ASTM_D_2837_-_13e1.pdf

Designation:D2837131Standard Test Method forObtaining Hydrostatic Design Basis for Thermoplastic PipeMaterials or Pressure Design Basis for Thermoplastic PipeProducts1This standard is issued under the fixed designation D2837;the number immediately following the designation indicates 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()indicates an editorial change since the last revision or reapproval.1NOTETable 8 was editorially corrected in April 2014.1.Scope*1.1 This test method describes two essentially equivalentprocedures:one for obtaining a long-term hydrostatic strengthcategory based on stress,referred to herein as the hydrostaticdesign basis(HDB);and the other for obtaining a long-termhydrostatic strength category based on pressure,referred toherein as the pressure design basis(PDB).The HDB is basedon the materials long-term hydrostatic strength(LTHS),andthe PDB is based on the products long-term hydrostaticpressure-strength(LTHSP).The HDB is a material propertyand is obtained by evaluating stress rupture data derived fromtesting pipe made from the subject material.The PDB is aproduct specific property that reflects not only the properties ofthe material(s)from which the product is made,but also theinfluence on product strength by product design,geometry,anddimensions and by the specific method of manufacture.ThePDB is obtained by evaluating pressure rupture data.TheLTHS is determined by analyzing stress versus time-to-rupture(that is,stress-rupture)test data that cover a testing period ofnot less than 10 000 h and that are derived from sustainedpressure testing of pipe made from the subject material.Thedata are analyzed by linear regression to yield a best-fitlog-stress versus log time-to-fail straight-line equation.Usingthis equation,the materials mean strength at the 100 000-hintercept(LTHS)is determined by extrapolation.The resultantvalue of the LTHS determines the HDB strength category towhich the material is assigned.The LTHSPis similarlydetermined except that the determination is based on pressureversus time data that are derived from a particular product.Thecategorized value of the LTHSPis the PDB.An HDB/PDB isone of a series of preferred long-term strength values.This testmethod is applicable to all known types of thermoplastic pipematerials and thermoplastic piping products.It is also appli-cable for any practical temperature and medium that yieldsstress-rupture data that exhibit an essentially straight-linerelationship when plotted on log stress(pound-force per squareinch)or log pressure(pound-force per square in.gage)versuslog time-to-fail(hours)coordinates,and for which this straight-line relationship is expected to continue uninterrupted throughat least 100 000 h.1.2 Unless the experimentally obtained data approximate astraight line,when calculated using log-log coordinates,it isnot possible to assign an HDB/PDB to the material.Data thatexhibit high scatter or a“knee”(a downward shift,resulting ina subsequently steeper stress-rupture slope than indicated bythe earlier data)but which meet the requirements of this testmethod tend to give a lower forecast of LTHS/LTHSP.In thecase of data that exhibit excessive scatter or a pronounced“knee,”the lower confidence limit requirements of this testmethod are not met and the data are classified as unsuitable foranalysis.1.3 A fundamental premise of this test method is that whenthe experimental data define a straight-line relationship inaccordance with this test methods requirements,this straightline may be assumed to continue beyond the experimentalperiod,through at least 100 000 h(the time intercept at whichthe materials LTHS/LTHSPis determined).In the case ofpolyethylene piping materials,this test method includes asupplemental requirement for the“validating”of this assump-tion.No such validation requirements are included for othermaterials(see Note 1).Therefore,in all these other cases,it isup to the user of this test method to determine based on outsideinformation whether this test method is satisfactory for theforecasting of a materials LTHS/LTHSPfor each particularcombination of internal/external environments and tempera-ture.NOTE1Extensive long-term data that have been obtained on com-mercial pressure pipe grades of polyvinyl chloride(PVC),polybutlene(PB),and cross linked polyethlene(PEX)materials have shown that thisassumption is appropriate for the establishing of HDBs for thesematerials for water and for ambient temperatures.Refer to Note 2 andAppendix X1 for additional information.1This test method is under the jurisdiction of ASTM Committee F17 on PlasticPiping Systems and is the direct responsibility of Subcommittee F17.40 on TestMethods.Current edition approved Nov.15,2013.Published December 2013.Originallyapproved in 1969.Last previous edition approved in 2011 as D2837 11.DOI:10.1520/D2837-13.*A Summary of Changes sectio