Kinder Morgan Inc.'s Natural Gas Pipeline Company of America (NGPL) warned shippers Tuesday that it will have to take a 35-mile portion of pipeline on its Amarillo leg between Harper, IA, and compressor station 110 in Geneseo, IL, out of service starting Sept. 1 and lasting for five to seven weeks in order to test and possibly repair the pipeline.
A recent in-line inspection by a smart pig uncovered stress corrosion cracking (SCC) of the metal in the 36-inch diameter pipe, which is among three parallel lines that run north from West Texas to Chicago. SCC has been responsible for many pipeline ruptures in the past, including incidents on Northwest Pipeline in 2003 and TransCanada PipeLines in 2002. NGPL clearly is taking no chances.
"This is nothing that leads us to believe that we aren't capable of operating the pipeline safely at this point," said spokesman Rick Rainey. "In East Texas in Harrison County we had a pipeline rupture in May. And that was a similar situation in that we did find evidence of stress corrosion cracking and have since taken steps to inspect that portion of our line." He said the company plans to closely examine the Amarillo line through hydrostatic testing to ensure it can be operated safely.
Stress-corrosion cracking (SCC) is a far more extensive problem on natural gas pipelines and hazardous liquid pipelines in Canada than in the United States, according to a study released last year by the Office of Pipeline Safety (OPS). The Interstate Natural Gas Association of America, which represents interstate gas pipelines, said SCC accounts for about 1.5% of the reportable incidents for pipelines in the U.S., while the National Energy Board reported that 15-20% of the failures in Canada were attributed to SCC, according to the study (see Daily GPI, Oct. 25, 2004).
SCC forms on the exterior surface of underground pipelines as a group of hairline cracks. It often is the result of the interaction between pipeline stress, corrosion and certain environmental soil conditions.
While NGPL determines the extent of SCC on its Amarillo leg, the outage is expected to reduce the available capacity in that part of the heavily used NGPL system. The company expects capacity to be reduced by about 134,000 Dth/d, requiring substantial restrictions on gas flows.
NGPL said shippers should expect 92% of their maximum daily quantity to flow. No secondary, out-of-path firm or interruptible transportation will be available. Shippers using firm service for no-notice deliveries into storage on the Amarillo leg should expect 92% of their maximum daily quantity to be available.
NGPL is encouraging shippers to use alternative paths to reroute gas around the constraint. It noted that Northern Border is available for alternate gas deliveries. Northern Border went several months this summer with a significant amount of its capacity unsubscribed.
NGPL also is seeking FERC approval of a few tariff changes that will help compensate shippers for this headache. It is seeking authorization to provide Amarillo leg shippers with "opposite leg rights," which allow them to use the Gulf Coast pipeline leg at discounted rates (4 cents/Dth/d or the shipper's current discounted reservation rate for such service).
In addition, the pipeline is offering shippers a waiver of tariff provisions governing sourcing requirements for no-notice storage injections, which will allow shippers to select the Gulf Coast receipt zone for injections at Amarillo line storage points. And among other actions, NGPL also is seeking FERC authorization to provide certain interruptible storage services at no cost during the outage.
"This will not affect our ability to provide adequate supplies for the upcoming winter season," said Rainey. "In addition, our storage volumes are where they need to be for this time of year and we are on track to meet customer requirements."
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