Parts of a Typical Valve- Written by the Valve Pipeline Staff
This quick article/diagram is intended to give you a quick tutorial on the parts of a valve. The diagram covers the major components of most typical valves. Basically a valve is an operator that works a closing mechanism. The closing mechanism is housed and insulated/packed in the bonnet of the valve. The closing mechanism rests or turns in seats to close the flow. (Check valves don't have an operator. The pressure/flow in the line opens them and prevents back-flow/closes with no pressure)
A valve also has a body, typically made of steel, and end connections (how the valve is fixed in line). Media typically enters from one end of a valve, passes through the port (tunnel of the valve), and out the other side. The valve's purpose is to allow, restrict or stop flow through its ports/body. Hopefully this diagram helps give a good visual representation of typical valve construction. (It's more complicated than this but this should get you started)
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If the valve is bigger than 8", or has an ANSI rating of 900# and above, odds are it will need a gear operator.