ARCHIVED – NEB SA 2004-01 Hydrates
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19 August 2004
To: All companies under National Energy Board jurisdiction,
Canadian Energy Pipeline Association, Canadian Association
of Petroleum Producers and provincial regulators
National Energy Board Safety Advisory
Attached is a safety advisory regarding the need to predict and control hydrate formation in pipeline systems. This advisory should be given wide circulation to technical personnel involved with pipeline operation and maintenance within your organization.
If you have any questions regarding this Advisory, please contact us toll free at 1-800-899-1265.
Michel L. Mantha
NEB SA 2004-01
On 15 May 2002, an 18-inch-diameter natural gas transmission pipeline ruptured near Fort St. John, B.C. releasing sour gas (0.41 % H2S). The escaping gas did not ignite. The diffusion of the plume required the evacuation of residents downwind of the release. The rupture occurred at an S-bend section of pipe where the pipe descends underground between a sending barrel and an isolation valve. A company employee was working on the sending barrel when the rupture occurred. The force of the rupture knocked the worker to the ground, but he was otherwise unhurt.
Cause of the Incident
The ensuing investigation revealed that the likely cause of the pipeline failure was a shock wave or impact created after a hydrate or ice plug blockage was released by a differential pressure. Though the pipe ruptured at an area of pipe weakened by a manufacturing defect, the increase in pressure would have caused a rupture of the pipe somewhere between the isolation valve and the barrel door.
Companies can generally predict and control hydrate formation and can anticipate potential problem areas within pipeline systems. Great care is required to dissolve hydrates that have formed as ruptures and other damage to pipeline components can occur. Gas gathering and transmission companies should develop an increased awareness amongst their pipeline operations and maintenance staff regarding the hazards and control of hydrate formation in at risk pipeline systems, and should have procedures in place to disintegrate hydrates once they have formed.
Measures for the prevention, control and handling of hydrates are outlined in the Canadian Association of Petroleum Producers (CAPP) Guideline for Prevention and Safe Handling of Hydrates – January 1994. [Publication #1994-0002]
For further information on the pipeline rupture of 15 May 2002, see the Pipeline Incident Report – Natural Gas Pipeline Rupture near Fort St. John, British Columbia
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