As part of an ongoing service programme for a UK power station, we received a clarified water pump for overhaul.
Once out of service, it was noted that the impeller was suffering from severe cavitation within the suction eye area. It also had considerable loss of material right across the vanes. Due to the amount of damage, the impeller was deemed to be “beyond economic repair” by the client.
After investigation by Corroserve’s pump manager, it was discovered that the original manufacturer no longer produced this type of pump. This left only two options – to reverse engineer the impeller, or repair it. As reverse engineering would involve a new pattern for casting, it would be an extremely long and expensive option. Corroserve therefore proposed to repair the impeller as part of the pump overhaul.
After stripping the pump down, the impeller was measured and pre-machined, a template being made from the best surviving vane. All wetted areas were abrasive blast cleaned to ISO 8501-1 Sa 2½ with a blast profile of 50μm. The coated areas were primed using Corroglass 632 and the vane profile built up using 600 laminating resin and multi-directional glass matting. The impeller was then brought back to original thickness using Corroglass 600 series coating. A top coat of Corroglass 652, blue drill guard, was applied for protection.
The impeller was finally post machined back to original sizes, including re-instating the correct wear ring running clearances in accordance with international pump standards and check balanced to ISO Grade G6.3 in accordance to BS6861 Part 1/ ISO standard 1940-1. The client was very satisfied with the quality of the work, which was completed at a fraction of the cost of replacement.
Impeller before repair Impeller Laminated Impeller Repaired