What does a hydraulic pressure gauge indicate when the charge in a diaphragm-type accumulator is lost?

When the charge in a diaphragm-type accumulator is lost, the hydraulic pressure gauge indicates zero pressure. This is because the purpose of the accumulator is to store hydraulic fluid under pressure. The diaphragm is a flexible membrane that separates the hydraulic fluid from a gas charge (often nitrogen). When the gas charge is intact, it provides the necessary pressure to maintain hydraulic system performance.

If the gas charge is lost, there is no longer any force to compress the hydraulic fluid, leading to a state where the pressure in the system drops to zero. This condition also typically indicates that the accumulator can no longer effectively store energy or assist in maintaining system pressure, which can have critical implications for the operation of the hydraulic system. Thus, a reading of zero pressure on the gauge clearly reflects the absence of pressurized fluid in the accumulator resulting from the lost charge.