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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.
A simple control system for a water well. Referring to the figure on the left, a submersible water pump is installed in a well. The pressure switch turns the water pump on when it senses a pressure that is less than P lo and turns it off when it senses a pressure greater than P hi. While the pump is on, the pressure tank fills up.
In addition to air horns, Leslie Controls manufactures control valves, shutoff valves, control instrumentation, steam conditioning systems, steam water heaters and regulators. [2] Leslie has a service center located in Tampa, which remanufactures valves made by a number of major companies.
The most common final control element in the process control industries is the control valve. The control valve manipulates a flowing fluid, such as gas, steam, 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. [1]
An air-operated valve, also known as a pneumatic valve, is a type of power-operated pipe valve that uses air pressure to perform a function similar to a solenoid. As air pressure is increased, the compressed air starts to push against the piston or diaphragm walls which causes the valve to actuate. Whether the valve opens or closes depends on ...
Because certain combinations of check valve failure and/or system backpressure cause the relief valve to discharge, the device must be mounted in a location where the drain will not become flooded. An example of where backflow would harm the water supply is the use of well washing devices inside underground sewerage pumping stations.
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When the well has been drilled, it is completed to provide an interface with the reservoir rock and a tubular conduit for the well fluids. The surface pressure control is provided by a Christmas tree, which is installed on top of the wellhead, with isolation valves and choke equipment to control the flow of well fluids during production.