The self-operated regulating valve is used to adjust the process parameters such as medium flow, pressure, temperature and liquid level in the field of industrial automation process control. According to the control signal in the automation system, the opening of the valve is automatically adjusted to achieve the adjustment of the medium flow, pressure, temperature and liquid level.
First, the working principle of self-operated temperature control valve (heating type)
The temperature regulating valve works according to the principle of incompressibility and thermal expansion and contraction of the liquid. The self-operated temperature regulating valve for heating, when the temperature of the controlled object is lower than the set temperature, the liquid in the temperature pack shrinks, the force acting on the actuator push rod is reduced, and the valve core member opens the valve under the action of the spring force. Increase the flow rate of heating medium such as steam and hot oil, so that the temperature of the controlled object rises until the temperature of the controlled object reaches the set value, the valve closes, and after the valve is closed, the temperature of the controlled object drops, the valve opens again, and the heating medium is again Entering the heat exchanger, the temperature is raised again, so that the temperature of the controlled object is constant. The valve opening degree is related to the difference between the actual temperature and the set temperature of the controlled object.
Second, the working principle of self-operated temperature control valve (cooling type)
The working principle of the self-operated temperature regulating valve for cooling can be referred to the self-operated temperature regulating valve for heating. However, when the valve core member is opened and closed under the action of the actuator and the spring force, the valve body passes through the cold medium, and is mainly used in the valve body. Temperature control in the cooling unit.
Third, the working principle of the self-operated flow regulating valve After the medium input valve is controlled, the pre-valve pressure P1 is input into the lower diaphragm chamber through the control line, and the pressure Ps after the throttling of the throttle valve is input into the upper membrane chamber. The difference between P1 and Ps is △ Ps = P1 - Ps is called effective pressure. The thrust generated by P1 acting on the diaphragm and the thrust difference generated by Ps acting on the diaphragm are balanced with the spring reaction force to determine the relative position of the spool and the valve seat, thereby determining the flow rate through the valve. When the flow rate through the valve increases, that is, ΔPs increases, and as a result, P1 and Ps act on the lower and upper membrane chambers respectively, so that the valve core moves toward the valve seat, thereby changing the flow area between the valve core and the valve seat, so that The Ps increases, and the increased thrust of the Ps acting on the diaphragm plus the spring reaction force and the thrust of the P1 acting on the diaphragm balance the new position to achieve the purpose of controlling the flow.
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