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How to adjust the ratio if the pneumatic control valve is not closed tightly


Release time:

2021-06-07

Pneumatic control valveIt is composed of pneumatic actuators and regulating valves. First of all, pneumatic actuators transmit signals through the bearing control system and drive the valve core of the regulating valve to adjust the flow, pressure and temperature of the process device. Therefore, it is sometimes unavoidable to use it. There will be a state of lax closure.

How to adjust the ratio if the pneumatic control valve is not closed tightly

Pneumatic control valveIt is composed of pneumatic actuators and regulating valves. First of all, pneumatic actuators transmit signals through the bearing control system and drive the valve core of the regulating valve to adjust the flow, pressure and temperature of the process device. Therefore, it is sometimes unavoidable to use it. There will be a state of lax closure.
1. When the output force of the pneumatic actuator is insufficient, the output force of the pneumatic actuator, as the power part driving the valve core of the regulating valve, is greater than the force required when the valve is closed, otherwise it will not be tightly closed. Then why is this situation? The valve core is pushed open by the medium pressure, and the internal leakage phenomenon will occur in the pneumatic regulating valve. How can this accident be avoided, therefore, users must pay attention to the need to verify the differential pressure value of the process pipeline during selection, while ensuring that the pneumatic actuator has a satisfactory output force to close the valve.
2. If the type of regulating valve is not correct, it will also lead to the problem of lax closing. The standard pressure difference of each standard regulating valve is different. The sleeve regulating valve and the double-seat regulating valve are larger than the pressure difference of the single-seat regulating valve. The pressure difference of the angular stroke V-shaped regulating ball valve and the eccentric rotary valve is larger. Under the condition of larger pressure difference, the electric regulating valve is extremely important for the reasonable selection of the pneumatic regulating valve.
In the process of automatic control, the quality of pneumatic control valve will make the automatic control process lose high-quality regulation, poor flow characteristics will affect the quality of regulation, large leakage and unreliable action will make the regulation fail, which will cause great loss in the production process and increase labor intensity. Therefore, people pay more and more attention to the selection and use of pneumatic control valve.
The accuracy of the pneumatic control valve can be expressed by the change of logistics energy and flow rate. The adjustment control energy of the control valve can be judged by adjustable ratio. Adjustable ratio refers to the ratio of large flow rate and small flow rate that the control valve can control when the difference between the two sides of the control valve is a fixed value. When the control valve is used in series pipelines, the adjustable ratio is proportional to the square root of the pressure drop ratio, the smaller the control capacity, when there are 2 or more than 2 control valves in parallel and work at the same time, the need to pay attention to the degree of bypass, in actual production, in addition to the control valve, there are other pipelines, so the pressure difference before and after the control valve will change, called the working flow characteristics, specifically linear valve, equal percentage valve and parabolic valve, of which equal percentage valve is widely used and adaptable.