Alaskan Pipeline experiences mysterious shiftgreenspun.com : LUSENET : Grassroots Information Coordination Center (GICC) : One Thread
Trans-Alaska oil pipeline shift a mysterious event 20-05-00 A section of the trans-Alaska oil pipeline shifted abruptly, shearing anchor bolts and damaging some vertical supports that hold the line above the ground, according to a spokesman for the Alyeska Pipeline Service. He said the company should have some explanation of why a section of pipe about 1.5 miles (2.4 km) long shifted between 1-1/4 inch and 10 inches, company spokesman Tim Woolston said. The affected section is on the south slope of Atigun Pass in the Brooks Range and about 170 miles (275 km) south of Prudhoe Bay, the company and regulators said. The shift was strong enough to pull out some of the bolts that anchored the pipeline to some of its vertical supports, Alyeska said. The damage was reported, said the Joint Pipeline Office, the consortium of federal and state agencies that oversees Alyeska's operations. Six anchor bolts were broken and aluminium webbing designed to absorb shocks was crushed. Other portions of the vertical-support system were damaged, although there was no damage to the actual pipeline, said JPO spokeswoman Rhea DoBosh. "The mysterious event was unusual in Alyeska history," she added. "We haven't found anything even remotely close to this." "It is not uncommon for one or even two of the anchor bolts to break but to have six anchors, all in a row, with this amount of support damage is extremely significant." Alyeska is a consortium owned by oil companies with interests on Alaska's North Slope. Major owners are BP Amoco and Exxon.
Source: Reuters via Energy24
-- meg davis (email@example.com), June 09, 2000
Thanks so much. This is quite interesting to say the least.
-- Paula Gordon (firstname.lastname@example.org), June 10, 2000.
Yes Paula, it is very interesting. I think there is a common causal thread running through all the pipeline breaks, subterranean utility problems (fires, manhole covers blowing off, sewer, water and gas main breaks), melting of the permafrost in the Alps and Canada, accelerated melting of the polar caps, increase in magnitude 5.0 earthquakes and what seems to be the progression into a worldwide drought. I think it would be reasonable to start questioning why we are seeing an increase in geological and environmental phenomena.
-- Philip Maley (email@example.com), June 10, 2000.
When did the actually occur? could it be related to the solar flares? Yes, this maybe grasping, but the pipeline is a big piece of metal. And magentism is a very strong force.
-- perry (firstname.lastname@example.org), June 10, 2000.
I would be interested to see a record of the pipeline system pressure plotted against the pump drive motor current draw at the first pumping station upstream of the damaged area. Without trying to be too simplistic, this sounds like water hammer on a grand scale! SCADA systems with embedded microprocessor date-related problems (Y2K) have been responsible for some of the "unexplained" problems experienced by the refinery and sewage-treatment industries. The loss of feedback or inaccurate feedback by system sensors could have resulted in a pressure surge.
-- Frank Hill (email@example.com), June 10, 2000.
Article last updated: Wednesday, June 21, 2000 6:52 AM MST Gas pocket blamed for pipeline shift By DOUGLAS FISCHER Staff Writer
The violent compression and collapse of a gas pocket in a low-lying section of pipe jarred the trans-Alaska oil pipeline enough to shift it nearly 21 inches, Alyeska Pipeline Service Co. officials said Tuesday.
The shift, which occurred south of Atigun Pass shortly after an April 17 restart, went undetected until crews doing routine reconnaissance on May 15 noticed seven anchor assemblies had tripped.
The Brooks Range pass, at 4,738 feet, is the pipeline's highest point.
Oil gushing down the pipeline after pumping restarted met a wall of vapor resting atop oil that had pooled at the bottom of the pass, near where the pipe emerges from the ground, Alyeska said. The vapor condensed to the point where it couldn't condense anymore, then collapsed, generating a pressure wave strong enough to shear off steel connecting bolts down a mile-long stretch of the pipeline.
"The good thing is we learned a lot from this incident," said Alyeska Senior Vice President Bill Howitt. "The great thing is the support system for the pipeline worked exactly as it was supposed to.
Steps have been taken--including lower, slower surveillance flyovers and the painting of orange alignment stripes on key pipeline anchors-- to ensure future incidents do not go undetected for so long, added Alyeska spokesman Curtis Thomas.
But the head of a local pipeline watchdog group wonders how the problem went undetected for so long. And with production declining on the North Slope, he bets decreased oil moving through the pipeline will make problems like this more common.
"They knew it had to have been an incredible pressure hammer," said Ross Coen, director of the Alaska Forum for Environmental Responsibility. "Suppose it happened and we have oil on the ground? ... Suppose it happened where the pipe is buried?"
While the collapse was quick and violent, the pipeline was never above maximum stress levels, Thomas said. Though sensors never detected the buildup, engineers collecting data on the scene could calculate the bubble's impact, and Alyeska said it fell within the accepted range.
The month-long gap in detection, however, is not good, Thomas acknowledged. "That is a problem. And that's a problem we're going to fix."
The company has lowered its minimum flyover height from 300 feet to 200 feet and has instructed pilots to fly slower and further from the center of the pipeline to better see its supports, Thomas said. "That's where the orange stripes will come into play."
Crews from Fairbanks and two nearby pump stations moved the 48-inch pipe back into place, erecting temporary cribbing to support the pipe and reseating anchors and the shoes that sit on those anchors. That work was done May 26.
"Though this looked like a violent act--and it was a violent act--the key to this is that everything performed the way it was supposed to," Thomas added. "The systems we have in place are like shock absorbers, and they did exactly that: They absorbed the shock and the pressure and withstood the impact."
-- Martin Thompson (firstname.lastname@example.org), June 21, 2000.