A control valve is a valve used to control fluid flow by changing the size of the flow passage as guided by a signal from a controller. This permits the direct control of flow rate and the charge of process quantities like pressure, temperature, and fluid level. Electrical, hydraulic or pneumatic actuators usually perform the opening or closing of automatic control valves. Normally with a modulating valve, which can be set to any position between fully closed and fully open, valve positioners are used to ensure the valve accomplishes the desired degree of opening. Are you searching for control valves? Check out the previously mentioned site.
Valves are used because of their simplicity, as they require a compressed air source, whereas electrically-operated valves require cabling and switchgear, and valves required high-pressure supply and return lines for the hydraulic fluid. A range of control operation and valve types exist. There are two chief forms of activity; the action and the sliding stem. The most common and versatile kinds of control valves are V-notch ball a sliding-stem globe, butterfly and angle types. Their popularity the many options available as well as derives from construction that make them suitable for many different process applications. It’s used primarily for throttling functions.
It may be thought of as a general purpose flow control valve high temp application. Quicker to open a form of seating, or close, throttling to control the flow to any degree. The most common control element in the process control industries is the control valve. The control valve manipulates a fluid, such as steam, gas, water, or chemical compounds, to compensate for the load disturbance and keep the regulated 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 reason is usually the instrument engineer’s unfamiliarity with areas of engineering disciplines like vessel and piping design, metallurgy, noise management, and fluid mechanics, terminologies, and the many aspects which could be involved depending on the severity of service conditions.
Any control loop usually consists of a sensor of this process condition, a transmitter and a controller that compares the “process variable” obtained 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 detectors of the process variables are the eyes, the controller the brain the last control element is the hands of the control loop. This makes it the most important, alas sometimes the least understood, part of an automatic control system. This comes about as a result of our strong attachment to computers and digital systems causing some neglect in the proper understanding and proper use of the all-important hardware.