1、Designation: F 1734 03An American National StandardStandard Practice forQualification of a Combination of Squeeze Tool, Pipe, andSqueeze-Off Procedures to Avoid Long-Term Damage inPolyethylene (PE) Gas Pipe1This standard is issued under the fixed designation F 1734; the number immediately following
2、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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers
3、qualifying a combination of asqueeze tool, a polyethylene gas pipe, and a squeeze-offprocedure to avoid long-term damage in polyethylene gas pipe.Qualifying is conducted by examining the inside and outsidesurfaces of pipe specimens at and near the squeeze to deter-mine the existence of features indi
4、cative of long-term damage.If indicative features are absent, sustained pressure testing inaccordance with Specification D 2513 is conducted to confirmthe viability of the squeeze-off process. For assistance withspecimen examination, an Adjunct, ADJF1734, is availablefrom ASTM.1.2 This practice is a
5、ppropriate for any combination ofsqueeze tool, PE gas pipe and squeeze-off procedure, and isparticularly appropriate for pre-1975 Polyethylene (PE) pipe,and for pipe sizes of 8 in. or above, because of a greaterpossibility of long-term damage.1.3 This practice is for use by squeeze-tool manufacturer
6、s,pipe manufacturers and gas utilities to qualify squeeze toolsmade in accordance with Specification F 1563; and squeeze-offprocedures in accordance with Guide F 1041 with pipe manu-factured in accordance with Specification D 2513.1.4 Governing codes and project specifications should beconsulted. No
7、thing in this practice should be construed asrecommending practices or systems at variance with governingcodes and project specifications.1.5 Where applicable in this guide, “pipe” shall mean “pipeand tubing.”1.6 UnitsThe values stated in inch-pound units are to beregarded as standard. The values gi
8、ven in parentheses aremathematical conversions to SI units, which are provided forinformation only and are not considered standard.1.7 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 establi
9、sh appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 2513 Specification for Thermoplastic Gas Pressure Pipe,Tubing, and Fittings2D 3350 Specification for Polyethylene Plastics Pipe andFittings
10、Materials2F 1041 Guide for Squeeze-Off of Polyolefin Gas PressurePipe and Fittings2F 1563 Specification for Tools to Squeeze-Off Polyethylene(PE) Gas Pipe or Tubing2ADJF1734 Adjunct: Interpretation Aid for Squeeze-OffDamage33. Terminology3.1 Definitions:3.1.1 squeeze-off, na technique used to tempor
11、arily con-trol the flow of gas in a polyethylene gas pipe by flattening thepipe with a mechanical or hydraulic device.3.1.2 squeeze process, nthe combination of the squeezetool, the pipe being squeezed, and the squeeze-off procedurebeing used.3.1.3 wall compression (WC), nthe percentage extent towhi
12、ch the pipe walls are compressed when the pipe issqueezed. (See Fig. 1.) It is defined as:WC,%5S1 2L2tD3 100 (1)where:L = distance between the squeeze tool bars as shown in Fig.1, andt = uncompressed pipe wall thickness, expressed in thesame units as L.3.1.3.1 DiscussionWhen the distance between the
13、squeeze tool bars is greater than twice the wall thickness, thepipe walls are not compressed, which yields a negative valuefor the wall compression percentage. The value becomespositive when the L value is less than the 2t value. Typicalsqueeze tool stops are set for 30 % or less wall compression1Th
14、is practice is under the jurisdiction of ASTM Committee F17 on PlasticPiping Systems and is the direct responsibility of Subcommittee F17.60 on Gas.Current edition approved August 10, 2003. Published September 2003. Origi-nally approved in 1996. Last previous edition approved in 1996 as F 1734 96.2A
15、nnual Book of ASTM Standards, Vol 08.04.3Available from ASTM Headquarters. Order Adjunct:ADJF1734.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.based on maximum wall thickness (a distance that is 70 % oftwice maximum wall thickness
16、 when the squeeze tool is closedto the stops). Maximum wall thickness is the minimum wallthickness plus the wall thickness tolerance.4. Summary of Practice4.1 Pipe of the size and material of interest is cut intospecimens at least 1 ft long or 3 diameters long whichever isgreater, and attached to a
17、supply of pressurized gas. Withpressurized gas flowing through the specimen, the specimensare squeezed with the tool of interest, using the procedure ofinterest, until the desired level of flow control is achieved.Using Eq 1, the wall compression percentage at the desiredlevel of flow control is det
18、ermined. Let this level of wallcompression be called WCnom. Additional specimens aresqueezed to obtain squeeze levels that are 5 % greater, 10 %greater, 5 % less and 10 % less than WCnom. This squeezerange brackets levels of wall compression for flow control.NOTE 1For example, if the desired level o
19、f flow control wereachieved at 25 % wall compression, additional specimens would beprepared at 35 %, 30 %, 20 % and 15 % wall compression. In researchtests, a flow of 0.1 ft3/h was considered equivalent to stopping the flow.4,54.2 The squeezed samples are split along their length at 90degrees to the
20、 squeeze “ears” (See Fig. 1). The area containingthe ears is examined visually using the unaided eye, thenmagnification. Features such as crazing, small voids, or cracksindicate permanent damage and disqualify the squeeze-offprocess.4.3 Where the results of the visual screening do not indicateperman
21、ent damage, additional specimens are squeezed at theWC level where damage is not indicated, and sustainedpressure tests in accordance with Specification D 2513 areperformed. When sustained pressure test specimens meet therequirements of Specification D 2513, the squeeze-off processhas been verified.
22、4.3.1 When damage is identified at WCnom less 5 % orWCnom less 10 % levels, a wall compression percentage wheredamage does not occur should be identified. Prepare additionalspecimens by lessening wall compression in 5 % increments,and then examine the specimens to identify a wall compressionpercenta
23、ge that does not indicate damage.NOTE 2This practice uses flow through the squeezed-off pipe as aparameter. For some combinations of tool, pipe and procedure, it is notpossible to stop flow completely without causing permanent damage to thepipe, particularly for pipes greater than 2 in, nominal size
24、.4.4 Using a desired squeeze-off procedure, tests conductedat different pipe temperatures with various sizes of tools andpipes can be used to verify a range of temperatures, tool sizes,and pipe sizes for which the squeeze-off process is applicable.5. Significance and Use5.1 Squeeze-off is widely use
25、d to temporarily control theflow of gas in PE pipe. Squeeze tools vary depending on thesize of the pipe and the design of the tool. Squeeze-offprocedures vary depending on the tool design, pipe material,and environmental conditions.5.2 Experience indicates that some combinations of poly-ethylene mat
26、erial, temperature, tool design, wall compressionpercentage and procedure can cause damage leading to failure.5.3 Studies of polyethylene pipe extruded in the late 1980sand thereafter show that damage typically does not developwhen the wall compression percentage is 30 % or less, whentemperatures ar
27、e above 50F (10C), and when closure andrelease rates are typical of field conditions for screw-driventools.4With tools meeting Specification F 1563, acceptableflow control at typical gas service pressures is achieved at wallcompression percentages between 10 and 20 % for pipe diam-eters less than 6
28、in.4,5Because damage does not develop inthese materials at such squeeze levels, the references citedindicate that squeeze-off flow control practices using toolsmeeting Specification F 1563 and qualified procedures meetingPractice F 1041 are effective for smaller pipe sizes.4,5NOTE 3Specification F 1
29、563 provides a procedure for evaluating toolflow control performance.5.4 This practice provides a method to qualify a combina-tion of squeeze tool, pipe size and material, and squeeze-offprocedure to ensure that long-term damage does not occur.This practice is useful for polyethylene gas pipe manufa
30、cturedbefore 1975, for new or revised polyolefin gas pipe materials,for pipe diameters of 8 in. or above, for new or revised squeezetool designs, and for new or revised squeeze-off procedures.6. Interpretation of Results6.1 This practice relies on a screening process using visualinspection followed
31、by sustained pressure testing as describedin Specification D 2513 to qualify a squeeze-off process.4Stephens, D. R., Leis, B. N., Francini, R. B., and Cassady, M. J., Volume 1:Users Guide on Squeeze-Off of Polyethylene Gas Pipes, Topical Report GRI-92/0147.1, NTIS PB93-161032, Battelle Columbus for
32、Gas Research Institute, Febru-ary 1992.5Stephens, D. R., Leis, B. N., Francini, R. B., and Cassady, M. J., Volume 2:Technical Reference on Squeeze-Off of Polyethylene Gas Pipes, Topical ReportGRI-92/0147.2, NTIS PB93-161040, Battelle Columbus for Gas Research Institute,October 1992.FIG. 1 Definition
33、 of Wall CompressionF17340326.2 The area of wrinkling at the ears on the inside diameter(ID) of the pipe and the area on the outside of the pipe oppositethe ears are examined . Evidence of any one or a combinationof void formation, cracks or extensive localized stress whiten-ing, or failure during s
34、ustained pressure testing disqualifies thesqueeze-off process.6.3 Unacceptable features implying long-term damage areshown in the photographs in adjunct, ADJF1734.7. Apparatus7.1 Squeeze-off Tools, meeting Specification F 1563 that areto be covered by the squeeze-off process.7.2 Pipe Cutters and Saw
35、s, capable of cutting the PE pipe.7.3 Jewelers Loupe or (Stereo) Optical Microscope, pro-viding 103 or higher magnification.7.4 Vernier Caliper or Ball-End Micrometer, with an accu-racy of at least 0.001 in.7.5 Stopwatch, that can indicate time to at least the nearestsecond.8. Materials8.1 Polyethyl
36、ene pipe meeting Specification D 2513.9. Safety Precautions9.1 Care should be taken and appropriate protective equip-ment for eyes and persons is required when working withhydraulic and power tools that may be used in the squeeze-offprocess. Personal hearing protection is required when com-pressed g
37、as is discharged from open-ended specimens.10. Preparation of the Sample and Equipment10.1 Select pipe samples at least 3 pipe diameters long butnot less than 1 ft long.10.2 Measure the pipe wall thickness at 15 incrementsaround the pipe, and identify the location of maximum wallthickness.10.3 Condi
38、tion samples to the temperature of interest.Studies show that at very low temperatures or on thicker-walled pipe significant hold times are necessary to reachthermal equilibrium. Experience with smaller-diameter, lowerSDR pipe (for example, 2 to 6-in. SDR 11 pipe) indicates thata minimum of 24 h is
39、required for the sample to reachequilibrium.11. Procedure11.1 Orient the sample in the squeeze tool so that thethickest portion of the pipe wall forms one of the squeeze-offears. Locate the squeeze tool at the midpoint of the samplelength so that the tool is centered on the sample and square tothe c
40、enterline of the sample.11.2 The squeeze bar shims or stops, or both, must be within1 % of the target level.11.3 Operate the tool in accordance with the procedure ofinterest, close the bars to the distance required for the desiredwall compression, and hold for at least 30 min. Closure stopsmay need
41、to be removed or smaller stops or shims may beneeded to obtain the closure distance required.11.4 Release the squeeze in accordance with the procedureof interest.11.5 If re-rounding is included in the procedure of interest,re-round the sample accordingly.11.6 Allow the sample to sit undisturbed with
42、out externalforce at the desired temperature for 24 h.11.7 Cut a ring from the pipe sample. The ring is to be atleast 2 pipe diameters in length with the squeeze in the middleof the ring. Cut the ring lengthwise with the squeeze-earsoriented 90 to the plane of the cut.11.8 Visual ExaminationWith the
43、 unaided eye, and thenwith magnification, examine the interior of the sample at eachsqueeze ear for stress whitening, crazing, or cracking. Examinethe exterior of the sample at the squeeze ears for evidence of adimple centered at the ear. Examine first with the unaided eye.Samples that pass unaided
44、eye visual examination are thenvisually examined under 103 magnification.11.8.1 Unaided-Eye Visual Examination:11.8.1.1 Wrinkling of the interior of the squeeze-off ear isexpected to occur. Some stress whitening along the ridges andin the valleys of wrinkles is also expected to occur. Stresswhitenin
45、g should be limited to these ridges and valleys in theregion where wall thinning occurs in response to the squeezeprocess. Stress whitening should be diffuse in appearancerather than an intense white band.11.8.1.2 Cracking or voids on the inside or a dimple on theoutside disqualify the squeeze-off p
46、rocess.11.8.1.3 A dimple on the outside of the pipe, or stresswhitening strung out along a severe wrinkle on the inside of thepipe, at WCnom plus 5 %, WCnom, WCnom less 5 % orWCnom less 10 % levels disqualify the squeeze-off process.11.8.2 Magnified Visual Examination:11.8.2.1 At 103 magnification,
47、examine the interior of thesqueeze ear of samples that pass the unaided-eye examination,Cracking or voids disqualify the squeeze-off process.11.8.2.2 At 103 magnification, stress whitening strung outalong a wrinkle is evidence of damage that can grow with time.Judgment, depending on the severity of
48、the features, the serviceconditions, and the utilitys service record for that pipe, candisqualify the squeeze procedure if such features are found.11.8.2.3 General widespread evidence of changes in color,such as intense stress whitening or crazing, is evidence ofdamage and indicative of possible sub
49、surface damage. Judg-ment based on experience related to the service record of thepipe involved should be considered in qualifying proceduresthat produce such features. Examination of cross sectionsprepared on a cut through the ear can be used to determine ifsubsurface damage has occurred in such cases. Indications ofsmall voids in cross sections disqualifies the squeeze-offprocess.11.9 Sustained Pressure Tests:11.9.1 If the squeeze-off process is not disqualified bymagnified visual examination, prepare additional samples ofsqueezed pipe at WCnom plus 5 % and subject the
