SW Hydrostatic Pressure Testing Water Mains Version B Feb 2017

Transcription

1 Introduction and Background The purpose of this hydrostatic pressure testing procedure is to ensure that all hydrostatic pressure tests undertaken on all new mains installed within Scottish Water are conducted safely and effectively. The purpose of pressure testing any new water main or service connection is primarily to identify its structural integrity for any leakage and also for verifying the performance of the new main or service laid for adoption and acceptability. Hydrostatic pressure testing is used to identify if there are any faults, leaks or defects from, 1 Poor pipe laying procedures or workmanship during the construction of the main or pipe. 2 Damaged to any pipework, materials or fittings during construction. 3 Non- conforming fusion joints or tapping bands or saddles, flange sets, or mechanical joint. 4 Any manufacturing defects of Mains, Pipe, Materials or Fittings. Hydrostatic Pressure Test (General Criteria) SW requires that hydrostatic pressure testing of all PE mains & pipe work must be tested using a TYPE 2 test and is carried out in strict accordance with IGN Issue 2 Pressure Testing of Pressure Pipes and Fittings for Use by Public Water Suppliers. Ductile Iron & Steel mains shall be Pressure tested using the Volume of added Water & Volume of Water Loss methods. There are a number key factors which must be consider below which will affect both the choice of test section and its length and also the results of a hydrostatic pressure test these include but are not limited to, The length and diameter of main being tested and the number of joints and fittings. The availability of a suitable potable water supply to fill and pressure test the main. The location of a suitable discharge point for the water used after testing. To prevent an Environmental Pollution Incident (EPI) Any difference in elevation to meet the System Test Pressure (STP) and or the % of trapped Air within the main. Any temperature variations on site especially for PE pipelines and creep factors. The size of pump and its capacity including its maximum pressure and flow. Mains Rehabilitation i.e. (Pipe Bursting / Slip Lining / Roll Down) The above mains rehabilitation techniques require a separate type of hydrostatic pressure test to be undertaken which is a 10 minute test which is suitable for mains up to 180mm outside diameter and 200mtrs in length with a low number of joints. Page 1 of 29

2 Anywhere a new main is being inserted into a host main as the new main can be damaged by existing services or where the existing main has been cut out for new service to be reinstalled or from shards from pipe bursting etc. Larger diameters mains or longer section of mains shall be undertaken using the type 2 pressure test. Any new main laid as part of mains rehabilitation program using the Open Cut method shall be pressure tested using a type 2 pressure test. Safety Note This document sets out the requirements for undertaking, checking and validating pressure tests in Scottish Water using industry best practice. It also provides the basic guidelines for the safety and protection of personnel on site and the general public during pressure the hydrostatic test. It is the responsibility of the individual hydrostatic pressure testing company and its staff to further develop its own appropriate generic and or site specific safety plans and control measures and with their implementation to safely carry out hydrostatic pressure testing of Water Mains & Fittings in Scotland as well as complying with any other appropriate legislation or documentation relating to hydrostatic pressure testing in the UK as per. The Health Safety Executive documents referenced below, Safety requirements for pressure testing Guidance Note GS4 Working alone INDG73 (rev3) Providing and using work equipment safely INDG291 (rev1) Hydraulic injection injury RR976 Note: SW deems Pressure testing as being a high risk activity and a TWO man operation on site using the above Health Safety Executive documentation and IGN section 3.1 Safety as points of reference. Hydrostatic Pressure Test (Proforma & Documentation) Scottish Water requires it s new Pressure Test proforma to be completed to allow SW to standardise testing, improve, validate and reduce the need for SW staff to be onsite for all witness testing and to give quicker authorisation for connection to the live distribution network. SW requires a more robust process with either supplementary Video or Photographic evidence provided for each of the various elements of a hydrostatic pressure test that includes full analysis in both an electronic format and PDF and to check and confirm the results in compliance with this procedure for SW authorising a Pass to any pressure testing that is undertaken. Any pressure test submitted without the new SW Pressure test proforma and either No Video or Photographic evidence will result in SW being unable to confirm compliance and validation of the pressure test and will deem the pressure test as having failed and will be required to be undertaken again with an onsite witness test by SW staff. SW requires its new pressure test proforma to be completed for all pressure test undertaken which requires site specific information recorded by the company carrying out the pressure test. The profoma can and should be used as a check list for all staff on site to correctly check and implement the control measures required to mitigate any issues which will affect and prevent a pressure test being undertaken successfully. Page 2 of 29

3 The company carrying out the hydrostatic pressure test is also required to submit and confirm all the recorded measurements, Data of the pressure and water flow and volumes used during the pressure rise phase (Ramp Up). Electronic copies of the hydrostatic pressure test submitted must include the pressure tests Incremental readings (i.e. print outs 20sec), Pressure Decay Graphs, Flow meter readings with the relevant supporting video or photographic evidence for validation. SW also requires a site drawing with the highlighted section of main / mains being tested. Geo tagged Photographic & or Video evidence Must now be provided with all hydrostatic pressure test submission and include the following: Hydrostatic Pressure test set up. SW Licenced stand pipe and serial number. Bored & Tapped Blank Plates used with additional valves to allow the safe removal of air. Electronic Data Logger with serial number & the calibration date. 200mm Pressure Gauges or calibrated digital gauges. Flow Meter. (Readings for Before & After the Ramp Up Time to STP to confirm volume of water used to calculate the Air Content and test duration i.e. 30x or 45 x ramp) Dual Functional Logger if applicable with serial number & the calibration date. GEO TAGGING Photos Geo tagging is the process of adding a location, date and time to your photographs and is now required by SW as part of the validation process to confirm compliance with the various elements of the hydrostatic pressure test has been correctly undertaken on each site. Here's how to do it: (Example for SW Samsung phones) Open up the stock Samsung Camera app on the phone. Look for the Settings 'Gear' icon and tap on it. On the grid of settings that presents itself scroll down a little until you see "Location tags" Tap to enable/disable as desired! IPhone s by default are already set to record the location information on photos and videos taken using the camera app. Photo editing apps and services, such as Lightroom, Aperture, iphoto, Picasa, and Flickr, also support geotagged images. Page 3 of 29

4 Pressure Test Proforma Page 1 Page 4 of 29

5 Pressure Test Proforma Page 2 Page 5 of 29

6 Hydrostatic Pressure Test Criteria (Test Pressures) Testing of Polyethylene Pressure Pipelines & Testing of Ductile Iron, PVC, GRP & Steel Pressure Pipelines. Scottish Water has now standardised its approach to hydrostatic pressure testing and has now included simple charts below and within the New Pressure test proforma and its Standards & Specification documents to use & confirm the correct limits of pressure testing requirements for the various pipe materials and pipe ratings. For SDR 17 Pipe Systems the Pressure Test will be 1.5 times Rated Pressure of the pipe. 15 Bar. For SDR 11 Pipe Systems the Pressure Test will be the working pressure + 5 Bar with a minimum test pressure of 15 Bar. Testing of Ductile Iron, PVC, GRP & Steel Pressure Pipelines (SURGE HAS BEEN CALCULATED) STP + MDPs + 1 Bar Testing of Ductile Iron, PVC, GRP & Steel Pressure Pipelines (SURGE Has NOT been Calculated) STP = MDPa X 1.5 or STP = MDPa + 5 Bar (whichever is the least) Page 6 of 29

7 Hydrostatic Pressure Test Criteria (Lengths & Diameters) Scottish Water requires that separate hydrostatic pressure testing must be undertaken for separate pressure rated pipes and fittings. (i.e. SDR17 pipework shall be tested separately from SDR11). Separate pressure testing must be also undertaken where there is any change in pipe material is required. I.e. MDPE / Ductile Iron mains etc must be tested separately. Note: Barrier Pipe & HPPE / MDPE Mains can be pressure tested at the same time within the same test only if the pipe is the same SDR rating. Pressure testing of various pipe lengths and pipe diameters is permissible within SW only if the mains being pressure tested are all of the same pipe material and SDR rating and the total length of all mains within the pressure test does not exceed 1 km, I.e. 63mm up to 200mm diameter mains should be no greater than 1km in length. Diameters 200mm and above should be no greater than 200m in length. Any testing of mains 200mm and above with a length greater than 200m shall require a wavier by Scottish Water. SW wavier process requires a full method statement and risk assessment with confirmation on the pump type being used include size and capacity (Pressure & Flow rates) to meet the maximum 30 min Ramp up time. Is should also be noted that the longer the type 2 hydrostatic pressure test section is the more difficult it becomes in general to successfully achieve a pass test result. Especially to check all joints and or to locate any leakage or to identify if it is the test has failed as a result of an actual leak or the result of trapped air in the main or pipeline. The minimum length of Hydrostatic pressure test section shall be 11m. I.e. 2 x 5.5m lengths. Page 7 of 29

8 Schematic Plan of a typical pipe section for pressure test Blank Plate 9 8 Hydrant Distance piece 6 Stub Flange either Electro 1 2 fusion or Butt Weld Stub Flange either Electro fusion or Butt Weld Coils of pipe and branch connection. A typical new main / pipe section for pressure testing will have at least 4 joint being tested. If the hydrant requires an additional 2 nd or 3 rd distance piece due to depth of man this will increase the number of joints being tested. 7 Blank Plate Note: SW Preference is preferably to have a hydrant fitted at the end of the pipe test section for the safe removal of Air and also to minimise and possible contamination being syphoned back into the main. Blank Plate 10 9 Hydrant Distance piece 6 Blank Plate Distance piece Duck Foot Bend Stub Flange either Electro 1 2 fusion or Butt Weld Stub Flange either Electro fusion or Butt Weld 7 8 Stub Flange either Electro fusion or Butt Weld 1 2 Coils of pipe and branch connection. A typical new main / pipe section for pressure testing using a single coli will have at least 4 joints being tested. If the hydrant fitted requires an additional 2 nd or 3 rd distance piece due to depth of man this will increase the number of joints being tested. 3 4 Blank Plate Distance piece Duck Foot Bend If the branch section of main is the same SDR rating as the spine main then both Pipes can be tested at the same time and test. Note: Each Section of pipe must be swabbed correctly with the correct size of swab and checked that there is NO contamination before pressure testing commences. Page 8 of 29

9 Schematic Plan of a typical pipe section for pressure test If the Branch Main / Pipe being Pressure tested is a different SDR rating from the spine main then a separate test must be undertaken for each Main. The main should be split and blank plates fitted. Note: Each Section of pipe must be swabbed independently and correctly with the correct size of swab and checked there is NO contamination before pressure testing commences. New Section of Pipe / Main Hydrant Distance piece Duck Foot Bend Stub Flange either Electro fusion, or Butt Weld or mechanical Terminal Hydrants should be fitted only if Pressure testing at the same time with the Spine main Blank Plate Valve Distance piece Hydrant All Flanged Tee Valve Valve Blank Plate Distance piece Stub Flange either Electro fusion, or Butt Weld or mechanical Valve Stub Flange either Electro fusion, or Butt Weld or mechanical Valve All Flanged Tee Hydrant Distance piece Valve New Section Of Pipe / Main Stub Flange either Electro fusion, or Butt Weld or mechanical Duck Foot Bend Stub Flange either Electro fusion, or Butt Weld or mechanical Hydrant Distance piece Duck Foot Bend New Section of Pipe / Main Terminal Hydrants should be fitted only if Pressure testing at the same time with the Spine main If the branch section of main is the same SDR rating as the spine main then both Pipes can be tested at the same time and test. Note: Each Section of pipe must be swabbed correctly with the correct size of swab and checked that there is NO contamination before pressure testing commences. 1 Stub Flange either Electro fusion, or Butt Weld or mechanical Blank Plate Distance piece Duck Foot Bend 2 3 Coils of pipe and branch connection. A typical new main / pipe section for pressure testing will have at least 4 joint being tested. If the hydrant requires an additional 2 nd or 3 rd distance piece due to depth of man this will increase the number of joints being tested. 4 Page 9 of 29

10 Hydrostatic Pressure Test Criteria (Ramp up Time, Incremental readings & Test Duration) The ramp up time and the type of pump, size of pump used for a hydrostatic pressure test is critical to achieving successful test & pass. It is critical that the data logger used is set up correctly & configured to accurately record enough readings at the correct intervals during the ramp up time and also throughout the duration of the test. All pressure tests should have the data logger set and configured to take incremental readings at 20 second intervals. Note: Some loggers require the ramp up time to be divided by between 6-10 for a test with a ramp up time, up to 1 minute. All tests shall have a graph(s) showing the time line with suitable increments and time period to validate the pressure decline throughout the test duration. All pressure tests should have a minimum of 1 minute Ramp Up time & Maximum Ramp up time of 30 minutes. The minimum Pressure test duration for SW is 1 hour. The maximum Test Pressure duration for SW is 10 hours. I.e. 30min Ramp up Time. Any Pressure Test that requires being longer than 10 Hours in duration due to excessive lengths of the main being tested or as a result of trapped air content etc should be notified to SW and follow the SW waiver process in advance of the test. Note: There is a higher likelihood of a pressure test failing when using incorrect pumps (Undersized or Oversized) and ramp up times. Short lengths of pipe work wherever possible should be undertaken using a hand Pump. The use of the hand pump will be based on the volume of water required to be added for pipe pressurisation to STP and calculation of the Ramp Up / Load times effecting the duration of the pressure test. Litre / Minute (Pump out put) affect the Ramp Up time. Note: There is No requirement to use a Flow meter if using a hand Pump. However the volume of water used must still be physically recorded. Any test that is not undertaken with a hand pump requires a Flow meter to be used. A calibrated flow meter, with a resolution of 1 litre or better must be used to accurately measure the volume of water added during the pressure rise phase to STP. SW preference is for dual functional data loggers to be fitted to record Flow & Pressure. Photographs are a mandatory requirement for recording the flow meter readings taken both before & after the Ramp up Time to (STP) to confirm volume used & Air Content, unless they are recorded on an electronic GPS Logger. A Photograph IS still required for confirming the GPS Logger make and model used. Page 10 of 29

11 Hydrostatic Pressure Test Criteria (Ramp up Time, Incremental readings & Test Duration) All hydrostatic pressure tests shall have the following calculations which are required to accurately check and validate a hydrostatic pressure test. t2 = x 8 times the ramp up time. t3 = x 20 times the ramp up time. An added value for t4 is required for any test with air content between 4% < 6% requires 30 x times the ramp up time. An added value for t4 is required for any test with air content between 6% < 8% requires 45 x times the ramp up time. The removal of Air is a critical factor to a successful pressure test as the presence of air in a main will have a number of effects especially in relation to the rise time to STP being increased and also as Air will distort the interpretation of pressure decay results. Please Note: If the air content cannot be reduced to 4% or less, the test must be either extended or abandoned. Any hydrostatic pressure test with Air content above 8% must be aborted and air removed before restarting the test. Please Note: if the pressure test has a ramp up time of 3min or less then the t3 time is taken at 1 hour from t0. I.e. (2minute ramp x t3 20x = 2 min ramp x 20 is only 40min t3 now moves to 1hour) Extended Test Pressure due to Air content Page 11 of 29

12 By taking this additional pressure reading (PA at t4), a further n value (n3) can be calculated using the following formula: n3= [log(paat t3) log (PAat t4)][log(tc4) log(tc3)] 15 t1 30 Min TEST Period 1 Hour TEST Period All Pressure test will eventually go to ZERO if the test is left on long enough!! Time Verse Pressure is the relationship between the rate of decay over time. If the rate of decay is to sharp a decline it highlights an unacceptable Leak. 25% Threshold accurately measure the drop off t2 t3 t4 BAR 0 The rate of decay on both graphs looks fine if the test and the data is only on for example 30min. It is difficult to the untrained eye to identify the small margin. The rate of decay is more evident on the graph when taken to the 1 hour or above the 1 Hour timescale if applicable. SUCCESSFUL TEST FAILED TEST TIME DURATION N1 is the calculation between [log (PA at t1) - (log PA2 at t2)] [log (t2c) log (t1c)] N2 is the calculation between [log(pa at t2) log (PA at t3)] [log (t3c) log (t2c) N3 is the calculation between [log(pa at t3) log (PA at t4)] [log (t34) log (t3c) The 25% threshold ( n2 can not be 25% Greater than n1 value ) There is a bigger margin with higher n1 values than lower n1 values. If n1 is % of n1 = 0.01 ( n2 can not be greater than 0.05 ) n / n = 1.25 If n1 is % of n1 = ( n2 can not be greater than ) n / n1 0.1 = 1.25 Hence the reason it is harder to achieve a pass on a pressure test with low n values due to Air Content etc and the reason why a Pressure Test is left on for either 30 Times or 45 Times the ramp up to STP for Air content above 4%. Small Lengths and diameters especially being pressure tested, will be more prone to failure due there being a lesser margin between the n values. Small test section with even a small drip will effect the pressure test result and exaggerate the failure. Other factors may also be the main not being isolated correctly or still connected to the pump effecting the test results. These issues can be highlighted within the test data. Page 12 of 29

13 All Pressure test will eventually go to ZERO if the test is left on long enough!! Time Verse Pressure is the relationship between the rates of decay over time. If the rate of decay is to sharp a decline it highlights an unacceptable Leak. Example: Graph showing 2 rates of decline over time. Hydrostatic Pressure Test (Pump Selection) Scottish Water New Pressure test proforma includes supporting documentation for pressure testing companies to use regarding calculation for the correct size of pump required to achieve an adequate ramp up time. Populating the relevant blue cells with the volume of water required to achieve STP will automatically calculate the size of pump and also calculate the ramp up time and test duration. All pumps should be adequate to smoothly raise the main to the correct System Test Pressure of the pipe work being tested. The pump must be able to pump to the both the correct System Test Pressure STP of the main being pressure tested and with the flows required to get to the System Test Pressure within 30min. Note: Using an Undersized or Oversized pump will affect the ramp up time and pressure test duration and the test results. Too small a pump will extend the test duration and too big a pump will prevent accurate control of the test pressure and affect the ramp up time. The pump used should also have a blow off valve or safety device / regulator fitted to prevent the pump from continually adding pressure to the main above the required STP System Test Pressure. (See attached table / chart as guidance for selecting a suitable size pump for the length and alternatively the contractor can calculate their own pump size using the relevant pipe material and or SDR rating as per IGN pages 16, 17) Page 13 of 29

14 New Mains Pressure Testing & Commissioning Prior to pressure testing, each length /section and branch of the main should be individually swabbed with the correct size / diameter of foam swabs pushed through the entire length of main by water fed into the main by an approved system of temporary pipework which must incorporate a double check valve to ensure there is no possibility of back siphonage into the existing main. When to Pressure Test the new main? Pressure testing should be undertaken preferably immediately after the main has been flushed and swabbed. (Provided the swab is clean and the main if free of debris) Water used for pressure testing must always be drawn from a clean source of treated water. Raw, untreated water (burns, rivers, surface water reservoirs) must never be used to charge and pressure test a new main even prior to flushing and disinfection. All water to be used for Flushing Swabbing and Pressure testing must be potable water (clean, treated water) and disposed of with due care to the environment. Under NO circumstance should any Swab be inserted and left in the main by the main laying team prior to the physical testing and commissioning of any new main. Swabs must only be inserted into the main on the actual day when physically carrying out either swabbing or disinfecting the main using swabs with the correct amount of chlorine tablets. Page 14 of 29

15 Swabs shall be used once only unless otherwise approved by SW & all swabs must be accounted and recovered from the main. Any work that does not follow this sequence of stages will be considered non-compliant with respect to application of this Scottish Water DOMS procedures and Hygiene Code of Practice. SW Licensed Stand Pipes The filling of new mains for Flushing, Swabbing, Pressure Testing & Commissioning mains should only be done through a SW Licenced 25mm hydrant standpipes fitted with double check valve to prevent back flow siphonage into the live distribution network. SW may allow the use of 2 standpipes in exceptional circumstance for only filling long sections of mains & or larger diameters prior to Pressure testing, However THESE MUST be authorised by SW Operational staff in advance to protect and prevent any Water Quality issues or Interruption to supplies to our Existing Customers. For more information on our standpipe licensing scheme contact our Standpipe Service Desk on or standpipeservicedesk@scottishwater.co.uk or refer to SW DOM-WN-PRC Hydrant Standpipe Hire Procedure. Unauthorised use of fire hydrants and taking water without permission are criminal acts. Continued use of non-approved standpipes may lead to prosecution. Preliminary Conditioning Mains There is no requirement for preliminary conditioning PE Mains prior to pressure testing. Ductile iron, Steel pipes with epoxy linings or GRP pipes with socket and spigot joints, require the main to be raised to the System Test Pressure (STP) and allowed to settle for at least 15 min prior to the hydrostatic pressure test. Ductile iron & steel pipes with cement linings should be allowed to settle overnight. Pressure test set up The pressure test i.e. the Logger / Pump / Flow meter etc should be set up at the lowest elevation of the section of main being tested. Any pressure test not installed at the lowest elevation must be notified to SW and be recorded on the proforma when submitting the test. The main should be slowly filled with potable water from the lowest point of the main to vent and remove all the air from the highest point of main through an open valve on the blank plate at the end of the main or at highest elevation with any air valves open to prevent any trapped air in the main or dissolved air which will affect the pressure test and potentially disguise a leak. Any Air valve on the test section should be left opened unless it is a non-self-sealing type. Any test section of main with a volume of static head must also be calculated and the total static head recorded on the test report and on SW Pressure test proforma. The logger should always be fitted at the lowest end of the pressure test to accurately measure and record the static pressure within the test section. Page 15 of 29

16 Starting Pressures The starting pressure for any hydrostatic pressure test should preferably be zero to accurately check and validate the ramp up time of the pressure test being undertaken. The starting pressure within the main should not exceed 1 bar or the natural static head within the main being tested whichever is the greater. Any pre-pressurisation within the main must be recorded on the SW proforma to accurately validate the pressure test. Any attempt to shorten the pumping phase by increasing the initial pressure to local mains pressure (pre-pressurisation) using an adjacent main is not allowed and will result in the test being classed as invalid. Only once the main has been slowly filled with potable water (prior to pressurisation), MUST the data logger be connected and all information logged. (Unless using a dual functional logger) Start Time & Ramp Time The true pressure testing starting time starts when the pump is actually started to pressurise the main to the required (STP) System Test Pressurise and Ramp up time ends when the main reaches the required STP. The pressure should then be raised to the correct level of System Test Pressure (STP) by pumping in a controlled manner. Page 16 of 29

17 Any hydrostatic pressure test with the data logger fitted after ramping up the main and reaching System Test Pressure (STP) will be an automatic fail. Note: Photographs are a mandatory requirement for recording the flow meter readings taken both before & after the Ramp up Time to (STP) to confirm volume used & Air Content, unless they are recorded on an electronic GPS Logger. A Photograph IS still required for confirming the GPS Logger make and model used. Pressure Test Set Up Pressure Testing using Squeeze Offs, valve to valve or hydrant to hydrant is not be permitted within SW. Bored and Tapped blank plates must be fitted and used when pressure testing mains. As per IGN Oct 2015 page 5. Note: There is a Health & Safety risk to the person or person s undertaking the pressure test especially with any air trapped within the main and the hydrostatic pressure test set up detailed in the diagrams above and below. SW Preference is to have Bored & Tapped blank plates fitted to the top flange of Duckfoot bends at each end of the pressure test section to aid the removal of air and protect the main from ground water entering the main. This will facilitate and allow for the removal of as much air as possible from the test section. Page 17 of 29

18 Pressure Test Set Up (Thrust Bocks & Anchorage) Thrust Blocks & or Suitable anchorage is required for pressure testing water mains due to excessive higher pressure s being required for pressure testing. Any thrust blocks or other anchorages used must be sufficient to withstand the forces generated by the pressure test with any concrete used being adequately cured. Note: Pressure testing is a high-risk activity due to applying stored energy to any main being tested, especially with excessive levels of Air trapped within the test section. Pressure testing mains especially with excessive air content only increases the risk to the Health and Safety to the individuals carrying out the test or any other persons within or near the test area. SW requires geo tagged photographic evidence to be provided of either of the above set ups Pressure Test Set Up Prior to hydrostatic pressure testing the main being tested, it should be adequately backfilled to prevent any potential movement either lateral or from axial contraction of the pipeline with all joints preferably exposed to visually check for leaks during the test. Pressure Test Set Up (Service Connection) It is good practice that No service connections are fitted onto the main prior to the hydrostatic pressure test. Service Connection(s) must Not be tapped & bored prior to pressure testing as this is essential element for a successful pressure test. Any Service connection found to be tapped & bored prior to pressure testing will invalidate the test. Page 18 of 29

19 Pressure Test Set Up (Private Mains & Fire Mains) All pressure tests on private mains and or Fire Mains require the double check valve / Non return Valve to be removed and pieced through to accurately complete the pressure test of the main. Only on completion of the successful pressure test shall the double check valve / Non return Valve be reinstalled for chlorination and de-chlorination and sampling stages of commissioning the main. Pressure Test Set Equipment (Flow Meter & Data Loggers) All Pressure tests require either a Flow Meter & Pressure Gauge or Dual Functional Logger to capture the volumes of water required and used for the ramp up to STP (System Test Pressure). Note: Where short lengths of small bore main are being tested where a hand pump is being used and volume of water added during ramp up can be measured in the pump reservoir, it will not be required to use a flow meter. However the volume of water used must still be physically recorded on the SW proforma. SW preference is for data loggers to be fitted with GPS capabilities or requires Geo Tagged Photographic evidence to be submitted with the test report for each hydrostatic test. All Pressure test loggers must have UKAS Calibration Certifications & be traceable through UKAS standards. It is critical that the data logger is calibrated and set correctly to accurately record enough readings at the correct intervals during both the ramp up time to check for the presence of Air and to measure the rate of decay throughout the duration of the test. SW now requires all pressure tests to be submitted in both PDF and in an electronic format to check, interrogate and validate the test data. Pressure Testing Ductile Iron & Steel Mains in SW When applying either the Water Loss or Water Added method to a hydrostatic pressure test for pressure testing Ductile Iron and Steel Mains in Scottish Water the pump being used must be adequate to raise the pressure in a controlled manner and be able achieve the correct STP required. Any hydrostatic pressure test that is using the Water Added method requires a separate, specialised pump. This pump must also be able to maintain and pump continuously in a controlled manner at the required test pressure of the main / pipe being tested while measuring the volume of water being pumped into the main to maintain the test pressure. This pump should also have data logging capabilities to accurately measure the volumes of water being used. This pump can if required also be used with the Water Loss method to accurately measure the water required to bring the pipeline back to STP. Alternatively, a hand pump could be used for the Water Loss method. After preliminary condition of the main, the main must be raised to its System Test Pressure and a measurement taken with the amount of water required for either maintaining the STP using the water added method or for calculating the volume of water lost using the water loss method and must be accurately recorded. The following is the basic principal and steps required to set up to undertake either a Water Added or a Water Loss Test. Page 19 of 29

20 Water Added Pressure Testing Method Water Added Test Step 1 Requires the main to be Preliminary soaked & conditioned for a period of time prior to pressure testing (I.e. Overnight for Cement lined pipe). Step 2 Take the new main up to its System Test Pressure STD and record the time taken to achieve STP and also record the actual STP i.e. 15 BAR. (Is it necessary to record the time to reach STP?) Step 3 Maintain the STP, by pumping and adding water into the main / pipe as necessary. Step 4 Record the volume of water used to maintain STP for a period of one hour by using a volumetric container and accurately measuring the volume of water it takes to achieve this. Step 5 If the volumes of water recorded are in excess of the permissible / allowable water loss i.e. table 2 on IGN page 11 the test is a fail. Step 6 If test fails, Check main / pipe for leaks for leakage and re do the test. Water Loss Pressure Testing Method Water Loss Test A water Loss test is the calculation of the water lost within a section main after it has been raised to it STP and left for 1 hour A volumetric container must be used and be a calibrated container, which is suitable to accurately measure the expected volume loss in the main being tested. Typically a 200 ml measuring cylinder would be suitable for smaller volumes. Step 1 Requires the main to be Preliminary soaked & conditioned for a period of time prior to pressure testing (I.e. Overnight for Cement lined pipe). Step 2 Take the new main up to its required System Test Pressure STD and record both the time taken to achieve STP and also record the actual STP i.e. 15 BAR Step 3 Maintain the STP, by pumping and adding water into the pipe as necessary, the main /pipe should have the STP maintained by additional pumping for an hour. Step 4 Isolate the pump and leave the main to stand for 1 hour. Step 5 Then after one hour (no less) measure how much pressure has been lost in that period i.e Bar. Step 6 After 1 hour reconnect the pump and take the main / pipe back to up to the STP at the beginning of the test (no less)i.e. 15 BAR Step 7 At STP Isolate the pump and then draw off the pressure that was lost in the initial hour and measure that volume of water using a volumetric container accurately measure the volume of water required to be removed to get the main to test pressure recorded after 1 hour i.e Bar. Step 8 If the volumes of water recorded are in excess of the permissible / allowable water loss i.e. table 2 on IGN page 11 the test is a fail. Step 9 If test fails, Check main / pipe for leaks for leakage and re do the test. If the volume of Water Added or the volume of Water Lost (i.e. removed and drawn off) is less than the ALLOWABLE volumes in the table below the test s is a PASS. If the volume is greater than the allowable volumes the test is a fail. These are small volumes measure and record and require a pressure gauge to be 0.01 bar or less accuracy to accurately measure the System Test Pressure. Small errors in the pressure s recorded will affect the volumes of water added or drawn off and will ultimately affect the test result. Page 20 of 29

21 Standard Allowable Volumes of leakage by diameter (Litres / Per Kilometre / Per Hour) Please Note If the volume of water loss is calculated to be less than Litres, then a pressure loss test of 0.2 bar per hour should be used over the 1 hour test period. Regardless of which method is used both test methods have the same allowable rate of leakage as per the table above. To accurately calculate the volume of water used for either Water Loss Calculation of Water Added Calculation the following formula is used. Water loss = (Measured Pressure Decay Rate/ APDR) * * (ID)2 the values of the Allowable Pressure Decay Rates (APDR) are given in Table 2. Example Water Loss calculations for 900mm Steel Main 2970m Long. 900 x 900 x /1000 x 2970 = Allowable Rate of leakage is 43.3 Litres. Validation & Authorisation The companies who are carrying out hydrostatic pressure testing are required to calculate their own volumes of water required and used as well as the calculation of Air content using the table and charts within IGN Scottish Water Hydrostatic Pressure Test Proforma (Validation & Authorisation) Scottish Water new proforma as per below will be used for checking and providing validation of a hydrostatic pressure test Pass result using the information provided from both the electronic data submission and the information record on the new proforma. Page 21 of 29

22 This section of the proforma will only be available and used only by SW staff to check and validate a test result. By confirming and populating the Start Time / Ramp Up time and the relevant pressures recorded at t1, t2, and t3. (t4 if applicable.) Page 22 of 29

23 Note: SW Customer Connection staffs are required to send back confirmation and acceptance of test results submitted for contractors to proceed to the next stage of commission mains Pressure Test Volumes Calculation As part of the validation of a hydrostatic pressure test SW staff will use the new proforma and following tables and charts below for checking and confirmation of the volumes of water required against those used to achieve System Test pressure STP. This shall be cross reference with the data provided from the Flow meter to confirm any Air content which may / will affect the pressure test graph and test result SDR 17 Pressure Test Volumes Calculation Page 23 of 29

24 Ductile Iron Hydrostatic Pressure Test (Air Content Volume Calculation) It is possible to calculate the volume percentage of air present from the actual volume of water pumped into a pipeline when the pressure is raised to its test pressure (STP) using equation below Initial air content (%) = (Vw Ex) / Av1 Scottish Water s new pressure test profoma has the facility to carry out confirmation on the volumes of Air content present within a Hydrostatic Pressure test. SW will use this section of the proforma as part of validation process for authorising a successful hydrostatic pressure test result. Page 24 of 29

25 Pressure Test Graphs & Test Results A secure pipeline that is free of leakage etc should have a graph that displays the pressure decay with a constant logarithmic slope and graph. If there is either a dramatic or a consistent increase in slope during the test this would indicate leakage. If n2/n1 values are 1.25, then the test is a pass. Or alternatively if t4 calculation are used then, If n3/n1 values are 1.25, then the test is a pass. For PE pipes the longer term slope should not be above 0.13 as this rate of decay is unacceptably high and indicates a leak on the pipe. Please Note: If there is a 25% difference or Greater in either N2 or N3 values from the N1 value the test is a fail. Example 1 If n1 = 0.04 and 25% of the N value is 0.01 and the N2 value is for example 0.05 it is a pass as 0.05 / 0.04 = 1.25 and on the limit. Example 1a If n1 = 0.04 and 25% of the N value is 0.01 and the N2 value is for example 0.06 it is a failure as 0.06 / 0.04 = 1.5 and a fail. If the values are significantly less than the minimum identified, then there is too great a volume of air in the pipeline. This air will have to be removed before a satisfactory test can be performed. PE pipes: The expected slope (n) for most PE materials is between 0.07 and There are a number of factors that can affect a pressure test and the result which include the following examples, The type of pipe material being tested to its incorrect pressure rating. Pressure testing different pipe materials at the same time. Page 25 of 29

26 Excessive lengths of mains being tested. The number of sections of mains being tested at the one time. The height difference in the pipeline elevation and or the location of the pressure test set up. Static Head or Pre pressurisation of mains. The size of pump and the maximum test pressure of the pump used its flow rate for pressurisation. The presence and % of air in the system. The accuracy of the testing equipment especially if not calibrated. When the test starts and finishes and the correct t1, t2, t3 and t4 values are taken. Any actual leakage. The length of time the pressure test is required to be completed. The number of joint and fittings including Air valve or service connections if bored & tapped. Any ground movement or movement with any mechanical fittings etc Weather condition especially regarding temperature fluctuation and its effect on the creep factor of HPPE / MDPE mains No, Poor and or Inadequate pipe bedding or backfill and compaction etc. Pre Pressure Test Check List The following check list is the basic safety guidelines and the generic minimum requirements to be applied within SW that any company carrying out hydrostatic pressure testing should apply for protecting the environment and the safety of any site personnel and the general public if applicable prior to and during the hydrostatic pressure test. The Hydrostatic pressure testing company should apply their own comprehensive checks in conjunction with any other site specific requirements. Has the main being fully constructed and the main and all fittings checked, inspected and signed off ready for pressure testing? Complete a site specific Health & Safety Risk Assessment for Slips, trips and falls. Flooding. Freezing over depending on weather conditions. Traffic and pedestrian access and egress. Complete Onsite environmental assessment. If an onsite assessment confirms a risk of causing either environmental damage to an ecosystem or an environmental Impact to aquatic life in the water course, the local SEPA office should be contacted to determine what control measures may be required prior to SEPA allowing the task to proceed; thereafter the SW EPI Team must be notified. Contact SW Environmental Pollution Incident (EPI) Team. Update SW EPI admin team (planned / confirmed start dates and when work is complete) EPI Helpline: remember to report, update & close all EPI events. If applicable set up appropriate environmental protection. Has an assessment been carried out on both the duration and volumes of water required for the flushing, swabbing, filling and pressure testing activities to be undertaken and the Impact to the existing water distribution network from both a water supply and water quality perspective? Page 26 of 29

27 Do you have a SW Licenced stand pipe for filling and pressure testing? Note: The hydrant stand pipe must be fitted with a double check valve. Has the main been suitably flushed, swabbed and confirmed as being clean and free from construction debris and any other foreign matter? Does the main require preliminary conditioning? Is the test area adequately signed & barricaded to keep unauthorized personnel out of the test area and at a safe distance that is sufficient to protect both site personnel and the general public if applicable from unanticipated pressure release or equipment failure. During the pressure test distinct warning signs, should be erected such as DANGER PRESSURE TESTING IN PROGRESS should be posted at the each end of the pressure test and additional locations identified in the site specific safety plan. When pressure testing in a populated area, i.e. Main rehabilitation work etc additional requirements may be required to inform and protect the public from hazards associated with pressure testing operations. Has the pressure test equipment and the main and or any pipe materials and fittings been checked and verified that they are correctly rated to withstand the test pressures. I.e. is all temporary equipment such as any hoses, connection fittings, blank flanges, isolation valves, etc, rated higher than the maximum hydrostatic pressure? Has the main been suitably back filled and the test area (blank flanges and valves etc) secured and suitably anchored to prevent either any lateral movement or axial contraction during the test. Has the pipeline elevation profile been checked and analysed, Is additional swabbing required to remove and prevent entrapped pockets of air within the test section? Are all joints left exposed for visual inspection and possible re-torqueing during or after testing? Are all Air Valves checked and left open for testing. Note: ONLY Non self-sealing should be closed. Pressure testing should preferably be undertaken during dry weather as pressure testing in wet weather or if the main is in water filled trenches it may mean that leaks are not identified or detected. Are all inline valves open to allow the passing and venting entrapped air? Has the pump to pressurise the main to STP been correctly sized? Too small of a pump will extend the test duration, and too large of a pump may prevent the control of the test pressure. Is all pressure test equipment calibrated and within date. I.e. data logger, pressure gauges, Flow Meters, temperature recorders etc Pipe material pressure test checked and confirmed i.e. SDR 17 tested to15 Bar test. Pre Pressure Test Failure During the pressure test, No staff or site employees etc must ever tamper with or tighten any bolts, fittings, joints connections, hoses etc while the main or any component are under pressure. If a leak does occur the main must be depressurize to a safe level and a repair carried out. Always check that complete depressurization in the main has occurred through the use of both pressure gauges and with visible checks before any repair is carried out. Page 27 of 29

28 After the leak on the main has been found and repaired should the pressure test be repeated and only after a time period 4 times greater than the original pressure test duration has elapsed to allow the main to fully recover from creep deformation. Hydrostatic Pressure Test Wavier Process & Criteria Any request for removal of compliance with any part of the SW DOMS Document shall be done through SW Wavier process using MCL 2211 Waiver Request Form Edition G and submitted to SW. standardsinfoline@scottishwater.co.uk Document Control This document is a CONTROLLED DOCUMENT when viewed on Wavelength. The document becomes UNCONTROLLED if printed or downloaded from Wavelength or any other source. Refer to the Wavelength site for the latest version of this document. Change Request A change to this document can be requested by completing a Change Request Form - refer to document DISTRIBUTION OPERATION and MAINTENANCE STRATEGY GOVERNANCE (DOM-WN-GOV ) for change request procedure. Legal Notice Copyright of this document is owned by Scottish Water. The document may not be copied or reproduced in any way. This document and the intellectual property rights in it belong to Scottish Water and except where you are specifically licensed to use this document, you have no right to re-use it. Disclosure of this document under freedom of information does not change the position on (i) ownership and (ii) re-use. Record of Changes and Amendments Page 28 of 29

29 Document Section/ Reference Number Document / Section Title Vers ion Num ber Date Archived Document / Section Text Affected Archived Document / Section Replaced By Safety Note B Feb 2017 Health & Safety Doc referenced W Langan Lengths & Diameters B Feb 2017 Drawing added with test requirements for various sections. W Langan Ramp Up B Feb 2017 Extended Test For Air Content W Langan Pump Selection B Feb 2017 Safety Blow Off Valve W Langan Pressure Test Set Up B Feb 2017 Pressure test Set up and location W Langan Pressure Test Set Up B Feb 2017 Start Time & Ramp Up Time W Langan Pressure Test Private Mains & Fire Mains. B Feb 2017 Pressure Testing Private Mains & Fire Mains. remove Double Check Valve / Non return Valve Water Loss Step added and guidance Pressure Testing DI & Steel Mains B Feb 2017 Pressure Test Graphs & Test Results B Feb 2017 Added Example W Langan W Langan W Langan Page 29 of 29