Cavity Style vs. Suction Shoe Style Pump Heads

Pump-head design comparison for gear pumps

This article discusses the differences between the cavity style and the suction shoe pump heads for gear pumps. Pump heads for gear pumps are available as with the suction shoe or the cavity style design. Each of these pump head designs has their specific advantages and disadvantages.

Cavity style pump heads (Series GJ)

Cavity style pump heads can be used for viscous media and applications with a certain suction height. The maximum suction height with water and a flooded (primed) pump-head is 8m, depending on pump head and tubing. Cavity style pump heads allow pumping out of a vacuum of up to 200 mbar. They are based on tradition gear pump technology and are suitable for applications with moderate pressure. A cavity style head can deliver fluids from a viscosity between 0.2 and 1,500 cP, some pump heads allow for delivering a fluid up to 2,000 cP.


  • Excellent chemical resistance.
  • Smooth operation at a low noise level
  • Low internal friction.
  • Ideal for applications requiring suction lift, frequently cycling, or a pressurized inlet.

Available gear materials:

  • PTFE
  • PEEK
  • PPS
  • NiC (Z-150W only)

Suction shoe style pump head (Series GA and GB)

This type of pump-head design has a seal plate mounted with a deliberate play in the suction part of the pump chamber—hence the expression “suction shoe”. Discharge pressure keeps the Suction Shoe seated tightly on top of the gears which prevents flow from decreasing in high-pressure applications. A suction shoe style head can deliver fluids from a viscosity between 0.2 cP and a maximum of 1,500 cP.


  • Temperature range from –46 to 177°C (–51 to 350°F).
  • The suction shoe acts as a dynamic seal element which results in a temperature and pressure-independent pump chamber.
  • Ease of servicing due to fewer parts. The service kit, including the suction shoes, enables an extended pump life; conventional pumps require more frequent replacement.
  • Ideal for applications requiring high initial differential pressure and precise flow rates.

Available gear materials:

  • PEEK
  • Graphite
  • PPS

Comparison: Cavity Style vs. Suction Shoe Style Pump Heads

Series Pump Type Reverse delivery Max. suction height (dry/primed) Use Temperature range Suction from vacuum Flow Range (Min) Flow Range (Max) Differential Pressure (Min) Differential Pressure (Max)
GJ Cavity Yes 1 m/8 m High flow rate 54°C, 77°C or 99°C, per seals 200 mbar 158 mL/min 6,800 mL/min 5.5 bar 21 bar
GA Suction Shoe Style No 30 cm/3 m High diff. pressure –46° to 177°C No 8.5 mL/min 506 mL/min 5.2 bar 21 bar
GB Suction Shoe Style No 30 cm/3 m       131 mL/min 6,400 mL/min 8.6 bar 21 bar