SHAFTED A misalignment between the pump and motor shafts had been causing failures at a coal mine
Last month, mechanical seal and pumps supplier Mechanical Rotating Solutions (MRS) was asked to address the multiple failures experienced by a coal mine in Mpumalanga as a result of coupling misalignment between the pump shaft and the motor shaft.
MRS MD Franscois Steenkamp suggests that after investigating, it has found that shaft and coupling misalignment accounted for over 50% of breakdowns in plants.
“Pump shaft misalignment occurs when one shaft or surface is moved from its preferred position,” says Steenkamp. He adds that this can be as a result of the initial installation not being 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 five years,” he regards.
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 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.
Steenkamp highlights that some vibration is normal in pumps. However, even excellent alignment of the pump’s shaft centres does not guarantee the absence of vibration. “It is best to have someone experienced in vibration determine if the cause is indeed pump shaft misalignment as well as if it is severe enough to affect the pump’s performance.”
While replacing the long-coupled pump solved the client’s 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 so in situations where the above is not possible.
These include for applications involving high temperatures, high viscosity liquids, and high power requirements.
MRS supplies some of the most well-known and proven brands worldwide such as mechanical seals and support systems Aeseal, including Labtecta bearing isolators; pipe coupling supplier Straub; industrial protective coatings Belzona; and pumps manufacturers KSB and HPC pumps, among others.
MRS offers a complete turnkey supply and service of pumps. The company further specialises in complementary pump products including flotation devices, complete pump refurbishment, mobile dewatering solutions and proven water and energy saving solutions.
Steenkamp concludes that MRS 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.