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Self-operated control valve

Self-operated control valve

2020-07-10

Self-operated control valve

The self-operated control valve is used to regulate the flow, pressure, and liquid level of the medium. According to the signal of the adjustment part, the opening of the valve is automatically controlled to achieve the adjustment of the medium flow, pressure, and liquid level.

Self-operated control valve relies on the pressure and temperature of the medium flowing through the valve as an energy source to drive the valve to work automatically, without the need for external power supply and secondary instruments. This self-operated control valve uses the feedback signal (pressure, pressure difference, temperature) at the output of the valve to pass through the signal tube to the actuator to drive the valve plug to change the opening of the valve to achieve the purpose of regulating pressure, flow, and temperature. This kind of control valve is divided into the direct-acting type and indirect-acting type.

Self-acting control valve direct-acting type is also called spring-loaded type, its structure has elastic elements such as spring, bellows, bellows-type temperature envelope, etc., using the principle of balance between elastic force and the feedback signal.

Indirect-acting control valve, a pilot (pilot valve) is added which amplifies the feedback signal and then drives the valve flap of the main valve to change the valve opening through the actuator.

If it is a pressure regulating valve, the feedback signal is the outlet pressure of the valve, which is introduced into the actuator through the signal tube.

If it is a flow control valve, there is an orifice plate (or other resistance devices) at the outlet of the valve. The differential pressure signal is taken out from both ends of the orifice plate and introduced into the actuator.

If it is a temperature regulating valve, there is a temperature sensor (or temperature envelope) at the outlet of the valve to drive the actuator through the thermal expansion and contraction of the medium in the temperature sensor.


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