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There are requirements regarding the inflation pressure. The mechanical design manual recommends that the inflation pressure P0 should be in the range of 0.9P1 > P0 > 0.25P2, where P1 represents the lowest pressure in the system； P2 represents the maximum pressure of the system*. Hedek company provides different recommended values depending on the intended use. The gas filled in a pneumatic accumulator should be an inert gas that is non-toxic, flame-resistant, and non-explosive. It is generally only permissible to fill the air bag when there is no pressure on the pressurized side; the filling pressure depends on the function of the accumulator: for shock absorption, the filling pressure is either the operating pressure at the installation site or slightly higher ； When used for absorbing pulsations, the inflation pressure is 60% of the average pulsation pressure ； When used as an emergency or auxiliary power source, the inflation pressure should be 25% higher than the system’s maximum operating pressure and less than 90% of the system’s minimum operating pressure; it is generally around 85% of the system’s minimum operating pressure ； When used to compensate for pressure changes caused by temperature variations in a closed loop, the inflation pressure should be equal to or slightly lower than the lowest pressure in the loop. The pressure P0 of the accumulator should be determined separately depending on the application: 1. When used as an auxiliary power source, the pressure P0 is generally set at 80~90% of the minimum operating pressure P1, with it being ensured that P0 ≥ 0.25P2 (the maximum operating pressure) ； 2. When used to absorb impact pressure: P0 should be equal to or slightly higher than the normal operating pressure at the set point of the accumulator; it can also be taken as 60~70% of the pressure before the valve at the installation location is closed ； 3. When used to absorb pulsating pressure: P0 shall be 60% of the average operating pressure (P1+P2)/2, or the lowest operating pressure of the system ； 4. Used as a thermal expansion compensator to absorb the excess volume of oil that occurs when a hydraulic system in a closed loop heats up, due to the higher expansion coefficient of the oil compared to that of the tube material, thereby keeping the system pressure within safe limits. In this case, the charging pressure of the accumulator should be equal to or slightly lower than the lowest operating pressure of the closed circuit of the hydraulic system ； 5. When used as a multi-functional element that simultaneously serves as a system energy accumulator and absorbs pressure fluctuations and impact pressures, the inflation pressure P0 can be set within the range of 40–80% of the average operating pressure. Proportion of operating pressure for bladder accumulators: It is recommended to use 25%P3 ≤ P1 ≤ 90%P2, with P3 ≤ 3P2. (In the formula, P1 is the inflation pressure, P2 is the minimum operating pressure of the system, and P3 is the maximum operating pressure of the system.) When P3≈P2, it should be selected as a percentage of the maximum operating pressure ranging from 47% to 25% when used as an auxiliary power source; choosing a value that is too high reduces the effectiveness of the accumulator. If the nominal capacity of the accumulator is relatively large, then it can be charged to a higher pressure.