# ASTM F725-03 (Reapproved 2013)

Designation F725 03 Reapproved 2013Standard Practice forDrafting Impact Test Requirements In Thermoplastic PipeAnd Fittings Standards1This standard is issued under the fixed designation F725; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice describes a procedure for setting up impacttest requirements on the basis of test data obtained by Test D2444.1.2 This practice is applicable to thermoplastic pipe andfittings.1.3 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for ination onlyand are not considered standard.1.4 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 health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards2D2444 Test for Determination of the Impact Resis-tance of Thermoplastic Pipe and Fittings by Means of aTup Falling Weight3. Terminology3.1 Definitions of Terms Specific to This Standard3.1.1 binomial probability equationthe equation that de-fines the chance for exactly r specimens to pass, when n aretested, given p, the chance that a single specimen chosen atrandom will pass. It is expressed as followsrPn5nrn 2 r pr1 2 pn2r1NOTE 1The factorial of zero is one.3.1.2 binomial testa test that has only two possible resultsfor example, pass or fail, heads or tails, true or false.3.1.3 mean strengththe average strength of the total popu-lation see Note 2.3.1.4 OC curve operating characteristic curve a graphthat illustrates the chance of success or failure when a givenspecification at is employed, given any quality level from0 to 1 0 to 100 passing in the lot from which test specimensare selected.3.1.5 probability graph papercommercially availablegraph paper that provides straight-line plots when the distribu-tion of attributes is normal. For a discussion on the use ofproability graph paper, see Test D2444 Appendix X2.3.1.6 specification atthe rules set forth by the testrequirement, including the number of specimens to be testedand the minimum acceptable number of passes.3.1.7 standard deviationa statistical term that relates tothe size of the expected variation in test results.NOTE 2The terms “mean,” “normal distribution,” and “standarddeviation” are dealt with in elementary statistics textbooks.4. Summary of Practice4.1 Round-robin tests of representative pipe and fittingsspecimens are pered to identify the energy levels at which90 or more of the specimens in acceptable lots will pass. Apreferred test at is listed. The B-tup and the V-blockholder, and room-temperature conditioning and tests are pre-ferred choices.5. Significance and Use5.1 This practice is used for drafting impact test specifica-tion requirements, and it presupposes no special familiaritywith statistical s. It provides for specification valuesthat will pass acceptable lots with a high degree of certainty.The impact test requirement is intended to discriminate be-tween acceptable materials and manufacturing s andthose which are not; it is not a simulated service test.6. Procedure6.1 Test thermoplastic pipe or fittings specimens in accor-dance with Test D2444, and plot the test results onprobability graph paper.1This practice is under the jurisdiction of ASTM Committee F17 on PlasticPiping Systems and is the direct responsibility of Subcommittee F17.40 on Tests.Current edition approved Aug. 1, 2013. Published October 2013. Originallyapproved in 1981. Last previous edition approved in 2008 as F725 0320081.DOI 10.1520/F0725-03R13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume ination, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States16.2 It will be clear, from the probability paper plot, that theenergy level where 98 or 99 of all specimens would passwill be low. On the one hand, when the test at requires thatfive of five, or six of six, or nine or ten of ten tested shall pass,or the lot rejected, then the specified energy levels mustcorrespond to these levels see Fig. 1, the operating character-istic OC curve for the “nine or ten of ten” test at. On theother hand, five of five, six of six, and nine or ten of ten testsat low energy levels will not screen marginal or poor lotseffectively. See Fig. 1 again.6.3 A at which will accept reliably when 90 or moreof the specimens in acceptable lots would pass, and rejectreliably when 60 or fewer would pass, is as follows6.3.1 “X.X Test ten specimens. When nine or ten pass,accept the lot. When six or fewer pass, reject the lot. Whenseven or eight pass, test ten additional specimens. When 17 ormore of 20 pass, accept the lot. When 13 or fewer of 20 pass,reject the lot. When 14, 15, or 16 pass, test 20 additionalspecimens. When 32 or more of 40 pass, accept the lot. When31 or fewer pass, reject the lot.”6.3.2 The OC curve for this at is illustrated in Fig. 2.6.4 Specimen LengthThe pipe specimen length should be6 in. 150 mm 614 in. 6mm.6.5 Choice of Tup and HolderThe B tup is preferred. Itprovides a good compromise between energy concentration inthe specimen and therefore reduced test energy levels, andresistance to damage in service. The V-block holder is pre-ferred for pipe specimens; it provides for greater energyconcentration, and for failures in a range of thin-walledspecimens which would merely flatten on the flat-plate holder.6.6 Test ConditionsRoom-temperature tests are preferred.They can be pered by the manufacturer on a timely basis,so that the size of questionable or defective inventories isminimized. Binomial tests are relatively crude, unless largenumbers of specimens are subjected to test. The expense andinconvenience of low-temperature conditioning render it a poorchoice study Fig. 1 together with a data plot pered inaccordance with Test D2444 to fully grasp the meritsof this statement.7. Multiple-Product Standards7.1 Many thermoplastic pipe and fittings specifications listlarge numbers of products. Test D2444 requires that atleast 100 test specimens shall be employed for each single testrun in order that the impact properties can be measured withuseful accuracy. The cost of round-robin tests on each size ofthe products in the standard may approach or exceed the valueof the ination to be obtained.7.2 Testing costs can be significantly reduced by peringpreliminary tests on the largest sizes listed, to determinewhether or not a cut-off point exists above which all specimenswill pass at an energy level of 300 ftlbf 407 J ordinarily thehighest test energy level listed in a thermoplastic pipe orfittings impact test requirement.7.2.1 Following these tests, a limited number of represen-tative sizes can be selected, and round-robin testing pered.7.2.2 The results of these tests are analyzed. List the energylevels where the failure level was 10 for each size tested, anddivide the energy levels by the specimen volumes in cubicinches. Plot the results against the specimen outside diameters,and label the points if it is a multiple SDR specification. In aspecification which included 25 sizes of pipe, and seven SDRseries, for example, three sizes each of three different SDRseries of pipe might be tested preliminarily. The points for eachSDR series would be connected with a curve, and from theplots the appropriate trial energy levels for six untested sizesand SDRs calculated.7.3 One hundred test specimens of each of the six untestedsizes would be prepared, and subjected to test. If 85 to 95specimens in each lot passed, the degree of correlation wouldbe good.7.4 Depending upon the degree of correlation obtained,proceed to calculate the test energy levels for each untestedFIG. 1 O.C. Curve for Nine or Ten of TenFIG. 2 O.C. Curve for Section 6.3F725 03 20132size, factor all energy levels back by an appropriate amount anddraft the test specification proposal, or else conduct additionaltests.7.5 The tup weight and style listed in the proposal should bethe same as that used for the preliminary tests.8. Special Considerations8.1 FittingsThe flat-plate holder is employed for fittingsimpact tests. Shims may be required, depending on fittingsconfiguration. Fittings should be impacted on a horizontalsurface, as close to the center of mass as is practical.Ordinarily, the specification will require that half the fittings beimpacted on one side, and half on the other.8.2 Thin-Walled PipeThin-walled pipe may undergo com-plete closure without failure particularly if the flat-plate holderis employed. Impact testing may still serve a useful purpose,however, since the energy levels required to flatten acceptablespecimens may result in failure of improperly manufacturedspecimens.8.3 Yard-Aged PipeThe impact test is not ordinarily speci-fied on yard-aged pipe since many thermoplastic pipe materialsare subject to reduction in impact strength as the result ofexposure to ultraviolet rays.9. Keywords9.1 drafting impact; drafting impact requirements; impact;plastic pipe; plastic tubing; thermoplastic pipe; thermoplastictubingAPPENDIXESNonmandatory InationX1. THE OPERATING CHARACTERISTIC OC CURVEX1.1 PurposeThe OC curve gives an accurate picture ofthe impact-test relationship between a particular test sampleand the total population. Specifically, the curve provides thechance of success of a sample when given testing regimen isemployed. This relationship is ordinarily too complex to bearrived at on the basis of guesswork.X1.2 Constructing the OC CurveStart by listing the num-ber of ways in which success can be achieved For example, ina “7 or more out of 10” specification at, the lot is acceptedwhen 7, 8, 9, or 10 out of 10 specimens pass. Use the binomialprobability equation to obtain an expression for the chance thateach of these events will occur. See example. uate thechances, substituting values for p ranging from 0 to 1. Sum thechances of success, for each chosen value of p. Plot the resultschance of success, against p to obtain the curve.ExampleOC Curve for a “7 or more out of 10” specificationat. The chance that 7 out of 10 will pass equals,1073p71 2 p3or 120 p71 2 p3X1.1Substitute values ranging from 0.1 to 0.9 for p, and tabulatethe resultsp7P100.10.0000.20.0010.30.0090.40.0420.50.1170.60.2150.70.2670.80.2010.90.057In like manner, tabulate the chance that 8, 9, or 10 will pass.p 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9Odds of 7 0.000 0.001 0.009 0.042 0.117 0.215 0.267 0.201 0.0578 0.000 0.000 0.001 0.011 0.044 0.121 0.233 0.302 0.1949 0.000 0.000 0.000 0.002 0.010 0.040 0.121 0.268 0.38710 0.000 0.000 0.000 0.000 0.001 0.006 0.028 0.107 0.349Totals 0.000 0.001 0.010 0.055 0.172 0.382 0.649 0.878 0.987When the totals are plotted against p, the OC curve results.Note that calculation increments smaller than 0.1 will providemore accuracy. A spreadsheet is useful in uating thebinomial probability equation.F725 03 20133X2. MEASURING CONANCE TO EXISTING TEST REQUIREMENTSX2.1 A variety of impact test specification ats are incurrent use. The ination provided in the OC curve for eachof them can be expressed in mathematical terms. To identifythe chance that a given manufacturing process will pass the testrequirement, select at least 100 test specimens, and subjectthem to the impact test listed. Express the decimal percentpassing as p, and substitute in the appropriate equation For a5 out of 5 test requirement, Psuccess p5For a 6 out of 6 test requirement, Psuccess p6For a 10 out of 10 test requirement, Psuccess p10For a 12 out of 12 test requirement, Psuccess p12Fora5of5or9of10test, Psuccess p515p45p5Fora6of6or11of12test, Psuccess p616p56p6Fora9ormore out of 10 test, Psuccess p9109pFora7ormore out of 10 test, Psuccess 120 p7 315p8 280p984p10For the procedure listed in 6.3, the ula is 3 225p361 p475300p351 p5 828 750p341 p6 5 728 500p331 p7 62 312 400p321 p8 570p171 p 345p181 p210p91 pp10X2.2 The results from a 100-specimen test may not corre-late accurately with the quality level in the population. Thestandard error for a 100-specimen test is approximately 0.0568 of the time the measured results will not be in error bymore than 0.05, and 95.5 of the time they will not be in errorby more than 0.10. If better accuracy is required then morespecimens should be tested. The approximate equation for thestandard error is P1 P/N1/2.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. 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