Published on 02/10/23 481 Views

A pinhole leak was discovered on a pipe elbow in the naphtha side draw line of a crude distillation unit (CDU). Operators immediately attempted to isolate the leak while the CDU remained on stream by closing 4 valves. Subsequent inspection of the piping revealed significant thinning of the line, requiring a large section of pipe to be replaced. After numerous unsuccessful attempts to isolate and drain the corroded section of pipe, a work permit was issued authorising workers to drain and remove the corroded section even though draining of the line could not be verified and the CDU was on stream. The maintenance supervisor directed workers to make 2 cuts in the pipe with a pneumatic saw. The second cut 24m (78’ 7’’) above grade was stopped when naphtha stared weeping out. About 33 minutes later, naptha started to blow through the open end at the top of the pipe and ignited (probably on hot equipment or piping). The resulting fire quickly engulfed 5 workers on the CDU tower and temporary scaffold structure, killing 4 workers and seriously injuring another.

Ask yourself and your crew:

How can something like this happen here (e.g. on our site)?
What safety measures (i.e. procedures, controls/barriers) do we have in place to mitigate the risk?
How do we know the risk controls/barriers are working?
What improvements or changes should we make to the procedures, controls/barriers or the way we work?

Original content courtesy of IChemE Safety Centre