【国外标准】 Standard Practice for Estimating the Quality of Extruded Poly (Vinyl Chloride) (PVC) Pipe by the Heat Reversion Technique

2.1 This practice is applicable to distinguish between properly and improperly extruded PVC plastic pipe. It can be used to:2.1.1 Reveal incomplete exsiccation of compound before or during extrusion (Note 1),2.1.2 Determine the presence of stress in the pipe wall produced by the extrusion process (Note 2),2.1.3 Determine whether unfused areas are present, and2.1.4 Reveal contamination.NOTE 1: Residual moisture in the compound vaporizes at extrusion temperatures and is normally evacuated as it forms vapor. Pockets of moisture trapped in the pipe wall result from incomplete exsiccation of the compound, and may reduce the physical properties of the pipe.NOTE 2: Minor residual stress in the pipe will not impair field performance and handleability. High-residual stress has no proven effect on performance, but may impair handleability during installation.1.1 This practice covers a procedure for estimating the quality of extruded poly (vinyl chloride) (PVC) plastic pipes by observing the reaction of pipe specimens after exposure to hot air in the oven at 180 °C ± 5 °C (356 °F  ± 9 °F) for 30 minutes minimum time duration.1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.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.