1、Designation: F948 94 (Reapproved 2011)Standard Test Method forTime-to-Failure of Plastic Piping Systems and ComponentsUnder Constant Internal Pressure With Flow1This standard is issued under the fixed designation F948; the number immediately following the designation indicates the year of originalad
2、option or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the time-to-failure of pl
3、astic piping products under constant internalpressure and flow.1.2 This test method provides a method of characterizingplastics in the form of pipe, components, and systems underany reasonable combination of internal and external tempera-tures and environments, under the procedures described.1.3 Thi
4、s test method can be used to characterize the testedplastic materials or products, or both, on the basis of pressure-,or stress-rupture data developed under the conditions pre-scribed.1.4 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathema
5、ticalconversions to SI units that are provided for information onlyand are not considered standard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and healt
6、h practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D543 Practices for Evaluating the Resistance of Plastics toChemical ReagentsD2122 Test Method for Determining Dimensions of Ther-moplastic Pipe and FittingsD2837 Test Method
7、 for Obtaining Hydrostatic Design Basisfor Thermoplastic Pipe Materials or Pressure Design Basisfor Thermoplastic Pipe ProductsD2992 Practice for Obtaining Hydrostatic or Pressure De-sign Basis for “Fiberglass” (Glass-Fiber-ReinforcedThermosetting-Resin) Pipe and FittingsD3567 Practice for Determini
8、ng Dimensions of “Fiberglass”(Glass-Fiber-Reinforced Thermosetting Resin) Pipe andFittingsE177 Practice for Use of the Terms Precision and Bias inASTM Test Methods2.2 PPI Documents:TR-2 Policies and Procedures for the Listing of Thermoplas-tic Pipe, Fittings, and Fixture Materials When EvaluatedUnde
9、r Constant Internal Pressure With Flow3TR-3 Policies and Procedures for Developing Recom-mended Hydrostatic Design Stresses for ThermoplasticPipe Materials33. Terminology3.1 Definitions:3.1.1 failurebursting, cracking, splitting, or weeping(seepage of test fluid through the wall of the product) duri
10、ngthe test, which results in the inability of the specimen tomaintain pressure or contain the internal test fluid, shallconstitute failure of the test specimen. Failure may sometimesoccur by ballooning, an excessive extension leading to struc-tural failure. When failure occurs by ballooning the degr
11、ee ofdistension should be recorded. Assemblies may also fail tojoint leakage or separation.NOTE 1Overall distension, which results from creep caused bylong-term stress, is not considered to be a ballooning failure.3.1.2 hoop stressthe tensile stress in the wall of the pipingproduct in the circumfere
12、ntial direction due to internal pres-sure. Units will be reported as pounds per square inch (psi) ormega pascals (MPa). Hoop stress will be calculated by thefollowing ISO equation:S 5 P D 2 t!/2twhere:S = hoop stress, psi (MPa),1This test method is under the jurisdiction of ASTM Committee F17 on Pla
13、sticPiping Systems and is the direct responsibility of Subcommittee F17.40 on TestMethods.Current edition approved Aug. 1, 2011. Published August 2011. Originallyapproved in 1985. Last previous edition approved in 2006 as F948 94(2006). DOI:10.1520/F0948-94R11.2For referenced ASTM standards, visit t
14、he ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Plastics Pipe Institute (PPI), 105 Decker Court, Suite 825,Irving, TX 75062, http:/w
15、ww.plasticpipe.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1D = average outside diameter, in. (mm),P = internal pressure, psig (MPag), andt = mimimum wall thickness in. (mm).NOTE 2Hoop stress should only be determined on straig
16、ht hollowcylindrical specimens. Products of more complex shape may be evaluatedby Option 2 of Appendix X1 based on pressure.3.1.3 make-up fluidan exchange of internal fluid withfresh fluid at a minimum rate of 10 % of the total systemvolume per week.3.1.4 maximum internal surface temperaturethat tem
17、pera-ture attained when increased fluid velocity results in no furtherincrease in the outside surface temperature of the specimen(see X2.7).3.1.5 pressurethe force per unit area exerted by the testfluid in the piping product. Units will be reported as pounds persquare inch gage (psig) or mega pascal
18、s gage (MPag).3.1.6 test assemblycomponents (such as, pipe, fittings,valves, etc.) tested separately or together in an array that maysimulate an actual field system that might include joints,fusions, plastic-to-metal transitions, etc.4. Summary of Test Method4.1 This test method consists of exposing
19、 specimens ofextruded, molded, or otherwise manufactured pipe or compo-nents (such as fittings, valves, assemblies, etc.) to a constantinternal pressure by a flowing test fluid of controlled tempera-ture and composition, while in a controlled external environ-ment. Time-to-failure and specimen surfa
20、ce temperatureshould be measured during exposure under the test conditions.Unless otherwise specified the internal fluid shall be water andthe external environment will be air.5. Significance and Use5.1 The data obtained by this test method are useful forestablishing pressure, or hoop stress where a
21、pplicable, versusfailure-time relationships, under independently controlled in-ternal and external environments that simulate actual antici-pated product end-use conditions, from which the design basis(DB) for piping products or materials, or both, can be deter-mined. (Refer to Test Method D2837 and
22、 Practice D2992, andAppendix X1 of this test method.)NOTE 3Reference to design basis (DB) in this test method refers tothe hydrostatic design basis (HDB) for material in straight hollowcylindrical shapes where hoop stress can be easily calculated, or is basedon applied pressure design basis (PDB) fo
23、r complex-shaped products orsystems where complex stress fields seriously prohibit the use of hoopstress.5.2 In order to characterize plastics as piping products, it isnecessary to establish the stress-to-rupture-time, or pressure-to-rupture-time relationships over two or more logarithmicdecades of
24、time (hours) within controlled environmental pa-rameters. Because of the nature of the test and specimensemployed, no single line can adequately represent the data.Therefore, the confidence limits should be established.5.3 Results obtained at one set of environmental conditionsshould not be used for
25、 other conditions, except that highertemperature data can be used for a design basis assignment forlower application temperatures, provided that it can be dem-onstrated that the application conditions present a less stringentenvironment. The design basis should be determined for eachspecific plastic
26、 material and each different set of environmentalconstraints. Design and processing can significantly affect thelong-term performance of piping products, and thereforeshould be taken into consideration during any evaluation (seeAppendix X2).5.4 Specimens used must be representative of the pipingprod
27、uct or material under evaluation (see Appendix X2).6. Apparatus6.1 Constant-Temperature System:6.1.1 Controlling the Internal Environment of TestSpecimensAny system that will ensure that the test fluidentering and exiting the test specimen is maintained at aconstant temperature within6 3.6F (62C) th
28、roughout theduration of the test.6.1.2 Controlling the External Environment of TestSpecimensAny system that will ensure constant externalenvironment temperature within 63.6F (62C) throughoutthe duration of the test.6.2 Dynamic Flowing Pressure SystemAny device that iscapable of continuously applying
29、 a constant internal pressurewithin the tolerance limits defined in Table 1, while allowing acontinuous flow through the test specimens. The flow rateshould be substantial enough to control the internal tempera-ture of each test specimen. The device shall be capable ofreaching the test pressures wit
30、hout exceeding it, and holdingthe pressures within the tolerances listed in Table 1 for theduration of the test.NOTE 4Pressure variations from pumps may exceed the tolerancelimits. (See X2.6.)6.3 Pressure GageA pressure measuring instrument ca-pable of determining the internal pressure of the test s
31、peci-men(s) within the limits as required in Table 1.6.4 Timing DeviceAny timing device or system capable ofdetermining the time-to-failure for each test specimen, withinthe tolerances listed in Table 1.6.5 Specimen HolderAny device that will support thespecimens, but will minimize externally induce
32、d stresses.Provisions shall be made to allow for normal bidirectionalthermal expansion of the test specimen.6.6 Feed-and-Bleed SystemProvisions shall be made tointroduce fresh make-up fluid to the system while bleeding offan equivalent amount necessary to maintain a constant volumeand ensure constan
33、t composition of the test fluid. This systemshould be designed to maintain composition of the internalfluid within prescribed limits.TABLE 1 Tolerances for Testing Thermoplastic Piping ProductsTest Periods, h Pressure, % Time, %0 to 10 0.5 0.510 to 100 0.5 1.0100+ 1.0 2.0F948 94 (2011)26.7 Other Pro
34、visionsAdditional provisions may be neces-sary to maintain constant composition.6.8 Flow ControlProvisions shall be made to ensure thatthe internal fluid velocity shall be adequate to ensure constantinternal temperature in the specimen within 63.6F (62C). Inthe special case of hot water inside/ambie
35、nt air outside,provision shall be made to ensure maximum internal surfacetemperature of the specimen within 63.6F (62C).7. Test Specimens7.1 MaterialMaterial evaluation shall be done on cylin-drical test specimens molded or formed by the same process asthe actual product. Unless otherwise specified
36、the part shallmeet the specimen requirements as follows:7.1.1 Injection MoldedThe test specimens shall be injec-tion molded tubes with as uniform a wall as technicallypossible. The mold shall be side-gated so that a bond line iscreated lengthwise along the tubular test specimens (see Note5). The wor
37、king exposed length of the specimen in the testshall have a minimum length to actual outside diameter ratio of5to1.NOTE 5The PPI Hydrostatic Stress Board is currently evaluating thequestion of side versus end gating as part of a broad study of theforecasting of the long-term strength of fittings.7.1
38、.2 ExtrusionThe specimen length between end clo-sures shall be not less than 5 times the nominal outsidediameter of the pipe, but in no case less than 12 in. (300 mm).7.1.3 OthersFor manufacturing processes other than thosespecified, straight hollow cylindrical shapes produced by theprocess should b
39、e used as specimens for evaluating thematerial. Restriction of 7.1.2 should apply.7.2 End-Use ProductsActual commercial designs simu-lating end-use products shall be representative of the finalproduct design and manufacturing process (see Appendix X2).7.3 Systems and AssembliesSystem or subsystem de
40、signsthat include joints or other assembly techniques which repre-sent field installations, or both, may be tested.7.4 MeasurementsDimensions shall be determined in ac-cordance with Test Method D2122 or Practice D3567, whereapplicable.8. Conditioning8.1 If the external environment is gaseous, test s
41、pecimensshall be conditioned in the external air or gaseous environmentfor a minimum of 16 h before pressurizing the internal testfluid. If the external environment is a liquid, test specimensshall be conditioned for a minimum of 1 h. This conditioningperiod may be concurrent with internal condition
42、ing usingflowing internal test fluid. Refer to Table 2.8.2 The internal test fluid shall be circulated through the testspecimens for a minimum of1hifliquid, or 16 h if gaseous,before applying test pressure. Refer to Table 2.9. Procedure9.1 Attach the specimens or assemblies to the systemsupported in
43、 a manner that will minimize externally inducedstresses and minimize entrapment of gas in the specimen whenthe internal fluid is a liquid.9.2 After conditioning the specimens as specified in Section8, adjust the pressure to produce the desired loading. Apply thepressure to the specimens and make sur
44、e the timing deviceshave started after reaching the assigned pressure. Pressuresshould be preset prior to loading test specimens in order toavoid overstressing the specimens during pressure settingprocedure.9.3 Periodically, measure the surface temperature of eachtest specimen (see X2.7) and the air
45、 temperature near the testspecimens surface.9.3.1 Any failure occurring within one pipe diameter of thejoining system of the test assembly to test apparatus should beexamined carefully. If there is any reason to believe that thefailure was attributable to the joining system, this data pointshould no
46、t be used in the regression equation computations.9.3.2 All data must be reported, whether employed in theregression analysis or not. Widely scattered failures may beindicative of performance to be expected in the field. Ifcircumstances can be determined for inconsistent testperformance, the reason
47、should be so noted with the failuretime.10. Report10.1 Report the following information:10.1.1 Complete identification of the sample, includingmaterial type, source, manufacturers name and code number,and previous significant history, if any.10.1.2 Specimen dimensions, including nominal size and,whe
48、n applicable, average and minimum wall thickness, aver-age outside diameter and length to diameter ratio.10.1.3 A sketch of the test specimen shall be included in thereport.10.1.4 Fluid temperatures inside and outside the specimen.10.1.4.1 For Water Inside/Ambient Air OutsideReportfluid temperatures
49、 entering and leaving the specimen, airtemperature around the specimens, minimum external surfacetemperature of the specimens, and method used to measuresurface temperature of the specimens.10.1.5 Test environments inside and outside the specimen.10.1.6 A table of pressures or stresses, or both, and therespective time-to-failure in hours for all the specimens tested.10.1.6.1 In those cases where pressure variations couldaffect the life performance, pressure variations should bereported (see X2.6).10.1.7 The nature of the failures in acco
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