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How to model a Combination Pressure Reducing Valve (PRV) and Pressure Sustaining Valve (PSV)

Product(s): WaterGEMS, WaterCAD
Version(s): Varies
Area: Modeling

Problem

How to model a Combination Pressure Reducing Valve (PRV) and Pressure Sustaining Valve (PSV)?

Solution

Application and Benefits

  • To maintain a minimum upstream and maximum downstream pressure or hydraulic grade.
  • This valve may be helpful when there is an upstream water source and a pump at a high elevation that distributes to a network at a lower elevation.
  • When an upstream pump shuts off, this valve would prevent the upstream network from emptying.
  • PRVs and PSVs can be modeled to use either hydraulic grade or pressure settings.

Example of this Valve

Cla-Val Model 92-01/692-01 Combination Pressure Reducing and Pressure Sustaining Valve

Example of this Valve

The following example model requires version V8i SELECTseries 6 of either WaterGEMS, WaterCAD, or HAMMER.

combination PRV PSV example.zip

Video

The above video is simulating a pump shut down.

Stage 1: As the upstream hydraulic grade decreases to 20ft (PSV's minimum hydraulic grade setting), the PRV gradually opens to maintain a downstream hydraulic grade of 10 ft (PRV's maximum hydraulic grade setting).
 
Stage 2: As the downstream hydraulic grade gradually decreases, the PSV gradually closes to maintain an upstream hydraulic grade of 20ft (PSV's minimum hydraulic grade setting).

NOTE: If you are using HAMMER, a transient analysis will not permit three pipes connected to the PSV or PRV. In this case, you will need to insert (split pipe with) an additional node on both sides of the valves (very close to the valve) and connect the bypass pipe to that node instead of connecting directly to the valve.

See Also

How does the Pressure Sustaining Valve (PSV) work?
How does the Pressure Reducing Valve (PRV) work?
Cla-Val Model 92-01/692-01 Combination Pressure Reducing and Pressure Sustaining Valve

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