In the world of process safety, every little detail adds up; so as one of my favorite bosses always said… “sweat the small stuff”! This became crystal clear during an incident investigation where a flanged connection was the point of release. Most people look at a flanged connection as a simple means to connect to ends of pipe together, but oh it is so much more and thus even the smallest of details can make or break your primary containment system at a flange connection. Here is the level of detail that we have to get to in order to prevent a LOPC event…
The flange had been leaking off and on for several months, so the decision was to replace the gasket with a new type of gasket. This flange was also on the nozzle of the process vessel so a leak was a significant concern as there would be NO MEANS to isolate the leak should we have a failure. A MOC was done and approved to use this new gasket that had a higher temperature rating, as it was determined that the original gasket was damaged due to process temperatures.
The new gasket was one the site had not used before and due to its thickness, it caused some concerns from the maintenance personnel who were installing it. Without going to the site, the unit engineer told them it was approved and to go forward installing it. They did, but in order to join the pipe to the nozzle, they needed longer bolts. Some of you may recall my many mentions of “short-threading”; it was at this facility where I learned all about this. The engineering manager was a stickler for the “3-threads showing” rule of thumb and it was very much a standard the facility followed. The HHC/EHS in this process was an exceptionally nasty one and even the faintest of smells caused quite the response from Unit and Management personnel. So these maintenance personnel informed the unit engineer that the thickness of the gasket AND following the torque valves of the manufacturer, the bolts/rods did not have “3-threads showing”. Now the guys did not tell the engineer exactly what the issue was, other than the gasket was too thick – in hindsight, the engineer claimed they should have been more clear on their concerns (sound familiar?). Anyway, the maintenance personnel went to the “stores” and got some bolts/rods that were 1″ longer; however, these longer bolts/rods were of DIFFERENT materials of construction AND this material was NOT compatible with the HHC/EHS. The gasket was installed, torqued properly, and leak tested. The PSSR was completed with everyone’s signature. The process was started up and 8 months later we had a 2,000-pound reportable release from that flange after the flange suffered what could only be called a catastrophic failure. Three (3) of the five (5) bolts/rods were completely destroyed from severe corrosion and the flange failed releasing the contents of the day-tank.
I can’t share the specifics as this case caused several severe injuries and countless lawsuits in our small community, but it was an event I will never forget. Just using some other bolts/rods or even the wrong washer or nuts can make a huge difference in the integrity of our primary containment systems. So yes, we MUST sweat the small stuff and even the slightest of changes MUST be reviewed by competent well-intentioned team members to understand the impact the change may have on our process safety.