The threaded plugs on the fin fan coolers were leaking to such an extent that drips trays have been installed under the header boxes. There had been a machining repair previously by another machining company, but despite this and the fitting of upgraded gaskets the plugs were still leaking. The gaskets on air cooler C4304 are of a two piece design whereby the inner plug (304SS) is compressed to the gasket (softened 304ss) by a driving threaded plug behind it. The sealing face is an angled face and requires a radius in the corner. The was also a maximum depth of the seat which if exceeded to scrap the cooler

Following a site visit and technical review, it was established that the end face was not square to the plug holes and therefore the thread of the hole would need to be used as the datum to ensure the sealing face was machined square. Reekie Machining developed a solution that mounted via the thread and not the end face (which ws previously done) and made up a bespoke spot facing tool to create the angled face and maintain the radius in the corner

The machining was completed in under the estimated timescale – 4 banks of 256 tubes a total of 2048 plug gasket seating faces we machined within 15 days including full pre and post machining inspections of all of the plug holes