INVESTIGATION OF TEMPERATURES ATTAINED BY PLASTIC FUEL GAS PIPE INSIDE SERVICE RISERS
|Publication Date:||1 March 2020|
The maximum allowable temperatures for plastic piping systems used for fuel gas distribution are defined by Part 192, Transportation of Natural Gas and Other Gas by Pipeline: Minimum Safety Standards, Subchapter l), Pipeline Safety, of Title 49, Transportation, of the U. S. Code of Federal Regulations. By an act of Congress, the U. S. Department of Transportation regulates pipeline safety.
Section 375, Service Lines: Plastic, of Part 192 of the U. S. Pipeline Safety Regulations allows the use of properly designed metal-sleeved plastic riser pipe. A point that must be considered in proper design is the temperature that can develop in the above-ground portion of the metal riser and its effect on the strength properties of the plastics gas carrier pipe. Section 121, Design of Plastic Pipe, of Part 192 limits the allowable operating temperature of a thermoplastic pipe to the highest value for which the pipes long-term hydrostatic strength has been established, except that it may not exceed 140°F.
There has been some concern that the portion of a plastic riser pipe that is brought up out of the ground inside a protective metal sleeve for connection to a gas meter located outdoors may experience considerably higher temperatures than buried pipe, possibly even above the 140°F limit for some period of time. Since metal-sleeved risers may be exposed to direct sunlight, they could become heated to higher than ambient temperatures. This report presents conclusions from test data gathered in a 2017-2019 study showing the temperatures that may be obtained by thermoplastics pipe installed inside a metal protective sleeve and the conditions under which those temperatures occur. The data from earlier testing in the 1970's has been included in APPENDIX B for historical reference to the maximum temperature study.