Western Machine Works


turbine Refurbishing – Hydro Headcover and Bottom Ring

A 1917 hydropower plant facility in the Pacific Northwest was undergoing major turbine refurbishment work. Our team worked closely with the customer to determine the best repair option for the headcover and bottom ring.  Given the technical requirements and the turnaround time, our thermal spray process using 420 stainless steel coating material was chosen as the most applicable repair option. Read more details below.


  • Part: Headcover and bottom ring
  • Details: 55″ dia. and 20″ thick
  • Customer: Hydroelectric utility


  • Temporary plugs had to be manufactured to maintain the integrity of the wicket gate bores during the metallization process.
  • Additional surface prep and cleanup were required to remove oil leakage from the original castings. This was a critical step to ensure that the thermal spray coating would adhere to the surface.

Engineered Solutions:

  • Technical inspection prior to machining.
  • Setup in vertical boring mill and verify dimensions.
  • Mask all surfaces and prep for spray.
  • Thermal spray of critical surfaces using 420 stainless steel coating.
  • Finish machine to 64 RMS surface finish and +/- .005″ tolerance.
  • QC inspection and final report.
  • Prep for shipping. 


  • All OEM specifications were achieved.
  • Completed all machining within the outage schedule.
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