【国外标准】 Standard Practice for Polyethylene Encasement for Ductile Iron Pipe

This practice covers the standard materials and installation procedures for polyethylene encasement to be applied to underground installations of ductile iron pipe for water or other liquids. It may also be used for polyethylene encasement of fittings, valves, and other appurtenances to ductile iron pipe systems. Linear low-density and high-density cross-laminated polyethylene films shall be manufactured of virgin polyethylene material, and shall conform to the required group, density, dielectric strength, and volume resistivity specifications. The polyethylene encasement material shall also be in accordance to the tensile strength, elongation, dielectric strength, impact resistance, and propagation tear resistance requirements. The polyethylene encasement shall be installed in such a way that it shall prevent contact between the pipe and the surrounding backfill and bedding material without intending to be a completely airtight or watertight enclosure. The polyethylene film shall be fitted to the contour of the pipe with sufficient slack to prevent stretching the polyethylene bridging irregular surfaces. For installations below the water table or in areas subject to tidal actions, or both, it is recommended that tube-form polyethylene be used with both ends sealed as thoroughly as possible with adhesive tape or plastic tie straps at the joint overlap.1.1 This practice covers materials and installation procedures for polyethylene encasement to be applied to underground installations of ductile iron pipe. It may also be used for polyethylene encasement of fittings, valves, and other appurtenances to ductile iron pipe systems.1.2 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.1.2.1 Important SI values are provided in brackets. Also, certain important SI values appear without brackets or parentheses.1.3 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.1.4 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.