natural gas distribution pipeline pressure

AGA recommends a minimum pipe depth for mains to be 24” (610 mm).If the burial installation falls outside of the AWWA M-55 Design Window, the PPI Design of PE Piping Systems, Chapter 6, Section 3 provides detailed calculations for verifying the capacity of the piping system to resist crushing. The calculations used basically follow the Iowa Formula for plastic pipe installation. Although these limitations are apparent, proper engineering design is used to offset these potential disadvantages.The maximum allowable operating pressure for gas distribution and transmission pipe in US federally regulated applications is determined by CFR Title 49 Part 192. The number of joints that need to be restrained to prevent bell and spigot pull out may be calculated using techniques recommended by the manufacturer of the alternate piping material. It is recommended that all piping exposed to outdoor weather be painted.Other piping materials include aluminum tubing, copper tubing, and corrugated stainless steel (CSST).According to 2008 seminar materials prepared by the Plastics Pipe Institute (PPI), 95 percent of the (new) piping materials installed for distributing natural gas is polyethylene (PE) pipe. Merely fixing the end of the PE to the mating material may result in upstream joints pulling apart unless those connections are properly restrained. If heat fusion joining of dissimilar polyethylene is required, special procedures are required and the joining methods need to be tested and qualified.

The owner’s representative needs to work closely with the natural gas supplier and follow his rules, regulations, and recommendations in any installation since the supplier will be most familiar with the local rules applicable to the project. This eliminates many of the fittings otherwise required for directional changes in piping systems and it also facilitates installation; i)  Temperature Resistance:  PE pipe’s typical operating temperature range is from 0°F to 140°F ( 18°C to 40°C) for pressure service; j)  Sustainable:  Requires less energy to produce and to join this type of piping than its metal counterparts, and; k)  Light Weight:  Easier to handle for installersAs with all materials there are limitations on the proper use of PE for gas distribution including:  PE is primarily limited to underground service due to potential affects from UV exposure; and the strength and rigidity of PE is not nearly as robust as its metal counterparts.

When the pipe size is nominal pipe size NPS-12 (DN 300) or less; the material is a PE 2708 or a PE 4710 as specified within ASTM D2513; and the design pressure is determined in accordance with the design equation defined in §192.121.Plastic pipe may not be used where (ground or) operating temperatures of the pipe will be:  (1) below -20°F (-29°C), or -40 °F (-40°C) if all pipe and pipeline components whose operating temperature will be below -20 °F (-29 °C) have a temperature rating by the manufacturer consistent with that operating temperature; or (2) above the temperature at which the HDB used in the design formula under §192.121 is determined.Standards for PE piping define acceptable materials in accordance with a standard designation code. Gas travels thru three regulators, taking a "double-cut", with some redundancy. This conforms to NFPA 54 and IFGC requirements.In accordance with CFR Part 192 Subpart H, the utility operator must install an excess flow valve (EFV) on any new or replaced service line serving a single-family residence after February 12, 2010, unless one or more of the following conditions is present:  The service line does not operate at a pressure of 10 psig (69 kPa) or greater throughout the year; The operator has prior experience with contaminants in the gas stream that could interfere with the EFV’s operation or cause loss of service to a residence; An EFV could interfere with necessary operation or maintenance activities, such as blowing liquids from the line; or  An EFV meeting performance standards in CFR paragraph 192.381 is not commercially available to the operator.The utility operator must mark or otherwise identify the presence of an EFV in the service line. PPI TR-3 provides information for interpolating the information between tested temperature limits.In CFR 192, paragraph 192.121 covers the design of plastic pipe.