A control valve is a valve used to control fluid flow by varying the size of the flow passage as directed by a signal from a control. This enables the control of flow rate and the consequential control of process quantities like pressure, temperature, and fluid level. Electrical, hydraulic or pneumatic actuators usually do closing or the opening of control valves. With a modulating valve, which can be set to any position between fully open and fully closed, valve positioners are used to ensure the valve accomplishes the desired level of opening. Air-actuated valves are used because of their simplicity, since they require a compressed air supply, whereas electrically-operated valves require cabling and switchgear, and valves required high-pressure supply and return lines to the hydraulic fluid. Are you looking for instrumentation? Browse the earlier talked about site.
A huge variety of valve types and control operation exist. There are two main forms of activity; the rotary action and the sliding stem. The versatile and most common types of control valves are V-notch ball a world, butterfly and angle types. Their popularity the many options available and derives from rugged structure which make them suitable for a variety of process applications. It is used primarily for throttling purposes. It may be thought of as a general purpose flow control valve high temp program. Quicker to open or close, a form of seats, throttling to control the flow to any desired level. The most common control element in the process control industries is the control valve.
The control valve manipulates a fluid, such as gas, steam, water, or chemical compounds, to compensate for the load disturbance and maintain the controlled process variable as close as possible to the desired set point. Control valves may be the most important, but sometimes the most neglected, part of a control loop. The main reason is usually the instrument engineer’s unfamiliarity with regions of engineering disciplines like vessel and piping design, metallurgy, noise control, and mechanics, terminologies, and the aspects which can be involved depending on the severity of service conditions. Any control loop usually contains a sensor of this process condition, a transmitter and a controller that contrasts the “process variable” received from the transmitter with the “set point,” i.e., the desirable process condition.
The controller, in turn, sends a corrective signal to the “final control element,” the final part of the loop and the “muscle” of the process control system. While the sensors of the process variables are the eyes, the control the brain the final control element is the hands of the control loop. This makes it the alas sometimes the least understood, part of an automatic control system. This comes about, in part, due to our attachment to computers and electronic systems causing some fail in the proper understanding and proper use of their hardware.