Tank Roof Collapse

Tank Roof Collapse

Portfolio Categories: Degassing.

One of Envent’s national customers contacted an Envent branch location regarding the need for a copy of Envent’s tank degas procedure “As soon as you can.” The customer indicated that a serious incident had occurred a few days earlier at one of their local petroleum processing facilities. Envent sent the tank degas procedure. For the purposes of hazard communication, the customer sent a copy of the safety bulletin and urged Envent to share with all employees. The safety bulletin indicated a tank cleaning and degassing company had been contracted to degas and clean a Gasoline storage tank. During degas the contractor had experienced a series of several small explosions inside the facility tank. The explosions were described as sounding like someone knocking on the side of the tank. After several “knocks” the degassing operation was shut down and the area evacuated. Investigators discovered the floating roof had torn away from several of the landing legs and the roof had partially collapsed.

In the following weeks and after a thorough investigation, it had become apparent the cause behind the mysterious knocking sound during degas. The tank cleaning division of the contracted company had submitted a fixed price tank cleaning bid and was pressing the degassing division to expedite their scope of the project. What resulted was a decision to water wash the tank while the vapor space was at or near 100% LEL. The jet of water shooting into the tank caused static discharge and thusly, detonation of gasoline vapors that had combined with oxygen drawn into the tank by the degas equipment. Essentially, the water became the spark plug in a very large, very powerful internal combustion engine; the floating roof acting as the engines piston. Since the close of the investigation, the customer has incorporated Envent’s degassing procedure into its project bid requests and master tank cleaning and degassing sequence. That procedure and sequence specifies no water washing until tank vapor space is tested and confirmed to be below 50% LEL. The customer has also understands the importance of keeping tank cleaning and tank degassing as two completely separate scopes of work.

Having one company provide both services creates a conflict of interest where checks and balances are compromised. Among several other vapor service lines, Envent degasses tanks. Being a tank degassing specialist, Envent does not dilute its attention to detail in an effort to capture more work scope and therefore more project revenue. Envent has not, does not, and will not clean tanks. Leave tank cleaning to the experts. Leave tank degassing to Envent.

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