Without more information, that is a little difficult to answer. What conditions do the 2 different settings relate to? A PRV itself only can have one setting at a time...which is set by the pilot, and typically the pilot is set on site and left as is.
A couple of typical examples where there can be more than 1 "setting":
1. Some make/models of PRVs have limited flow ranges (typically older ones), and instead 2 PRVs, one small...one large, are installed in parallel, to give a wider controllable flow range. The small one takes care of normal and low flows, and has the highest set-point, with the large one catering for peak flows, but has a lower set-point (it only starts to operate when the small PRV can no longer maintain its set-point). Modelling-wise, you only simulate this as 1 PRV, typically with the larger PRV's set-point (since most often simulating pressures at peak flow conditions).....but there are many exceptions to this, depending on how they actually operate, what their functions are, and what scenarios modelling wise you are interested in.
2. Typical new PRV installations in a water utility network in developed countries (but seeing a lot now in developing countries as well) now often has a separate pilot controller (eg. Driven by a stepper motor), or the pilot is removed entirely and replaced by pneumatic or hydraulic lines with solenoid valves. Both drive the PRV downstream pressure settings higher/lower according to a logic controller on-site (or sometimes via SCADA). They give far greater control (especially for leakage management), but more costly to build and need regular maintenance. These have multi "set-points" because the controller unit is typically programmed with a flow vs pressure curve. Low pressures in low demand periods/nighttime, higher pressures when demands increase. Older controllers were simpler and typically programmed with a nighttime (low) pressure and daytime (high pressure) according to clock time.
If you can find out more about your PRV installations, I'm sure we can give some appropriate modelling pointers! ;-)
Hello,
The PRV element controls the downstream pressure. So, it seems that you should use the lower reading as your PRV setting. If you look at the "results" section of the PRV properties after computing your model, you'll see the status, upstream and downstream pressures. These may help you better understand how the valve works.
Also, you might consider entering PRV settings in terms of hydraulic grade instead of pressure, to reduce error due to possible inaccurate elevations.
Regards,
Jesse
Jesse DringoliTechnical Support Manager, OpenFlowsBentley Communities Site AdministratorBentley Systems, Inc.
Well, if it functions as a PRV then use the control valve set-point relates to its downstream HGL. PRVs only have one setting.
However, you CAN have 2 settings on a subtley different type of control valve......a combination Pressure Reducing and Sustaining Valve. (eg. http://www.mmcontrol.com/Claval/PDFs/claval%20pressure%20reducing/E-92-01.pdf ). These have 2 pilot valves. There is no WaterCAD element equivalent to this type of device....and is tricky to simulate. Because by default these operate usually in PRV mode, if I had to try to simulate it I would probably model it as a PRV, and ignore the the upstream set-point for modelling purposes. If you really did need the PSV function, you could insert a parallel PSV (Initially Closed) to the PRV in the model, with it becoming Active through Controls (and the PRV closed) using whatever trigger(s) that causes the upstream pressure to drop (eg. Tank Inlet Valve opening/closing).