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25 Cards in this Set
- Front
- Back
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What is a pressure reducing valve? |
A control valve that operates by sensing and maintaining a set pressure on the outlet side of the control valve |
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What type of valve is not recommended where there is a high flow differential? |
Single seated valves |
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If load demand is less than the orifice capacity, what happens to the system? |
Pressure builds up in the system. This causes the pushes against a spring and causes the valve disk to throttle the flow and reduce the size of the orifice. |
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What type of valve should be used on a dead end (not continuous "on/off") service? |
Single seated valve |
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What valves are used to control pressure of steam supplied to a heating system from a central station (constant demand)? |
Double seated valves |
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What are the 2 types of pilot operated valves? |
Standard and remote |
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What is the most familiar form of an internally balanced pressure reducing valve? |
A gas regulator |
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At what ratio of pressure reduction should you use series PRVs? |
10 to 1 |
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What ratio should the second valve in a series be at to prevent wire drawing? |
5 to 1 |
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What is the min distance of the pressure sensing line? (From the control valve) |
10 pipe diameters downstream |
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Valves installed in series should be spaced how far apart? |
10' |
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What must be installed between two reducing valves? |
A trap station |
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When would you install pressure reducing valves in parallel? |
Load demands vary over a wide range (Demand may drop over 10% of max capacity for long periods of time, such as in cold climate areas) |
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What happens when a sustained flow below 5% occurs? |
Valve seats will erode and has a destructive effect on other controls |
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What split of capacity is used in a parallel PRV station? |
1/3, 2/3 split |
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What orientations would a strainer be installed and where in a PRV station? |
On its side, and upstream of whatever components it is protecting. |
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Where are pressure gauges installed in a PRV station? |
On both sides of the PRV to monitor the valves performance. On the downstream side it must be min 10' from the valve |
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Where is the safety valve installed in a PRV station? |
On the reduced pressure side |
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True or false. The use of bypass lines and valves are not recommended. |
True |
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What is another name for a backpressure regulator? |
A surplussing valve |
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What does a surplussing valve do? |
Removes partial upstream pressure |
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What is the condition in a PRV where the valve disc is throttling close to its seat and it does not know whether to open it close? |
Hunting |
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Why should you increase the surge pipe size downstream of a PRV? |
To not restrict flow |
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The Cv factor gives the GPM of water that a valve will pass with what pressure drop? |
1PSI |
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Condensate from the steam entering the PRV should be removed by what device? |
A separator. |
