The technician of a the nitrogenous solution loading station heard the safety valve open and saw a 2 to 3 m flame surge from the exhauster duct near the pump. An abrupt explosion occurred and the solution gushed out of the tank in huge quantities. The new team had just clocked in 15 min. back after the previous shift which had completed all loading operations, stopped pumps and had left all valves open except the valve in the loading station. An explosion occurred at the elbow of the 10 to 15 cm diameter, ascending steam-insulated and -traced part of the exhauster duct. This was due to the decomposition of the nitrogenous solution upon passing through the holes created by corrosion of the elbow weld into the insulating material made of aluminium. Furthermore, maintaining the steam tracing temperature contributed to the explosion. A similar explosion had occurred in a transfer pipe of the same unit on 25 May 1966 while the steam tracing was not commissioned.