Power stations using steam turbines to drive generators rely 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.
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.
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 an alternate pump repair specialist.
Sulzer assembled a team of specialist pump and mechanical engineers to conduct a study of the existing installation and to assess the most suitable solution. Having analysed 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 customised pump with the hydraulic design based on its MD series.
In addition, Sulzer also supplied automatic recirculation (ARC) valves, drive couplings, seals and some additional lube oil pipework. The project saw Sulzer deliver all the design and manufacturing aspects as well as supplying the ancillaries and civils works.
Once the shutdown was in place, Sulzer’s field service team started removing the original pumps and installing the replacements. The design enabled this process and the commissioning to be completed in just two weeks.
Although some additional lubrication piping was required, the remainder of the surrounding infrastructure was unchanged.
Sulzer’s 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. The project was delivered within the shutdown period.
The custom pumps from Sulzer have been in operation for two years. The new boiler feed pumps have ensured uninterrupted operational continuity for the power plant and allowed the maintenance team to focus efforts on other areas in need of optimisation.