1、Designation: D3681 121An 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 indicates
2、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.1NOTEEditorially corrected Table A1.2 in March 2014.1. Scope
3、*1.1 This test method covers the procedure for determiningthe chemical-resistant properties of fiberglass pipe in a de-flected condition for diameters 4 in. (102 mm) and larger. Bothglassfiberreinforced thermosetting resin pipe (RTRP) andglassfiberreinforced polymer mortar pipe (RPMP) are fiber-glas
4、s pipes.NOTE 1For the purposes for this standard, polymer does not includenatural polymers.1.2 Inch-pound units are to be regarded as the standard. Thevalues given in parentheses are for information only.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with
5、 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. Specific precau-tionary statements are given in 9.5.NOTE 2There is no known ISO equivalent to this standard.2.
6、 Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD1600 Terminology forAbbreviated Terms Relating to Plas-ticsD3567 Practice for Determining Dimensions of “Fiberglass”(Glass-Fiber-Reinforced Thermosetting Resin) Pipe andFittings2.2 ISO Standard:3 Preferred NumbersSeries o
7、f Preferred Numbers33. Terminology3.1 Definitions:3.1.1 GeneralDefinitions are in accordance with Termi-nology D883 and abbreviations are in accordance with Termi-nology D1600 unless otherwise indicated.3.2 Definitions of Terms Specific to This Standard:3.2.1 end pointthe passage of the fluid throug
8、h the pipewall unless otherwise stated. The failure mode may becatastrophic, characterized by a sudden fracture through thepipe wall in the area of greatest strain, parallel to the axis of thepipe, with the fiber reinforcement cleanly broken at the edge ofthe fracture. Visual evidence of surface etc
9、hing or pitting mayor may not be present.3.2.2 fiberglass pipetubular product containing glass fiberreinforcements embedded in or surrounded by cured thermo-setting resin. The composite structure may contain aggregate,granular or platelet fillers, thixotropic agents, pigments, ordyes. Thermoplastic
10、or thermosetting liners or coatings may beincluded.3.2.3 reinforced polymer mortar pipe (RPMP)fiberglasspipe with aggregate.3.2.4 reinforced thermosetting resin pipe (RTRP)fiberglass pipe without aggregate.3.2.5 strain-corrosionthe failure of the pipe wall causedby the exposure of the inside surface
11、, while in a strainedcondition, to a corrosive environment for a period of time.4. Summary of Test Method4.1 This test method consists of exposing the interior of aminimum of 18 specimens of pipe to a corrosive test solutionwhile the pipe is constantly maintained in a deflected conditionat differing
12、 induced initial ring flexural strain levels, and1This test method is under the jurisdiction ofASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.23 on Reinforced PlasticPiping Systems and Chemical Equipment.Current edition approved April 1, 2012. Published May 2012.
13、Originallyapproved in 1978. Last previous edition approved in 2006 as D3681 06. DOI:10.1520/D3681-12E01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standard
14、s Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700,
15、 West Conshohocken, PA 19428-2959. United States1measuring the time to failure for each strain level. Testtemperatures are obtained by testing in an air environmentwhere the temperature is controlled.4.2 The long-term resistance of the pipe to the test solutionis obtained by an extrapolation to 50 y
16、ears of a log-log linearregression line for initial strain level versus time.NOTE 3It is the consensus of Subcommittee D20.23 that the logloglinear regression analysis of test data is a conservative approach and isrepresentative of standard industry practice. However, a task group hasbeen formed to
17、evaluate alternative non-linear analysis methods.5. Significance and Use5.1 This test method evaluates the effect of a chemicalenvironment on pipe when in a deflected condition. It has beenfound that effects of chemical environments can be acceleratedby strain induced by deflection. This information
18、 is useful andnecessary for the design and application of buried fiberglasspipe.NOTE 4Pipe of the same diameter but of different wall thicknesseswill develop different strains with the same deflection. Also, pipes havingthe same wall thickness but different constructions making up the wallmay develo
19、p different strains with the same deflection.6. Apparatus6.1 Use parallel plate apparatus suitable to maintain aconstant deflection on the pipe. In order to achieve uniformstrain along the pipe, use 0.25-in. (6-mm) thick elastomericpads between the parallel plate (channel) surfaces and the pipering
20、(see Note 5). Foil type, single element strain gages suitablefor strain levels to 1.50 % strain and a length appropriate to thediameter of the pipe are required when initial strain is to bedetermined by Procedure B (see Note 6). An example of theapparatus required is shown in Fig. 1.NOTE 5Elastomeri
21、c pads with a hardness of Shore A15 to 70 havebeen used successfully.NOTE 6Strain gages of14 and12-in. (6 and 13-mm) length have beenfound to be effective for pipe diameters 12 through 24 in. (305 through610 mm). Consult the strain gage manufacturer for gage length recom-mendations for other pipe di
22、ameters.7. Test Specimens7.1 The test specimens shall be ring sections taken from asample of pipe selected at random from a normal productionrun. The test specimens shall have a minimum length of onenominal pipe diameter or 12 in. (300 mm) 6 5 %, whicheveris less.8. Test Conditions8.1 The standard t
23、emperature shall be 73.4 6 3.6F (23 62C).9. Procedure9.1 GeneralDetermine the initial strain level induced inthe pipe by calculation, or strain gage measurement, or both.Procedure A describes the determination of initial strain bycalculation; Procedure B describes the determination of initialstrain
24、as obtained by use of foil-type resistance strain gages.9.2 Determination of Test Level:9.2.1 Test Procedure A:9.2.1.1 In accordance with Practice D3567 measure the wallthickness to the nearest 0.001 in. (0.025 mm) in at least fiveequally spaced places along the bottom of the pipe specimen ona line
25、parallel with the pipe axis, and average the measure-ments.9.2.1.2 In accordance with Practice D3567 measure thevertical inside diameter to the nearest 0.01 in. (0.25 mm) atboth ends prior to deflection and average the measurements.NOTE 7It is recommended that the vertical inside diameter bemeasured
26、 with the axis vertical.9.2.1.3 Place the pipe specimen in the test apparatus (Fig. 1)with the measured wall thicknesses at the bottom and applyforce to the apparatus to deflect the specimen while keeping thetop and bottom plates (channels) of the apparatus as nearparallel as possible. When the desi
27、red deflection is obtained,lock the apparatus to maintain the specimen in the deflectedcondition.NOTE 8Alignment of the specimen within the channels is critical. TheFIG. 1 Strain-Corrosion Test ApparatusD3681 1212channels must not only be parallel with the load points 180 opposite, butthe pipe must
28、be centered between the rods.9.2.1.4 Measure the vertical inside diameter of the deflectedpipe specimen at both ends to the nearest 0.01 in. (0.25 mm).Average the measurements and determine the deflection bysubtracting the average vertical inside diameter after deflectionfrom the measurement determi
29、ned in 9.2.1.2.9.2.1.5 Calculate the initial strain level using the followingequation which includes compensation for increased horizontaldiameter with increasing deflection.T5 428t!SDm12D2where:T= initial strain, %,t = average wall thickness at bottom, in. (mm), = average deflection, in. (mm),Dm= m
30、ean diameter, in. (mm) D+t,andD= average inside pipe diameeter, free state, in. (mm).NOTE 9The calculation assumes that the neutral axis is at the pipewall midpoint. For pipe wall constructions that produce an altered neutralaxis position, it may be necessary to evaluate results substituting 2y for
31、t.(y is the distance from the inside pipe surface to the neutral axis.) Neutralaxis position must be determined with strain gage couples. See also Note11.9.2.2 Procedure B:9.2.2.1 Carefully align and attach three strain gages on theinside bottom surface of the pipe specimen in the circumfer-ential d
32、irection to measure initial circumferential strains. Placethe gages perpendicular to the pipe axis as follows: one in themiddle and the other two at the quarter points along the invertof the specimen.The adhesive used to attach the gages shall notcover more than 37 % of the pipe specimen length alon
33、g theinvert. Zero-in the gages while the pipe is circular in shape.NOTE 10It is recommended that the pipe specimen be placed with itsaxis vertical to maintain roundness when the bridge is balanced to “zero”the instrument.9.2.2.2 After installing the strain gages, place the specimenin the test appara
34、tus (see Fig. 1) with the strain gages at thebottom. Extreme care should be taken to ensure that the gagesare located at the point of maximum strain (6 oclock position).NOTE 11Alignment of the specimen within the channels is critical.The channels must not only be parallel with the load points 180 op
35、posite,but the pipe must be centered between the rods.9.2.2.3 Apply force to the apparatus to deflect the specimenwhile keeping the top and bottom plates (channels) of theapparatus as parallel as possible. When the desired strain levelis reached, lock the apparatus to maintain the specimen in thedef
36、lected condition. Read the gages as soon as the apparatus islocked. Initial strain should be recorded within 2 min afterlocking the apparatus.At least two gages shall read within 5 %of each other for a valid experiment. If any gage reads morethan 5 % from the average of the other two gages, disregar
37、d theindication unless thickness verification implies the strain gagereading was accurate. Average the valid gage indications, andrecord as initial (indicated) strain. In addition, measure andrecord the deflection.9.3 When using ProcedureA, verify the strain level by usingstrain gages as described i
38、n Procedure B for at least onespecimen in every nine. Conversely, when using Procedure B,verify the strain level by measurement and calculation asdescribed in Procedure A for at least one specimen in everynine. If the calculated strain and the indicated strain do not varymore than 10 %, consider the
39、 strain levels accurate withinnormal experimental error.NOTE 12Deflections in excess of 28 % of diameter may cause localflattening of the pipe and lead to erratic strain distribution. For deflectionsapproaching 28 % improved accuracy is obtained by use of strain gages orby establishing, for a typica
40、l pipe, a calibration of deflection versusmeasured strain. This calibration technique is also useful at all deflectionlevels as a check of the calculations by 9.2.1.5, which assumes neutral axisat pipe wall midpoint.9.4 After the initial strain is obtained using Procedure A orB, install chemically i
41、nert dams using a flexible sealant so thatonly the interior surface of the pipe will be exposed to the testenvironment. The dams shall not add support to the pipespecimen.9.5 Place the apparatus containing the specimen in a chemi-cally resistant trough or pan and introduce the test solution.Thesolut
42、ion should be added within 30 min of locking theapparatus and the time should be recorded from the addition ofthe solution. (WarningSince the failure mode could becatastrophic, precautions should be taken to contain anysudden leakage that may occur. The use of spacers (such as,wooden blocks) under t
43、he apparatus is suggested to reduceattack of the apparatus after failure of the sample.)9.6 Periodically check and maintain the test solution within65 % of the specified strength or concentration for theduration of the test. Maintain the level at a depth of not lessthan 1 in. (25.4 mm) during the pe
44、riod of the test.NOTE 13As some solutions become more concentrated with theevaporation of water, care must be exercised in replenishment to preventa build-up in strength. It may be necessary, with some reagents, toperiodically clean the deflected specimen and replace the test solution witha fresh mi
45、xture. The use of plastic film, cut carefully to fit between thedams and floated on the top of the test solution, has been found helpful inreducing 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 Average inside pi
46、pe 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 pipewall, and9.7.7 Time to end point. Times are measured from theaddition of solution.9.8 To determine the regression line and the lower confi-
47、dence level for the report, a minimum of 18 samples isrequired. Distribution of data points should be as follows:D3681 1213Hours Failure Points10 to 1000 at least 41000 to 6000 at least 3After 6000 at least 3After 10 000 at least 19.9 Perform inspection of the test samples as follows:Hours Inspect a
48、t Least10 to 20 every 1 h20 to 40 every 2 h40 to 60 every 4 h60 to 100 every 8 h100 to 600 every 24 h600 to 6000 every 48 hAfter 6000 every weekRecord the time to end point for each specimen.NOTE 14The use of electronic timers is considered highly desirable inmonitoring failure time particularly on
49、short term tests.9.10 Analyze the test results by using for each specimen, thelogarithm of the strain in percent and the logarithm of thetime-to-failure in hours as described in Annex A1. Calculatethe strain at 50 years (YL).9.11 Those specimens that have not failed after more than10 000 h may be included as failures to establish the regres-sion line. Use of these data points may result in a lower orhigher extrapolated strain. In either case the requirements of9.14 must be satisfied.NOTE 15Non-failed specimens may be left und
