1、Designation: F 948 94 (Reapproved 2006)An American National StandardStandard Test Method forTime-to-Failure of Plastic Piping Systems and ComponentsUnder Constant Internal Pressure With Flow1This standard is issued under the fixed designation F 948; the number immediately following the designation i
2、ndicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determinat
3、ion of the time-to-failure of plastic 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
4、the procedures described.1.3 This 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 the standard.1.5 This
5、 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 health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents
6、2.1 ASTM Standards:D 543 Practices for Evaluating the Resistance of Plastics toChemical ReagentsD 2122 Test Method for Determining Dimensions of Ther-moplastic Pipe and FittingsD 2837 Test Method for Obtaining Hydrostatic DesignBasis for Thermoplastic Pipe Materials or Pressure DesignBasis for Therm
7、oplastic Pipe ProductsD 2992 Practice for Obtaining Hydrostatic or Pressure De-sign Basis for “Fiberglass” (Glass-Fiber-ReinforcedThermosetting-Resin) Pipe and FittingsD 3567 Practice for Determining Dimensions of “Fiber-glass” (Glass-Fiber-Reinforced Thermosetting Resin) Pipeand FittingsE 177 Pract
8、ice for Use of the Terms Precision and Bias inASTM Test Methods2.2 PPI Documents:TR-2 Policies and Procedures for the Listing of Thermo-plastic Pipe, Fittings, and Fixture Materials When Evalu-ated Under Constant Internal Pressure With Flow2TR-3 Policies and Procedures for Developing Recom-mended Hy
9、drostatic Design Stresses for ThermoplasticPipe Materials23. Terminology3.1 Definitions:3.1.1 failurebursting, cracking, splitting, or weeping(seepage of test fluid through the wall of the product) duringthe test, which results in the inability of the specimen tomaintain pressure or contain the inte
10、rnal 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 degree ofdistension should be recorded. Assemblies may also fail tojoint leakage or separation.NOTE 1O
11、verall 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 circumferential direction due to internal pres-sure. Units will be reported as pounds per square inch (psi)
12、ormega pascals (MPa). Hoop stress will be calculated by thefollowing ISO equation:S 5 P D 2 t!/2twhere:S = hoop stress, psi (MPa),D = average outside diameter, in. (mm),P = internal pressure, psig (MPag), andt = mimimum wall thickness in. (mm).NOTE 2Hoop stress should only be determined on straight
13、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.1This test method is under the jurisdiction of ASTM C
14、ommittee F17 on PlasticPiping Systems and is the direct responsibility of Subcommittee F17.40 on TestMethods.Current edition approved Aug. 1, 2006. Published August 2006. Originallyapproved in 1985. Last previous edition approved in 2001 as F 948 94(2001)e1.2Available from Plastics Pipe Institute, D
15、ivision of The Society of the PlasticsIndustry, 250 Park Avenue, New York, NY 10017.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.4 maximum internal surface temperaturethat tem-perature attained when increased fluid velocity re
16、sults in nofurther increase in the outside surface temperature of thespecimen (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 pascals gage (MPag).3.1.6 test assemblycomponents (such a
17、s, 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 specimens ofextruded, molded, or otherwise manufac
18、tured 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 surface temperatureshould be measured during exposure un
19、der 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 applicable, versusfailure-time relationships, under
20、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 D 2837 and Practice D 2992, andAppendix X1 of this test meth
21、od.)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) for complex-shaped products orsystems where complex
22、 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 time (hours) within controlled environmental pa-r
23、ameters. 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 other conditions, except that highertemperature
24、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 material and each different set of environmental
25、constraints. 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 pipingproduct or material under evaluation (see Appendix X2
26、).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) throughout theduration of the test.6.1.2 Controllin
27、g 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 a constant internal pressurewithin the tolerance
28、 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 without exceeding it, and holdingthe pressures withi
29、n 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 speci-men(s) within the limits as required in Tabl
30、e 1.6.4 Timing DeviceAny timing device or system capableof determining the time-to-failure for each test specimen,within the tolerances listed in Table 1.6.5 Specimen HolderAny device that will support thespecimens, but will minimize externally induced stresses.Provisions shall be made to allow for
31、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 constant composition of the test fluid. This systemshoul
32、d be designed to maintain composition of the internalfluid within prescribed limits.6.7 Other ProvisionsAdditional 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 constantinte
33、rnal temperature in the specimen within 63.6F (62C). Inthe special case of hot water inside/ambient 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
34、 specimens molded or formed by the same process asTABLE 1 Tolerances for Testing Thermoplastic Piping ProductsTest Periods, h Pressure, % Time, %0to10 60.5 60.510 to 100 60.5 61.0100+ 61.0 62.0F 948 94 (2006)2the actual product. Unless otherwise specified the part shallmeet the specimen requirements
35、 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 working exposed length of the specimen in the t
36、estshall 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.7.1.2 ExtrusionThe specimen length between end
37、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 thanthose specified, straight hollow cylindrical shapes produced bythe process should be used as specimens for evaluating themateri
38、al. 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 designsthat include joints or other assembly t
39、echniques which repre-sent field installations, or both, may be tested.7.4 MeasurementsDimensions shall be determined in ac-cordance with Test Method D 2122 or Practice D 3567, whereapplicable.8. Conditioning8.1 If the external environment is gaseous, test specimensshall be conditioned in the extern
40、al 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 conditioning usingflowing internal test fluid. Refe
41、r 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 a manner that will minimize externally in
42、ducedstresses 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 sure the timing deviceshave started after rea
43、ching 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 temperature near the testspecimens surfac
44、e.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 not be used in the regression equation compu
45、tations.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 test perfor-mance, the reason should be so noted with the failure time
46、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,when applicable, average and minimum wall
47、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 entering and leaving the specimen, air
48、temperature 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
49、 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 accordance with 3.1.1.Inthe case of test assemblies, the failure type and location (suchas, fitting, joint, seal, etc.) must be included.10.1.8 Any unusual behavior observed in the tests. Anychange in color, surface texture, or other change in appearancethat may be the result of a physical, chemical, or environmentaleffect must be reported, whether or
copyright@ 2008-2019 麦多课文库（www.mydoc123.com）网站版权所有
备案/许可证编号：苏ICP备17064731号-1