Energy Savings through Pump Refurbishment and Coating

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Abstract:

This report looks at the benefits to pump performance from mechanical refurbishment and coating the interiors of horizontal split case pumps (HSC) with brush on ceramic epoxy coatings. Based on the positive results of a previously conducted pilot study, in 2006 the MCWA applied for and received a grant from the New York State Energy Research and Development Authority (NYSERDA). The funding was provided to continue research on the benefits of mechanical restoration and the use of ceramic epoxy coatings on the inside casings of HSC pumps to restore and preserve pump performance and efficiency.

The NYSERDA study included nineteen HSC pumps ranging in size from 20 horsepower (hp) up to 600 hp. Restoration of the pumps was in most cases broken down into two steps, mechanical refurbishment and sandblasting & coating. On four pumps there was a third step added which was an evaluation of the benefits of coating a pump's impeller.

Regardless of which step was performed first, pumps were reassembled and reinstalled between steps for field testing. The first step was to either mechanically refurbished (rings, sleeves, bearings, etc.) or sandblast & coat the interior casing of the pump. After field performance testing, the pumps were then disassembled a second time and either sandblasted/coated (if the first step was mechanical refurbishment) or mechanically refurbished (if the first step was sandblasting/coating). Field performance testing was again performed to measure the performance enhancement from the second step of the process. The same procedure was followed on the four pumps that had their impellers coated as an independent third step.

Additionally, three sets of identical pumps were selected where one pump in each set was only sandblasted and left uncoated. The goal was to see if sandblasting & coating pumps had any greater initial performance and efficiency gains compared to just sandblasting (no coating) and to determine if performance of an uncoated pump declined more rapidly over time compared to a coated pump.

The overall results of the study showed that sandblasting and coating a pump on average increased pump efficiency by 6.2% and significantly increased pump head and flow while mechanical refurbishment increased pump efficiency by 5.4%. The average increase in pump efficiency from impeller coating was 1.5%. The study concluded that however much a pump's performance has declined over time compared to original manufacturer specifications, on average only 50% of the return back to manufacturer specifications can be achieved through mechanical refurbishment alone and that to restore the remaining 50% requires sandblasting and coating the interior of the pump.

Energy savings estimation from pump restoration revealed more or less the same thing. On average 50% of any energy savings associated with pump restoration can be attributed to sandblasting and coating. The energy savings pay back period based on the cost of restoration for pumps that run more or less continuous is often less than one year.

The pump sandblasting & coating comparison to sandblast only showed on average that the sandblasted & coated pumps had initial post restoration efficiencies 5.4% higher than that of the uncoated pumps. Additionally, in two of the three uncoated pumps, efficiency dropped greater than 4% two years after being put back in service, while the coated pumps remained at more or less their post restoration levels of efficiency dropping less than 1% over the same time period.

Subsequent inspections of the epoxy coatings on the inside of several of the first pumps coated has shown that although the coatings are often rust stained, the coatings have adhered well and remain in good shape without any significant signs of failure even after being in service for four years or more.
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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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