Boiler feed pumps with updated hydraulic design for 50 % less than replacement cost

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Power stations using steam turbines to drive generators are reliant on boiler feed pumps, among several other vital pieces of equipment, to ensure output to the grid matches demand from consumers. Periodic planned maintenance should ensure continued reliability, but as these pumps reach the end of their service lives, the frequency of interventions can increase and even affect the productivity of the plant. One facility in South Korea enlisted support from Sulzer to retrofit four boiler feed pumps.

After 28 years in service, the original group of four ring-section boiler feed pumps were starting to show their age. Typically, the pumps would have been overhauled every three years as part of a planned maintenance routine. However, more recently, the efficiency of the pumps had started to decrease and vibration levels were rising noticeably.

On-site root cause analysis by Sulzer’s experts.

For the maintenance team in the power plant, the increased frequency of interventions was becoming difficult to manage and this situation was compounded by the lack of support received from the local pump OEM. Having established the drop in performance and measured intense vibration at 8 mm/s, the decision was taken to appoint Sulzer as an alternate pump repair specialist.

Sulzer assembled a team of specialist pump and mechanical engineers to conduct a comprehensive study of the existing installation and to assess the most suitable solution. Having analyzed the condition of the original pumps, the team concluded they had reached the end of their service lives and replacements would be needed.

In terms of time and expense, the best design would be a drop-in replacement that required minimal alterations to the surrounding infrastructure. This proposal would allow Sulzer to design, manufacture and test the new pumps off-site in preparation for a planned outage, during which the pump changeover could be completed. By creating a pump with the same external connections, the time to carry out the switch-over would be kept to a minimum.

Using the measurements taken during the initial investigation, the Sulzer team engineered a fully customized pump with the hydraulic design based on its MD series. The aim was to deliver the same performance with improved efficiency, which was achieved through the optimized design.

In addition to the plug-and-play boiler feed pump, Sulzer also supplied automatic recirculation (ARC) valves, drive couplings, seals and some additional lube oil pipework. The turn-key project saw Sulzer deliver all of the design and manufacturing aspects as well as supplying the ancillaries and civils works, ensuring peace of mind for the customer and enabling the plant engineers to focus on their core operations.

Two-week turnaround

New pumps installed and commissioned.

Once the shutdown was in place, Sulzer’s field service team started the process of removing the original pumps and installing the replacements. The drop-in design enabled this process and the commissioning to be completed in just two weeks, to the great satisfaction of the plant’s operations team.

Although some additional lubrication piping was required, the remainder of the surrounding infrastructure was unchanged. This was in contrast to the proposal from the OEM that would have required considerable changes to the base plate as well as the suction and discharge pipework. In terms of investment, Sulzer’s solution was 50% of the amount required for a new pump replacement from the OEM.

Sulzer’s turnkey solution also included a training package for the operations and maintenance teams that involved both hands-on and theoretical learning that would help maintain optimum performance for the new pumps. However, of greater importance to the power plant was the timeframe in which the project was completed. Achieving the project delivery within the shutdown period was of crucial commercial importance.

The custom pumps from Sulzer have been in operation for two years and periodic vibration measurements have consistently returned values of just 2 mm/s – well within the acceptable range and a considerable improvement on the original pumps. Furthermore, the efficiency of the pumps has been improved.

www.sulzer.com

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