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There are several kinds of warranty valve fault protection program to solve
Regulating valve in the role of process control is well known in many control processes require the valve in a fault in a certain position to protect the process does not appear accident, which requires the design of the valve to achieve failure - Safe three off (off, power, off signal) protection measures. For the electric control valve, relatively simple, off the signal, the control module can be set to stay in the fully open, fully closed, to maintain any position, and power failure, the natural stay in the fault location, or belt The electric actuator with resetting device can also move the valve position to fully open or fully closed. For pneumatic control valve, the situation is more complicated, so we mainly discuss the three-position pneumatic control valve to protect the way. In general, when we choose pneumatic diaphragm valve, we must first determine whether to open the gas or gas closed, which is the choice of control valve when the gas is off the protection position, if the process requires the valve open when the gas is off, the choice of normally open ) Type control valve, the other is the election normally closed (open air) -style regulating valve. This is just a superficial solution. If the process requires three-out protection of the air-out, power-off and off-signals, the control valve needs to be equipped with some accessories to form a protection system to achieve the control requirements. The accessories mainly include the protection valve, the solenoid valve , Gas tank and so on. The following is a single-acting pneumatic diaphragm valve and double-acting pneumatic valve two kinds of Paul bit solution. First, the pneumatic membrane valve program (control valve equipped with electricity - gas valve positioner) The program consists of pneumatic valve, electric - gas valve positioner, loss of power (signal) comparator, single solenoid valve, Pneumatic retention valve, valve position signal return and other components. Its working principle is as follows: 1, the air source: When the control system air supply failure (loss of gas), the pneumatic valve will automatically close the positioner output signal pressure lock in the pneumatic control valve membrane chamber, the output signal pressure and control valve The reaction force generated by the spring is balanced and the valve position of the pneumatic control valve remains in the failed position. This retention valve should be set to start slightly below the minimum air supply. 2, power off: When the control system power failure (loss of power), loss of power (signal) comparator control single solenoid valve output voltage disappears, single solenoid valve loss of power, single solenoid The spool in the reversing valve slides under the action of the return spring, the solenoid valve is reversed, the pressure in the pneumatic chamber of the pneumatic retention valve is emptied, the pneumatic retention valve is closed, and the output signal of the positioner is pressure-locked to the pneumatic control valve Of the membrane chamber, the output signal pressure and control valve spring reaction force balance, pneumatic control valve position remains in the fault position. 3, the off signal: When the control system signal failure (loss of signal), the loss of power (signal) comparator detects, the single-off electromagnetic solenoid valve voltage signal is cut off, single-solenoid valve power loss, Sliding solenoid valves in a single solenoid valve slide under the action of a return spring, reversing the solenoid valve, emptying the diaphragm chamber pressure of the pneumatic valve, and closing the pneumatic pressure relief valve to lock the output signal of the positioner In the pneumatic control valve membrane chamber, the output signal pressure and control valve spring reaction force balance, pneumatic control valve position remains in the fault position. The position feedback signal is given by the valve position signal return. The advantages of this program: "three off" protection starts, the system response faster, quick action. The overall cost is cheaper. Disadvantages of this program: Long-term electromagnetic valve charged, affecting the service life. Equipped with more accessories, installation, commissioning a number of complex valve position feedback need to reprovision the valve position signal, with the use of hand wheel case, more complicated. Second, double-acting pneumatic control valve program (control valve with electric - gas valve positioner) The program mainly by the control valve, pneumatic control valve, positioner, self-locking valve, check valve, pressure reducing valve, gas storage Cans and other components. Its working principle is as follows: When the control system gas source failure (loss of gas), the self-locking valve (its role in the opposite way with the retention valve) to open, the pneumatic control valve reversing valve control air supply withdrawn, Of the slide valve reset under the action of the spring, one of the two pneumatic control valve exhaust, the other intake, one-way valve is closed, the gas source from the gas stored in the gas tank to the valve, In order to achieve full or full valve open. Full or fully open conversion can be achieved by adjusting the pneumatic control valve connection. If you want to achieve the valve retention, the installation of pneumatic retention valve and change the pipe connection, with self-locking valve directly control the retention valve, cancel the pneumatic valve, check valve, gas tank can be. To achieve the gas source, to ensure that the valve has several actions, the following program can be used. The program from the gas tank, one-way valve, lock valve, globe valve and other components. Its working principle is as follows: When the gas source failure (loss of gas), the one-way valve is closed, the lock valve is out of breath, the valve in the lock valve reset under the action of the spring, the gas line direction, disconnect the system of the source tube Road, connected to the gas tank pipeline, gas from the gas tank to the valve to ensure that the valve has several actions to achieve the purpose of continuous control. Due to the limited capacity of the gas tank and the pressure of the gas source in the gas tank, as the valve moves continuously, the gas tank can not be used for long-term supply of gas to the valve. The capacity of this program should be larger than the capacity of the gas tank for general protection. The program in the gas source, the number of valve action and the capacity of the gas tank. For the pneumatic diaphragm control valve retention scheme, there is another for reference: in the positioner and actuator tandem protection valve and two three-way solenoid valve, one in the expiration with the retention valve to keep the bit However, the solenoid valve must be linked with the positioner (set in the control program), that is, the positioner has a signal, the solenoid valve must have electricity, and once the positioner has lost the signal, Solenoid valve must be immediately cut off. More keyword search: Regulating valve