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Products  >  Control Applications Solutions  >  PRM - Two-stage, Hydraulic FlowModulated Pressure Reducing Valve  >    

PRM - Two-stage, Hydraulic FlowModulated Pressure Reducing Valve


Description:

Dorot model PRM (FR) is an automatic pilot controlled, pressurereducing valve activated by the pressure of the pipeline.The valve reduces upstream pressure to a dual set-pointdownstream pressure that shifts automatically in response tothe demand flow.The pressure into the zone is adjusted according to the zone'sactual demand, thus compensating for the system loss. The Dorot PRM (FR) will control from no flow, to maximal fullopen flow without any chattering or slamming.

Features:

  • Reduces background leakage
  • Reducing burst frequency
  • No power supply requirements
  • Maximal reliability: Bias chamber assembled on a standard PRV pilot and modulated by a standard flow control pilot valve.
  • Fast, real time response to demand changes
  • Simple to commission, operate and maintain
  • Completely stable down to no-flow demand. No throttling plug or by-pass valve used

Typical installation:




Pressure Settings
The pressure will change to a user selected two points:
1. Required valve low outlet pressure PL at a demand flowlower than Q.
2. Required valve high outlet pressure PH at a demand flowhigher than Q.

 

Design Notes

  • The PRV creates a defined minimum pressure differential(head loss). To this, one should add 1.5 mwc loss created bythe orifice plate. This loss should be incorporated in thedesign considerations. This note refers to cases where theupstream pressure may drop to near the maximal pressuresetting - PH.
  • Regulating valves may operate in destructive cavitationconditions. Refer to Dorot's relevant publications for furtherinformation.
  • Minimal pressure setting (PL) should be equal or larger thanthe required minimal pressure (PCN) plus the elevationdifference (ΔH) of the critical node in the system and thePRM location. PL ≥ PCN + ΔH
  • Maximal pressure setting (PH) should be equal or larger thanthe required minimal pressure (PCN) plus the elevationdifference of the critical node in the system and the PRMlocation plus maximal expected system losses (Δh) atmaximal demand flow.
    PH ≥ PCN + ΔH + Δh
 
Optional Features
  • Electric and or Manual On-Off control
  • Hydraulic check-valve function
  • Excessive Flow Shut-Off function..

    Where to use
    The PRM (FR) application is designed for the use in Pressure Management schemes where the target pressure in the zone (normally the AZP) changes asa result of varying demand. These changes are often associated with high leakage index and burst frequency.

    Where not to use
    Where constant logging option is required - considerusing electronically modulated PRV model PRM (EF)
    Where more accurate flow modulated pressure reducing is required - consider using models HyMod,PRM (EF) or EC
    Where there are no significant losses between thevalve location and the AZP - consider using fixed outlet PRV model PR


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