Thames Water - diesel/gas engine uppper liner landings refurb.

Upper liner landings of two Ruston 8AT engines used for power generation at Thames Water’s Long Reachworks were refurbished by Metalock Engineering UK recently to remove the effects of fretting corrosion sustainedover the years.

The in-line eight cylinder machines were dual fuel engine operating on diesel or sewage gas, with their exhaustheat used to generate hot water for the site via a waste heat boiler. During the stripdown for a major overhaulthere was evidence of severe fretting corrosion around the upper liner landings and bores. Clarke Energy, whohad been commissioned by Engenica, the maintenance arm of Thames Water, asked specialists Metalock,who they had successfuly used on many previous occasions, to carry out an initial survey and recommend thebest solution. This was to machine away the damaged areas on the sixteen cylinders and restore to originaldimensions using mild steel ring inserts.

To achieve this Metalock used one of its purpose designed, hydraulically driven in- situ facing and boringmachines set true to the existing bore axis with a support at the lower liner landing. To accept mild steel ringinserts each bore was machined out to 413mm(16.625 inches) diameter for a depth of 60mm(2.375 inches).Subsequently, each top face was counter-bored to 432mm (17inches) diameter 12.5mm (0.5 inches) deep.

Sixteen make-up rings had been manufactured to provide a precise interference fit, so that once cylinder blockmachining had been completed, checked and inspected, each one could be shrunk into position.

To achieve this, a ring was immersed in a container of crushed dry ice and constantly measured until it reacheda diameter that was at least 0.25mm smaller than the bore it had to enter. It was then fitted and rotated toensure a square fit. No further machining was necessary. The final operation was to secure the rings in postionby dowelling through the top face into the cylinder block.

After machining away the damaged area atthe top of each bore, mild steel ring insertswere shrink fitted into place thus restoringoiginal dimensions.