Advanced Flow Control Schematics Using Electronic Pressure Regulators and Back Pressure Regulators

  • schematic of two eprs fixed control valve differential

There are numerous ways in which electronic pressure regulators (EPRs) can be used to pilot dome-loaded back pressure regulators (DLBPRs) in precision computer automated flow control. The following schematics show some of the applications which can be used to accomplish computer automation of flow rate.


  • EPR: Electronic Pressure Regulator (sometimes E/P, I/P)
  • DLBPR: Dome-loaded Back Pressure Regulator
  • Control Valve: a manual control valve, automated control valve, or fixed orifice used to throttle flow and create a pressure drop
  • Aux Supply: a separate gas supply to the EPR, typically air or nitrogen
  • Media: (also unlabeled stream on bottom left) – process fluid that is being controlled
  • I: Inlet to EPR
  • O: Outlet to EPR
  • Ref: reference port that the EPR uses to gauge its pressure against (often open to atmosphere, but can be ported to other pressures)
  • Exhaust: The port that the EPR exhausts to in order to lower gas pressure

Establishing Fixed Pressure Differential Across Control Valve using EPR and BPR

Reference pressure to EPR if from media supplied to control avlve, thus allowing the EPR/BPR combination to control the delta pressure across the control valve. This can be useful for improving the stability of the performance of the control valve and/or extending the flow range of the control valve. A-Control-Valve-Fixed-Differential-Pressure

Using Process Media to Supply the EPR

EPR is supplied with the same gas media as is coming into the BPR. Optionally, the EPR exhaust can be collected into the output (vent) port of the BPR. A spring bias may be optionally used.



Porting EPR Exhaust into the BPR Outlet

Supply pressure to EPR is from an auxiliary source, while the EPR exhaust is common with the BPR outlet.


Porting EPR Exhaust into the BPR Outlet

A pressure transmitter converts the media pressure to an electronic signal, which commands EPR#1. EPR#1 is used to provide a reference pressure to EPR#2. This is useful when the media is corrosive, hot, or otherwise not compatible with the EPR. D-Two-EPRs-Fixed-Control-Valve-Differential

Controlling Density and Differential Pressure at Control Valve

EPR#1 sets the common mode (density) pressure while EPR#2 control the delta pressure across the control valve.


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