HAZMAT containers used for flammable, corrosive, and toxic liquids and gases will have a pressure/vacuum relief valve to prevent damage to the tank from changes in the internal pressure. These valves MUST be inspected and maintained in line with the manufacturer’s instructions. Some valve designs require a special tool to dismantle them for servicing. Investigations by HSE found a technician had welded a nut onto the top of the valve to allow it to be dismantled without the use of a special tool. The nut prevented the free movement of the valve stem, resulting in the valve sticking open and releasing hazardous vapors.
Following an incident, investigators found evidence that a pressure/vacuum relief valve, originally manufactured by Fort Vale Engineering Ltd, had been modified by a third party. The valve cap had a nut welded to the top, most likely to allow it to be serviced without the use of a special tool to remove the valve cap. The unauthorized modification prevented the valve’s safe operation.
 |
 |