BY DEPARTMENT of Transportation estimates, 10 people a year die in cargo tank accidents at repair shops. A large percentage of these accidents involve cargo tanks in refined petroleum service.
In many instances, an explosion or fire occurs when mechanics begin cutting or welding on a tank, some of the piping, or other hardware attached to the tank. Investigations point to a number of factors, including inadequate cleaning, as a key elements in these tragedies.
“We all know the dangers that can exist when a petroleum tank is brought into a repair shop,” said Trent Eubanks, Miller Transporters. “We need to make sure that we do a thorough job of communicating the risks to our shop workers.”
Good communication is only one part of the process, though. A comprehensive safety policy should be in place, and it must be enforced.
Tank repair shops need to be designed with safety in mind. For instance, there should be plenty of grounding rods in the work areas, and the grounding system should be tested at regular intervals.
Tank cleaning and steaming should be mandatory for any petroleum tank before it is brought into a repair shop, especially if welding or cutting will be done. Even hot work on cargo tanks in other maintenance bays can pose a risk.
Detailed cleaning procedures are needed for petroleum tanks, which have a multitude of hiding places for explosive and flammable vapors. Wash rack workers must be made aware of the need to thoroughly inspect the cargo tank during steaming and cleaning.
“Cleaners must look around the tank to find the places where vapors can be trapped,” Eubanks said. “They need to inspect the top rails, which are part of the vapor recovery system. Hose tubes must be cleaned out, as well as the voids between double bulkheads. It's important to make sure that any drain outlets remain open. All valves, including the API bottom outlets, must be open to ensure complete drainage.”
After cleaning, the cargo tank must be tested to determine whether flammable or explosive vapors remain. Testing is needed for any area where vapors might collect, including voids and piping. Meters used to check the atmosphere inside the tank need to be checked and calibrated at regular intervals to ensure that they are operating properly.
Throughout the time it is in the shop, the cargo tank should be forced-air ventilated. High-capacity fans are preferred.
Only by paying close attention to safety can the tank repair industry avoid the catastrophic accidents that have killed so many shop workers over the years.