A mechanical contractor was severely injured when working on renovating a commercial hot water heating system. After shutting down the steam heat exchanger and draining the hot water from the system, the contractor was beginning to install new piping when suddenly he was exposed to scolding water and vapor from the recently opened pipe. The worker fell from his ladder and suffered significant injuries. He claimed the event was caused by facility personnel re-energizing the system without warning.
Investigation of the event included review of the heating system piping and controls. Based on the testified sequence of shut down-drain down steps documented by the contractor, a virtual reenactment displayed the process to leave a large section of piping undrained from the floor above the location of accident. It was determined that this portion of pipe filled water was consistent with the quantity of water resulting from the spill. Further review of the system indicated that had the drain down procedure included a complete procedure, the only available source of the hot water in question would have been completely drained leaving no potential for the accident to occur. The virtual reenactment also depicted that had the event occurred as alleged, the system being re-energized by facility personnel, the hot water could not have been generated through a properly drained system.
This case, as many others, indicate the importance of early documentation of an accident scene and thorough analysis of these systems, performance, and controls prior to reaching early conclusions.
