At present, the valve system is mostly used by pneumatic actuators, electric actuators and electro-hydraulic actuators. According to the characteristics of the three actuators, we analyze their application in the valve system:
Pneumatic System: The pneumatic system relies on the Air compressor, which compresses the air, cleans it, supplies the pneumatic actuator, and drives the valve. The gas is discharged directly to the atmosphere in the process of driving the actuator, and the gas path system needs to deal with the gas source continuously. Therefore, air compressor in general need to use one, the main road and the actuator before the branch of air handling components, such as dryer, filter decompression, oil mist, etc. Need regular maintenance, replacement. There are a lot of air way joints, and regular inspection is also needed to prevent air leakage and affect the system pressure. Such a cumbersome work is actually only to ensure that the pneumatic actuator system needs to switch to the correct action. The pneumatic actuator of large diameter valve, that is, the cylinder, is generally selected according to a certain air source pressure, but the pneumatic actuator often does not move, or the action is not in place, or the action is slow and the action is not smooth This is usually due to the following:
When the air path contains moisture, if the air temperature is below zero, the water will freeze, freezing the pneumatic actuator, so that the pneumatic actuator can not move.
The gas path is not lubricated by oil mist, so the actuator is in dry state for a long time, which causes the friction to increase greatly. The actuator is stuck or unable to move.
The output pressure of the air compressor is insufficient or there is a leak in the air path, which causes the pneumatic actuator can not get enough driving torque to open the valve quickly or close the valve completely.
The difference of the coefficient of thermal expansion of gas in cooler and hotter environment leads to the difference of the whole travel time of pneumatic actuator.
The gas has compressibility, may cause the pneumatic actuator to run in the process to be not smooth, the sudden wrong movement.
If the request fast shut-off, the pneumatic actuator will generally be equipped with a gas tank itself, in Fast shut-off, even if the gas, power cut off, can still ensure fast on and off the valve, but because of limited capacity, fast shut-off time will not be very short.
Hydraulic System: Hydraulic station system and gas system operating mechanism is similar, need to produce high-pressure oil, need oil filter, need to lay oil. The difference is also the advantage of the hydraulic system, the hydraulic system is internal circulation, the oil pressure is generally about 40~120 kg, the hydraulic actuator is much smaller than the pneumatic actuator, and the hydraulic oil has no compressibility hydraulic cylinder running smoothly will not occur jam jitter phenomenon. The hydraulic system can completely solve the shortage of pneumatic system.
The advantage of hydraulic system itself is to ensure the valve reliable operation of the best choice, but high-pressure oil, such as improper maintenance, oil leakage will often occur. Hydraulic system components such as servo valves, filters, high-pressure pipelines, such as expensive, high maintenance costs.
Electric actuator: electric actuator is completely different from pneumatic actuator and hydraulic actuator, electric actuator is completely free from the bondage of air compressor and hydraulic station, only need to get power supply and signal to drive the bypass system. Compared with pneumatic system and hydraulic system, the electric actuator is compact, easy to install, and the maintenance workload is greatly reduced.
Post time: Jul-28-2021