Pneumatic actuator repair tips
Pneumatic actuator repair tips
I. Overview
Pneumatic actuators with oil-free compressed air as the driving force to actuate the valve or baffle action. There are the following types: pneumatic control valve, solenoid valve, pneumatic long stroke electric actuator.
Second, pneumatic control valve
Pneumatic valve by the pneumatic actuator and control valve of two parts. Pneumatic actuators with oil-free compressed air as the driving force, to accept the gas signal 20 ~ 100kpa and converted into displacement, drive control valve to regulate fluid flow. In order to improve the linearity of the valve position, to overcome the stem friction and eliminate the impact of changes in media pressure to be adjusted to improve the speed of action, the use of pneumatic valve positioner and control valve matching, so that the valve position can be adjusted according to the signal to achieve the correct Positioning.
Gas quality should be no obvious oil vapor, oil and other liquids, no significant corrosive gases, steam and solvents. The amount of solid particles contained in the air supply of the regulator with positioner should be less than 0.1g / m3 and the particle size should be less than 60цm and the oil content should be less than 10g / m3.
Commonly used pneumatic control valve consists of pneumatic diaphragm control valve and pneumatic piston control valve.
⒈ pneumatic film regulating valve
Pneumatic membrane actuator air pressure maximum 500kpa. Actuator positive action and reaction of two types, is the role of signal pressure increases, the valve is closed, also known as air-off; reaction is the signal pressure increases, the control valve is also open, also known as open air.
⒉ pneumatic piston valve
Pneumatic actuator air pressure source maximum pressure of 700kpa. Compared with the pneumatic film actuator, it has great output force under the same stroke conditions, so it is especially suitable for high static pressure and high differential pressure situations.
⒊ pneumatic diaphragm valve
Pneumatic diaphragm valve according to the choice of diaphragm or lining material can be applied to a variety of corrosive media pipeline, as the flow control valve opening and closing valve. For example, chemical water treatment program control valve, often using pneumatic diaphragm actuator and solenoid valve with the valve to achieve full open or full close control.
⒋ valve positioner
There are two kinds of electrical signals and gas signals.
Pneumatic valve positioner and pneumatic control valve supporting the use of. The positioner's air supply pressure depends on the actuator type and its pressure signal range (or spring pressure range). For example, when ZPQ-01 positioner is matched with ZM series pneumatic film actuator, if the actuator pressure signal range is 0.02 ~ 0.1Mpa, the gas pressure will be 0.14Mpa; if the pressure signal range is 0.04 ~ 0.2Mpa, 0.28Mpa; If ZPQ-02 locator and ZS-02 series piston actuator supporting, the pressure signal range of 0.02 ~ 0.1Mpa, the gas source pressure of 0.5Mpa.
Electric signal valve positioner can also be called electric - gas valve positioner, 0 ~ 10mA or 4 ~ 20mA DC electrical signal into a standard gas signal driving the control valve.
⒌ pneumatic retention valve
Pneumatic relief valve for important pneumatic control system as a safety device. When the instrument air system fails, it automatically cut off the regulator and the valve access, so that the valve to maintain the original position. Pneumatic relief valve model ZPB-201, given the pressure adjustment range of 0.08 ~ 0.25Mpa, the channel pressure of 0.02 ~ 0.2Mpa.
Pneumatic valve positioner and pneumatic control valve supporting the use of. Depending on the pneumatic valve for each valve has a matching valve positioner. Valve positioner air pressure and the size of the actuator type and pressure signal range (or spring pressure range) related.
Third, debugging
Pneumatic actuator debugging main task is to purge the air tube, the valve action direction, the valve positioner adjustment, valve linearity adjustment.
Debugging steps:
⒈ in the field after the installation is complete, first check whether each part of the installation is correct and firm, check the gas source and gas circuit, the circuit is connected correctly.
⒉ from the main air source to the pneumatic actuator, sub-purge gas source pipeline. To ensure smooth piping, gas source in line with gas requirements. Purge the pneumatic actuator should be thrown off the Air Filter, purge to the gas source and then re-installed on the qualified.
⒊ Check the pressure in front of the filter regulator to meet the requirements of the regulator. Adjust the pressure after the pressure reducing valve, and the positioner or pneumatic actuator nameplate requirements of the gas source pressure.
⒋ the valve hit the "local control" file (some without this switch), and then manual operation of pneumatic actuators in place to confirm the correct direction of pneumatic actuator action, or should be replaced by the corresponding gas pipe. And the valve should not jam phenomenon. Pneumatic command signal 0.02 ~ 0.1Mpa corresponds to fully closed and fully open (open air actuator). For pneumatic actuator with pneumatic positioner, the pneumatic command signal is firstly positioned Amplifier and then drive the actuator; for the electric signal pneumatic actuator, 4 ~ 20mA signal corresponds to the pneumatic signal of 0.02 ~ 0.1Mpa, then the pneumatic signal-driven actuator action.
⒌ Check and adjust the output of the valve positioner when the valve is fully open and fully closed. The output of the valve positioner shall deal with the zero value (for example: 0.02Mpa or 4mA) of the gas signal and the electrical signal when the valve is fully closed, and the full value of the valve should correspond to the full value (for example: 0.1Mpa or 20mA).
打 the valve hit the "remote control" file (some without this switch), far from the remote control (such as control room) for remote control signal test. Valve movement direction should be correct. The actual opening of the valve, as well as the position of the valve on the spot and at the remote location, should correspond exactly to the operating command value sent to the valve.
气 pneumatic actuator with a linear adjustment function, but also should choose the point of operation (usually near the middle valve position) to adjust the linearity of its operating characteristics.
⒏ After commissioning, fasten all the screws and fittings together and tighten all the screws.
Frequent failures
The main reason for the valve jam is the gas source with water, compressed air failed, especially in the humid air during the rainy season, the water inside the valve is easy to jam. Pneumatic actuator gas source should be clean, pressure-stable compressed air, generally supplied by the oil-free compressed air machine, the storage tank and the overall filtration, decompression equipment sent to the air manifold, each pneumatic actuator Access the air supply from the mother pipe. If the degree of cleaning or pressure of the main pipe gas source can not meet the requirements of various types of pneumatic actuators, an air filter, an air pressure reducing valve or an air filter may also be installed before the air pipe of each actuator .
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