When most people think of steam, they will think of boiling a kettle to make tea or coffee. What people tend to forget is that we need steam to power our phones, televisions and other devices. Thankfully we don’t need to boil the kettle every time we want to use these; steam turbines produce the electricity that powers them. So, we all depend on the specialist maintenance providers to keep these important assets operational.
Each of the 188 blades was retained by three locking pins.
Each of the 188 blades was retained by three locking pins.

45-day deadline

Just before the Christmas period a steam turbine located in a large coal-fired power station in Malaysia suffered an unexpected blade failure. The operator contacted the original equipment manufacturer (OEM) of the turbine with a requirement to have it operational within 45 days. In order to meet this very tight deadline, the power plant contracted Sulzer to carry out the removal and installation of the new blades, while the OEM sourced the new parts.

The OEM located a set of replacement blades and was able to provide two technicians. No further manpower, tools or equipment were available, and these would certainly be required if the project was to be completed in the timeframe expected by the power station.

Sulzer’s experts in the region are located in Indonesia and when the project was given the go-ahead, the team gathered the tools and equipment it would need and shipped them to the power station in Malaysia. Although a simple process in theory, there was a significant amount of planning and paperwork required to ensure the earliest possible start date. It was this ability to react so quickly to a situation that impressed the engineering team at the power station.

Expert planning

Traditionally a holiday period, late December was a challenging starting period for the project, but Sulzer’s engineers could rely on their considerable network to repair this important asset. Together with assistance from the logistics team, the field support engineers prepared everything they would need for the repair project.

Following the shutdown of the turbine, the onsite maintenance engineers conducted a preliminary inspection and determined that one of the low-pressure blades had sheared off at the root causing damage to a number of the other blades. Once the damage had been inspected, it was decided that the best course of action would be to replace the blades from both sides of the low-pressure disk.

The low-pressure blades in this 500 MW turbine are very large and use a multiple finger design of blade attachment – the fingers are located inside the disk and are held in place by three pins to lock the blade in position.

The removal of 188 blades and 564 pins was a precise and time-consuming process.
The removal of 188 blades and 564 pins was a precise and time-consuming process.

Specialist tooling

The repair project would require the removal of 564 pins to allow the 188 blades to be released. The pin removal process involved a special procedure developed by Sulzer's engineering department and used a heavy-duty powder-actuated construction gun capable of delivering sufficient force to dislodge the securing pins.

Throughout the de-blading process, the engineers examined the components for damage to ensure that the new blades could be installed without unexpected problems. In view of the type of failure and the age of the turbine, it was decided that all blades would be replaced on the disk.

The process of re-blading the rotor requires considerable expertise as each blade must be positioned, drilled and reamed to ensure an exact fit of the retaining pin. The centrifugal forces generated in the blades means that only a perfect fit will deliver continued reliable service.

Professional finish

The position, size and surface finish of the holes in the turbine blades are critical in the installation process and Sulzer’s engineers were fully equipped to complete the re-blading procedure. Once complete, the rotor was dynamically balanced, and the steam turbine reassembled before being returned to service.

In this case the customer, which has called on Sulzer many times in the past, was expecting the project to be completed within 45 days. Thanks to the coordinated plan and experienced engineers on site, Sulzer was able to complete the project in just 29 days.

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