Butane leakage from open vent on steam cracker furnace

What happened?

Before the start‐up of a steam cracker furnace, a leak and pressure test was performed.
During the test, the pressure dropped slightly.
A leak test (soap test) was performed at the location of the flanges. No leak was detected.
The operator decided that the system was safe to start up.
When feeding the furnace with butane, approximately 16 tonnes was released to the atmosphere due to an open vent.
The production closed the valve immediately after noticing the leak.
Nobody was injured and no fire occurred.
Why did it happen?

A vertical vent situated at 30 metres/100 feet on the top platform of the furnace was left open.
The outside operator should have done a complete field check, to check all vents, before the start-up. The field check was incomplete and procedure not followed.
As steps were missed, the operators were not aware that a check-valve was located near the pressure management system.
What did they learn?

Always verify the lining‐up of a system before performing a pressure or leak test.
The lining‐up should be completed with all the available tools (piping and instrumentation diagrams (P&ID) and check-list).
Checklists are not optional. Every step should be respected.
Ask yourself or your crew

What could the operators have done differently?
Think about the pressure test: why do you think the operator assumed everything was OK? Put yourself in his shoes…
When have we assumed everything is OK?
How do we verify that the system is lined-up before start-up?

Published on 21/02/20 1565 Views

16 tonnes of butane were released into the atmosphere due to an open valve on a steam cracker furnace. A pressure and leak test were performed prior to start up, but no leak was discovered at the time.