Control Valve Disc Position-Holding Scheme II After Air Failure

This plan is mainly composed of control valves, pneumatic reversing valves, positioners, self-locking valves, one-way valves, pressure reducing valves, gas storage tanks, etc. Its working principle is as follows:

When the air source of the control system fails (lose air), the self-locking valve (the function of which is opposite to that of the retaining valve) will automatically open to cancel the control air source of the air-controlled reversing valve. Reset under the action of, one of the two air-controlled reversing valves is exhausted, the other is aired, and the one-way valve is closed. The gas source is supplied to the valve from the gas source stored in the gas storage tank, thereby realizing the full valve Close or fully open. The conversion of fully closed or fully open can be realized by adjusting the connection mode of the pneumatic control valve.

If you want to achieve valve position retention, install a pneumatic position retention valve and change the pipeline connection, use a self-locking valve to directly control the position retention valve, and cancel the pneumatic control reversing valve, one-way valve, and gas tank.

If you want to cut off the gas source and ensure that the valve has several actions, the following solutions can be used. To

This plan consists of a gas storage tank, a one-way valve, a blocking valve, a stop valve, etc. Its working principle is as follows:

When the air source fails (loss of air), the one-way valve is closed and the lock valve loses air. The slide valve of the lock valve is reset under the action of the spring. In the gas tank pipeline, the gas storage tank supplies air 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 storage tank, and the pressure of the gas source in the gas storage tank continues to decrease with the valve action, the gas storage tank cannot be used for a long time to supply air to the valve. The capacity of the gas storage tank for this plan should be larger than that of the general protection gas storage tank. In this scheme, when the gas source is cut off, the number of valve actions is related to the capacity of the gas tank.

For the position retention plan of the pneumatic membrane control valve, there is another reference: a position retention valve and a two-position three-way solenoid valve are connected in series between the positioner and the actuator, and the position retention valve is used to maintain the position when the air is cut off. When the signal is off, the solenoid valve is used to hold the position. However, the solenoid valve must be interlocked with the positioner (set in the control program), that is, the positioner has a signal, and the solenoid valve must have electricity. Once the positioner loses the signal, The solenoid valve must be de-energized immediately.