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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 controller. [1] This enables the direct control of flow rate and the consequential control of process quantities such as pressure , temperature , and liquid level.
These valves have two ports that help the valves regulate the flow of air into a system. These valves often provide a simple on-off function. 3-way valves can be normally closed, normally open, and offer a universal function where gas can be diverted through a third opening to move the valve into the normally closed or normally open position.
Isolation valves must effectively stop the passage of fluids. [4] Gate valves, ball valves and plug valves are generally considered to provide tight and effective shut-off. Globe valves and Butterfly valves may not be tight shut-off due to wear on the plug or the seat, or due to their design, and may not be appropriate to provide effective ...
Valves can be categorized into the following types, based on their operating mechanism: Ball valve, for on–off control without pressure drop. Ideal for quick shut-off, since a 90° turn completely shuts off, compared to multiple 360° turns for other manual valves; Butterfly valve, for on–off flow control in large diameter pipes
Tilting-disc inconel check valve Check valve symbol on piping and instrumentation diagrams.The arrow shows the flow direction. Vertical lift check valve. A check valve, non-return valve, reflux valve, retention valve, foot valve, or one-way valve is a valve that normally allows fluid (liquid or gas) to flow through it in only one direction.
After receiving an operation command, the actuator moves the valve in direction OPEN or CLOSE. When reaching the end position, an automatic switch-off procedure is started. Two fundamentally different switch-off mechanisms can be used. The controls switch off the actuator as soon as the set tripping point has been reached. This is called limit ...