In a nitrogen compound manufacturing plant, spraying boiling water burned 2 contractors performing a maintenance operation to replace the motor drive unit on an automatic valve located on the feed line of station dedicated to loading trucks with hot ammonium nitrate solution. The very hot water is used to drain and rinse the piping.

Both employees were hospitalised, one of which was seriously burned. This leak was due to the removal of the valve bonnet due to the non-compliant installation of the motor support on the valve (support directly mounted to the valve’s bonnet, while it should have been mounted on a clamp). In addition, the operators thought that the installation had been isolated and emptied of all product, as it was the day before.

The incomplete, imprecise and sometime erroneous work authorisation issued by the operator did not indicate the type of product used, or its pressure and temperature, for example. The operator must conduct an inventory of the entire site, valves/servo-actuators not in compliance with the manufacturers’ recommendations and bring them up to standard, draw up a lock-out procedure for equipment conveying dangerous fluids and thus prohibit all intervention by personnel (except in an emergency situation) on installations that have not been drained and isolated.