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What Are the 3 Common Pneumatic Valve Problems?

Views: 322     Author: Site Editor     Publish Time: 2021-03-31      Origin: Site

Some important valves such as light oil regulating valve and quick closing valve, desuperheating water regulating valve and quick closing valve, ammonia injection regulating valve and quick closing valve must ensure that the valve can be fully opened or fully closed. From the perspective of equipment division, valves are under the jurisdiction of the maintenance profession, and cylinder pistons and positioners are under the jurisdiction of the thermal control profession. Due to the presence of springs and other elements, the stroke of the cylinder is always greater than the stroke of the valve. In order to avoid the situation where the pneumatic piston cylinder is in the end, but the valve of the locomotive is not in place, when connecting pneumatic actuated valves, care should be taken to place the two ends of the cylinder piston of the air powered actuator in the middle of the full stroke of the cylinder.


Pneumatic control valve uses compressed gas as power source, cylinder as actuator, and uses valve positioner, converter, solenoid valve, retaining valve, gas storage tank, gas filter and other accessories to drive the valve to achieve the switch value or proportional adjustment. In this way, the control signal of the industrial automation control system is received to complete the adjustment of the pipeline media: flow, pressure, temperature, liquid level and other process parameters. The air actuator control valve is characterized by simple control, fast response, and intrinsically safe, without additional explosion-proof measures.


16-1-pneumatic actuated valves

Pneumatic Valve Positioning


The key to the positioning of the actuator pneumatic valve lies in three points. One is that the two end positions of the control valve are in the middle of the full stroke of the cylinder piston. The second is to listen to the sound to judge whether the valve is closed in place. The third is to use Huff to adjust the piston position.


Pneumatic Valve Connection


The keystone pneumatic positioner and the valve part will be disassembled and separated during the maintenance process of the pneumatic regulating valve. For the regulating valve that must be able to close tightly, make sure that the cylinder piston has a little margin at the end and a little gap when reinstalling.


Take the desuperheating water regulating valve as an example. Before connecting the pneumatic water valve actuator and air actuated water valve, both will be adjusted to the off position. It is easier to check the closed position of the maintenance valve part, you can try it with a wrench.


The close position check of the actuator under the control of thermal control is explained in detail as follows. You must confirm that all the bypass valves are in the closed position, send the total air source and check that the pressure is normal after the pressure reducing valve, shake the hand wheel, align the hand and automatic shaft connecting eyes, insert a pin to close the valve hand wheel tightly. In some cases, it is necessary to retract the manual shaft to a point below the automatic shaft to prevent the manual shaft from entrapping the automatic shaft and causing the valve to fail to close. Check that the pneumatic air actuator can be closed to the end and there is no gap at the top shaft of the cylinder.


16-2-air powered actuator

Adjustment of Pneumatic Valve Positioner


In the adjustment process of the positioner, the most important thing is to meet the positioner's zero position and range, the valve's zero position and stroke, and the cylinder's zero position and stroke. In the positioner range setting, it is necessary to ensure that the range of the positioner is greater than the stroke of the cylinder and the valve to prevent the positioner's command from being executed and the valve and the cylinder are already in place.


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