Advanced Manufacturing and reverse engineering of Multi-Stage Steam Turbine Blade

A special-purpose, multi-stage condensing steam turbine in a refinery in Saudi Arabia failed during operation. Upon internal inspection of the compressor, it was found that one of the turbine blades was cracked and needed replacement.

This turbine is a multi-stage one, installed in 1978, and drives a Hydrocracker Unit (HCU) recycle gas compressor operating at 10,660 revolutions per minute (RPM). It is an unsparing compressor, and its failure would cause the entire hydrocracker unit to shut down.

During the repair process, a crack was found on one of the turbine blades. Reverse-engineering the blade was the best option due to the long lead time required to obtain a new bucket or rotor. To succeed in this project, a plan was laid out with all necessary actions, starting from scanning the blade to testing and verification.

The process began with 3D scanning the blade at the RE center, followed by creating a 3D model to obtain professional engineering drawings that could be provided to an in-Kingdom contractor for fabrication. The material used for fabrication was SS 410, a slightly higher-grade alloy than the original one, AISI 403.

For testing and verification, numerous tests were conducted on the fabricated turbine blade to ensure its mechanical properties were within acceptable limits. Non-destructive testing (NDT), magnetic particle inspection (MPI), hardness tests, radial and vertical clearance checks of the new blade inserted into the turbine wheel, and finally, a natural frequency test of the new blade were performed.