Abstract: At approximately 11:20 p.m. on May 12, 1997, Employee #1, of Gary Drilling Tool in Bakersfield, CA, had just started his shift. He was walking around a mud pump when the pump's blow-off assembly exploded from the machine and struck his upper left leg. The blow-off valve had been set at 2,750 psi, and while its pin was not broken, it was bent. The main causal factor was that the 3 in. pipe that ran into the pump flange from the blow-off valve had been cross-threaded and could not sustain the pressure that had been applied. The employer was issued a general citation as a result of this accident.