Rockies Express Pipeline on Friday said a girth weld separation caused the November leak in southeastern Ohio that required operator Kinder Morgan to declare a force majeure and shut in a section of the natural gas line.

In a filing with the US Federal Energy Regulatory Commission, REX said the November 14 incident involving a loss of gas and drop in pressure was "due to a separation in the pipe at or near a girth weld." The filing is the first indication of what led to the shut-in a month ago.

A girth weld connects of two lengths of pipe with a circumferential weld at the joint, according to US Pipeline Inc. engineer Lowell Brien.

"In a good weld, that is the strongest part of the pipe," he said, adding that general causes of such a leak can range from poor materials to the quality of the weld. Other cases, like corrosion, are more often seen in older pipes that have been in operation for a year or more.

The leak occurred on a section of the pipe east of the Chandlersville compressor station in southeastern Ohio near the 1,660-mile pipeline's terminus in Clarington.

Pipeline and Hazardous Materials Safety Administration representative Damon Hill said an investigator was initially sent out in November as a matter of routine to examine the leak. "Our investigation into the REX situation is still incomplete at this time and there has not been an approval from our agency to restart the failed line," Hill said.

Meanwhile, Kinder Morgan said in a December 7 posting on its web site that it was consulting appropriate regulatory bodies and preparing a plan to return the pipeline section to service.

The leak occurred just two days after the start of flows on the REX-East extension that linked the Lebanon, Ohio, hub to Clarington. Volumes to Clarington hub fell to zero from the 980,000 Mcf/d capacity, shutting interconnections with Tennessee Gas Pipeline, Dominion Transmission and Texas Eastern Transmission.

--Adam Bennett, adam_bennett@platts.com