Depressurisation valve

A depressurisation valve for a pressurised cooling circuit, the depressurisation valve comprising:

• an inlet for coupling to the cooling circuit;
• an outlet;
• a main valve configured to move between an open position and a closed position, the closed position preventing fluid flow through the main valve from the inlet to the outlet;
• a pilot line fluidically coupled to the inlet and closable by a first control valve, the first control valve controlled by pressure at the inlet to open above a low pressure threshold;
• a second control valve controlled by pressure at the inlet and configured to open above a high pressure threshold, the high pressure threshold being greater than the low pressure threshold;
• a valve dome containing a first piston coupled to the main valve, the valve dome being fluidically coupled to the pilot line, wherein:
• in normal operation, the pilot line is operable to transmit fluid pressure from the inlet into the valve dome to apply pressure on a first face of the first piston, the first piston thereby applying a first force to the main valve urging it into the closed position, and
• when in operation the pressure in the coolant circuit is lower than the low pressure threshold, the first control valve is configured to close and remove the pressure from the face of the first piston and allowing the main valve to open,
• when in operation the pressure in the coolant circuit is higher than the high pressure threshold, the second control valve is configured to open and transmit fluid pressure to apply a second force to the main valve opposing the first force to urge the main valve to the open position.