The New Frontier of Natural Gas Distribution: A Case Study of Bimodal PE 2708 Gas Pipe Application

Session 11B
4:10 pm

Brian Moidel, Dominion East Ohio Gas

This case study is for the use of Bi-modal PE2708 gas pipe at the Dominion East Ohio Gas Company headquartered in Cleveland Ohio. The new frontier of natural gas distribution is to ensure the improved reliability and integrity of pipeline systems. The polyethylene (PE) gas pipe industry consists of gas utilities, resin producers, pipe manufacturers, regulators and industrial organizations who work together to deliver a safer, more durable and efficient pipeline system. The new trend is to use larger diameter gas pipes and/or for higher operating pressures. Manufacturing responds to this frontier by offering new bimodal technology that has dramatically improved the performance of PE gas piping materials in almost all categories. The Department of Transportation (DOT) has increased the maximum allowable operation pressure from 100 psig to 125 psig for PE gas pipe which further embraces this new frontier.

Industrial standards provide the foundation for the frontier through the inclusion of high performance PE pipe materials, such as PE 2708 and PE4710 into the PPI and ASTM standards. The application parameters at Dominion East Ohio gas, a major gas utility located in eastern Ohio, include a broad range in temperatures, operation pressures and pipe diameters. Slow crack growth (SCG) is the major failure mode observed in the field. Higher temperatures accelerate the SCG process. Improvement in SCG resistance is always desired by gas utilities and it delivers a longer service life against SCG failure. Rapid crack propagation (RCP) is a rare but catastrophic failure mode. Lower temperature makes PE gas pipe more vulnerable to RCP failure. RCP resistance is a big concern especially for a utility such as Dominion where the ambient temperature can be very low in the winter time. RCP resistance decreases with the increase in pipe diameter, wall thickness and/or operation pressure. With the trend to move to larger diameter pipe, RCP resistance might be a limiting factor. Good pipe begins from a good material. In order to achieve safe long term operation with the least maintenance, an excellent PE material is the premise. While you cannot make a good pipe from a poor resin, you can make a poor pipe from a good resin. A higher standard in pipe quality is a must. To better serve its customers, Dominion East Ohio has successfully converted to bimodal PE2708 and bimodal PE4710 gas pipe by working with a resin producer and a pipe manufacturer. This case study will focus on Dominion’s experience in using the high performance bimodal PE2708 gas pipe. The experience of using PE4710 gas pipe will be reported later in a separate case study.

Brian Moidel, Principal Engineer, Dominion East Ohio Gas
Jimmy Zhou, Sr. Development Specialist, Dow Chemical
Allison Crabtree, Senior Technical Engineer, PolyPipe Inc.