Pneumatic angle control valve commissioning and fault repair
The pneumatic angle regulating valve is composed of a pneumatic multi-spring diaphragm actuator and an angle regulating valve. The pneumatic diaphragm angle regulating valve is widely used for precise control of gas, liquid and other media. Process parameters such as pressure, flow, temperature and liquid level are maintained. Value. Pneumatic film angle control valve is especially suitable for the high viscosity, small suspension, and particulate matter adjustment that allows the leakage pressure to be small before the valve. It can avoid coking and clogging, and is convenient for self-cleaning and cleaning.
This series of products are available in various types such as normal temperature type, adjustable cut-off type, bellows seal type, high temperature type, and jacket insulation type. The nominal pressure rating of the product is PN10, 16, 25, 64, 100; the valve body diameter range is DN20-DN200. The leak level is IV or VI. The applicable fluid temperature ranges from -200 °C to +560 °C, and the flow characteristics are linear or equal percentage. A variety of specifications are available.
Pneumatic angle control valve commissioning
1, tracheal connection
There are two air pipe connections: one is the air supply interface, marked with “SUP†gas supply, and the other is the positioner output interface, marked with the word 'OUT' (output). Please be careful not to let the sealing tape or dirt when the gas pipe is connected. The material enters the pipeline. The gas pipe can use φ6mm or φ8mm copper pipe. The positioner is generally equipped with φ6mm ferrule type gas pipe joint. If you need to use φ8mm copper pipe, please specify when ordering.
2, circuit connection
1) Remove the cover of the junction box and connect the positive and negative poles of the input signal line to the positive and negative poles of the junction box. Securely and not loose.
2) Explosion-proof locator should ensure that the creepage distance between the two wires is ≥4mm, the signal inlet port can be connected by explosion-proof flexible hose, the interface thread is G1/2., the thread length is ≥22. Cable can also be used. Direct connection, the outer diameter of the cable is φ8±1mm, the cross-sectional area of ​​the wire is >1.5mm2, and the sealing plug and washer should not be removed at will. The compression nut must be pressed tight to ensure a seal. After changing, tighten the locking screws.
3) The intrinsically safe positioner must be used in conjunction with the associated equipment safety barrier. The installation and commissioning of the safety barrier must be carried out in strict accordance with the instructions of the safety barrier. Connection wire or cable zui high distribution capacitance <0.03uF, zui high distribution inductance <1.0mH. The wiring diagram is as follows: 
3. Note:
1 Open the cover after disconnecting the power supply.
2 The case is grounded.
3 The site must comply with the safety regulations for explosion-proof electrical equipment.
4 Explosion-proof external wiring joints shall comply with the dIICT explosion-proof grade requirements.
5 Intrinsically safe external wiring joints shall comply with the iaIICT5 explosion-proof grade requirements.
6 The connecting wires and cables of the safety barrier and the positioner allow the distributed capacitance and inductance values ​​to be greater than 0.03uF and 1.0mH.
7 Intrinsically safe cable core cross-sectional area S>0.5mm2, the shielding layer is grounded in a safe place.
8 The installation and commissioning of the safety barrier must comply with the relevant regulations of the safety barrier instruction manual.
Adjustment
When the positioner is newly installed on the regulating valve, or the stroke of the regulating valve does not meet the requirements of the input control signal, it needs to be adjusted. The method is as follows:
Adjustment
1) The air supply line is connected to the actuator through the pressure reducing valve, and the pressure of the air supply is adjusted by the pressure reducing valve so that the valve stem of the actuator is located at the center of the stroke.
2) Then, check if the positioner is 90° to the feedback lever. Please refer to the chapter “Installationâ€.
3) Remove the air supply line from the actuator, connect it to the air supply port (SUP) of the positioner, and connect the output interface (OUT) of the positioner to the air chamber of the actuator.
4) The zero adjustment step is as follows: input a 4 mA signal to make the actuator start to operate (standard input signal 4-20 mA), adjust the zero point adjustment handwheel, and make the zero point meet the requirements.
5) The range adjustment is as follows: Enter a 20 mA signal to record the stroke of the valve. If the stroke is less than the rated range, loosen the span adjustment screw and turn the span adjustment handwheel to move the screw in the direction of the arrow. After adjusting, fix the locking screw.
6) Repeat steps 4) and 5) above to bring the range and zero to the specified value.
2. Positioner positive and reaction type interchange
The interchange step of the linear positioner action type and the other type of feature positioner interchange step, the position of the positioner range adjustment mechanism depends on the action type of the actuator. Figure II shows the assembly position of the range adjustment mechanism mounted on the reaction actuator. For the positive acting actuator, the span adjustment mechanism should be installed on the "positive acting actuator installation", that is, the span adjustment mechanism shown in Fig. II is reversed. The installation direction is shown by the arrow on the arrow in Figure II. The arrow indicates the positive action type and the arrow direction indicates the reaction type.
The steps to change the installation position of the span adjustment mechanism are as follows:
First, use a needle-nose pliers or tweezers to remove the feedback spring connection from the side of the baffle from the spring bolt.
Next, loosen the mounting bolts and remove the adjustment mechanism. To install the span adjustment mechanism, simply reverse the above steps.
Pneumatic angle control valve physical map
Pneumatic angle control valve fault repair
(1) The regulating valve does not operate. The symptoms and causes are as follows:
1. No signal, no air source. 1 The gas source is not open, 2 Because the gas source water freezes in winter, the air duct is blocked or the filter and the pressure reducing valve are blocked, 3 compressor failure; 4 gas source manifold leakage.
2. There is a gas source and no signal. 1 regulator failure, 2 signal tube leakage; 3 positioner bellows leakage; 4 regulation mesh diaphragm damage.
3. The positioner has no air supply. 1 filter blocked; 2 pressure relief valve failure I3 pipe leakage or blockage.
4. The positioner has a gas source and no output. The orifice of the positioner is blocked.
5. There is signal, no action. 1 valve core is off, 2 valve core is stuck with the society or with the valve seat; 3 valve stem is bent or broken; 4 valve seat valve core is frozen or coke block dirt; 5 actuator spring is rusted due to long-term use.
(2) The operation of the regulating valve is unstable. The symptoms and causes are as follows:
1. The gas source pressure is unstable. 1 The compressor capacity is too small; 2 The pressure reducing valve is faulty.
2. The signal pressure is unstable. 1 The time constant of the control system (T=RC) is not appropriate; 2 The regulator output is unstable.
3. The air supply pressure is stable and the signal pressure is stable, but the action of the regulating valve is still unstable. 1 The ball valve of the amplifier in the positioner is not tightly worn by the dirt, and the output oscillation occurs when the gas consumption is particularly increased; 2 the nozzle flapper of the amplifier in the positioner is not parallel, the baffle cover cannot cover the nozzle; 3 output tube The line is leaking; 4 the rigidity of the actuator is too small; 5 the frictional resistance in the valve stem is large, and there is a blockage in the contact part.
(3) Adjust the valve vibration. The symptoms and causes are as follows:
1. The regulator valve vibrates at any opening. 1 support is unstable; there is vibration source near 2; 3 valve core and bushing wear seriously.
2. The regulator valve vibrates as it approaches the fully closed position. 1 The regulating valve is selected to be large, and is often used at a small opening; 2 The flow direction of the single seat valve is opposite to the closing direction.
(4) The movement of the regulating valve is slow. The symptoms and causes of dullness are as follows:
1. The valve stem is slow to operate in only one direction. 1 diaphragm breakage leakage in pneumatic diaphragm actuator; 2 "O" seal leakage in the actuator.
2. The valve stem is dull when reciprocating. 1The valve body is stuck with glue; 2Teflon filler metamorphic hardening or graphite-asbestos filler lubricating oil is dry; 3The packing is too tight, the frictional resistance is increased; 4The frictional resistance is large due to the stem is not straight; 5 The positioner's pneumatic control valve can also cause slow movements.
(5) The leakage of the regulating valve is increased. The reasons for the leak are as follows:
1. The leakage is large when the valve is fully closed. 1 The valve core is worn, the internal leakage is serious, and the 2 valves are not adjusted well.
2. The valve does not reach the fully closed position. 1 The pressure difference of the medium is too large, the rigidity of the actuator is small, the valve is not tight; 2 the valve has foreign matter; 3 the bush is sintered.
(6) The adjustable flow range becomes smaller. The main reason is that the valve core is corroded and becomes small, so that the adjustable small flow of zui becomes large.
Understand the failure phenomenon and cause of the pneumatic regulating valve, and take measures to solve the problem.
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