Maintenance concerns in the 501F gas turbine

Sulzer Turbo Services has identified the following maintenance concerns in the 501F gas turbine.

The size and weight of a large turbine like the 501F places particular demands on any maintenance provider. Disassembly, inspection, repair, balancing and reassembly operations all require large and highly specialized equipment.

The overhaul work scope on a machine as large and complex as the 501F is determined by the customer’s requirements and the operating history of the equipment. Typically, a service will begin with disassembly and inspection of the full rotor unit followed by cleaning, non-destructive testing (NDT) and life-cycle assessment.

A common issue in the 501F is wear or failure of the anti-rotation tabs that hold the air baffles in place. The failures cause the baffles to fret, wear or even break away completely, resulting in severe damage to the turbine.

In cases of failure at the forward end of the compressor through-bolt on the 501F, severe damage can occur to the machine caused by the passage of the liberated fastener. Analysis of the failed parts suggests that the issue is most likely the result of loading on the last full thread of the fastener, combined with insufficient loaded surface area between the fastener and hub to mitigate movement. This allows a crack at the end of the bolt to propagate during operation.

In the 501F, a frequent cause of vane failure stems from problems with the flow of cooling air. This can result in the loss of the necessary air dam at the leading edge of the vane, or insufficient flow through the pin hole channels leading to the trailing edge.

Sulzer has developed a range of solutions to address these problems.