Minor loss in PRV's

Hello Abdelkrim,

I'm not sure I understand exactly what you are trying to accomplish. Perhaps an explanation of how PRVs function in Bentley's water products may help.

The diameter field for a PRV (or PSV) is only used when the valve is set to "inactive" (fully open). When the valve is active (controlling), the diameter does not matter, because the program is only concerned with the head loss necessary to achieve the desired downstream pressure.

In other words, when the PRV is active (throttling), the program will apply a minor loss to the PRV to make the downstream pressure match the defined pressure/hydraulic grade.

See:

Changing PRV or PSV diameter does not change results

How does the Pressure Reducing Valve (PRV) work?

Why do I see such a large headloss through my FCV, PSV or PRV?

 

Abdelkrim,

The Minor Loss engineering library is a generic library for bends, contractions, tees, generic valve opening (e.g. Angle Valve - Open, Check Valve - Clearway, Check Valve - Conventional, etc...) , expansions, crosses, pipe entrances/exits, tees, and wyes. If you need to add a specific minor loss for the PRV's you're modeling you should check with the manufacturer and create an entry for the minor loss in the engineering library. This wiki explains how you can add or modify an entry.

communities.bentley.com/.../7478.modifying-and-adding-entries-to-engineering-libraries

Regards,
Mark

I would like to add to my previous post.

When the PRV/PSV property "Valve Coefficient Type" is set to "Minor Loss", and "Specify Local Minor Loss" is set to "True", the "Minor Loss Coefficient (Local)" field can be defined. That minor loss will only be applied to the valve when it is fully open (inactive).

Are you looking for typical values to enter for that minor loss (dependent on the valve diameter property)?

To my understanding, the typical headloss values for a valve are dimensionless and are found empirically.

See: Minor Loss in Pipe or Duct Components