New Measurement Data Has Implications For Quantifying Natural Gas Losses From Cast Iron Distribution Mains

EPA/GRI Study
By Carey Bylin, Luigi Cassab, Adilson Cazarini, Danilo Ori, Don Robinson and Doug Sechler | September 2009 Vol. 236 No. 9

Natural Gas STAR partner company Consolidated Edison Company of New York (Con Edison) has reported implementation of another innovative approach for reducing losses from distribution mains. Con Edison supports ULC Robotics in the deployment of the Cast Iron Joint Sealing Robot (CISBOT). CISBOT is a live main sealing technology that can be used to seal joints in mains between 6 and 12 inches in diameter and can traverse up to 300 feet of pipeline through a single excavation (150 feet in each direction from the launching port.) It is equipped with a video camera with illumination, support arms, a drill head, and a sealant injector.

To use CISBOT, operators excavate a section of pipe and install a permanent fitting through which the robot’s launch tube is installed. The operator inserts CISBOT head-first into the launch tube through a valve (all with no gas escaping) and navigates it using the video camera with illumination to rehabilitate each joint starting at 150 feet away. To repair a leaking joint, CISBOT extends support arms to stabilize the robotic head, and it drills through the spigot into the joint seal at several points around the circumference of the joint. The drill bit is shaped to create a chamfer at the drill hole that allows the injection nozzle to create a clean, tight seal. Then anaerobic sealant is injected through the nozzle into the old jute, thus resealing the joint. Once the CISBOT system has completed the repair of joints within its 150-foot range, it is re-launched in the opposite direction.

CISBOT has patrolled Con Edison’s low-pressure cast iron network since 2000, sealing more than 5,000 joints. The robot minimizes excavation and repaving costs while eliminating any service disruption to customers. Con Edison estimates it reduced rehabilitation costs 30 to 40% over traditional trenched spot repair operations, particularly on streets that are about to be repaved.

Conclusion

The EPA/GRI and Comgas measurement study results show that the average volume of natural gas lost from cast iron distribution networks can vary and points to the need for further study of loss rates globally. Accurately assessing loss rates will help natural gas distribution companies prioritize maintenance activities and quantify resulting environmental, economic and efficiency benefits. By replacing cast iron mains with plastic pipeline, inserting plastic liners, or utilizing innovative technologies such as CISBOT, distribution companies can prevent much of this gas loss and reduce system maintenance costs associated with responding to citizen reported leaks. In addition to more efficient gas delivery to customers, companies are reducing losses of a valuable clean energy source and reducing emissions of methane, a potent greenhouse gas.

Carey Bylin is with the U.S. Environmental Protection Agency. She manages the Agency’s Climate Change Division’s domestic and international oil and gas work under the Natural Gas STAR Program and the Methane to Markets Partnership. Bylin.Carey@epamail.epa.gov.

Luigi Cassab is with Comgas. In 2009, he graduated in Mechanical Engineering at FEI University Centre. He works at Comgás Operational Area and supports all Control Room Area administrative activities.