Low Differential Pressure Valve -

Low Differential Pressure Valve

Low dP valve with high speed control

  • schematic of low dp valve in mbar pressure control
In some applications there is a need for a low differential pressure valve, where the overall system pressure is low, and the user wants to avoid pressure loss.

For instance, a facility has a fan or a blower with a maximum pressure capacity of 18 inH2O (44.5 mbar) and they want to regulate the pressure at 15 inH2O (37 mbar). If the facility has access to a control valve that requires a high actuation pressure, perhaps 10 psi, to start regulating the system due to the energy required to operate the springs and O-rings, they cannot use that control valve with the 18 inH2O pressure available in the system.

schematic of low dp valve in mbar pressure control

However, an Equlibar precision dome-loaded back pressure valve (BPV), with its low actuation pressure, would be an excellent solution in this situation. The nearly 1:1 pilot control means it only takes 15 inH2O pressure to the pilot valve in order to control the the Equilibar BPV at 15 inH2O (44.5 mbar). The 15 inH2O pressure required to drive the Equilibar BPV can be fed to the pilot valve directly from the process line.

In another example, the user wants to control flow through the system using electronic process control. The system fan once again has a low pressure capacity. An Equilibar BPV can be controlled with an electronic pilot valve in this system. The Equilibar BPV has high speed control with nearly instantaneous reponse to changed in setpoint coming from the electronic pilot valve. The pressure differential across the Equilibar BPV is very low. The low dP valve ensures good flow control. The low valve authority means the system has fewer losses and better energy efficiency.

sketch of low differential valve to flow control

In the below application, the system needs to be kept at a precise pressure for the application. Once again, the pilot valve can be driven by the process pressure and the Equilibar BPV has the precision to maintain the pressure to within 0.1 inH20.

sketch of precision low differential valve in pressure control application


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For related low pressure applications, link to our tank blanketing application page or our glovebox pressure control application.


photo of BD industrial back pressure valve
An Equilibar BD Series back pressure valve (BPV) is shown above with an manual pilot valve.



Case Study - biogas digester uses Equilibar

Case study discusses the use of an Equilibar BPV in low pressure control of biogas digester system. The low differential characteristic of the Equilibar BPV helps save energy.

Key words:
  • Low differential valve
  • low differential pressure valve
  • low differential pressure regulator
  • Low dp valve
  • Low authority valve


  • small pressure can regulate system – don’t need large initial pressure to get valve to perform
  • relevant for low pressure, i.e. inches of water, mm of water, mbar
  • 1:1 pilot
  • Precise to tenths of inches of water
  • Low actuation pressure
  • High speed control (instantaneous response)


  • Valve authority is the ratio of the pressure drop across the fully open valve compared to the pressure drop across the entire circuit at design flow conditions.
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