Abstract: At about 11:50 a.m. on October 14, 1991, Employees #1 and #2 were hydro-testing a superheater. One of the employees noticed a leak near the manifold cap joint; however, the exact location of the leak could not be pinpointed and the workers increased the system pressure to about 2,150 psi. Employee #2 was on top of the heater looking for the leak. Employee #1 was on the ground observing the manifold cap gauge. The manifold cap exploded off the manifold pipe due to air expansive force. The concussion struck Employee #2 and knocked Employee #1 backwards and against metal portions of the heater. Employee #1 was pronounced dead on arrival by responding EMS personnel. Employee #2 was hospitalized.