Event Description
A water heater located in the forward galley exploded. Post-incident examination focused on the electrical and pressure components.
Relay Findings
The contacts of the water heater relay, which supplies power to the three heater elements when energized, exhibited roughness, ragged edges, discoloration, and excessive erosion. According to the manufacturer, when a relay surpasses its intended service life, contact surfaces may wear and erode, potentially causing the contacts to remain stuck in the closed position.
Pressure Relief Valve Findings
The pressure relief valve, specified to crack open at 65 psi, was subjected to a test pressure of 300 psi without opening. Subsequent disassembly revealed that the O-ring had migrated from its normal seating position into the lower valve body. It became lodged between the inside diameter and the head of the poppet. In this configuration, the O-ring created a complete blockage of flow, preventing the valve from opening.