1、PPI Guidelines for QualificationTesting of Mechanical Couplingsfor PE Pipes in PressurizedWater or Sewer ServiceTN-22/011825 Connecticut Ave., NW Suite 680 Washington, DC 20009P: 202-462-9607F: 202-462-9779www.plasticpipe.org2ForewordThis report was developed and published with the technical help an
2、d financialsupport of the members of the PPI (Plastic Pipe Institute, Inc.). The membershave shown their interest in quality products by assisting independent standards-making and user organizations in the development of standards, and also bydeveloping reports on an industry-wide basis to help engi
3、neers, code officials,and users.This report has been prepared by PPI as a service to the industry. Theinformation in this report is offered in good faith and is believed to be accurate atthe time of its preparation, but is offered without any warranty, expressed orimplied, including WARRANTIES OF ME
4、RCHANTABILITY AND FITNESS FORA PARTICULAR PURPOSE. Any reference to testing of a particular proprietaryproduct should not be construed as an endorsement by PPI who does notendorse the proprietary products or processes of any manufacturer. Theinformation in this report is offered for consideration by
5、 industry members infulfilling their own compliance responsibilities. PPI assumes no responsibility forcompliance with applicable laws and regulations.PPI intends to revise this report from time to time, in response to comments andsuggestions from users of this note. Please send suggestions for impr
6、ovementsto the address on the cover. Information on other publications can be obtainedby contacting PPI directly or visiting the web site.The Plastics Pipe Institute, Inc.1-888-314-6774http:/www.plasticpipe.orgSeptember 20013PPI Guidelines for Qualification Testing of MechanicalCouplings For PE Pipe
7、s in Pressurized Water or SewerServiceScope and Purpose:The test methods given below apply to mechanical coupling products used to joinbutt-ends of polyethylene (PE) pipe made to AWWA C906 or 4” and larger pipesmade to ASTM F714 and used in pressurized water service for force mains,sewers, and potab
8、le water.Passing all test methods below provides reasonable assurance that themechanical coupling product may be used successfully on PE pipe at the fullpressure rating and capacity of the pipe. Testing other than what is containedherein may be required depending on the materials and design of the m
9、echanicalcoupling. The mechanical coupling manufacturer is responsible for determining ifadditional testing is required.The recommended test methods consider joint integrity and are intended formechanical couplings that both seal and restrain butt-ends of pipe. If amanufacturer wishes to test only f
10、or sealing or only for restraining, an additionaldevice for restraining or sealing is required for the in-service application.Durability and corrosion issues are not addressed in this procedure. The couplingmanufacturer must establish durability and corrosion resistance based on thecoupling material
11、 and application.Mechanical couplings for PE pipes must withstand not only the operating linepressure but also recurrent surges to 1.5 times the rated pressure, occasionalsurges to two times the rated pressure, axial loads imposed by temperaturechanges and axial loads caused by Poisson effect contra
12、ction. (See AWWAStandard C-906 for definitions of recurrent and occasional surges.)The four test categories are: (1) 1000 Hour Pressure Test to verify sealing andresistance to steady-pressure and axial pulling forces. (2) Repeated Surge Testto verify long-term surge resistance for sealing and restra
13、ining. (3) Slow CyclingTest to verify resistance to creep and stress relaxation. (4) Short-term PressureTest to provide a 1.5 safety factor against surge pressure in the coupling andrestraining components.These tests are for design qualification, and may not be applicable formanufacturing quality co
14、ntrol tests. To verify compliance with applicable4specifications, the coupling manufacturer should establish appropriatemanufacturing quality control tests.IntroductionWhen mechanical couplings are used to join PE pipes to other PE pipes or toother types of pipe, pullout restraint must be provided.
15、Water flow thrust forcesthat develop at bends or at end closures can push an unrestrained mechanicalcoupling device or an unrestrained directional fitting off the pipe end. Likewise,axial shortening from thermal contraction or from pressurizing (Poisson effects)may pull pipe out of an unrestrained m
16、echanical coupling device.Thermoplastic materials that are subjected to constant load may creep. Overtime, creep may reduce the effectiveness of clamping or restraining systems andlead to a gradual reduction in resistance to pullout or leakage. Therefore, a timecomponent is required in testing mecha
17、nical coupling devices for thermoplasticpipes. Long-term creep and stress relaxation effects may be modeled by slowpressure cycling tests that apply periods of high pressure, followed by non-pressure to enhance creep and stress relaxation.Water service applications may have occasional or recurrent p
18、ressure surges.PE pipes have exceptional resistance to surge pressures. Mechanical couplingsmust also accommodate repeated surges. In this recommended testingprocedure, surge resistance is modeled by rapid pressure cycling between ananticipated surge pressure and a baseline pressure. When the pipe i
19、s atbaseline pressure for longer time periods, the pipe undergoes stress relaxation.Fatigue tests are a means to accelerate aging and evaluate long-termperformance. Traditional accelerated aging tests for PE pipes employ elevatedtemperature or stress, or aggressive chemical environments. These tradi
20、tionalmeans, however, can be improper for mechanical coupling devices made fromnon-PE materials. In this recommended testing procedure, fatigue from rapidpressure cycling provides a means to accelerate long-term testing withoutresorting to elevated temperature or stress, or aggressive chemicals.The
21、test methods given below are for design qualification of field-assembled orfactory-assembled mechanical butt coupling devices that have been assembledin accordance with the manufacturers established recommendations.Mechanical Butt Coupling DescriptionA mechanical butt coupling is any mechanical devi
22、ce, used to couple (join)straight plain PE pipe ends to each other or to couple a plain PE pipe end toanother type of pipe in such a manner as to develop a seal and restrain the endstogether. Mechanical butt couplings may also be used to join pipe to fittings or5fittings to fittings, where the fitti
23、ngs have an end that is essentially a plain pipeend.Test MethodsTesting must be conducted safely, however, this guide does not purport toaddress all of the safety concerns, if any, associated with its use. It is theresponsibility of the user of this guide to establish appropriate safety andhealth pr
24、actices and to determine the applicability of regulatory limitationsprior to use. These tests are intended for use by the manufacturer to verifyor qualify a joint design or components of a joint design. These tests arenot intended to be used in the field to test installed systems.The test methods de
25、scribed herein are for design qualification and periodicquality assurance. They are not intended to be routine quality controltests. Manufacturers should determine appropriate quality control testsfor their devices.Sample and Specimen SizeTo qualify a particular mechanical design, testing may not be
26、 required for eachand every diameter size and DR. In general, testing should be conducted onsizes that define the intended service range, for example maximum and minimumDR and maximum and minimum diameter. If the intended service range is large,intermediate DRs and sizes should also be tested. The m
27、echanical butt-coupling manufacturer should determine suitable pipe sizes and DRs that coverthe range of the coupling design. At a minimum, the following guidelines arerecommended for consideration:Test the lowest and highest DR pipe for which the coupling ismanufactured.Test the smallest and larges
28、t diameters for which the coupling style ismanufactured. The manufacturer of the coupling is to determine iftesting is required on the intermediate sizes.The number of specimens to be tested per coupling size and DR in Item 2above should be determined by the coupling manufacturer. It isrecommended t
29、hat at least three specimens per diameter be tested ineach of the test methods.The test temperature for pipes that are intended for buried services belowthe frost line is 73 oF (23 oC). For above ground applications orapplications where the fluid temperature is above 100 oF (38 oC),6additional tests
30、 at elevated temperatures up to 140 oF (60 oC) may beappropriate. For above ground applications, additional tests that arenot discussed in this guide such as thermocycling (repeated cyclingbetween low temperature/high axial load and high temperature/lowaxial load) may also be conducted.Angular Defle
31、ctionPerform all pressure testing at the manufacturers recommended maximumallowable angular deflection, for mechanical couplings that are recommended forangular deflection by the coupling manufacturer. Bracing or restraints may berequired to hold pipe at angular deflection during testing.Test Pressu
32、reTest pressures given in each of the four test methods are for mechanicalcouplings designed for the full rated pressure of the pipe. Where the coupling isdesigned for less than the full rated pressure of the pipe, the test pressure maybe adjusted accordingly. (The coupling manufacturer is responsib
33、le for notifyingusers of the rated pressure of the coupling.)1. 1000-Hour Pressure Test at 73oF (23oC)Warning Take all precautions to ensure personal safety when conductingtests at high internal pressure.The 1000-hour pressure test is used to test the capacity of the restraint and sealsfor over pres
34、surization such as surge and for axial forces such as thermalcontraction. The test shall be conducted at a pressure producing a stress equalto the hydrostatic design basis (i.e. 1600 psi for PE 3408 materials.)1.1 Specimen LengthThe mechanical coupling being tested is installed between two equalleng
35、th sections of PE pipe. For 6” and smaller pipe, the lengthbetween end closures shall be five times the outside diameter but notless than 12”. For pipes larger than 6”, the minimum length shall bethree times the outside diameter or 30” whichever is larger. Endclosures are attached mechanically or fu
36、sed to the ends of the pipesections. Restraint or blocking of end closures that would prevent thedevelopment of full end thrust load due to pressurization shall not beused.71.2 Specimen ConditioningFill the specimen with water and condition in air for at least 16 hours orin water for at least 1 hour
37、 at the test temperature.1.3 PressurizationMaintain the test specimens at the pressure of two times the pipesrated pressure (Working Pressure Rating, WPR) at the testtemperature for a period of 1000 hours at the test temperature (73oF,unless otherwise specified.)1.4 Failure DefinitionFailure is defi
38、ned as any leakage through the joint or wall of the pipe or acoupling that breaks, slips off the pipe, tears the pipe, or otherwisedisengages from the pipe. Remove the coupling and inspect the pipesurface. There shall be no surface damage to the pipe other than theordinary marks and impressions due
39、to the restraining device. Cracks,splits, or delaminations extending from any impressions will be consideredfailure.2. Cyclical Pressure TestWarning Take all precautions to ensure personal safety when conductingtests at high internal pressure.Cyclical testing is used to assess the mechanical couplin
40、gs resistance to surgepressures that may occur in water and force main sewer applications.2.1 Specimen PreparationAs described above for the 1000-hour pressure test, end caps may befused or attached to the plain ends of the pipe before or after couplingassembly. Other than the mechanical coupling, n
41、o restraint or blockingshall be applied to the specimen that would prevent the PE pipe fromdeveloping the full end thrust load due to pressurization.2.2 Specimen LengthThe mechanical coupling being tested is installed between two equallength sections of PE pipe. For 6” and smaller pipes, the specime
42、nlength between end closures shall be five times the outside diameterbut not less than 12”. For pipe sizes larger than 6” but not more than20”, the minimum length shall be three times the outside diameter or30”, whichever is larger. For pipe sizes greater than 20”, the specimenlength shall be three
43、times the outside diameter but not greater than72”. Restraint or blocking of end closures that would prevent thedevelopment of full end thrust load due to pressurization shall not beused.82.3 ConditioningFill the specimen with water and condition in air for at least 16 hours orin water for at least
44、1 hour at the test temperature.2.4 Cyclical pressurizationCyclical pressurization consists of increasing the internal pressure ofthe pipe from the pipes base pressure to a peak pressure equal twotimes the pipes rated pressure (Working Pressure Rating, WPR).Base pressure is defined as the rated press
45、ure for the tested DR at thetest temperature (73oF, unless otherwise specified). Bring thespecimen from base pressure to peak pressure and back to basepressure at the rate of 6 to 10 cycles/min. A device for counting thecycles shall be built into the test device along with a method ofdetecting leaka
46、ge and recording the number of cycles at leakage.2.5 Minimum Number of CyclesThe minimum number of cycles for the test specimen is 1,000,000cycles from base pressure to peak pressure.2.6 Failure DefinitionFailure is defined as any leakage through the joint or wall of the pipe ora coupling that break
47、s, slips off the pipe, tears the pipe, or otherwisedisengages from the pipe. Remove the coupling and inspect the pipesurface. There shall be no surface damage to the pipe other than theordinary marks and impressions due to the restraining device. Cracks,splits, or delaminations extending from any im
48、pressions will beconsidered failure.3. Slow Cycling Pressure TestWarning Take all precautions to ensure personal safety when conductingtests at high internal pressure.This test is intended to determine the effects of creep and stress relaxation onjoint integrity. The slow cycling test is intended to
49、 model a connection that hasbeen pressurized, and then allowed to be depressurized for an extended timeperiod. This would simulate a system that after leak testing, is idle for a timebefore being placed in service, or a system that has been in service, and is thencompletely depressurized for maintenance or power loss or the like.3.1 Specimen PreparationAs described above for the 1000-hour pressure test, end caps may befused or attached to the plain ends of the pipe before or after coupling9assembly. Other than the mechanical coupling, no restraint or blockingshall
