Marathon - FSO, West Coast of Africa, pump repair
Metalock Engineering has recently restored a vertical pump - used for the transfer of sweet crude on a MarathonOil floating storage and offloading (FSO) vessel operating off the West Coast of Africa – to full working condition.
The pump had sprung a leak, and on investigation, it was found that due to a loosened locknut the impeller haddropped, causing considerable damage to the volute form of the casing and the lower gland seal area of thepump.
Metalock was called upon to investigate whether a repair was possible. Once the pump had been dismantled,the extent of the damage was assessed and a decision taken that a successful repair could be effected. Therepair would involve the application of a specialist flake glass-filled coating material. Before this could bedone, damaged wear ring lands and internal areas of the pump casing had to be machined, and the entireinternal surface shot blasted to ensure a positive bond between the bronze pump body and the glass flake filledcoating.
The blasting and coating work to the internal surface area of the pump was carried out for Metalock by UKcorrosion engineering specialists Corrocoat, using experienced personnel from the organisation’s applicationfacilities in South Africa. The coating system selected was from the company’s own Corroglass 600 range,comprising a vinyl ester base loaded with glass flake. For this application, the product was brush applied incoats to build up the excessively worn surfaces, curing swiftly to offer high levels of chemical resistance in use.
Once the new lining and restored areas were completely cured, Metalock dressed the joint faces of the twohalves of pump casing before setting up a boring machine in the bottom half casing to recut the wear ringlands. The two halves were then bolted and dowelled together, and the relevant areas machined using appropriateMetalock on-site line boring equipment. On completion the casing top half was removed and all dimensionsinspected prior to fitting new bearings and a replacement impeller.
The alternative to on-site repair would have been a completely new pump. As this particular type is no longera stock item, production and delivery lead times would have been extensive and very costly. The necessarydowntime was unacceptable, hence a repair which has successfully restored the vertical pump to full operationin a fraction of the time.
The Metalock repair, carried out offshore, involved theapplication of a flake glass coating material followed bymachining using line boring techniques to recut wearring glands.