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Pumping System Wear Components



In this article, we are going to look at the whys and wherefores of using polymer composites for pumping system wear components.  More specifically, we are going to focus on polymer composite wear rings.

What is a Wear Ring?

A wear ring is used in a centrifugal pump between the pump casing and/or impeller to provide a running clearance.  A running clearance is necessary in order to prevent wear of the impeller or pump casing itself.  The wear ring also serves to prevent the fluid from recirculating from discharge back to suction.  When that happens, it results in a significant loss of efficiency.  One of the goals is to keep the running clearance as small as possible to boost pump efficiency. 

Wear rings also help support the shaft, reducing its deflection and vibration, which in turn can increase the potential life of mechanical seals and bearings.  They are sacrificial components, and are thus replaced regularly.


Issues with Metal Wear Rings

The more the clearance is decreased, the higher the efficiency will be.  However, metal wear rings limit the potential efficiency increase because attempts to further decrease clearance can quickly result in seizure.  In addition, metal rings can heat up and increase friction, and suffer from friction-welding.  As these issues combined can result in catastrophic failures at high energy levels.


Polymer Composite Wear Rings

High performance polymer composites have become the primary alternative to metal wear components.  Non-metallic wear rings allow the clearance to be reduced much more.   They have been found to increase efficiency and mean-time-between-repairs, as well as reducing overall repair costs.  They can virtually eliminate pumps seizures, and with the smaller clearance they make possible, they can serve as a damper to greatly reduce shaft vibration.


What to Look For

Not all high performance polymers and polymer composites are appropriate for use as wear components.  Here are the major characteristics you should be looking for:

v  Low friction
v  Dimensional stability, and especially low thermal growth
v  Toughness and durability
v  Dry-run capabilities
v  Appropriate range of service temperatures
v  Chemical compatibility
v  Ease of manufacture
v  Ease of installation
v  Non-galling and non-seizing


Preferring Polymers

Polymers are a great alternative for pump wear components because, when properly designed and installed, they can increase efficiency, reduce mean-time-between-failures, and reduce overall operating costs.


For more information on High Performance Polymer Materials download Advanced EMC Technologies Polymer Bearing Material Comparison Charts.


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