Near miss with high pressure gas due to incorrect procedures
What happened
A crew narrowly avoided potentially serious problems with a high pressure gas supply by stopping and thinking things through. The near miss occurred whilst a crew were setting up for pigging of high pressure gas mains lines. A change to the flow configuration on two high-pressure gas mains to test flow rate was required; on the second to last step of the procedure, they closed a valve at the valve set.
Since one employee was unfamiliar with the location because it was not in their work area, they questioned the operator at the location to clarify what closing the valve actually did to the system flow. After a brief conversation they realized that closing the valve would actually isolate the pipeline and prevent the flow of gas to a downstream valve set that they were intending to flow to.
Work was stopped immediately and the valve returned to its normal position
What went right
After returning the valve to normal position, all parties involved at the location reviewed the procedure and figured out what went wrong. They discovered that the procedure was written using an old drawing of the valve set and did not represent the current valve configuration.
At that point all work was stopped, and valve sets were returned to normal until the procedure was updated using the correct drawings for the site.
Had they continued with following the incorrect and outdated procedure, they would have caused a compressor station to trip on low suction and possibly created other downstream supply issues.
Members may wish to refer to:
Safety Event
Published: 3 August 2023
Download: 
IMCA SF 19/23
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