Pneumatic actuator, also known as pneumatic head, is another name for cylinder. It is a device that uses air pressure to drive the opening/closing or regulating of valves. The description of Chinese valve pneumatic actuator
The pneumatic device is composed of components such as cylinder, opening indicator, travel limit, pneumatic components, manual mechanism, signal feedback, etc. The connection size between the pneumatic device and the valve should comply with the provisions of GB/t12222 and GB/t12223. Pneumatic devices with manual mechanisms should be able to open and close the valve through their manual mechanism when the air source is interrupted. When facing the handwheel, turn the handwheel or handle counterclockwise to open the valve and clockwise to close the valve. If there are internal and external threads at the end of the piston rod, there should be a wrench mouth suitable for standard wrenches. The piston sealing ring should be easy to replace and maintain the pneumatic device with a buffer mechanism. The stroke length of the buffer mechanism can refer to Table L for pneumatic devices with adjustable buffer mechanisms. There should be a mechanism for adjusting the buffer effect on the outside of the cylinder body. The thread size of the cylinder inlet and outlet should comply with the requirements of GB/T7306.1, GB/T7306.2, and GB/T7307. Common pneumatic valves such as pneumatic butterfly valves should have performance
The rated output force or torque of the pneumatic device should comply with the provisions of GB/t12222 and GB/t12223. Under no-load conditions, the air pressure specified in Table 2 should be input into the cylinder, and the action should be smooth, without jamming or creep. At a pressure of 0.6 MPa, the output torque or pushing force of the pneumatic device in the opening and closing directions should not be less than the value indicated on the pneumatic device label, and the action should be flexible. Deformation and other abnormal phenomena are not allowed in various parts. When conducting a sealing test at the highest working pressure, the air leakage on each back pressure side should not exceed (3+0.15d) cm3/min (standard state); The air leakage of the end cap and output shaft shall not exceed (3+0.15d) cm3/min, and the strength test shall be conducted at 1.5 times the maximum working pressure. After maintaining the test pressure for 3 minutes, there should be no leakage or structural deformation of the cylinder end cover and static seal. Action life: Pneumatic device simulates valve action. Under the condition of maintaining bidirectional output torque or thrust capability, the number of opening and closing operations shall not be less than 50000 times (the opening and closing cycle is XNUMX times). For pneumatic devices with buffer mechanisms, the piston movement to the end of the stroke shall not impact the surface and appearance
The end cap, end flange, and housing of the cast cylinder should be free of scratches, cuts, air holes, and burrs. The paint or chemical treatment layer on the outer surface of the pneumatic device should be flat, smooth, uniform in color, free of oil stains, indentations, and other mechanical damage testing methods
Empty load test 1. The pneumatic device should be placed horizontally, and the air pressure specified in Table 2 should be alternately applied on both sides of the cylinder. The exhaust side should be open to the atmosphere so that the pneumatic device can be opened and closed.
The test results should meet the requirements of (Performance 2)
The cylinder with a buffer mechanism should have the buffer valve fully open during the no-load test, and a strength test should be conducted using a mixture of 70% kerosene and 30% spindle oil or compressed air as the medium. The pressure is alternately applied to the cylinder at 1.5 times the maximum cylinder working pressure (maximum allowable high pressure value). After holding the pressure for 3 minutes, observe the appearance of the cylinder and disassemble it for inspection. The result should meet the requirements of (Performance 5). Safety precautions must be taken during air testing
Load test: Install the pneumatic device on the test bench, apply 0.6MPa compressed air to the cylinder, and gradually apply torque or thrust to the output shaft. Measure the output torque or thrust of the pneumatic device at this time, and the value must not be less than the specified value on the pneumatic device label. At the same time, check the manual mechanism, opening indicator, travel limit, information feedback and other components one by one, and the results should meet the requirements of (Performance 3)
Under no-load conditions, the sealing test pneumatic device should apply compressed air at 1.1 times the maximum working pressure from two intake ports to check for air leakage at the piston and output shaft. Maintain pressure for 3 minutes, and the leakage rate should meet the requirements of (Performance 4). Another inspection method for sealing test: check the pressure gauge to indicate the pressure for 5 minutes, and if the gauge pressure does not decrease, it is considered qualified. Either of the two methods.
It can be divided into angular stroke pneumatic actuators, mainly matched with ball valves, butterfly valves, plug valves and other straight stroke valves; Straight stroke pneumatic actuator, mainly equipped with globe valves, gate valves and other straight stroke valves.