1、Designation: D3681 121D3681 18 An American National StandardStandard Test Method forChemical Resistance of “Fiberglass”(GlassFiberReinforced Thermosetting-Resin) Pipe in aDeflected Condition1This standard is issued under the fixed designation D3681; 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 () indicates an editorial change since the last revision or reapproval.1 NOTEEditorially corrected Table A1.2 in March 201
3、4.1. Scope*1.1 This test method covers the procedure for determining the chemical-resistant properties of fiberglass pipe in a deflectedcondition for diameters 4 in. (102 mm) and larger. Both glassfiberreinforced thermosetting resin pipe (RTRP) andglassfiberreinforced polymer mortar pipe (RPMP) are
4、fiberglass pipes.NOTE 1For the purposes for this standard, polymer does not include natural polymers.1.2 Inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.1.3 This standard does not purport to address all of the safety concerns, if any, ass
5、ociated with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use. Specific precautionary statements are given in 9.5.NOTE 2There is no kno
6、wn ISO equivalent to this standard.1.4 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Or
7、ganization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD1600 Terminology for Abbreviated Terms Relating to PlasticsD3567 Practice for Determining Dimensions of “Fiberglass” (Glass-Fiber-Reinforced Thermosetting Resin) Pi
8、pe and Fittings2.2 ISO Standard:3 Preferred NumbersSeries of Preferred Numbers33. Terminology3.1 Definitions:3.1.1 GeneralDefinitions are in accordance with Terminology D883 and abbreviations are in accordance with TerminologyD1600 unless otherwise indicated.3.2 Definitions of Terms Specific to This
9、 Standard:3.2.1 end pointthe passage of the fluid through the pipe wall unless otherwise stated. The failure mode may be catastrophic,characterized by a sudden fracture through the pipe wall in the area of greatest strain, parallel to the axis of the pipe, with the fiberreinforcement cleanly broken
10、at the edge of the fracture. Visual evidence of surface etching or pitting may or may not be present.1 This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.23 on Reinforced Plastic PipingSystems and Chemical Equipment.Curre
11、nt edition approved April 1, 2012Aug. 1, 2018. Published May 2012August 2018. Originally approved in 1978. Last previous edition approved in 20062012 asD3681 06.D3681 121. DOI: 10.1520/D3681-12E01.10.1520/D3681-18.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Cu
12、stomer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to
13、the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summar
14、y of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.2 fiberglass pipetubular product containing glass fiber reinforcements embedded in or surrounded by cured thermosettingresin.
15、The composite structure may contain aggregate, granular or platelet fillers, thixotropic agents, pigments, or dyes.Thermoplastic or thermosetting liners or coatings may be included.3.2.3 reinforced polymer mortar pipe (RPMP)fiberglass pipe with aggregate.3.2.4 reinforced thermosetting resin pipe (RT
16、RP)fiberglass pipe without aggregate.3.2.5 strain-corrosionthe failure of the pipe wall caused by the exposure of the inside surface, while in a strained condition,to a corrosive environment for a period of time.4. Summary of Test Method4.1 This test method consists of exposing the interior of a min
17、imum of 18 specimens of pipe to a corrosive test solution whilethe pipe is constantly maintained in a deflected condition at differing induced initial ring flexural strain levels, and measuring thetime to failure for each strain level. Test temperatures are obtained by testing in an air environment
18、where the temperature iscontrolled.4.2 The long-term resistance of the pipe to the test solution is obtained by an extrapolation to 50 years of a log-log linearregression line for initial strain level versus time.NOTE 3It is the consensus of Subcommittee D20.23 that the loglog linear regression anal
19、ysis of test data is a conservative approach and isrepresentative of standard industry practice. However, a task group has been formed to evaluate alternative non-linear analysis methods.5. Significance and Use5.1 This test method evaluates the effect of a chemical environment on pipe when in a defl
20、ected condition. It has been foundthat effects of chemical environments can be accelerated by strain induced by deflection. This information is useful and necessaryfor the design and application of buried fiberglass pipe.NOTE 4Pipe of the same diameter but of different wall thicknesses will develop
21、different strains with the same deflection.Also, pipes having the samewall thickness but different constructions making up the wall may develop different strains with the same deflection.6. Apparatus6.1 Use parallel plate apparatus suitable to maintain a constant deflection on the pipe. In order to
22、achieve uniform strain alongthe pipe, use 0.25-in. (6-mm) thick elastomeric pads between the parallel plate (channel) surfaces and the pipe ring (see Note 5).Foil type, single element strain gages suitable for strain levels to 1.50 % strain and a length appropriate to the diameter of the pipeare req
23、uired when initial strain is to be determined by Procedure B (see Note 6). An example of the apparatus required is shownin Fig. 1.NOTE 5Elastomeric pads with a hardness of Shore A15 to 70 have been used successfully.NOTE 6Strain gages of 14 and 12-in. (6 and 13-mm) length have been found to be effec
24、tive for pipe diameters 12 through 24 in. (305 through 610mm). Consult the strain gage manufacturer for gage length recommendations for other pipe diameters.FIG. 1 Strain-Corrosion Test ApparatusD3681 1827. Test Specimens7.1 The test specimens shall be ring sections taken from a sample of pipe selec
25、ted at random from a normal production run.The test specimens shall have a minimum length of one nominal pipe diameter or 12 in. (300 mm) 6 5 %, whichever is less.8. Test Conditions8.1 The standard temperature shall be 73.4 6 3.6F (23 6 2C).9. Procedure9.1 GeneralDetermine the initial strain level i
26、nduced in the pipe by calculation, or strain gage measurement, or both.Procedure A describes the determination of initial strain by calculation; Procedure B describes the determination of initial strainas obtained by use of foil-type resistance strain gages.9.2 Determination of Test Level:9.2.1 Test
27、 Procedure A:9.2.1.1 In accordance with Practice D3567 measure the wall thickness to the nearest 0.001 in. (0.025 mm) in at least five equallyspaced places along the bottom of the pipe specimen on a line parallel with the pipe axis, and average the measurements.9.2.1.2 In accordance with Practice D3
28、567 measure the vertical inside diameter to the nearest 0.01 in. (0.25 mm) at both endsprior to deflection and average the measurements.NOTE 7It is recommended that the vertical inside diameter be measured with the axis vertical.9.2.1.3 Place the pipe specimen in the test apparatus (Fig. 1) with the
29、 measured wall thicknesses at the bottom and apply forceto the apparatus to deflect the specimen while keeping the top and bottom plates (channels) of the apparatus as near parallel aspossible. When the desired deflection is obtained, lock the apparatus to maintain the specimen in the deflected cond
30、ition.NOTE 8Alignment of the specimen within the channels is critical. The channels mustshall not only be parallel with the load points 180 opposite,but the pipe mustshall be centered between the rods.9.2.1.4 Measure the vertical inside diameter of the deflected pipe specimen at both ends to the nea
31、rest 0.01 in. (0.25 mm).Average the measurements and determine the deflection by subtracting the average vertical inside diameter after deflection fromthe measurement determined in 9.2.1.2.9.2.1.5 Calculate the initial strain level using the following equation which includes compensation for increas
32、ed horizontaldiameter with increasing deflection.T 5428t!SDm12D2where:T = initial strain, %,t = average wall thickness at bottom, in. (mm), = average deflection, in. (mm),Dm = mean diameter, in. (mm) D + t, andD = average inside pipe diameeter, free state, in. (mm).D = average inside pipe diameter,
33、free state, in. (mm).NOTE 9The calculation assumes that the neutral axis is at the pipe wall midpoint. For pipe wall constructions that produce an altered neutral axisposition, it may be necessary to evaluate results substituting 2 y for t. (y is the distance from the inside pipe surface to the neut
34、ral axis.) Neutral axisposition must be determined with strain gage couples. See also Note 11.9.2.2 Procedure B:9.2.2.1 Carefully align and attach three strain gages on the inside bottom surface of the pipe specimen in the circumferentialdirection to measure initial circumferential strains. Place th
35、e gages perpendicular to the pipe axis as follows: one in the middle andthe other two at the quarter points along the invert of the specimen. The adhesive used to attach the gages shall not cover morethan 37 % of the pipe specimen length along the invert. Zero-in the gages while the pipe is circular
36、 in shape.NOTE 10It is recommended that the pipe specimen be placed with its axis vertical to maintain roundness when the bridge is balanced to “zero” theinstrument.9.2.2.2 After installing the strain gages, place the specimen in the test apparatus (see Fig. 1) with the strain gages at the bottom.Ex
37、treme care shouldshall be taken to ensure that the gages are located at the point of maximum strain (6 oclock position).NOTE 11Alignment of the specimen within the channels is critical. The channels mustshall not only be parallel with the load points 180 opposite,but the pipe mustshall be centered b
38、etween the rods.D3681 1839.2.2.3 Apply force to the apparatus to deflect the specimen while keeping the top and bottom plates (channels) of the apparatusas parallel as possible. When the desired strain level is reached, lock the apparatus to maintain the specimen in the deflectedcondition. Read the
39、gages as soon as the apparatus is locked. Initial strain shouldshall be recorded within 2 min after locking theapparatus. At least two gages shall read within 5 % of each other for a valid experiment. If any gage reads more than 5 % fromthe average of the other two gages, disregard the indication un
40、less thickness verification implies the strain gage reading wasaccurate.Average the valid gage indications, and record as initial (indicated) strain. In addition, measure and record the deflection.9.3 When using ProcedureA, verify the strain level by using strain gages as described in Procedure B fo
41、r at least one specimenin every nine. Conversely, when using Procedure B, verify the strain level by measurement and calculation as described inProcedure A for at least one specimen in every nine. If the calculated strain and the indicated strain do not vary more than 10 %,consider the strain levels
42、 accurate within normal experimental error.NOTE 12Deflections in excess of 28 % of diameter may cause local flattening of the pipe and lead to erratic strain distribution. For deflectionsapproaching 28 % improved accuracy is obtained by use of strain gages or by establishing, for a typical pipe, a c
43、alibration of deflection versus measuredstrain. This calibration technique is also useful at all deflection levels as a check of the calculations by 9.2.1.5, which assumes neutral axis at pipe wallmidpoint.9.4 After the initial strain is obtained using Procedure A or B, install chemically inert dams
44、 using a flexible sealant so that onlythe interior surface of the pipe will be exposed to the test environment. The dams shall not add support to the pipe specimen.9.5 Place the apparatus containing the specimen in a chemically resistant trough or pan and introduce the test solution. Thesolution sho
45、uld be added within 30 minminutes of locking the apparatus and the time shouldshall be recorded from the additionof the solution. (WarningSince the failure mode could be catastrophic, precautions should be taken to contain any suddenleakage that may occur. The use of spacers (such as, wooden blocks)
46、 under the apparatus is suggested to reduce attack of theapparatus after failure of the sample.)9.6 Periodically check and maintain the test solution within 65 % of the specified strength or concentration for the duration ofthe test. Maintain the level at a depth of not less than 1 in. (25.4 mm) dur
47、ing the period of the test.NOTE 13As some solutions become more concentrated with the evaporation of water, care must be exercised in replenishment to prevent a build-upin strength. It may be necessary, with some reagents, to periodically clean the deflected specimen and replace the test solution wi
48、th a fresh mixture. Theuse of plastic film, cut carefully to fit between the dams and floated on the top of the test solution, has been found helpful in reducing evaporation.9.7 Record the following data:9.7.1 Average pipe wall thickness,9.7.2 Average inside pipe diameter before deflection,9.7.3 Ave
49、rage inside pipe diameter after deflection,9.7.4 Percent deflection,9.7.5 Initial strain and method of determination,9.7.6 Type, location, and time of any distress of the pipe wall, and9.7.7 Time to end point. Times are measured from the addition of solution.9.8 To determine the regression line and the lower confidence level for the report, a minimum of 18 samples is required.Distribution of data points shouldshall be as follows:Hours Failure Points10 to 1000 at least 41000 to 6000 at least 3After 6000 at least 3After 10 000
