Control Valve

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Control Valve

Post  landoo on Thu Feb 28, 2013 12:11 am

Control valve plays a very important role in the automatic control of the modern factory, correctly allocate and control the flow of the medium depends on the production of these factories. These control whether the exchange of energy, a decrease in pressure or a simple container feeding, are required in some final control element to complete. Final control elements that is automatically control physical. In the low energy regulator middleweight and between the execution flow of fluid control required high energy level function, final control elements to complete the necessary power amplification.
The control valve is the most widely used type of final control element. Other final control element comprises a metering pump, the regulating dampers and shutters baffle (a butterfly variant), a variable inclination of the fan blades, the current regulating means as well as different from the motor of the valve positioning means.
Variable resistance from the control valve in the pipeline. It changes the degree of turbulence of the process fluid, or in the case of a laminar flow to provide a pressure drop, the pressure drop is by changing the valve resistance or "friction" caused. This pressure reduction process is commonly called "throttling." For gases, which is close to the temperature adiabatic state deviation depends on the degree of non-ideal gas (Joule-Thomson effect). In the case of a liquid, the pressure is compared to the turbulence or the viscous friction consumption, both cases regarded pressure converted to heat, causing the temperature is slightly elevated.
The common control circuit comprises three main parts, the first part is a sensitive element, which is typically a transmitter. It can be used a measuring apparatus is adjusted to the process parameters, such parameters, such as pressure, level, or temperature. The transmitter output is sent to the regulating instruments - the regulator, it is to determine and measure to the deviation between the actual value of the given value or expected value of the process parameters, one after the correction signal is sent to the final control element - adjust valve. Valve to change the flow rate of the fluid, so that the process parameter has reached the expected value.
Can be used when a pneumatic control valve and electrically adjustable supporting the use of electric-gas valve positioner or electric stretch converter. The gas supply system of the compressed air conditioning system can be used in the full pneumatic to consider.
In terms of regulation theory, the regulating valve both static characteristics and dynamic characteristics, and thus it affects the whole the success or failure of the control loop. The static characteristics or gain entry valve flow characteristics, it depends on the size of the valve plug and seat combination structure, the type of the implementing agencies, valve positioner, valve before and after pressure and fluid nature.


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