In this study, the DuraSpindle exhaust valve reconditioning of a two-stroke diesel engine was studied. In the operating vessel, the economical efficiency of the new exhaust valve spindle and the reconditioning of the existing exhaust valve has been evaluated. The reconditioned exhaust valve spindle has a low purchase price of 70%~80%, and reduced delivery time half of the new nimonic exhaust valve, which are very competitive.
In order to recondition the exhaust valve spindle, it is necessary to initially check the condition of the exhaust valve spindle to evaluate whether reconditioning is possible, and additional following processes of initial machining step to remove the hardened surface, GMAW, heat treatment. There is a need for final machining and inspection steps to ensure that the spindle machined to exact dimensions.
Reconditioning is only available for a company that have receiver FTA from engine maker. Initial evaluation of availability of reconditioning during initial inspection, machining, welding(GMAW), rolling, heat treatment, final machining and final inspection steps are recommended.
Inconel 625 or 309L should be used as the base material for the initial processing, and grooves of the sheet surface should be coated with Inconel 718. Both GMAW and GTAW can be applied to Inconel 625 and 718 coatings. The rolling speed should be at a speed of 130m/min, a 2 ton increase in load every 30 seconds and a final load should be of 8~9 tons. Heat treatment of Inconel 718 should be initially heat up 100℃ per hour, maintain 8 hours at 720℃, 6 hours at 620℃ and initiate air cooling at 400℃ and finalize heat treatment.