Careers HVTS® Prevents Boiler Tube Leaks at UK Waste-to-Energy Plant
Summary
A UK-based waste-to-energy facility operating two boiler lines was experiencing significant chlorine-induced corrosion in its boiler waterwall tubes. Non-destructive testing (NDT) revealed concerning tube thinning patterns in the third pass of both boiler units.
The facility’s maintenance team had established a detailed three-year maintenance plan but recognized the need for proactive measures to prevent unexpected tube leaks that could result in unplanned outages. This concern was heightened by similar corrosion issues previously encountered in an older boiler at another plant within their portfolio.
T24-26885
Potential Consequences of Boiler Tube Corrosion
If left unaddressed, the thinning waterwall tubes would have eventually failed, resulting in:
- Unexpected boiler shutdowns
- Emergency repair costs
- Loss of revenue from facility downtime
- Potential damage to adjacent equipment
- Disruption to scheduled maintenance activities
- Safety risks for personnel
The facility recognized that addressing the issue proactively during planned outages would be far more cost-effective than dealing with emergency repairs after failures occurred.
Solution Options Considered
The facility evaluated two primary solutions for protecting the tubes.
Option 1 – Weld Overlay
Pros:
- Established technology with a proven track record
- Relatively thick protective layer
- Familiar to many maintenance contractors
Cons:
- Time-consuming application process
- Simultaneous operations difficult — tubes must be filled with water, preventing concurrent panel replacement work by other contractors
- Can cause structural distortion
- Creates heat-affected zones and potential distortion, especially on division walls
- Longer outage times required for installation
Option 2 – High Velocity Thermal Spray (HVTS®)
Pros:
- Two to three times faster than weld overlay application
- No structural distortion of tubes
- No heat-affected zone
- Unlike other thermal spray processes, HVTS can be locally repaired, making it a true cladding rather than a typical thermal spray “coating”
- Bespoke alloy selection tailored to specific corrosion or erosion conditions
- Compatible with existing weld overlays, helping extend their service life
Cons:
- Requires specialized application equipment and expertise
- Relatively thinner protective layer compared to weld overlay
- Many vendors claim to offer thermal spray but deliver porous, non–corrosion-resistant coatings rather than true HVTS cladding
Selected Solution
After careful consideration, the facility selected High-Velocity Thermal Spray (HVTS®) cladding with IGS 5470 alloy to protect the identified at-risk areas. This NiCrMo-based alloy was specifically chosen for its exceptional resistance to chlorine attack and its proven ability to provide corrosion protection in the boiler’s high-temperature environment.
Implementation
The HVTS® cladding was applied to 62 square meters, covering the most vulnerable sections of the waterwall tubes in both boiler lines. The project was completed efficiently during a planned outage in October 2024, following the schedule below:
- Site mobilization: October 8, 2024
- HVTS cladding application: October 9–13, 2024
- Site cleanup and equipment breakdown: October 14, 2024
Results and Benefits
The HVTS® application was completed on schedule and without safety incidents, delivering measurable operational and financial advantages.
- Minimal Downtime
The rapid HVTS process enabled corrosion protection to be completed within the planned outage window, avoiding additional downtime costs. - Long-Term Reliability
The applied cladding is expected to provide durable protection against chlorine corrosion, preventing unexpected tube leaks between scheduled maintenance outages. It also extends the life of existing weld overlays and can be easily reapplied when required. - Comprehensive Protection
By targeting areas identified through NDT with reduced wall thickness, the facility proactively safeguarded critical assets before failures could occur. - Operational Efficiency
The HVTS application was non-intrusive, allowing other maintenance activities to proceed simultaneously during the outage. - Cost-Effective Solution
By mitigating future tube failures and avoiding unplanned shutdowns, the facility anticipates significant long-term cost savings over the lifespan of the protection system.
The facility will continue to monitor HVTS cladding performance through regular inspections during planned outages to ensure continued integrity and identify any new areas requiring protection.
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