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

Mechanical leakage control

Loss of hydraulic fluid is automatically compensated by FELUWA pumps. For these situations the pumps are provided with a unique mechanical leakage control and compensation device within the hydraulic chamber. This system operates fully automatically, neither requires a separate oil pump nor a control system and is moreover easy to maintain.

During the suction stroke, the diaphragm (either hose-diaphragm or flat diaphragm, depending on the pump type) is drawn towards the hydraulic chamber of the piston or plunger. If the hydraulic oil volume decreases due to leakage, the diaphragm will actuate a control disc, which in turn opens the compensation valve via a lever. Further backward movement of the piston/ plunger causes a vacuum in the actuation chamber, since the diaphragm cannot move any further.

As soon as the vacuum exceeds the setting range of the compensating valve (make-up valve), the valve opens. The actuation fluid that had been displaced into the oil reservoir during the delivery stroke is replenished during the increased suction stroke. By this means, the missing volume of hydraulic fluid is replaced in the hydraulic chamber. Since the compensating valve cannot open unless the leakage control valve is mechanically opened by a lever, it is ensured that the diaphragms cannot be overstretched.

Mechanical leakage 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