An isolation valve is a valve in a fluid handling system that stops the flow of process media to a given location, usually for maintenance or safety purposes.[1] They can also be used to provide flow logic (selecting one flow path versus another), and to connect external equipment to a system.[2] A valve is classified as an isolation valve because of its intended function in a system, not because of the type of the valve itself. Therefore, many different types of valves can be classified as isolation valves.
To easily understand the concept of an isolation valve, one can think of the valves under a kitchen or bathroom sink in a typical household. These valves are normally left open so that the user can control the flow of water with the spigot above the sink, and does not need to reach under the counter to start or stop the water flow. However, if the spigot needs to be replaced (i.e. maintenance needs to take place on the system), the isolation valves are shut to stop the flow of water when the spigot is removed. In this system, the isolation valves and the spigot may even be the same type of valve. However, due to their function they are classified as the isolation valves and, in the case of the spigot, the control valves. As the isolation valve is intended to be operated infrequently and only in the fully on or fully off positions, they are often inferior quality globe valves. These less expensive styles lack a bonnet and stem seal in favor of threading the stem directly into the body. The stem is covered with a rubber washer and metal cap similar in appearance to a gland nut. Because they lack a stem seal they will leak unless fully closed and installed in the correct direction or fully open, causing the disk to compress the top washer against the stem.
^Nesbitt, Brian (19 April 2011). Handbook of Valves and Actuators. p. 82. ISBN 9780080549286.
^Royals, William T. (1997). Flammability and sensitivity of materials in oxygen-enriched atmospheres. American Society for Testing and Materials. p. 433. ISBN 0-8031-2401-5.
An isolationvalve is a valve in a fluid handling system that stops the flow of process media to a given location, usually for maintenance or safety purposes...
operated control valves. After the construction of unit 1, the following units were designed with new open-cycle reactor core isolation cooling (RCIC) systems...
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pressure (caused, for example, by the actuation of the main steam isolationvalve (MSIV) from the reactor) will result in a sudden decrease in the proportion...
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in both cylinders. These manifolds may be plain or may include an isolationvalve in the manifold, which allows the contents of the cylinders to be isolated...
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a Christmas tree, which is installed on top of the wellhead, with isolationvalves and choke equipment to control the flow of well fluids during production...
is regulated by the flow control valve (FCV). One FCV is installed for each PACK. A normally closed isolationvalve prevents air from the left bleed system...
eight named backflow assemblies all have two resilient seated isolation/shut off valves with properly located test ports. These assemblies have the distinct...
accumulator, a Pump & Control Valve Package (PCVP) containing a firmware controller, startup heaters, isolationvalves, and various sensors for monitoring...
interconnecting units holding fluids have isolationvalves between them. If there is a leak in a unit, its isolationvalves can be shut to "isolate" the unit...
for isolation of lines penetrating the containment wall. Each large pipe penetrating the containment, such as the steam lines, has isolationvalves on...
malformed bicuspid aortic valve. This defect is characterized by the presence of only two valve leaflets. It may occur in isolation or in concert with other...
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wastes gas. In upstream valve regulators or regulators with an isolationvalve at the second stage, such as the bailout valve on a surface supplied helmet...
twins. A manifolded twin set with isolationvalve is a special case. It is a redundant air supply when the isolationvalve is closed, as the cylinders are...
block valve and one bleed valve is also known as an isolationvalve or block and bleed valve; a block and bleed manifold with multiple valves is also...
In a reactor core isolation cooling system ("RCIC"), an isolation condenser (IC or iso. condenser; also isolation condenser system) is one of the emergency...
shutoff valve to the building to be automatically closed to prevent flooding. A very effective precaution is to install a shutoff or isolationvalve which...
flammable gases were released through an open valve almost instantaneously. During routine maintenance, isolationvalves were closed and compressed air hoses that...