This case study gives an overview of how Rocksavage Power Station experienced a failure of one of their IP intercept control valves due to delaminated Stellite overlay during outage recommissioning procedures. Rocksavage had been given a lead time of 8 months by the OEM for replacement components and needed help to meet their generation commitments.
SpiralWeld™ implemented our ReManufacture+ service which repaired the IP control valve in 4 weeks to the original manufactured dimensions and improved the component by replacing the Stellite® with hard-facing overlays.
Whilst backing out of their 2015 maintenance outage, Rocksavage engineering and production staff noticed that the right hand IP intercept control valve was not responding to control inputs. Subsequent inspection found the Stellite® overlays had delaminated from the substrate and collected “downstream” of the strainer basket.
Rocksavage were offered new components by the OEM outage contractor with a lead time of 8 months! This was obviously not a reasonable option, as until a new component was sourced generation could not take place, which meant heavy financial losses. The OEM outage contractor had run out of acceptable options; Rocksavage needed a better solution and approached SpiralWeld™
Solving the Problem
The SpiralWeld™ team responded with a plan to ReManufacture the control valve spindle and bonnet assemblies:
- Remove pilot valve seat from the bell type valve body.
- Remove the valve spindle.
- Remove all failed “Stellite®” overlays from the bell type valve body.
- SpiralWeld™ ReManufacture+ with SpiralWeld™ Ultimet® alloy overlays.
- Bell type valve body – seat upgrade with Ultimet® alloy overlays.
- Recovery of pilot seat with equivalent consumables.
- Reassembly of the bell type valve body and pilot seat with a new spindle.
- Full recovery of the bonnet guide and labyrinth bores with equivalent consumables followed by Post Weld Heat Treatment.
Spiral Welds 27 years of experience in Mission Critical Component ReManufacture for the power industry, allowed us to mitigate the risk of “Stellite” delamination downstream of the steam strainer. SpiralWeld™ have successfully introduced hard-facing overlays and cladding with advanced high Cobalt/Chromium alloy consumables that do not crack or delaminate in service whilst providing superior resistance to erosion, wear, galling and corrosion.
The delaminated overlays to these components were replaced with SpiralWeld™ advanced high Cobalt/Chromium alloy alternative.
A successful outcome
SpiralWeld™ successfully completed works on this intercept control valve in 4 weeks. To put this into context the OEM had originally quoted Rocksavage 8 months lead time to manufacture replacement parts.
SpiralWeld™ saved Rocksavage embarrassing generation losses by returning these components to service in 4 weeks, with less risk to turbine plant and extended mean time to failure.
This what our client had to say:
“SpiralWeld™ are one of only a very few companies worldwide with the knowhow and procedures to confidently recover these mission critical components within this time frame”
“The total project spend was very cost effective in comparison to the other options available to us”
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