Sulzer breathes new life into older pumps with reverse engineering
Over the years, pump manufacturers have created many different designs of pumps for a host of applications and each one used the technology available at the time. As older models continue in service, access to spare parts becomes ever more difficult until the original equipment manufacturer (OEM) has none available and they need to be created on a one-off basis. In some cases, the OEM may have gone out of business but the pumps still require continued maintenance.
Where the OEM is available, it may be possible to order new components, even if they have to be manufactured from the original drawings as a special build.
The advantage here is the drawings which provide the necessary detail to create a new component. The problem is usually the lead time. Most manufacturers’ fabrication facilities are dedicated to the current pump models and re-assigning them to a one-off task may incur an additional delay.
The second issue with this approach can be cost. OEM parts are unique to their products and manufactured to certain standards, so carry a price premium. As the stock of spare parts for the older pumps diminishes, creating new parts has a higher cost threshold which can increase prices further.
Recreating an original design. The alternative is to find a third party with the engineering capability to create a new component without drawings or reference material. In the past, this has been common practice for less intricate components but the complex geometry of pumps has made this task very difficult. The advent of sophisticated co-ordinate measuring machines, 3D solid modeling software and laser scanning has made it possible to recreate complex designs.
In addition to new manufacturing technology, there have also been significant developments in materials. Older pumps are often created using materials that cannot be easily welded such as cast iron and bronze. In many cases, the original materials can be upgraded; replacing bronze with stainless steel is common.
Pumps, especially large ones, are often used in abrasive or corrosive conditions which can significantly reduce the expected operational life of components such as the impeller. Upgrading the base material causes a relative increase in the initial repair cost which will improve the service life and reduce the over-all cost of ownership.
In addition to the materials used to create the pump, the detailed design can also be improved as part of this process. The purpose or performance requirements may have changed since the original pump was installed and this can be addressed as part of the design process when creating a reverse engineered component. The hydraulic design is critical to the performance of the pump and the latest design software and computational fluid dynamics (CFD) can be used to deliver the optimum design.
Improved manufacturing processes. Modern technology has also improved the manufacturing process. It’s no longer necessary to build a pattern and ship it to the foundry; a computer model can now be emailed. Foam cores and patterns can be made for one-off components reducing both the expense and the time to complete the process. In addition, 3D printing can be used to create molds for smaller components, again speeding up the replacement.
Delivering reverse engineered projects still takes time but the process can be estimated accurately, allowing equipment owners to plan shut-downs and minimize the effect of the maintenance project. In some industries, such as power generation, a pump failure may have to be rectified with a temporary solution until a scheduled outage when the pump can be removed and repaired with a more robust solution. In such cases, the detailed measurements and modeling can be done during the initial repair allowing the new component to be manufactured before the scheduled outage to minimize downtime.
Rejuvenation after 100 years’ service. Sulzer has adopted all of the technological advances in pump component manufacturing and applied them to projects around the world. Recent examples include a pump that was built in 1912 and used as a dry dock pump. It had suffered considerably from corrosion to both the volute and the impeller but there was no possibility of finding a replacement part off the shelf.
With a vertically driven impeller, the volute weighed 25,000 lb (11 tonnes) and was built in two halves, while the impeller itself weighed 5,000 lb (2.25 tonnes). Pump engineering specialists from Sulzer accompanied site service engineers to help with the removal of the pump before its shipment to the Mobile Service Center where new components were manufactured.
A similar service was provided for a Westinghouse cooling pump that needed a new impeller and matching suction bell. The new impeller was manufactured from 316L stainless steel and weighed 5,000 lb (2.25 tonnes) while the new suction bell was fabricated from 304L stainless steel. The matched components were installed during a planned outage at the power generation plant.
These, and many other examples, show that it is possible to deliver precision-crafted replacement parts for large pumps cost-effectively in a much shorter time frame than can the OEM, assuming it still exists. Furthermore, advances in design technology enable significant improvements in performance and durability to be included, reducing the longterm cost of ownership.