Pig Trap Ruptures
Effective Date: 1/18/1980
 | Minerals Management Service Gulf of Mexico OCS Region |
Notice No. 094
January 18, 1980
OCS Operations Safety Alert
Pig Trap Ruptures
A pig trap on an offshore pipeline platform recently ruptured during pipeline water removal operations.
A 12" pipeline connecting the platform to a transportation pipeline was being dewatered prior to placing the line in service. Two pigs were in the line near the connection to the transportation line and the 1000 psi gas pressure in the transportation line was used to force the pigs toward the platform where the water was evacuated through two open valves on a pig trap. The process proceeded normally until parts of the first pig plugged the open valves. The riser valve was shut, the pig trap was bled to atmosphere, and pieces of the pig were removed. When the riser valve was reopened the second pig extruded through the valve and passed into the trap causing a severe hydraulic hammer. The trap and main valve split on two sides allowing gas to escape.
There was no injury to personnel or other property damage. To prevent a recurrence of the accident the pipeline company is taking the following action on future installations:
1. A dewatering point will be incorporated on the trap side of the pig trap valves.
2. Only one pig will be used (nonmetallic wiper type).
[signed] D.W. Solanas
Oil and Gas Supervisor
Operations Support
Gulf of Mexico Area