Design Guide for Polyethylene Gas Pipes Across Bridges

Objective:
The object of this report is to provide for the design and installation of PE distribution gas pipe on bridge crossings (here the main in the ground is PE. Design considerations, basic design equations, examples of gas pipe installations on bridges and example problems of above ground installations are included in this report.

Technical Perspective:
There is historical evidence that it is safe to use PE pipe to transport gas across bridges in local distribution systems. However, the Code of Federal Regulations, Title 49, Part 192, 192.321(a) states that plastic pipe must be installed below ground level and unless a waiver is obtained to use PE pipe, a utility must install transition fittings to switch from PE pipe in the ground to steel pipe on a bridge. Three utilities in the United States obtained waivers and installed PE gas pipe on bridges in 1979, 1984 and 1985 respectively. There have been no reports of difficulties in the operation or the maintenance of these bridge crossings. It can be shown that in most circumstances the use of PE pipe instead of steel pipe for bridge crossings will result in an installation that is both economical and safe. Several utilities have obtained waivers and installed PE gas pipe on numerous bridges.

Technical Approach:
Information was gathered from utilities that had obtained waivers from state governments and had experience installing PE gas pipe on bridges. These utilities were generous in supplying drawings and sharing procedures developed specifically for installation of PE pipe on bridges. In addition, the latest rules and regulations of AASHTO and Federal DOT Pipeline Safety Regulations were reviewed in conjunction with the information gathered from the utilities.