【国外标准】 Standard Practice for Qualification of a Combination of Squeeze Tool, Pipe, and Squeeze-Off Procedures to Avoid Long-Term Damage in Polyethylene (PE) Gas Pipe

5.1 Squeeze-off is widely used to temporarily control the flow of gas in PE pipe. Squeeze tools vary depending on the size of the pipe and the design of the tool. Squeeze-off procedures vary depending on the tool design, pipe material, and environmental conditions.5.2 Experience indicates that some combinations of polyethylene material, temperature, tool design, wall compression percentage and procedure can cause damage leading to failure.5.3 Studies of polyethylene pipe extruded in the late 1980s and thereafter show that damage typically does not develop when the wall compression percentage is 30 % or less, when temperatures are above 50 °F (10 °C), and when closure and release rates are typical of field conditions for screw-driven tools.4 With tools meeting Specification F1563, acceptable flow control at typical gas service pressures is achieved at wall compression percentages between 10 and 20 % for pipe diameters less than 6 in.4,5 Because damage does not develop in these materials at such squeeze levels, the references cited indicate that squeeze-off flow control practices using tools meeting Specification F1563 and qualified procedures meeting Practice F1041 are effective for smaller pipe sizes.4 ,5NOTE 3: Specification F1563 provides a procedure for evaluating tool flow control performance.5.4 This practice provides a method to qualify a combination of squeeze tool, pipe size and material, and squeeze-off procedure to ensure that long-term damage does not occur. This practice is useful for polyethylene gas pipe manufactured before 1975, for new or revised polyolefin gas pipe materials, for pipe diameters of 8 in. or above, for new or revised squeeze tool designs, and for new or revised squeeze-off procedures.1.1 This practice covers qualifying a combination of a squeeze tool, a polyethylene gas pipe, and a squeeze-off procedure to avoid long-term damage in polyethylene gas pipe. Qualifying is conducted by examining the inside and outside surfaces of pipe specimens at and near the squeeze to determine the existence of features indicative of long-term damage. If indicative features are absent, sustained pressure testing in accordance with Specification D2513 is conducted to confirm the viability of the squeeze-off process. For assistance with specimen examination, an Adjunct, ADJF17342, is available from ASTM.1.2 This practice is appropriate for any combination of squeeze tool, PE gas pipe and squeeze-off procedure, and is particularly appropriate for pre-1975 Polyethylene (PE) pipe, and for pipe sizes of 8 in. or above, because of a greater possibility of long-term damage.1.3 This practice is for use by squeeze-tool manufacturers, pipe manufacturers and gas utilities to qualify squeeze tools made in accordance with Specification F1563; and squeeze-off procedures in accordance with Guide F1041 with pipe manufactured in accordance with Specification D2513.1.4 Governing codes and project specifications should be consulted. Nothing in this practice should be construed as recommending practices or systems at variance with governing codes and project specifications.1.5 Where applicable in this guide, “pipe” shall mean “pipe and tubing.”1.6 Units—The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.