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Regulating valve for regulating the flow rate of the manipulated variable, and therefore, known as the previous valve. The overall look from the control system, a control system to control how well should be achieved by adjusting the valve. For the following reasons, the control valve becomes very important.
① regulating valve is a throttle device, below the movable member, the load change detection element and the transmitter, the controller comparison, a control process, the need to constantly change the valve orifice flow area, so that the manipulated variable change to accommodate a or changing operating conditions. Therefore, the regulator valve assembly seals, pressure, corrosion and other higher demands. For example, the seal will increase the friction valve, regulating valve dead zone to increase, resulting in deterioration of the quality control system to control and so on.
② regulating valve moving parts is caused by "running", "take", "drop", "leak" the main reason, it is not only a waste of resources or materials, but also pollute the environment, cause an accident.
③ control valve trim in direct contact with the process medium, and detection components in contact with the process medium differs as follows
a. Regulating valve assembly into contact with the contact medium may be different from the medium detection elements, corrosion resistance of the valve, the strength, stiffness, and other materials have higher requirements.
b. Sensing elements can be isolated liquid dielectric isolation methods and processes, but the control valve is usually in direct contact with the process medium, difficult to use the method and process isolation dielectric isolation.
④ throttle valve so that the interior trim energy is consumed, therefore, reduce energy consumption, reduce the pressure regulating valve damage, and to ensure balance between the rational choice and better quality control.
⑤ throttle valve for fluid and also cause noise. For example, when the valve outlet pressure below the vapor pressure of the liquid, resulting in a flash; when the valve downstream pressure is higher than the vapor pressure of the liquid, causing cavitation. Noise and regulating valve flow path design control valve caused by the operating pressure, the accused and other media properties, and therefore, reduce noise, reduce pressure losses, higher demands on the control valve.
⑥ valve strong adaptability. It is mounted in a variety of production processes, low production process, high temperature, high pressure, high flow, minimal flow, and other operating conditions of the control valve needs to have various functions, the control valve should be able to adapt to the requirements of different applications.
⑦ detection development components and transmitters, controllers and other fast input of manpower and material resources and more. Relative term, usually considered a simple valve structure, therefore, the control valve into research and development relative lack of human and material resources.
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