1、Designation: D 2774 08An American National StandardStandard Practice forUnderground Installation of Thermoplastic Pressure Piping1This standard is issued under the fixed designation D 2774; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, 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.This standard has been approved for use by agencies of the Department of Defense.INTRODUCTIONIn general, therm
3、oplastics pressure piping materials behave as ductile materials under load, meaningthat they can undergo considerable deformation without damage. Piping made from such materials hasthe ability to bend under a load without breaking and to deform in other ways, while offering continuedresistance. This
4、 flexibility allows ductile thermoplastic pipe to activate through pipe deformationlateral soil forces which create a pipe/soil system capable of safely supportingeven in pipes subjectto little or no internal pressurethe earth and superimposed loads which are encountered in most pipeinstallations. H
5、owever, proper installation techniques are required to ensure that the necessary supportat the bottom and passive soil pressures at the sides of the pipe are developed and maintained.Soils in which trenches are dug shall be examined and identified and the trenches prepared andbackfilled in accordanc
6、e with sound bedding procedures and this practice.1. Scope*1.1 This practice governs procedures and references ASTMspecifications for underground installation of thermoplasticpressure piping, 63-in. (1372-mm) nominal size and smaller. Itis beyond the scope of this practice to describe these proce-du
7、res in detail since it is recognized that significant differencesexist in their implementation depending on kind and type ofpipe material, pipe size and wall thickness, soil conditions, andthe specific end use.1.1.1 This practice assumes that over the range of antici-pated operating conditions, incl
8、uding maximum external load-ing and minimum internal pressure, the soil/pipe system willoffer sufficient structural stability to resist possible excessivediametrical deformation, or even collapse. In cases, particu-larly with large diameter thinner-walled pipe, for which thevalidity of this assumpti
9、on may be in question, the selection ofpipe and recommended installation conditions shall be deter-mined by a qualified engineer.1.1.2 Specific pipe characteristics and end-use requirementsshall dictate addition to, or modification of the proceduresstated or referenced herein.1.2 The values stated i
10、n inch-pound units are to be regardedas the standard.1.3 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 o
11、f regulatory limitations prior to use. Specific precau-tionary statements are given in Sections 10 and 11.2. Referenced Documents2.1 ASTM Standards:2D 1600 Terminology for Abbreviated Terms Relating toPlasticsD 2487 Practice for Classification of Soils for EngineeringPurposes (Unified Soil Classific
12、ation System)D 2488 Practice for Description and Identification of Soils(Visual-Manual Procedure)F 412 Terminology Relating to Plastic Piping Systems2.2 AWWA Standard:C 651 Standard for Disinfecting Water Mains33. Terminology3.1 Definitions:1This practice is under the jurisdiction of ASTM Committee
13、F17 on PlasticPiping Systems and is the direct responsibility of Subcommittee F17.61 on Water.Current edition approved March 1, 2008. Published April 2008. Originallyapproved in 1969. Last previous edition approved in 2004 as D 2774 04e1.2For referenced ASTM standards, visit the ASTM website, www.as
14、tm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American Water Works Association (AWWA), 6666 W. QuincyAve., Denver, CO 80235, http:/www.awwa.org.1*A Summa
15、ry of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.1 Definitions are in accordance with Terminology F 412,unless otherwise specified. Abbreviated terms are in accor-dance with
16、 Terminology D 1600. Installation terminology usedin this practice is illustrated in Fig. 1.3.1.2 The term pipe refers to both pipe and tubing, unlessspecifically stated otherwise.3.1.3 protective sleeve, na short section of pipe installedover system piping where there is a transition from relativel
17、yrigid piping or structure to relatively flexible piping or structureto protect the transition region from excessive bending or shearstresses. For example, protective sleeves are installed atconnections between plastic or non-plastic mains and plasticlateral branch or service lines (such as service
18、or branchconnections to tapping tees or saddles), where plastic pipeenters or exits a casing, or where plastic pipe penetrates abuilding or vault wall.4. Significance and Use4.1 This practice may not apply to products which shall besubject to failure at relatively low strains. For low ductilitymater
19、ials, the installed pipe/soil system shall be sufficientlyrigid to prevent pipe deformations which could strain thepiping material beyond its safe strain limit.5. Joining5.1 Plastic pipe shall be joined together or to other pipes ofdissimilar material using a number of different techniques.Commonly
20、used procedures, joining materials, and fittings aredefined by various standards. (See Appendix X1.) The tech-nique used shall be suitable for the particular pipes beingjoined to one another. Manufacturers shall be consulted forspecific instructions not covered by existing specifications.When reques
21、ting information, the intended service applicationshall be made known.5.2 Skill and knowledge on the part of the installer arerequired using recommended techniques to obtain qualityjoints. Training of new installers shall be made under theguidance of skilled individuals. Detailed written proceduresa
22、nd visual aids used to train personnel are available frompiping and joining equipment manufacturers.5.3 The use of fittings and joining procedures which are notcovered by a recognized standard is subject to the judgmentand discretion of the purchaser. Each fitting and joiningprocedure used shall be
23、qualified by investigation, testing, andexperience to establish its suitability and safety for the intendedservice. Fittings and joints shall have long-term pressurecapabilities equal to or greater than the systems maximumanticipated sustained operating pressure.5.3.1 Thrust transmitting joints such
24、 as heat fused or solventcemented, shall be capable of restraining maximum anticipatedpipe pull-out forces generated by any unbalanced forces frominternal pressure or pipe expansion/contraction, or both.5.3.2 Gasketed and other non-thrust transmitting joints shallbe restrained by means of properly e
25、ngineered external re-straints (thrust blocks) or joint restraint devices (see 7.3).NOTE 1Where there are unbalanced momentum forces and thrust istransmitted through the joints, consideration shall be given to the designcapacity of each joint in the system to safely resist maximum anticipatedaxial t
26、hrust (see 7.3). Where a piping section having thrust transmittingjoints is connected to a piping section having non-thrust transmittingjoints, measures shall be taken to anchor or restrain the end of the thrusttransmitting joint section against longitudinal movement so that contrac-tive forces shal
27、l not be transmitted and cause disjoining of non-thrusttransmitting joints.6. Trenching-Recommended Installation Procedure6.1 Trench StabilityDuring trench excavation, ensure thatthe trench sides shall be stable under all working conditions.The trench walls shall be sloped or appropriate supportspro
28、vided to comply with all applicable local, state, and federalrequirements for safety.6.2 Trench WidthThe width of the trench at any pointbelow the top of the pipe shall be sufficient to provide adequateroom for each of the following requirements: (1) joining thepipe in the trench if this is required
29、; (2) snaking of small-diameter, heat fused or solvent cemented pipe from side-to-sidealong the bottom of the trench, when the effects of contractionare not otherwise accommodated; (3) filling and compactingthe side fills; and (4) checking the elastomeric seal joints.Minimum trench widths shall be p
30、ermitted to be utilized withmost solvent-cemented and heat-fused pressure pipe materialsby joining the pipe outside the trench and lowering the pipeinto the trench after adequate joint strength has been attained(see 10.5). This practice shall be permitted to be used forgasket joint pipe, with manufa
31、cturers approval, providing careis taken to not disassemble the joints during lowering.6.3 Trench BottomThe trench bottom shall be preparedfor the direct replacement of the pipe and shall be continuous,relatively smooth, free of rocks, and provide uniform support.For bell-ended or coupled pipe, suit
32、able “bell-holes” shall beprovided at each joint to permit the joint to be assembled andthe pipe to be supported properly.6.3.1 Where ledge rock, hardpan, or boulders are encoun-tered, it shall be required to pad the trench bottom with abedding of at least 4-in. (100-mm) thickness of compactedFIG. 1
33、 Installation TerminologyD2774082granular material. In situations where rapid movement of watertakes place through this bedding, the granular material usedshall have gradation that prevents loss by migration of any pipeembedment material (see 9.8).6.4 Trench Depth and Pipe CoverExcavation for pipetr
34、enches shall be to the lines, grades, and dimensions shown onthe contract drawings. Sufficient cover shall be maintained toadequately reduce the traffic or other concentrated and impactloads.6.4.1 Reliability and safety of service shall assume majorimportance in determining minimum cover for any int
35、endedservice. Local, state, or federal codes shall also govern. Pipeintended for winter water service shall have a minimum coverequal to or greater than the maximum expected frost penetra-tion depth.6.4.2 Aminimum cover of 24 in. (610 mm) for pipe shall berequired when subjected to heavy overhead tr
36、affic. In areas oflight overhead traffic a minimum cover of 12 to 18 in. (305 to457 mm) is required.6.5 “Trenchless InstallationSome types of thermoplas-tic pressure pipe shall be permitted to be installed usingmethods that do not require excavation.7. Pipe Placement7.1 Pipe Joint AssemblyPipe assem
37、bly shall be conductedin accordance with the manufacturers published recommen-dations. Above ground joining of pipe joined by solventcementing, heat fusion or some other thrust transmittingconnection shall be permitted. After the joint is appropriately“cured” (see Section 10) the pipe is lowered int
38、o the trench.This practice shall be permitted to be used for gasket joint pipe,with manufacturers approval, providing care is taken to notdisassemble the joints during lowering.7.2 Pipe BendingAssembled thermoplastic pipe may bebent longitudinally if the bending radius is within limitsprescribed by
39、the manufacturer. There shall be two limits, onefor pipe without joints and the other for pipe sections withjoints.7.3 Thrust RestraintWhen installing piping systems withjoints that cannot transmit the anticipated maximum longitu-dinal thrust, thrust restraint shall be required at changes indirectio
40、n, or terminal ends, to prevent joint disengagement.7.3.1 Where the piping system employs non-self restrainingjoints (for example, elastomeric seal bell and spigot type joints)at points where line shift or joint separation at system operatingpressure can be anticipated, that is, pump discharge, dire
41、ctionalchanges, reducers and dead ends, thrust restraint shall berequired to prevent joint disengagement and ensure the properperformance of the pressure piping system.7.3.2 Where the piping system employs self-restrainingjoints (for example flanges, heat fusion, mechanical jointrestraint or solvent
42、 cement joints) at these points in the system,thrust blocking shall not be required for thrust restraint.7.4 Thrust Restraint MethodsThrust restraint shall beachieved by use of mechanical thrust restraint devices or by useof concrete thrust blocking.7.4.1 Mechanical Thrust Restraint Devices:7.4.1.1
43、Devices used for thrust restraint of PVC pipe shallconform to Standard F 1674.7.4.1.2 Consult device manufacturer for design assistance.7.4.2 Cast In Place Concrete Thrust Block Construction:7.4.2.1 The thrust block shall be constructed of cast in placeconcrete having a compression strength of 2000
44、psi (14 MPa)or more. Precast concrete blocking, wood blocking, or stoneblocking with wood wedges, are not acceptable.7.4.2.2 The thrust block acts as an anchor between pipe orfitting and the solid trench wall. The size of the thrust blockshall be adequate to prevent pipe movement at the point ofthru
45、st. Consult the system designer.7.4.2.3 The thrust block cavity shall be hand dug intoundisturbed soil and framed, with soil or wood to hold freshlypoured concrete. The earth bearing surfaces shall be undis-turbed.7.4.2.4 Before pressurizing the line, adequate time shall berequired for the concrete
46、thrust blocks to gain sufficientstrength.7.4.2.5 Precast concrete thrust blocks shall not be used indirect contact with thermoplastic fittings for buried pressurepiping systems.7.5 Protecting Transition RegionsA transition region be-tween relatively rigid piping or structures and relativelyflexible
47、piping is subject to intensified localized bending orshear stresses, especially during soil consolidation after initialinstallation. In these transition regions, plastic pipe is protectedagainst excessive stresses with a protective sleeve and stablebedding and backfill, or with stable bedding and ba
48、ckfill. Thepreferred practice is the combination of a protective sleeve andstable bedding and backfill.7.5.1 Protective sleeves are usually plastic tubes, eitherextruded for the purpose or cut from lengths of plastic pipe, butthey shall be permitted to be any material of sufficient strengthand durab
49、ility. Protective sleeves extend from rigid piping ofstructure across the transition region and along the plastic pipefor a length that ensures that plastic pipe at the transition regionis not subject to excessive stress. The protective sleeve isappropriately secured to remain in place during backfilling.Where plastic piping penetrates a building or a vault wall, oneend of the protective sleeve shall be embedded in the wall.7.5.2 The diameter, wall thickness and length of the protec-tive sleeve provide greater bending and shear resistance thanthe plastic pipe it pro
