Water Distribution Manual | Pipe (Fluid Conveyance)

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This manual is part of a series of guides devised by the Oxfam Public Health Engineering Team to help provide a reliable water supply for populations affected by conflict or natural disaster. Wherever possible, water supplies in emergency conditions should be obtained from underground sources by exploitation of springs, tubewells, or dug wells. No filtration will then be needed. However, if sources are not available or cannot be developed, the use of surface water from streams, rivers, lakes or ponds becomes necessary. Usually these surface sources are polluted. The level of faecal contamination can be measured by use of the Oxfam/Delagua Water Test Kit (see Section C). Where a serious level of faecal pollution exists, it is essential firstly to try to reduce the cause of contamination, and secondly to treat the water to make it suitable for human consumption. The Filtration equipment provides a simple, long-term physical and biological treatment system that requires no chemicals (except small amounts of chlorine required during filter cleaning) and needs only simple regular maintenance.
Transcript
  1 Oxfam Water Supply Scheme for Emergencies This equipment is part of several packages devised by the Oxfam Public Health Engineering Teamto help provide a reliable water supply for populations affected by conflict or natural disaster. Theequipment is designed to be used with any or all of the following Oxfam water equipment: Water Storage equipment, Water Coagulation and Disinfection equipment, Water Filtration equipment,Water Pumping equipment, Well Digging equipment, and Water Testing Kit. All are designed usingavailable, easily transported equipment which is simple, rapidly assembled, and fully self-contained,to provide an adequate, safe water supply at moderate cost. The principles used in these packagesmay often be useful in long-term development projects.The Oxfam equipment packages, which consist of “Oxfam” tanks (steel sheets, rubber liners), dieselwater pumps, 3” PVC pipes etc, have been used successfully in the last two decades in often harshenvironments, ranging from tropical to temperate climatic areas. Although this equipment isdesigned for emergencies, if installed and protected adequately it can give many years of usefulservice, though some up-grading works will be necessary to prolong its life. This equipment can bedismantled and re-used elsewhere.However, these Oxfam equipment packages, while being simple to erect over a period of days, yetdurable enough to last several years, do not lend themselves to very rapid deployment in a fewhours. Increasingly, the nature of work which Oxfam has been called on to undertake has requiredequipment that can rapidly deployed then dismantled and moved to other locations. This has led tothe development of the so called “rapid response kits” since the mid-1990s. This type of equipmentis seen as a necessary complement to the srcinal Oxfam equipment and is best used to provide astart up package in the absence of a detailed assessment and where affected populations are likelyto be highly mobile. The relatively higher equipment costs and lack of suitability for anything other than short term water supply means that the deployment of the “rapid response kits” should be usedonly where appropriate. Read this manual through before starting installation. Contents SECTION A - EQUIPMENT USE AND SYSTEM DESIGN 2 Types of pipe and fittings 2Design criteria 3 SECTION B - LISTS OF KITS AND INSTRUCTIONS FOR USE 8 Water Distribution kits 8Installation instructions 9 SECTION C - OPERATIONAL INFORMATION 16SECTION D - DETAILS OF KITS AND SUPPLIERS 18 Full list of kit contents 18List of suppliers 20Final reminders and recommendations, references and acknowledgement  2 SECTION A - EQUIPMENT USE AND SYSTEM DESIGN The Distribution equipment is designed todeliver water to users from Oxfam Storageequipment or any other suitable storage facility.The 90mm (nominal 3”) pipe can be used for pumping and distribution mains, while the 63mmPE pipe coils can be used for smaller distribution and pumping mains or for branchesto 90mm mains. Where possible, water shouldbe distributed by gravity from storage tanks,which may be achieved by siting the storagetanks at the top end of a gently sloping site or on a local point of higher elevation, and bydesigning the system to keep head losses to aminimum. Where this is not possible, theequipment is designed to be used also with theWater Pumping equipment, for a pumpeddistribution system.The package of equipment comprisesdistribution main kits, distribution stand kitscomplete with 6 No. Water saving valves,distribution pipe, and a distribution fittings kit. Adistribution adaptation kit is also provided, with arange of fittings that allow the Oxfam 90mm (3”)system to be connected into other agencies’kits, water trucks, and existing water supplysystems. Types of pipe and fittings There are several different pipe types used byOxfam, found in different kits and used indifferent ways. 1.  Layflat hose is the pipe most recently used byOxfam in its emergency response and isincluded in distribution/layflat rapid fittings kit(Oxfam code DLR). 75mm diameter layflat hose(fire hose) is provided in the kit, which iscompact, easily transported and quickly laid out,though is only suitable for short term use, as thepipe is not as strong as rigid wall pipe systems,it has higher head losses and cannot be buriedin trenches. Thus the DLR kit should usuallyonly be considered for use with the rapidresponse bladder and onion tanks. 2.  90mm diameter UPVC main (pipe with wallthickness of about 4mm, made of a fairly rigidplastic), using simple push-fit joints. UPVC ismuch cheaper to buy and freight, is easier topurchase locally, and has the advantage of incorporating couplings as an integral part of thepipe. However, it does need burying immediatelyas the joints have no end load resistance, it isrelatively brittle and easily damaged anddegrades in sunlight. Thus it is not suitable for use in very rocky ground or on roads andpavements where trench excavation is notpossible. 3.  PE main (pipe with wall thickness of about10mm for 90mm diameter pipe, made of a softer plastic) joined either by using compressioncouplings or by butt fusion (heat) welding. PEpipe comes in 50m or 100m coils, or in straightlengths, usually 6m, but 4m can be specified.However coils of 90mm pipe are about 3.0m indiameter, which makes air freighting very costlyand in some areas moving coils this size bytruck is very difficult. Straight lengths on theother hand require purchase of numerouscompression couplers or butt fusion weldingequipment, which are either expensive to buy or slow to make. Thus the use of PE is usuallyrestricted to 50m length coils of 63mm diameter pipe (1.7-1.9m diameter, weight 25kg) which canbe laid out quickly and used to extend branchesfrom the distribution main a long way into thecommunity. 4.  3” low-pressure rated green flexible hose,which is used for some pump suction anddelivery hoses, and making connections intotanks. For the 4” pumps, some 4” hose isprovided for suction pipe and some higher-pressure hose for delivery pipe.For very large populations it may be moreappropriate to order either 110mm or 160mmPVC, for which specifications have beenprepared, but not included in this manual.Various sorts of valves are used in the Oxfamkits and a brief explanation of each is givenbelow: 1.  Gate valves operate by a simple wind up anddown “gate”, and these are used throughout thekits as flow isolators.  3 2.  Globe/ball valves are used with some of thepump and other kits and can be used for flowcontrol as well as isolation, where flow mayneed to be adjusted to suit requirements. 3.  Non return/check valves only allow flow inone direction, particularly used in the pump kits,e.g. foot valves used at the end of a suctionhose to stop it emptying when not is use. 4.  Float valves automatically maintain the water level in a tank by closing up when a tank is full,which is useful to prevent accidental overfilling.While they are included as part of the SSF kit,these valves have to be ordered separately if required elsewhere in a system.In addition two other valves and water metersmay be ordered if required: 5.  Air valves, which are usually placed at highpoints in a pipeline to allow accumulated air trapped in a pipe to escape and to let it enter when a pipe is emptying. Ferrules straps couldbe used as a manual air bleed point in the shortterm, but an automatic air release valve shouldbe ordered if required. The Oxfam code G3.37,is a 6 bar rated valve, used in conjunction with aferrule strap on a 90m pipeline, which needs tobe installed in a vertical position. 6.  Pressure reducing valves reduce pressure ina pipeline, and may be required where gravitysupply from a tank to tapstands at the bottom of a hill creates too much pressure in the taps.Pressures higher than about 2 bar in tapstandscause flows to be excessive and the Talflo tapsare hard to open and “kick” when operated.While adjustments on the ferrule strap and gatevalves fitted to the branches can providereduction in flows, they do not reduce the statichead on the tap and are thus not recommendedsolutions as taps are difficult to open under highpressure. The Oxfam code G3.39, is a 3” classT pressure reducing valve, costs about £500and is available to be placed on the 90mmdiameter mains and provides a pressurereduction between inlet and outlet of the valveof;3 barfor flow of 13l/sec20 barfor flow of 18l/sec 7.  Water meters, which measure cumulativewater flows, can be useful to monitor systemproduction when installed at pump/tank outlets,though at a cost of about £350- its purchaseneeds to take this into account. The Oxfam codeG3.38 is a Helix 3000 bulk water meter rated to136m 3 /hr (head loss 4.2m), supplied withflanges to join to 3” BSP threads. Design criteria The move towards production of metric pipemeans that Oxfam now uses metric pipe for bothPE and UPVC, though threaded galvanised pipeis still available and specified in imperial sizes.Metric pipe has slightly different pressure ratingsfrom imperial pipe, but still comes in a variety of different maximum working pressure ratings.While the 63mm PE pipe is only available in12.5 bar (SDR11, PE80), the 90mm PE pipe ismanufactured in several ratings, of which thefollowing may be useful 8 bar (SDR17, PE80),12.5 bar (SDR11, PE80) and 16 bar (SDR11,PE100). 90/110/160mm UPVC pipe is availablein the same pressure ratings. The pipe andfittings used in the Oxfam kits have a minimum 8bar rating. Where 8 bar pressures will beexceeded, this should be made clear in theequipment order.It should be noted that the maximum pressurerating for UK manufactured pipe is for a designlife period of 50 years and actual pressure atfailure is over twice the rated pressure, so thereis some margin for safety if pipe is pressuredbeyond its rating. However, this probably doesnot apply for pipe manufactured in developingcountries, as water industry standards (if theyexist) are less demanding and production qualitycontrol is likely to be poorer  . Thus where it is proposed to purchase pipes locally, it is suggested that in the absence of proof of pipe quality, that the next pressure rating up is used, i.e. use 12.5 bar pipe where system pressures will reach 8 bar. Where locally procured compression couplers are used,these should be dismantled when jointing pipes to ensure full depth insertion and inserts may be required for locally procured pipes 90mm or larger, as compression couplers may otherwise squash the pipes on tightening  .  4  As a minimum, SPHERE recommends a figureof 15 litres/person/day and one outlet (tap) per 250 people (assuming a minimum flow of 0.125l/sec can be achieved). However, as this isa minimum and may lead to considerablequeues developing at peak times (early morningand late afternoon/evening), it is suggested thatone tap per 200 people with a flow of 0.2 l/secfor each tap, i.e. 1.2l/sec per tapstand (eachtapstand having 6 taps) is used. SPHERErecommends that no dwelling should be further than 500 metres from a water point. (UNHCRrecommends the figure of 100 metres, which isdifficult to achieve and can promote too muchdisparity between the affected population in thecase of refugees and the surrounding hostpopulation in rural areas.) However, these areminimums for guidance and different situationsmay demand different standards.The Oxfam distribution stands are fitted with sixself-closing Talflo taps. Each Talflo tap will givethe following flows for the given heads:Flow (l/s)0.050.120.20.38Head (m)0.11.0310Where possible, layout of the system and pipediameters should be chosen to give about 0.2litres/sec, requiring a residual head of around 3metres at each tap. If the rate is greater, water may be wasted; if it is less, long queues mayform at distribution points. Where flat sites don’tpermit a 3m head at each tapstand, for designpurposes the numbers of people usingtapstands should be reduced from 1200 to alower number.It is assumed that the reader has a basicunderstanding of water-distribution systemdesign; hence only head-loss tables and twoshort examples are included below. If this is completely new to the reader or more complex system analysis needs to be undertaken, they    should refer to texts that have more detailed information such as Gravity-flow Water Systems (Jordan) or Engineering in Emergencies (Davis/Lambert). Worked design examples and head-loss tables Though the kits have predetermined pipe sizes,there is some choice in the way these are usedand some simple design checks should beundertaken. Where possible, a survey of the siteshould be made and the results used to make asimple check on what pipe size should be used,and whether it is strong enough to withstand thepressure. The survey should measure heightdifference and distances between thereservoir/pump and distribution stands/water treatment works.Head (friction) losses in pipes and secondarylosses in fittings must be taken into account inorder to estimate how much water will flow in aparticular system. The head losses in pipes canbe estimated using head loss tables (includedhere) or by calculation (not shown here). In veryshort lengths of pipe the secondary losses atinlet, outlet and valves will be significant andmust be taken into account. Note that the twoexamples below do not take into account headlosses in fittings, though estimates for these aregiven at the end of the examples. Pipe velocityshould also be checked at this stage, using thehead loss tables and it is desirable to have flowvelocities between 0.7m/s to 2m/s, outside thisrange allows sedimentation of particles or abrasion of pipe by particles.
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