PUMP IMPELLER Polymeric coatings are specifically designed to improve the efficiency of fluid handling systems and protect metals against the effects of erosion-corrosion
Coating technology can help decrease efficiency and performance losses in fluid handling equipment, caused by physical or mechanical damage, and localised erosion and corrosion, thereby increasing a pump’s performance and reducing operational costs, says industrial products and services provider Belzona Polymeric marketing assistant Alice Jucquois.
Jucquois states that, with pumping equipment, it is possible to reduce power consumption and improve the hydraulic properties by changing the pump surface finish.
Frictional forces created between the fluid and the walls, the acceleration and the slowing down of the fluid, and the changes in the fluid flow direction all impair efficiency.
Therefore, the smoother the pump walls, the more fluid turbulence will be reduced, thus reducing the energy required for the pump to move the fluid through the hydraulic passage.
o get the best performance possible, pumps manufacturers seek to create the smoothest surface possible to reduce the turbulence of the fluid, Jucquois says, noting that this can be achieved by applying an erosion-corrosion resistant efficiency coating on the pump’s volute and impeller.
These polymeric coatings are specifically designed to improve the efficiency of fluid handling systems and to protect metals against the effects of erosion-corrosion. The unique combination of properties such as self-levelling application, hydrophobicity and hydraulic smoothness makes these coatings ideal candidates for lining the hydraulic passages of pumps.
The coatings possess a low electronic affinity towards water molecules and result in a smooth glossy finish once applied onto a metallic surface, allowing aqueous solutions to easily slide on the surface of the coating.
The smoothness of these hydrophobic epoxy coatings has been proven. The surface condition of Belzona 1341 (Supermetalglide), a high-performance coating designed to improve efficiency of pumps and other fluid handling equipment, while protecting them from the effects of erosion-corrosion, was measured as 15 times smoother than polished stainless steel.
The test was performed by the British National Engineering Laboratories and the pump, in uncoated condition and running at 1 300 rpm, was originally found to deliver 875 m3/h at 26.5 m head and with overall peak efficiency of 83.5%, where overall efficiency is defined as the ratio of water power output to mechanical power input at the shaft.
The Belzona 1341 coated pump gave a maximum of 6% increase in the peak efficiency and a reduction in power consumption of 5.1 kW at duty point.
Assuming a 5 000 hours a year operating cycle, the power savings over this period would amount to 25 500 kW.
Pumps manufacturers worldwide have measured similar results, and feedback on industrial equipment protected with this coating shows that it is possible to achieve a return, which exceeds that of a new pump.
Pump Efficiency Enhancement
In 2013, a water elevation plant in Portugal was looking to improve its hydraulic efficiency. The plant was chosen because of its high-energy consumption and costs, with yearly consumption of 1.7 GW and a volume of water propelled of 1.2-million m3/y, recorded in 2012.
An internal pump coating was chosen to increase water flow and reduce energy consumption while reducing internal wear and reducing future maintenance actions.
The pump was disassembled and all internal surfaces were grit blasted to remove the previous coating, creating a substrate cleanliness of at least SA2.5 and a surface profile of at least 75 μ.
After grit blasting, the application areas were masked for the application of Belzona 1111 (Super Metal), an epoxy paste grade composite for metal repair.
This was used to reconstruct the areas damaged by corrosion, rebuilding the original surface profile. This solvent-free composite provides excellent corrosion resistance and ensures the substrate is protected when it comes into contact with an abrasive material.
Within the two-hour over coating window, the first coat of Belzona 1341 (Supermetal-glide) was applied, followed by a second coat to obtain a total dry film thickness of 500 μ.
This coating was specified because it provides protection against erosion and long-term corrosion of equipment, while improving the efficiency of the pump.
The results were a reduced in energy consumption during nonpeak hours of 44.9% to 39.3% (a 12.5% reduction), a reduction in total energy consumption of 14.9% (kW/m3), and a 20.3% cost reduction.