MRS addresses long-coupled pump failure on Mpumalanga Coal mine

Long-Coupled Centrifugal Pumps have always proved popular due to the availability of the motors used and the fact that the motor and pump can be serviced individually. These pumps however require careful coupling alignment when assembled in order to avoid misalignments failures.

Mechanical Rotating Solutions (MRS) was asked to address the multiple failures experienced by an Mpumalanga coal mine as a result of coupling misalignment between the pump shaft and the motor shaft.

According to Franscois Steenkamp, Managing Director of MRS, shaft and coupling misalignment account for over 50% of breakdowns in plants. “Pump shaft misalignment occurs when one shaft or surface is moved from its preferred position. This can be due to the initial installation not done properly or can also be a wear and tear or vibration issue. These movements can lead to misalignment in the entirety or partial sections of a pumping system.”

In addressing the issue MRS replaced the long-coupled centrifugal pump with a closed-coupled AIX 65/26 – Single Stage End Suction Centrifugal Pump.  “Misalignment of the pump shaft can be one of the leading causes of failure and even a minor misalignment of the pump and driver of just 0.0001 inches can reduce the pump’s ability to operate by up to 5 years.”

The Long-Coupled Centrifugal Pump showing the coupling between the pump shaft and the motor shaft.

The MRS installed closed-coupled AIX 65/26 – Single Stage End Suction Centrifugal Pump

With a close-coupled pump, the pump and motor never have to be aligned in the field. The pump casing will be a registered fit to the face of the motor ensuring proper alignment. Long coupled centrifugal pumps, as mentioned earlier, include a coupling between the pump shaft and the motor shaft and are very popular because the motor and pump can be serviced individually, without disturbing the entire pump set. Its Achilles heel however remains the possibility of frequent misalignment leading to pump failure. “Some vibration is normal in pumps. However, even excellent alignment of the pump’s shaft centres does not guarantee the absence of vibration. It’s best to have someone experienced in vibration determine if the cause is indeed pump shaft misalignment,  as well as if it’s severe enough to affect the pump’s performance.”

Whilst the replacing of the long coupled pump solved the clients immediate needs there are also scenarios where a long coupled pump will better serve the needs of a client. A long coupling assembly is more expensive but often necessarily in situations where the above is not possible. These include for applications involving high temperatures, high viscosity liquids, and high power requirements.

“Mechanical Rotating Solutions has a range of products and solutions it can call upon to make sure the right decision is made in minimising the client’s downtime, optimising efficiency and addressing the problem with a fit for purpose solution.”


Mechanical Rotating Solutions (MRS) is a leading South African supplier of mechanical seals, pumps, integrated pump systems and complementary pump products. Drawing upon some of the most well-known and proven brands worldwide such as AESEAL mechanical seals and support systems, STRAUB pipe couplings, Belzona industrial protective coatings, Labtecta Bearing Isolators, and KSB and HPC pumps amongst others, MRS sets the standard in terms of reliability, innovation and world class customer service. Working within the guidelines of ISO 9001:2000, and ISO 14001:2004 quality and environmental standards as well as the OHSAS 18001:1999 Occupational Health and Safety standards, MRS offers a complete turnkey supply and service of pumps. The company further specialises in complementary pump products including floatation devices, complete pump refurbishment, mobile dewatering solutions and proven water and energy saving solutions.