Pump retrofit eliminates EUR 150k annual maintenance cost
New pump internals from Sulzer solve reliability issues and improve productivity for chemical processing plant
Counting the cost
Within the vast array of equipment at the processing facility, three pumps, which were originally installed in 1968, are tasked with the onerous job of pumping the ammonia feedstock for the production of nitrogen fertilizer. Two of the between bearing design, type BB3, twin impeller axial flow pumps are powered by steam turbines and one by a fixed-speed electric motor. In addition to this, an extra pump is kept as a spare.
From the outset, the pumps have suffered from poor reliability, with a mean time between failure of around 12 months, which has incurred high maintenance costs for the plant. The engineers had to deal with high vibration, excessive wear and broken impellers, all of which were causing a loss of performance and annual maintenance costs of around EUR 150’000.
Over the years, several design changes and mechanical improvements have been made to the pumps. In 1996, due to the corrosion that was also being experienced, the OEM suggested all the internal components were changed for parts made using Super Duplex stainless steel.
Searching for the solution
However, the material change did not address the inherent design issues, and the pumps continued to suffer from jammed wear rings, damaged impellers and excessive wear. The resultant loss of performance and high maintenance costs continued to cause issues, to the point that the pumps were identified as a major cause for concern in the nitrogen process.
Sulzer became aware of the issues being experienced with the pumps and offered to provide an engineered solution that would deliver long-term performance and reliability. Having appreciated the benefits that Sulzer could deliver, Sitech Manufacturing Services supplied the spare pump to the local service center in the Netherlands as the impeller was broken and the pump needed to be repaired.
The retrofit process was preceded by a root cause analysis to determine the weak points in the existing design, and enabled Sulzer to establish the best solution for this application.
The first step was to use a laser scanner to create a precision model of the entire pump. Once this was complete, the design work could start on the new impellers and driveshaft. Sulzer’s high energy pump experts in Leeds, UK, supported the project with their extensive equipment knowledge and application experience.
Starting with Sulzer’s own BBT-D pump design as a reference, the engineers focused on the impeller characteristics as well as the wearing parts, which required improved durability. Once complete, the plans were sent to the manufacturing site for this project in Germany, which created the new impellers and shaft.
Ben Lauwerijssen, Regional Sales Manager, Benelux for Sulzer explains:
Ben Lauwerijssen, Regional Sales Manager, Benelux for Sulzer
“The continued vibration monitoring has shown that Sulzer’s design modifications have not only greatly improved the MTBF, but readings are xx% lower than those for the original pumps. This is a good indication of continued performance and long-term reliability, which will continue to save the company money year on year.”