Pressure Tank Explosion

According to our driver who talked to the driver of the tanker, he was blowing off lime @ 7 psi. The driver stated that the hose felt heavy and he was walking along the hose to locate the problem when it blew. He thought that he had blown the hose until the air cleared. The tank had two 15 psi relief valves (condition unknown) He also told our driver that the tank had recently been repaired (welded). The incident happened early morning when it was still a little dark. This was an out of state contractor, so I doubt the exact cause will ever be known.
There were no injuries!!

Thanks for the share FC!