Been reviewing this fire at a Refinery in Corpus Christi, Texas a few years ago where the Chemical Safety Board investigated. One disturbing point they found was a flange had been having a slight leak for 6 months and had not been address barely at all! Quote from CSB report “In late January of this year, maintenance was performed on the flange, tightening the existing bolts, but the leak persisted. Further maintenance was performed on February 10 – over three weeks prior to the actual incident. At that time workers replaced the flange bolts and a work order was submitted to order a clamp to enclose the leak.”
What I find interesting is they did not mention the gasket anywhere! It seems to me they first did a “re-tightening” effort that might of been with a torque wrench but as you can see in the photo there were NO FLAT WASHERS! Also hard to see any anti-seize on the bolts but hard to say. Either way, the torque would have some errors. Second it seems they might of replaced bolts but kept the gasket in place since they did not bring the system down.
In summary, a flange leak in one of the most dangerous parts of the plant was left to leak and eventually caused massive damage to the plant. leaks are not something to take lightly in a refinery!
The CBS Letter here.
Report on CSB news conference here.