These valves are mounted in order to protect the accumulator in case of gas overpressures higher than the value of the maximum allowable working pressure. So the calibration of the valve must be equal or lower than this value.
This valve is characterised by a port size of 9,5 mm and by a copra-aluminium disc with flat seat. Seals are not provided; valve tightness is ensured by an accurate lapping of disc surfaces. The body is made of steel A105, the disc is made of AISI 431.