THIS MONTH'S PUZZLER
An explosion killed a welder who was using a torch in an attempt to cut loose an anchor bolt on top of a polymer atmospheric overflow tank, in preparation for removing the tank's agitator. The original work permit covered removal of the anchor bolts by pneumatic tool but the bolts were rusted to the nuts and wouldn't budge. Because the window for removing the agitator was closing, maintenance higher-ups okayed using the torch. The welder thought he could get at the bolts from the outside, away from the agitator shaft, which didn't include a seal. The clearance space between the tank and agitator shaft was open; calculations showed the monomer didn't produce sufficient vapor pressure to form a flammable mixture at normal temperatures — so, the vessel was classified as an uncovered process. The overflow tank was connected by vent to two others. Lockout procedures were deemed safe: all the intake lines were isolated except for the common vent. The plant continued to operate, filling the adjacent overflow tank while the welder worked. Hydrocarbon sniffing took place before the welder began but not during the welding. Safety decided the mishap was the welder's fault. What do you think?
CONNECTIONS DEMAND CAUTION
This note is based on Chemical Safety Board findings, so I don't feel right in taking credit for all of this response since others did the investigation.
With that said, it is not the welder's fault. Maybe he should have been aware of the potential for conditions to change, but most maintenance personnel are not completely familiar with all the equipment connections on every piece of equipment in a plant. That is why they rely on others more familiar with the specific process/equipment to prepare and validate equipment-specific isolation and hot work procedures. This was an incident where the safety risk of the common vent allowing flammable vapors to be displaced from the tank being filled and forced into the overflow tank was overlooked. This is a great reminder of two fundamental principles of process safety: 1) every connection is a potential hazard source that must be accounted for; and 2) expect the unexpected. When performing hot work in an area where flammable materials are processed, assume that conditions can change and that unexpected events will occur. To guard against such an eventuality it should be standard practice to require continuous monitoring of the area during hot work rather than only at the start.
Len Riker, operations project leader
Penford, Cedar Rapids, IA
DON'T BLAME THE WELDER
I believe the question is "whose fault was it?" Either it was the fault of the maintenance higher-ups who okayed the use of an open flame in an area where the accepted procedure was for mechanical removal, or it was the fault of health and safety. The question is was the original work permit amended? If not, the maintenance higher-ups violated the work permit, which did not allow for hot work when first issued. If the health and safety department okayed hot work, they did so on the basis of either ignorance or inadequate information — both of which place the responsibility with them. It was most assuredly not the welder's fault as he did as he was told; I assume the welder was not tasked with the hydrocarbon sniffing. Safety should have required continual sniffing during the hot work, again their mistake. No wonder safety blamed the welder as this allowed safety to cover it's a**. I write as a former welder's helper!
Peter Watson, international business development manager
Armstrong Chemtec Group, West Chester, PA
MANY PEOPLE CONTRIBUTED
This is the first puzzler to really make me angry. The folks who came up with the lockout procedure that left the vent connected, the supervisor who let the man work on a live tank with an opening close to the hot work, and the safety folks who blamed it on the welder — all of these folks — will soon be on the losing side of a lawsuit, if not criminal charges.
THIS MONTH'S PUZZLER