and the portion that islandscaped.

Swimming pools vary widely in size from residential pools to Olympic sized pools.

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Example 4.4

If a swimming pool contains 100000 gallons of water and the circulating pump isdesigned to change the water in 6 hours, what is the capacity of the pump andwhat is the water demand load for makeup? You may assume that the demandload for makeup water is 2% of the pump circulation rate.

The use of water for research and processing in special buildings could be veryhigh.

Normally the water supply for fire protection systems is not included in thedomestic water system, however 2 components of a fire protection system may becombined with the domestic water system.

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Example 4.5

If the office building in example 4.1 is required to have one standpipe (fire pipe 500 GPM) and two rooms with 15 sprinklers each what demand load should beincluded in the domestic water system.

You may use the following information.For the standpipe, 500 GPMFor the water demand in one of the two areas with sprinklers = 15 sprinklers (1 @30 GPM) = 450 GPM.

Example 4.6

For the office building in example 4.1, estimate the gross and net system demandflowrate by considering the calculation you have performed in the previousexamples.

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Pressure drops can occur in pipes. The pressure losses can be due to friction.Pressure losses in pipe fittings such as elbows, tees, valves and controls aresignificantly higher that in straight pipes. The pressure losses for fittings anddevices is given in the unit of equivalent lengths (EL).

Example 4.7

If the most remote part of the plumbing system for the commercial building isabout 200 ft from the service entrance, what is the pressure loss due to the pipingsystem?

You may assume that the EL for this pipe system is 100 ft.

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Water required at floors higher that the water service entrance to the buildingmust overcome the force of gravity which provides static pressure owing to thedifference in elevation. F rom simple units of conversion, 1 psi = 2.31 ft w.c. Thus abuilding 231 ft high the plumbing fixtures on the top floor will require 100 psi of static water pressure to reach that elevation.

Example 4.8

IF a commercial building is 70 ft in height above the water service entry to thebuilding, what should be the minimum water pressure to serve the top floorplumbing fixtures?

The following water pressures are to be added.

Water meter 15 psi

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Tutorial Sheet 3

1. For the following office building calculate the cooling loads.a. The total heat gains to space (roof, doors, windows, lighting, appliances,

occupants sensible load, infiltration sensible load)b. The latent heat (occupants latent load, infiltration latent load)

Design conditions inside (78 oF), outside (95 oF )Construction wall, type F, U factor, 0.103, roof 2 insulation over metal deck, U factor, 0.16,

windows U factor , 0.56, shading coefficient, 0.65, doors U factor , 0.64, ceiling U factor, 0.30Outside air infiltration, ½ air exchange per hour, ventilation, 500 C F MLighting - 30 fluorescent fixtures with four 40 W lamps each, ballast factor 1.2: all heat to occupied

space.Appliances allowance of 1.5 W per square footOccupants (10) adults, general office workBtuh, sensible/occupant = 250Btuh, latent/occupant = 250W room = 0.017W oa = 0.010

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A TETD SC SHGF

Roof 30X50 81

Walls

North 11X50 15

South 11X50 26

East 11X30 37

West 11X30 19

Doors

North 3X7 21

East 3X7 28

Windows

North (3) 5X5 0.65 28

South (4) 5X5 0.65 29East (1) 5X5 0.65 26

West (2) 5X5 0.65 216

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Tutorial Sheet 3

2. Name the components in air-handling units and briefly describe them.

3. Describe what are water coil, steam coil, DX coil and electrical coil systems.

4. What are the 3 major characteristics of filters and how can filters be tested fortheir efficiency?

5. How are air filters classified?

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Tutorial Sheet 3

6. For a particular fan, the following information has been given.

Air quantity 33000 cfmStatic pressure 1.6 in wgFan speed 297 rpmBrake horsepower 10

What is the capacity, static pressure and horsepower if the speed is decreased to123 rpm?

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A hot water system is a subsystem of the domestic water system. Thedemand for hot water is included in that for domestic water. The useof hot water in buildings vary considerably from very little in officetype buildings to high in residences, restaurants and hotels.

The design of the hot water system is very similar to that of a coldwater system but with several added condsiderations.

Hot water is normally generated in the building by the installation of water heaters using oil, gas, steam or electricity as an energy source.

The demand flow rate (GPM) of hot water stays the same for aparticular application however the amount of water used dependson the length of time one uses hot water.

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Plastic is used increasingly for water distribution because of its lowercost, corrosion resistance, and low potential for scaling.

Pipes are usually insulated with thermal material such as fiberglass,mineral wool or foam plastic to maintain the temperature of water foreither chilled or hot water.

When the noise of water flowing in a pipe is annoying or disturbing aquiet space such as a conference room or residence, both cold and hotwater piping should be insulated for both thermal and acousticalpurposes.

When the ambient temperature to which the piping system is exposedis changed, the relative coefficient of expansion between the buildingand the piping material is different, a differential material will becreated between the piping and the building.

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Differential movement will also occur when the water temperature in the

pipe changes.F

lexibility must be built in the pipe for these changes. Themethods commonly used involve installing expansion loops or joints tocompensate for the physical expansion (or contraction) of the pipes. SeeF igure 8.14.

The water distribution system must be safeguarded against contamination.This is normally done by installing a check valve which allows water to flowin only one direction, a vacuum breaker which automatically opens thepiping to atmospheric pressure. When the piping drops below atmospherethe foul material in the pipe will not flow into the water distributionsystem.

A backflow preventer (B F P) is used at the entrance to the main watersupply and at critical branches to stop water from flowing backward intothe main system should there be a sudden drop in water pressure at themains owing to a break in the underground main pump failure or closing of

supply valves for maintenance activities.

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When the flow of water is abruptly stopped the kinetic energy of the

water must be stopped. If this does not happen the energy will beconverted into noise and vibration known as a water hammer.

To avoid this an air chamber is created at the end of a branch whichacts as a cushion. If space is limited mechanical shock absorbers canalso be installed. They consist of a large neoprene chamber thatoperates on the same principle. This is also known as a waterhammer arrester.

Water pressure required for water distribution is determined from anumber of design parameters.

Water demand (flow rate) Elevation Pipe sizes Material Routing

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Type of fittings

AccessoriesAll these factors contribute to pressure loss. If the water pressure doesnot have sufficient pressure to overcome the total pressure loss then apressure must be boosted using a pump. However pumps use energyand require maintenance and therefore must be avoided wherepossible.

4.2 Plumbing F ixtures and Components

The following are some plumbing fixtures commonly used for buildingservices.

Water closets (WC) Sinks (SK) Bidets (BD) Urinals (UR) Bathtubs (BT)

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Service sinks (SS)

Kitchen sinks (KS) Lavatories (LAV or LV)

Plumbing fixtures are normally made of dense, impervious materials.

WCs are normally made of vitreous china with hollow interior walls

to direct passage of water and integral water seal trap to separatethe fixture from the drainage system. WCs can be classifies asfollows.

Method of mounting: floor mounted or wall mounted. Wall mounted

are more costly to install, but cleaning is easier.Cleansing action of bowl: siphon jet and wash down varieties are thequietest in operation. The blow out type is more noisier.Method of water control: wither using a gravity tank, flushometer,pressure tank and vacuum type.

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F lushometer types are equipped with a flush valve.

Pressure tank types are equipped with a pressure tank within aconvention gravity tank.

The vacuum type operates on a central vacuum piping system.

For urinals, siphon jet, blow out and wash down varieties areavailable. They are also either wall mounted or floor mounted.

Lavatories are designed in a variety of sizes and shapes and fittings.

Stainless steel sinks are preferred because they are durable and easyto clean. They are mounted to the floor, wall or a recess in the floorand they can also be made of enameled cast iron, precast terrazzo,

or reinforced glass fiber.

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Bathtubs are made of cast iron, porcelian enamel on pressed steel

or fiberglass reinforced plastics.

Bidets are small baths for personal hygiene.

To prevent the backup of sewer gas into a building the drainage

connection of plumbing fixtures must be connected by means of atrapped seal.

The trap is a portion of piping in a U-shape and filled with a waterseal. It operates in a principle that two columns of water balanced

within the two legs of the trap prevents sewer gas, noxious fumesor vermin passing from the sewer side to the building.

In some cases, if not used often, the water evaporates. In this caseif some non-evaporative liquid is used to cover the water seal

liquid.

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To avoid the possibility of soil or waste contamination of thewater supply system, connections between the water supplysystem and the plumbing fixtures must be separated verticallythrough an air gap. This system is also similarly known as abackflow prevention system which can also make use of valves or

a vacuumed section.

A bathtub does not demand a high demand of water flow,however its drainage load is high. For this reason a fixture mayhave a water supply rating different from its drainage rating.Instead of a wsfu we have a dfu a drainage fixture unit. Thismeasures the probable discharge into the drainage systembyvarious plumbing fixtures.

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4.3 Sanitary Drainage Systems.

The following are the definitions of several terms commonly usedin drainage systems.

Waste (liquid) liquid discharged from water consumingequipment.

Sanitary waste liquid discharged from plumbing fixtures. Soil (waste) liquid discharged from plumbing fixtures

that contain solid matter. Sanitary drain main drain of the sanitary drainage system. Sanitary sewer extension of the sanitary drain at the

exterior of a building for a connection to thepublic sewer.

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The following are the definitions of several terms commonly usedin drainage systems.

Storm water rain water collected from building roofs andfrom exterior areas. Depending on the purity

of the water it can be classified as waste orfor re-use.

Storm drain main drain of the storm water drainagesystem

Storm sewer sewer that is exterior to a building and thatcontains storm water only.

Comb. sewer sewer that contains sanitary waste and!combination storm water.

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A sanitary drainage system is thus a drainage system designed to carry

away sanitary and soil wastes from building to a public sewer or to asewage disposal plant. The system may be designed to flow by gravitywithout mechanically or electrically powered equipment or it may bedesigned to flow under pressure by pumping.

Some of the important terms associated with a drainage-waste ventingsystem (DWV) and their definitions are as follows.

Stack vertical portion of a DWV piping systemWaste stack vertical portion of a waste piping system

Soil stack vertical portion of a soil piping systemStack vent open ended extension of a waste or soil stack above the

highest horizontal drain connected to the stack.Branch interval Section of a soil or waste stack corresponding to one story

in height

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Vent Pipe open to atmosphereVent stack Stack that does not carry waste of any kind and thatis installed primarily for providing circulation of air toand from any part of the DWV system

Branch vent branch vent of the venting system.

Common vent vent connected at the common connection of thetwo fixtures.

Circuit vent branch vent that serves two or more traps and thatextends from the downstream side of the highestfixture connection of a horizontal branch to the ventstack.

Crown vent vent connected to the crown of a trap.Developed length total length of a pipe measured along the

centerline of the pipe.

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The materials used for sanitary drainage systems are as follows.

Aboveground cast iron, plastics, copper and stainless steel.Underfloor (drains) plasticsUnderground (sewer) vitrified clay pipe, PVC sewer plastics with

pipe stiffness.The under nine no need to know.

All pipes and fittings must have the joining methods appropriatefor the material, such as the following.

Caulked joints for cast iron pipes. Threaded joints for steel or heavy wall plastic pipes. Soldered joints for copper DWV pipes. Brazed joints for heavy copper pipes only. Compression joints for cast iron and plastic pipes.

F lexible compression and solvent joints for plastic pipes.

Transition joints for joining different material.

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The capacity of (waste or soil) drainpipes of the DWV systemdepends on two major factors.

1. The slope of the pipes2. The dfu they serve

All horizontal drainlines should have a uniform downward slope inthe direction of flow. If the slope is not steep enough solidcontents in the liquid may drop out. If the slope is too steep,turbulence flow and erosion of the pipes may occur.

The capacity of vent pipes depends on three major factors, thesize of the stack, the number of dfu connected on the stack andthe developed length of the vent pipe.

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There are several design guidelines for a DWV system as follows.

1. The minimum size of DWV pipes is governed strictly by theplumbing code.

2. The piping design should be optimized through the propercoordination of pipe chase sizes and locations.

3. The layout of the toilet room is usually initiated by the

architectural plan, however it s the responsibility of theplumbing engineer to determine the need for floor drains andto coordinate with the architect on the location of thecleanouts etc.

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4. Indirect waste shall be provided for all equipment that containstoxic or harmful chemicals. The drainage shall be piped to aseparate receptor for sedimentation, nuetralization, or filtrationbefore being discharged into the public sewer system.

5. Other than intermittent discharges into the drainage system fromdishwashing and laundry equipment with water temperature of 140 oF or above, no high temperature waste or steam pipe shall

discharge into the drainage system without subcooling theeffluent prior to connecting the sanitary sewer.

6. All plumbing fixtures or drainage equipment without a built-intrap must be connected through an external trap.

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7. All traps must be vented.

8. All horizontal drainage piping shall be installed in alignment at auniform slope.

9. Cleanouts shall be installed at the base of drainage stacks and atthe beginning of main horizontal branches so that the entire DWVsystem can be cleaned and cleared to prevent clogging.

10.Grease laden waste from kitchens should be piped directly to thebuilding drain or stack whenever practical. A grease trap shall beinstalled for commercial kitchens prior to connection to the wastepipe.

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11. Waste containing high volumes of insoluble matter, such as sand,plaster, etc shall be intercepted by sediment basins or catch basins priorto discharging into the sewer.

12.Waster containing oil, such as drains from a commercial garage, shall beconnected through an oil interceptor.

4.4 Sewage Treatment and Disposal

To protect water resources and the greater environment, all waste frombuildings and industrial processes must be treated to meet certainstandards of quality. Domestic sewage from dwellings and DWV systemsin buildings are permitted to be discharged into the public sewer systemwhich provides the necessary treatment prior to its discharge in nature.

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When public treatment plants are not available, private seweragetreatment systems would have to be constructed.

The following are the definitions of some commonly used termsrelated to the subject of sewage treatment methods and disposalprocesses.

Digestion. That s the portion of the sewage treatment process inwhich the biochemical decomposition of organic matter takes place,resulting in the formation of simple organic and mineral substances.

Also known as aerobic (bacterial) digestion.

Influent. Untreated sewage flowing into a treatment system.

Effluent. Treated or partially treated sewage flowing out of a

treatment system.

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F iltration. Means of filtering out any solid matter from the effluent.

Disinfection. Process to disinfect the effluent with chemicals.

Porcelation. F low or trickling of a liquid downward through a filteringmedium or soil.

Drain field or leaching field. Set of trenches containing open endedor perforated pipes designed to allow the treated effluents toporcelate into the ground.

The sewage treatment process can be divided into three majorsteps.

1. Primary treatment which is subdivided into 2.Sedimentation and retention. Raw sewage is retained for thepreliminary separation on indigestible solids and the start of aerobicaction.

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Aeration. Introduction of air through natural convection or

mechanical blowers to accelerate the decomposition of organicmatter.

Skimming. Removal of scum that floats on top of partially treatedsewage.

Sludge removal. Disposal of heavy sludge at the bottom of treatedsewage.

2. Secondary treatment. The removal of fine suspended matter fromthe effluent through a filtration process such as the use of sandfilters, drain fields or seepage pits.

3. Tertiary treatment. The disinfection of effluent by the addition of

chemicals such as chlorine.

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Rather than a sewage treatment plant, the septic tank system is mostcommonly used in rural areas for small capacity applications. It consistsof a septic tank serving as primary treatment and a methof of filteringthe effluent as secondary treatment. See F igure 8.33 pp 278.

F iltering of effluent may be by means of a filter pit, sand filters or drain

fields. A drain field which consists of multiple runs of undergroundtrenches is popoular because it requires less maintenance. See F igure8.33 pp 278.

To design a septic tank system, the analysis if the sewage load based on

the number of occupants in and type of occupancy of the building on a24 hours basis.

Next a suitable location is selected which is normally away from heavytraffic and maintains at least a minimum distance from the building,

wells, water services, etc.

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The required size for septic tank for use in residences is determinedfrom either the number of fixture units (dfu) served or the numberof bedrooms in the residence.

For non residential buildings, the calculated daily sewage rate ismultiplied by a factor of 1.5.

The drain field must include drainage trenches that comply with: Trench construction Drain till size

Trench slope Trench depth Trench width Trench spacing Length of trench

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The absorption capacity of the soil is determined by the percolation test

to determine the time taken for water in the drain field trenched todrop by 1 in.

4.5 Storm Drainage System

A storm drainage system conveys rainwater or melting snow from abuilding or site to the points of disposal. Among the locations to bedrained are roofs, patios, and areaways of buildings and parking lots androadways, lawns and gardens on site. In general except for small orincidental areas all exterior storm drainage should be connected

externally to the building storm drainage system.

Some of the commonly used terms are Roof drain Area drain

Conductor or downspout (installed in the interior)

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4.5 Strom Drainage System

Roof drain Area drain Conductor or downspout (installed in the interior) Gutter Leader

Subsoil drain Controlled storm drainage system Primary drainage system Secondary drainage system (in case of heavy downflow) Sump Sump pump Projected roof or horizontal projected roof area

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4.5 Strom Drainage System

The fundamental design principle behind the design of stormwater systems is to install a piping or conductor system to lead thestorm water away from the building and site in a reasonable time.

The size of the system will depend on the rate of rainfall rather

that the total rainfall in a day or a year. The rate of rainfall varieswith intensity and frequency of occurrence.

To design a storm drainage system:1. Determine where drainage is required

2. Determine the location of roof drains3. Determine the roof drain criteria4. Select appropriate drain fittings5. Select the appropriate piping material and methods of

installation

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4.5 Storm Drainage System

When the lower level of a building is below ground there are 2potential problems.

Surface water may flow into the building through cracks orseepage of the basement walls and groundwater may push into

the building owing to hydrostatic pressure if the normalgroundwater level (known as the water table) is highest than thelowest floor level.

To avoid water seepage all belowground walls must first be

waterproofed and the grade next to the building is often slopedaway from the building. If the anticipated water table is close toor higher than the building floor level a subsoil drainage system isinstalled.

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5.0 Fire Protection Equipment and Systems

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5.1 Classification of F ire and Construction Hazards

There are 4 classes of fires.

1. Class A. F ires of ordinary combustible materials, such as wood, cloth, paper,rubber and many plastics.

2. Class B. F ires in flammable liquids, oils, greases, tars, oil base paints, lacquers,and flammable gases.

3. Class C. F ires that involve energized electrical equipment. In such fires it isimportant that the extinguishing medium not be a conductor of electricity.

4. Class D. F ires of combustible metals, such as magnesium, titanium, zirconium,sodium, lithium, and potassium.

F ire hazards may be grouped into three classes.

1. Light (low) hazard. Locations (buildings or rooms) where the total amount of Class A combustible materials, including furnishings, decorations, and othercontents, is a minor. Among these locations are offices, classrooms etc.

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2. Ordinary (moderate) hazard. Locations where Class A combustibles and Class B

flammables in total are present in greater amounts than expected under lighthazard occupancies. Ordinary hazards are grouped into 2. Group 1, stockpileslower than 8 ft. Group 2, stockpiles lower than 12 ft. These locations generallyconsist of mercantile shops and allied storage, light manufacturing, researchoperations, auto showrooms, garages, etc.

3. Extra (high) hazard. Locations with high or large quantities of highlycombustible materials and conditions are such that fires could develop quicklywith high heat release. Extra hazard Group 1 occupancies have few or noflammable liquids or are locations where combustibles are shielded fromsuppresion.

The requirements for fire protection in a building also are governed by how thebuilding is being used or occupied.

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The requirements for fire protection in a building also are governed by how the

building is being used or occupied.

The general classification of buildings by use group or occupancy are as follows.

Group A : AssemblyGroup B : Business

Group E : EducationalGroup F : FactoryGroup H : HazardGroup I : InstitutionalGroup M : MercantileGroup R : ResidentialGroup S : Storage

Group U : Utility

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5.2 Planning for F ire Protection

Planning for fire protection starts with architectural and engineering design in

all disciplines.

A well planned fire protection system usually operates sequentially as follows.

1. Step 1, detection. The presence of a fire is detected manually or automatically.2. Step 2, signaling. The buildings management, its occupants and the fire

department are notified of the presence of the fire. The occupants are advisedof the actions to take.

3. Step 3, suppression. Manual or automatic fire suppression equipment andsystems are used to extinguish the fire and remove the smoke.3A, initial effort. Portable and manual fire fighting equipment such as fire

extinguishers, fans, and a first aid hose are used to extinguish the fire and toremove smoke by dilution or exhaustion.

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5.3 F ire Safety Design

Some of the fundamental fire safety design criteria are as follows.

1. F ire-resistant construction. The construction of walls, partitions, ceilings andfloors shall meet or exceed the fire resistance ratings specified in the governingcodes. The required ratings vary with building occupancy size and height.

2. Smoke controls. In addition to fire resistant construction a building of any sizemust have proper smoke control by removal, dilution and/or confinement.Such control could be as simple as opening windows or as complicated asexhausting smoke with automated mechanical systems.

3. Length of travel. All exits shall be located so that the maximum length of travel

to access the exit measured from the most remote point to an approved exitalong the natural and unobstructed line of travel shall not exceed certaindistances.

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5.3 F ire Safety Design

Some of the fundamental fire safety design criteria are as follows.

8. Vertical transportation. Elevators are not recognized as exits. Elevator shaftsshall be vented or pressurized depending on the HVAC system. Escalator flooropenings shall be protected with fire shutters or protected by water curtains aspart of the sprinkler system.

9. Coordination with mechanical and electrical systems. Mechanical and electricalsystems shall be designed to meet the applicable codes.

10.Compliance with code requirements for specific use groups. The classificationis generally consistent with that of other building codes.

11.Coordination with fire department. The fire marshals must be consulted aboutthe required access to the building and the locations of fire hoses, firehydrants, electrical power disconnects, fire suppression and alarm systems.

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5.4 F ire Detection and Signaling Devices

Detection and signaling devices may be addressable or non-addressable. The

addressable type can be individually addressed and identified so that thesystem can immediately identify the type and location of the initiating devicesassociated with a given address.

A manual alarm station is an electrical switch specially designed for fireprotection that activates an alarm system such as bells, gongs, and flashinglights.

Thermal detectors are temperature activated sensors that initiate and alarmwhen the temperature in their immediate vicinity reaches a predeterminedsetting. Some common types are as follows.

F ixed temperature typeRate of rise typeCombination type

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5.4 F ire Detection and Signaling Devices

Single stroke bell, vibrating bell, buzzer, chime, horn, siren, light signal, etc.

F low detectors are devices that indicate or initiate an alarm when water isflowing in the fire suppression system.

Visual annunciation devices are displays that may consist of single or multiplelights with marked messages such as F ire , F ire Escape or Go to Area B .

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5.5 Automatic Sprinkler Systems

The major component of an automatic sprinkler system is the sprinkler, which

discharges water in a specific pattern for extinguishing or controlling a fire. Asprinkler head consists of 3 major components.

1. A nozzle2. A heat detector3. A water spray pattern deflector

The fusible link type of heat detector is constructed of an eutectic alloy whichmelts at a specific temperature rather than gradually softening. When the linktemperature reaches its melting point the link is pulled apart by the waterpressure and opens the nozzle. The frangible bulb type of detector contains a

glass bulb partially filled with a liquid that expands with temperature. At therated temperature the liquid will shatter the bulb and enter the nozzle.

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The spray pattern of sprinkler may be symmetrical or asymmetrical spray, a fine

mist or water droplets. Sprinklers may be mounted pendant, upright flush withthe ceiling, recessed into the ceiling, concealed in the ceiling or in a sidewall.

Response may be quick, quick response and extended coverage, quickresponse and early suppression or early suppression and quick response.

The hear sensing elements of a sprinkler may be fusible links or frangible bulbs.Or the sprinkler may be the open type or the dry type.

The flow rate of the sprinkler depends on the size of its orifice and the residualpressure of the water supply.

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There are numerous kinds of automatic sprinkler systems, each ideally suited

for certain spaces. Two major varieties are:

1. Wet systems Wet pipe, antifreeze and circulating closed loop.2. Dry systems Dry pipe, preaction, deluge and combined dry preaction.

A wet pipe system is a piping system containing sprinklers under waterpressure so that water discharges immediately from the sprinklers when theyare opened by heat from a fire.

A dry pipe system is a piping system filled with compressed air (or nitrogen).The air pressure prevents water from entering the pipes beyond a control valve

known as a dry pipe valve.

An antifreeze system is a wet pipe system containing antifreeze solutions usedin areas subject to freezing.

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A circulating closed loop system is a wet pipe system having non-fire-protection

connections in a closed loop piping arrangement for the purpose of utilizingsprinkler piping to circulate water for heating or cooling.

A preaction system is a dry pipe sprinkler system filled with air and having asupplemental detection system installed in the same area.

A deluge system is a dry sprinkler system equipped with open type sprinklers(no fusible links).

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Tutorial Sheet 4

1. What is a Backflow Preventer?

2. What are the design guidelines for a DWV system?

3. Describe the 3 steps of the sewage treatment process.

4. What are the 5 steps in designing a storm drainage system

5. Describe the Classes of F ire and the Classes of F ire Hazards.

6. Describe a well planned fire protection system.

7. What are the fundamental fire safety design criteria?

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