International effort gets impeller spinning again

Jon Lawson

Many industrial processes rely on compressors for a host of essential tasks, from powering machinery to squeezing industrial gases for storage and transportation. When one of its main compressors failed, a company in the Philippines faced high costs and the prospect of a long wait for a critical replacement part. So it turned to Sulzer for help.

Modern centrifugal compressors are high-performance machines. Used in the most demanding industrial applications, their job is to deliver air or other gases at high volumes and high pressures into storage, transportation pipework or to downstream machinery. The machines themselves can be very large indeed, consuming hundreds of kW of power, but the critical component at their heart is a precision-engineered high-speed impeller, which can be just a few cm in diameter.

For one company, damage to this vital part was to be the cause of a prolonged period of expensive disruption. When a large compressor failed, investigations showed that the machine had been operating out of balance for some time. The resulting vibrations had caused such extensive damage to the machine’s 7.4-inch (188 mm) diameter impeller that the part was beyond repair.

How to digitally model an impeller

The damaged impeller and shaft were removed from the casing and shipped to Sulzer’s facility in Indonesia. Once there, the local engineering team set about collecting all the data needed to recreate the part. Using a combination of laser scanning technology and conventional measurements, the team collected digital and dimensional inspection data to build a complete 3D representation.

The data was then used to build a 3D solid model of the replacement component. The damage to the impeller was extensive, so the team had few complete surfaces they could use as a basis for the model. By applying engineering analysis to the geometry of the broken part however, they were able to ‘undo’ the damage digitally and determine the precise geometry of the original component.

While they were working on the geometry, their colleagues were continuing their own work to reverse-engineer the component. They used x-ray fluorescence (XRF) analysis to establish the exact chemical composition of the impeller. That allowed Sulzer to source the same alloy in order to manufacture the replacement. Finally, the team used zebra analysis to determine the surface continuity quality in the 3D model that would affect the surface finish required for the new part during the machining process.

With the model, material and relevant manufacturing information now available, Sulzer’s CNC machining specialists stepped in. A manufacturing team in Houston produced the replacement part, which was machined from a single block using five-axis milling techniques.

After surface finishing, the part was spin tested at high speed in Houston to check for any imbalance before shipment to Indonesia. The Indonesian team assembled and balanced the new impeller on the original shaft before returning it to the customer for installation in the machine.

Hepy Hanipa, Head of Turbo Services South East Asia said, “This was a relatively small, but highly complex component and its performance was critical to our customer’s operations. Close cooperation between Sulzer teams working on opposite sides of the world allowed us to deliver a high-quality solution on a timescale that met the customer’s needs whilst delivering a 40% cost saving.”





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