Repair and Rebuild of Pumps and Impellers

Problem:

Excessive Corrosion was noticed on various pumps and impellers at a Thermal Power Station. Corrosion was primarily due to the inability of these pumps & impellers to handle the high-pressure circulation of seawater over a period. This resulted in the frequent dismantling of the corroded pumps, thereby not only causing delays but also drastically reducing the performance efficiency of these pumps.

Solution:

Upon assessing the situation and associated problems, Arudra identified that a 1– 1.5 mm thick Ceramic Coating and Lining of 100% solid epoxy would be required to protect and enhance the operational efficiency of these pumps & impellers.

i. Coating the Impellers:

The impeller was dismantled and blasted (copper slag) to prepare the damaged surface both internally and externally. The joints and dents were patched using Duromar – SAR, a 100% solid high temperature & chemical resistant ceramic putty that can be built up to the varying level of thickness(Approximately up to 25 mm).

Upon curing of the putty, Duromar EAC – LV, a 100%solid epoxy liner was used to coat the impeller both internally and externally. The epoxy ceramic liner’s smooth finish would help prevent any corrosion/erosion attacks whilst ensuring a smooth flow rate of the fluid.
Dynamic Balancing of the impeller was carried out after 24 hours of application of the coating – This is done to avoid any possibility of wear & tear of the coating caused very often by uneven balancing and rotation of an impeller.

ii. Coating of Pump Casing

Surface preparation is by far the most crucial function of any coating installation. Like the impeller, the surface of the pump casing was also prepared by copper slag blasting. The ceramic epoxy putty Duromar SAR was applied all through the casing as abase coat – This was built up to 1 – 1.5 mm, thus providing a solid foundation for the topcoat and filling up any cavities present. Duromar EAC – LV was then applied on top of the cured SAR base coat, to provide a smooth glossy finish that would help enhance circulation of the fluid.