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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]
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.
Where it is necessary to raise water to a height above that to which a suction or lift pump will operate effectively (about 7 metres), or to raise the pressure so that it will exit a nozzle with a strong force, such as through a fire hose, a force pump may be used. As with a suction pump, in its manual form it relies on an operator to pump a ...
A level control valve or altitude control valve is a type of valve that automatically responds to changes in the height of a liquid in some storage system. A common example is the set of ballcocks in a flush toilet , where each stage of the flush cycle is actuated by the emptying or filling of the tank.
The "box" is a cylindrical assembly, typically of bronze, comprising a sleeve threaded on one end to accept adjusting and locking nuts. A special purpose heavy-duty rubber hose attaches the stuffing box to a stern tube, also called a shaft log, that projects inward from the hull.
An eccentric rotary vane pump Another eccentric rotary-vane pump design. Note that modern pumps have an area contact between rotor and stator (and not a line contact). 1. pump housing 2. rotor 3. vanes 4. spring. A rotary vane pump is a type of positive-displacement pump that consists of vanes mounted to a rotor that rotates inside a cavity. In ...
A double check valve or double check assembly (DCA) is a backflow prevention device designed to protect water supplies from contamination. [1] It is different from the two-way check valves (sometimes erroneously referred to as double check valves) used in air brake systems on heavy trucks which select from the highest pressure source.
Most downhole safety valves are controlled hydraulically from the surface, meaning they are opened using a hydraulic connection linked directly to a well control panel. When hydraulic pressure is applied down a control line, the hydraulic pressure forces a sleeve within the valve to slide downwards.