September 2021

48 n SERVICE AND REPAIRS September 2021 www.drivesncontrols.com All at sea after critical FPSO fan motor fails W hen a critical Ex de induction motor drive on an FPSO (floating production storage and offloading) vessel failed prematurely, the operator asked the engineering service provider Quartzelec to investigate the problem. The 67kW, 690V cage induction motor, supplied by ABB, was being used to drive a critical fan on board the vessel. Despite being less than three years old, the machine had already suffered a series of equipment issues, before failing so badly that it was beyond salvaging. An initial inspection of the motor identified substantial damage, including failure of its DE and NDE bearings, multiple Atex defects, a melted cooling fan due to a bearing failure, core damage to the stator and rotor, plus significant winding damage. The immediate solution was to source and fit an identical direct replacement motor, which Quartzelec reinstated into the casing, before balancing and testing the new machine. This might have been the end of the project, but the repair teamwanted to identify the root cause of the problem. “Having been able to install an operational replacement machine, we quickly established that previous failure had been caused by a lack of regular maintenance, brought about by the fact that the motor greasing points were simply impossible to reach when the machine was in service,”explains Quartzelec Aberdeen’s project manager, Seoras Shaw.“Rather than simply having this failure potentially re- occur with the newly installed duplicate motor, we worked with both the client and the OEM to identify a viable solution. “Accessible greasing facilities have now been installed on the unit to allow the bearings to be maintained as part of the regular maintenance schedule and this should significantly increase the operational life of the machine and reduce the future risk of failure,”he adds. Quartzelec believes that had a condition- monitoring programme been implemented on the motor from the outset, the extensive damage, high replacement costs and the lengthy downtime could have been limited or even avoided entirely. Preventative maintenance and vibration monitoring can help to identify potential issues as, or before, they develop. Remedial maintenance can then be scheduled before a complete failure occurs. In this instance, the fan was critical to operations on the vessel and its failure resulted in operational issues for the operator, which had to manage for almost three months without a functioning fan. “The root cause of failure is often overlooked, but is critical when offering a repair solution to prolong machine lifespan and ensure longevity,”points out Quartzelec Aberdeen business manager, Paul Oliver.“In this instance, we could have realistically saved circa £17,000 the client had to spend on a newmachine plus eliminated all the associated costs and additional equipment downtime.” He adds that a vibration monitoring service would have identified the initial, first- stage bearing defects as they happened. “Appropriate action would have cost around £4,000 for replacement components and the time required for the replacement which could have been done as part of a scheduled maintenance programme in under a couple of weeks,”Oliver concludes . n When a critical motor on an offshore vessel failed after less than three years, a replacement machine had to be sourced and installed – a costly process that took almost three months and disrupted operations. If appropriate condition-monitoring measures had been implemented, the operator could have avoided the £17,000 replacement cost and the extended downtime. Operations on board the FPSO were disrupted for almost three months after the 67kW Ex de fan motor failed.