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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 ...
A shutdown valve (also referred to as SDV or emergency shutdown valve, ESV, ESD, or ESDV; or safety shutoff valve) is an actuated valve designed to stop the flow of a hazardous fluid upon the detection of a dangerous event. This provides protection against possible harm to people, equipment or the environment.
Zone valves can also be constructed using wax motors and a spring-return mechanism. In this case, the valve is normally closed by the force of the spring but can be opened by the force of the wax motor. Removal of electrical power re-closes the valve. This style of zone valve operates with a perfectly ordinary SPST thermostat.
If the valve is open when the solenoid is not energized, then the valve is termed normally open (N.O.). Similarly, if the valve is closed when the solenoid is not energized, then the valve is termed normally closed (N.C.). [1] There are also 3-way and more complicated designs. [2] A 3-way valve has 3 ports; it connects one port to either of the ...
There is a variety of manufacturers of these gauges, but most utilize either a three-valve or a five-valve design to test the RPZD in different ways. In the UK , [ 6 ] Illinois, New York , [ 7 ] Texas , [ 8 ] and Missouri ( RsMO 10c60-11 ), the RPZD valve must be tested at least every 12 months by an accredited tester.
Other examples of normally-closed valves are emergency shutdown valves, which are kept open when the system is in operation and will automatically shut by taking away the power supply. This happens when there is a problem with a unit or a section of a fluid system such as a leak in order to isolate the problem from the rest of the system.
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