Pneumatic actuator, also known as pneumatic head, is another name of air cylinder, which is a device that uses pneumatic pressure to drive the opening / closing or regulating valve,Description of pneumatic actuator of Chinese valve
structure
- The pneumatic device shall be composed of air cylinder, opening indication, travel limit, pneumatic element, manual mechanism, signal feedback and other components
- The connection dimension of pneumatic device and valve shall comply with the provisions of GB / t12222 and GB / t12223
- The pneumatic device with manual mechanism shall be able to open and close the valve with its manual mechanism when the air source is interrupted. When facing the hand wheel, the hand wheel or handle shall rotate counterclockwise to open the valve and clockwise to close the valve
- When the end of the piston rod is internally and externally threaded, there shall be a wrench mouth suitable for the standard wrench
- The sealing ring of the piston shall be convenient for replacement and maintenance
- For the pneumatic device with buffer mechanism, the stroke length of the buffer mechanism can refer to table L
- The pneumatic device with adjustable buffer mechanism shall have a mechanism outside the cylinder body to adjust its buffer effect
- The thread size of the air inlet and outlet of the cylinder shall comply with the provisions of GB / t7306.1, GB / t7306.2 and GB / t7307
Common pneumatic valves such as pneumatic butterfly valve
performance
- The rated output force or torque of the pneumatic device shall comply with the provisions of GB / t12222 and GB / t12223
- Under no-load condition, input the air pressure specified in Table 2 into the cylinder, and the action shall be stable without jamming and creeping
- Under the air pressure of 0.6MPa, the output torque or thrust of the pneumatic device in the opening and closing directions shall not be less than the value indicated on the label of the pneumatic device, and the action shall be flexible, and * deformation and other abnormal phenomena are not allowed at all parts
- When the sealing test is conducted with Zui high working pressure, the air leakage from the respective back pressure side shall not exceed (3 + 0.15d) cm3 / min (standard state); The air leakage from the end cover and output shaft shall not exceed (3 + 0.15d) cm3 / min
- The strength test shall be conducted with 1.5 times of Zui large working pressure. After the test pressure is maintained for 3min, the end cover and static sealing parts of the cylinder block shall be free of leakage and structural deformation
- Action life times: the pneumatic device simulates the valve action. Under the condition of maintaining the output torque or thrust capacity in both directions, the opening and closing times of the opening and closing operation shall not be less than 50000 times (the opening and closing cycle is one time)
- For the pneumatic device with buffer mechanism, no impact is allowed when the piston moves to the end of stroke
Surface and appearance
- The end cover, end flange and box body of the cast cylinder shall be free of scratches, cuts, air holes and burrs
- The paint layer or chemical treatment layer on the outer surface of the pneumatic device shall be flat, smooth, uniform in color, and free of oil, indentation and other mechanical damage
test method
No load test 1. The pneumatic device shall be placed horizontally, and the air pressure specified in Table 2 shall be alternately applied to both sides of the cylinder. The exhaust side shall be opened to the atmosphere, so that the pneumatic device can be opened and closed.
The test results shall meet the requirements of (performance 2)
- For air cylinder with buffer mechanism, the buffer valve shall be fully opened during no-load test
The mixed oil of 70% kerosene and 30% spindle oil or compressed air is used as the medium for the strength test. The pressure is alternately applied to the cylinder at 1.5 times the maximum cylinder working pressure (the allowable Zui high pressure value). After the pressure is maintained for 3min, the cylinder appearance is observed and disassembled for inspection. The results shall meet the requirements of (performance 5). Safety protection measures must be taken when testing with air
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 shall not be less than the specified value on the pneumatic device label. At the same time, the manual mechanism, opening indication, travel limit, information feedback and other components shall be inspected one by one, and the results shall meet the requirements of (performance 3)
Under no-load condition, the sealing test pneumatic device shall alternately apply compressed air 1.1 times the maximum working pressure from the two air inlets, and check the air leakage at the piston and output shaft. Keep the pressure for 3min, and the leakage shall meet the requirements of (performance 4). Another inspection method for sealing test: check the indicated pressure of the pressure gauge for 5min, and it is qualified if the gauge pressure does not drop. Either of the two methods.