Posted at 28-Jan-2021

If at first you don't succeed, ask the experts

Paul Skade
By Stewart Royle
Regional Engineering Manager, North & Scotland

Following my apprenticeship and formative years with an independent company, I joined WYKO in 2001 at the Preston Service Centre as an electro-mechanical engineer...

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If there’s one thing we know that gets on the nerves of an engineer, it’s an asset failure. But what’s even worse, is repeated failures of the same assets. And when one customer’s inverter drive motor was causing recurring problems, a fresh set of eye was requested for support.

 

Over and over again, the bearings on the 420kW motor, used to drive a water pump, had failed. Over and over again, they’d been replaced with the same standard bearings. Over and over again, they’d failed.

You don’t have to be Einstein to spot that there must be a better way. Perhaps you just have to be ERIKS. Which is why one more motor failure led to the customer contacting ERIKS to carry out a Root Cause Analysis.

All change

Simply changing one standard bearing for another had already proved inadequate. So this time, when the failing motor went to ERIKS’ workshop, ERIKS went back to basics.

This meant dismantling the motor, removing the bearings from the shaft, then splitting the bearings to reveal the running track and any tell-tale signs of how and why the bearings had failed.

 

A combination of investigation, analysis and experience led to the conclusion that strong bearing currents were the issue.

Now the new problem was how to prevent a repeat of the old problem.

Raising the standard

With the standard bearing solution being no solution at all, ERIKS brought together experienced engineers from two Product Business Units – Bearings and Lubrication – to provide a more comprehensive assessment of the way forward.

Engineers and customer had already been working together to understand the problem and develop the most cost-effective resolution.  Now, brought together at the workshop, they made the decision to adopt a three-pronged response.

Firstly, the standard action for problems of this type: an insulated bearing fitted on the non-drive end of the shaft. Secondly, ERIKS’ bearings expert recommended fitting an earthing ring to the drive end of the shaft. This would allow the electrical current to discharge more effectively. Thirdly, ERIKS’ lubrication specialist recommended a change of lubricant to Polyrex grease.

But this was only the start.

Above and beyond

The earthing ring required an additional component to make it work: a new adapter flange to enable fitting at the drive end. This had to be designed to fit, and specially manufactured by ERIKS.

 

By contrast, the new lubricant selected could work perfectly well on its own. ERIKS’ analysis and experience had revealed that the new grease was more resistant than others to separation, when subject to electrical discharge. Yet as a standard grease it was a highly cost-effective solution compared with a specialist lubricant.

Since utilities sites are often remote and unmanned, automated lubrication not only optimises lubricant usage, but can also reduce the number and duration of site visits by lubrication teams.

Rebuilding, realignment, reliability

The motor, with its new insulated bearing, earthing ring, adapter flange, and automatic lubricators, was fully reassembled at ERIKS’ workshop. 

This involved a complete overhaul of the unit including a Baker surge test static test on the stator, a steam clean, stove drying, and a revarnish of the winding. 

Once reassembled, it was returned to the customer’s site for the customer to install. Then ERIKS’ engineers carried out a laser alignment to ensure motor and drive were perfectly aligned for safe and efficient operation.

6 years on, the motor is still running reliably with no more bearing failures. The customer has been so satisfied with the result, that when vibration analysis revealed a developing problem in a second identical motor, they called in ERIKS before it had a chance to fail, to carry out the same adaptation .

 

Now ERIKS has repaired and adapted all three of the motors on site, to provide massively improved reliability, and a greatly reduced Total Cost of Ownership.

If at first you don’t succeed, you obviously didn’t call ERIKS.

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