Select the implementing agencies provided the main basis for the system of professional "maximum working pressure", the actuator output force must be greater than this pressure. On the "maximum working pressure", I say a few words more, for the period of insurance, the proposed maximum pressure valve before the pressure to choose as the largest source of gas pressure spring range is reasonable (when the valve is positive). Pressure valve when the valve is working properly before and after the calculated pressure as is often too small to allow pressure, probably due to the following:

1 at the time of the opening of the valve is not working properly may be small, so that the valve before the pressure greatly increased, and the maximum operating pressure differential value of meaning is likely to occur when the valve will be shut down, and in this case, outlet fluid transport equipment (such as pumps, fans, compressors) will reach maximum pressure equipment operation, its value is equal to the nominal outlet pressure of the fluid delivery device.

2 does not work when the pressure valve after the pressure vessel may be lower than the pressure vessel during normal working pressure. These two factors make the time during normal operation is not much larger than the pressure valve after pressure valve before the normal operation, such that during normal operation of the valve does not leak when the leak is not working properly. Industrial boiler feed water system, for example, 35t / h boiler feed pumps rated pressure is usually 6.0MPa, bubble pressure of 3.8MPa, the valve before the pressure is normal when 4.0MPa, the pressure valve when the valve is working properly before and after approximately 0.2 MPa, if you take this value as to allow pressure, almost any valve can meet the requirements. But with the sudden reduction of steam, the valve opening will also be reduced, the valve before the pressure increases until it reaches the feed pump rated pressure. At this point before and after the pressure valve for 2.2MPa, usually single-seat valve in this pressure is difficult to ensure no leakage.