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Side Channel Pumps

A side channel pump is a niche product in-between a displacement pump and a centrifugal pump. Originally, such liquid ring pumps were designed to pump air, gas and liquid mixtures. Side channel pumps can be used for a wide range of applications.

Side channel pumps have the following characteristics:

  • Automatic self-priming capability.
  • The ability to transport gas without interrupting the fluid flow or damaging the bearings due to dry running.
  • Maximum power consumption at their highest head and lowest flow rate.
  • Steep capacity-head (Q-H) curves ideal for pressure-dependent system regulation.
  • Very low suction head (NPSH) required.
  • Narrow columns (side channels) not suitable for abrasive particles in the fluids.

When started, the pump initially functions like a displacement pump due to its self-priming capability, but once the side channels are completely filled with liquid, it begins to operate like a centrifugal pump. The centrifugal effect causes collection of the liquid in the outer region of the side channel and impeller cells, thus forming the liquid ring necessary for the self-priming process.  The gas builds up in the inner region. Side channel pumps can also operate as vacuum pumps for a limited amount of time before the auxiliary liquid increasingly heats up and finally evaporates.

Besides its self-priming capability, this type of pump has the added advantage of being able to handle large gas flows with the liquid. In certain processes, it is essential that a pump can, at least temporarily, evacuate gases and vapours from the process without the liquid flow being interrupted. Normal radial centrifugal pumps have a very limited capacity to transport gas within the medium. Even at relatively low gas contents, the liquid flow can immediately interrupt or damage the pump bearings due to dry running.

The pressure build-up caused by the sum of the individual pulses during the liquid movement creates an internal multi-stage effect, even with just one impeller. Lower potential pump speeds are possible because of higher pump heads and therefore help to reduce the pump’s NPSH requirement compared to high-speed pumps. A slower pump speed has the additional advantage that mechanical loads, part load performance and noise can be controlled better and the pumps’ expected service life is generally increased.

The lower the specific speed of a pump is, the better its absorbency and the lower the risk of cavitation. Side channel pumps with variable vapour pressure are significantly less vulnerable to cavitation than radial centrifugal pumps.

CP’s side channel pump

CP’s plastic magnetic drive side channel pump is mainly recommended for low capacities (Q between 0.1 and 2.5 m³/h) and medium heads (H to 35 m). The choice of material depends on the pumped fluid and operating conditions. Either PTFE or PVDF can be used for the casing. The pump has no shaft seal, with drive torque being transmitted merely by a permanent magnetic synchronous coupling (magnetic drive).

CP's side channel pump: MSKS

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