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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. [ 1 ] Check valves are two-port valves, meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave.
Pipe marking on a natural gas pipe. In the process industry, chemical industry, manufacturing industry, and other commercial and industrial contexts, pipe marking is used to identify the contents, properties and flow direction of fluids in piping. It is typically carried out by marking piping through labels and color codes.
Example of symbol for a stop valve. A stopcock is a form of valve used to control the flow of a liquid or gas. The term is not precise and is applied to many different types of valve. The only consistent attribute is that the valve is designed to completely stop the flow when closed fully.
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.
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 piping and instrumentation diagram (P&ID) is defined as follows: A diagram which shows the interconnection of process equipment and the instrumentation used to control the process. In the process industry, a standard set of symbols is used to prepare drawings of processes. The instrument symbols used in these drawings are generally based on ...
Reed valves are commonly used in high-performance versions of the two-stroke engine, where they control the fuel-air mixture admitted to the cylinder. As the piston rises in the cylinder a vacuum is created in the crankcase beneath the piston. The resulting pressure differential opens the valve and the fuel-air mixture flows into the crankcase.
Control valve. 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. In automatic control terminology, a control ...