FELUWA MULTISAFE® double hose-diaphragm pumps
for abrasive, aggressive and toxic media

Bypass Flow Control

A bypass system which functions in the same manner as the pressure relief valve is fitted to the pump as an option for shortterm flow control. Essentially, with each delivery stroke of the pump, an infinitely adjustble portion of the hydraulic oil (VB) displaced by the piston/plunger is diverted into the hydraulic oil reservoir. Since the volume being displaced by the piston/ plunger onto the diaphragm (either hose-diaphragm or flat diaphragm, depending on the pump type) is reduced by the volume being diverted into the hydraulic oil reservoir, the output of the pump decreases accordingly.

The bypass control is only designed for a relatively low driving power up to 5.5 kW or for short-term control (e.g. during system startup). Alternatively, brief opening of the bypass valve during pump startup generally enables relatively rapid bleeding and diaphragm positioning in line with the design.

Bypass flow control using the example of a MULTISAFE® pump.


  • VF = volumetric displacement
  • VK = volumetric piston displacement
  • VL = continuous bleed volume
  • VLE = leakage compensation volume (via make-up device)
  • VSM = volumetric hose-diaphragm displacement
  • VÜ = volume diverted into the oil storage tank via the pressure relief valve