Coupon retrieval is a common process throughout the oil process and chemical industries and has been performed for decades. The same tools are used for coupon and probes, but the plug type is different: hollow for probe, solid for coupon. The retrieval process involves breaking into a hydrocarbon envelope with single isolation. Two personnel are involved with retrieval as the equipment is heavy.
On-line Retrieval Process Basic Steps
The steps involving:
1. loosen plug,
2. attach service valve,
3. attach retriever,
4. connect retriever to plug,
5. pull out plug until pressure is equalized to pipe pressure (usually within 3 turns),
6. fully unscrew plug from fitting (14 turns from fully closed),
7. extend retriever,
8. close service valve,
9. bleed to atmosphere, and
10. remove retriever.
Date: Thursday, March 27, 2008.
Location: Echo Compressor
Activities: Routine corrosion probe replacement. Two technicians were trying to remove a hollow plug from a 2” access fitting. Both member of Echo retriever team had more than 5 years experience of retrieval operations.
Injured person: One corrosion technician suffered from laceration between middle finger and ring finger of his left hand.
Corrosion team arrived at Echo on Wednesday, March 26th. Prior to commencing work the retrieval team attended the daily platform safety meeting. Prior to commencing work on March 27th the SOP and JSA were reviewed by platform personnel.
Incident located at Cellar Deck Echo Compressor. Two corrosion technicians were replacing corrosion probe at discharge pump of water flood. Access fitting is located at horizontal pipe @ 5 o’clock position. Work began around 08.20 at local time. Remove the access fitting cover (protective cover) by using a spanner wrench. Connect the service valve to the fitting. Connect the retriever to the service valve. Close all bleed valve on service valve and retriever. The carrier plug was slowly unscrewing using T-bar (handle).
It was still heavy to turn T-bar until approximately 10 turns. Both technicians didn’t realize that pressure was not equalized. No pressure gauge attached to retriever tools. The two technicians still continue unscrew carrier plug. As the final turn was applied, the carrier plug was expelled uncontrollably from the access fitting. Wheel handle rotated rapidly and hit technician’s left hand. The injured corrosion technician was then examined by the platform paramedic. Injured party returns to Jakarta on March 28th, and is examined at hospital. Service valve and retriever were left attached to the piping.
March 29th, the injured person examined in the hospital and able to go home in the afternoon. Medical resume from Pertamina Pusat Hospital: The person can perform light work with limitation on his left hand (ring finger). It is not recommended to perform any lifting activities. Two technicians were mobilized from KLA to ECHO, to dismantle the attached service valve and retriever. March 30th, service valve and retriever was successfully dismantled using retriever from KLA and new probe were installed. Corrosion monitoring activities is stop and rescheduled until safety stand down is held. Safety stand down was held on 31st of March.
What Went Well
Personnel using proper PPE (hand glove) during work execution. Injured personnel get medical treatment immediately.
What Went Wrong
No pressure gauge attached to retrieval tools. Lack of awareness during probe replacement process, they should ensure that equalizing process during probe replacement is mandatory. The pressure did not equalise between pipe and retrieval tools when the hollow plug was fully unscrewed from access fitting.
Possible Root Cause
The line was sea water, which might require more time to equalise compare to gas. Debris/sand and/or bad seal O-ring at hollow plug may block the pressure to release into service valve during unscrew of hollow plug. This condition causes no equalised pressure. Seal O-ring at hollow plug was in a good condition – found during dismantling the retriever on March 30.
Use correct and complete tools, ensure pressure gauge installed and function at retriever tools. Follow procedure & JSA, know the service of the line and ensure retriever is equalised.