An Introduction to Centrifugal Pumps

In every modern cleaning system there exists at least one pumping unit. With this in mind, understanding how it works and how to use it efficiently is critical to the successful operation and maintenance of that cleaning system. This blog will discuss centrifugal pumps in this context and take a look at important attributes to bear in mind when working with these systems.

In general, pumps are devices which impart energy to a flow of liquid.  Although there are different types of pumps based on the flow direction, blade designs, and so on, centrifugal pumps are in the majority of those used in cleaning systems.  Centrifugal pumps are simple, efficient, reliable, relatively inexpensive, and easily meet the needs of most cleaning system requirements including spraying, overflow sparging, filtration, turbulation and the basic function of moving liquids from one place to another using pressure.

A centrifugal pump uses a combination of angular velocity and centrifugal force to pump liquids.  The below figure illustrates the working principle of the centrifugal pump.

Centrifugal Pump

The pump consists of a circular pump housing which is usually made up of metals, (stain steels etc.) solid plastic, or ceramics.  The outlet extends tangentially from the diameter of the pump housing.  Inside the pump housing there is a rotating component an “impeller” which rotates perpendicular to the central axis and is driven by a shaft secured to its center of rotation.  The shaft, powered by an electric motor, enters the pump housing through a liquid tight seal which prevents leaking.  Liquid entering the pump through the inlet is swirled in a circular motion and displaced from the rotation center of the impeller by centrifugal force.  The combination of the swirling action (angular velocity) and centrifugal force (radial velocity) pushes the liquid out of the pump through the outlet.

When designing and working with centrifugal pumps, there are a number of important items to keep in mind. First, and foremost, the impeller must rotate in the correct direction.  In pumps operating from a single phase electrical source, this is not a problem.  In pumps operating from a three phase electrical source however, the proper phasing sequence of the three wires supplying power to the pump must be correct.  If any two wires are reversed, the three phase motor will rotate in the reverse direction.  Most centrifugal pumps have an arrow indicating the proper rotation direction located either on the pump body or on the motor.

Another important item to bear in mind is that although centrifugal pumps are relatively maintenance-free, there is one exception; specifically the seal on the rotating shaft.  These seals need to be replaced on a regular basis to negate either a decrease in performance (caused by an increased amount of fluid going through the seals) or on a larger scale, the threat of a catastrophic failure as warn seals can cause wobbling in the shaft which leads to vibrations and eventually results in the pump becoming noisy, overheating, and ceasing to function.

In addition, pump seals must be kept lubricated and cooled.  Both lubrication and cooling are normally provided by the liquid being pumped.  Because of this, centrifugal pumps should not be operated without liquid being present in the pump.  Failure of the pump seal due to overheating as a result of friction may happen in less than a minute of operation without liquid in the pump.

Although these are just a few tips to keep in mind, there are a number of steps and tools needed to successfully complete a market-ready centrifugal pump. Learn more about how AxSTREAM® can help you and your team here  or Contact Us for more information!

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