After loading several hundred pounds of sausage into the 4000 square foot commercial oven for the second batch of the mourning, the operator started the cook cycle.  When the operator started the cook cycle, the oven exploded, blew the 5’x10’ steel entry door across the factory floor, destroyed the furnace, and blew out the wall of the furnace enclosure.

We investigated the loss and determined that the factory staff had tampered with the flame control module: it was set to signal the control panel that the oven had been purged of flammable gasses regardless of condition.  We found that there was no debris trap in the gas supply line to the pilot control valve; this could have allowed debris to block the valve in the open position between cycles.  We found that the fresh-air inlet for the oven’s purge cycle was blocked to prevent it from being opened by the oven control panel.  We found that the vacuum lines to the purge exhaust damper were in questionable condition and might not have been working well enough to allow a proper purge.  Finally, we learned that the purge cycle was manually controlled and oven operator might have forgotten to run it; the altered flame control module could not detect this and an explosion would have occurred when the cook cycle started.