Careers How A Plant Reduced CFB Boiler Tube Repairs From 500 To 0 with IGS SMARTGard®
Boiler Units and Wastage Mechanisms
This US City Hybrid Energy Center operates two 300-MW CFB boilers that burn a combination of coal mixed with up to 20% biomass.
CFB boiler waterwalls are exposed to aggressive erosion and erosion-corrosion. In high-wear areas, sacrificial cladding can be applied and periodically refurbished to absorb this damage before it reaches the pressure-retaining tube material. IGS HVTS® cladding helps preserve tube wall thickness and reduce the likelihood of tube leaks and associated repairs.
PROBLEM
Thermal spray cladding applied by a previous vendor experienced premature deterioration and did not provide the intended protection to the underlying tubes. After one year in service, approximately 500 tube repairs were required where the tube material had been exposed to erosion-corrosion.
SOLUTION
Following technical discussions and a mid-year inspection that established the extent of the damage, IGS was engaged to rehabilitate the affected areas and implement a longer-term tube-protection strategy.
IGS, the asset owner, a 3rd party expert and a mechanical contractor worked as a unit to create a mitigation plan for the vast damage caused by the failure of the other contractor’s thermal spray cladding. IGS’ SMARTGard® service which uses HVTS Alloy Cladding was first installed in 2016 during a major rehabilitation project.
In the first year after the IGS cladding was applied, tube repairs decreased from approximately 500 to five. No further tube repairs have been required in the protected areas since that time.
Inspection Identifies Significant Wear and Damage
Inspection of a previously applied protection is a critical part of any project. During the inspection, IGS utilized both visual and magnetic lift-off (MLO) techniques to record any low readings.
Areas that were below the minimum specification were noted and recorded. Large areas of the existing cladding had worn significantly. In many locations, the cladding had been fully consumed, exposing the underlying tubes and, in the most severe areas, allowing tube gouging to occur. The amount of defects observed was significantly greater than expected, with 500 tube repairs performed.
Working in Partnership
The asset owner and IGS worked closely to mitigate problems during 2016. IGS developed a two-year plan to stabilize the affected areas, apply sacrificial protection to additional high-wear locations and establish a predictable inspection and refurbishment program.
The plant made investments in solving the problems the correct way and addressing wear areas proactively from Day 1.
2015 Cladding Failure – Result of Multiple Contributing Factors
Improper Installation and Surface Preparation
- Inadequate preparation and incorrect application parameters led to localized spalling and delamination of the competitor’s coating.
Breakdown in Quality Control
- Failure to detect poor bond integrity.
- Overlooked areas where cladding did not meet required specifications.
- Missed sections where cladding was agreed to be applied but was omitted.
Insufficient Application Procedures
- Poorly executed tapered transitions.
- Inconsistent adherence to nominal thickness requirements.
- Tie-ins from one cladded section to an adjacent section.
Lack of End-User Alignment and Specification Management
- No clear expectations set regarding future refurbishment needs.
- Absence of a customized specification tailored to wear zones.
Rehabilitation Process in 2016
1. IGS surveyed and mapped the problem areas.
2. IGS, Client, and the 3rd Party agreed on a repair procedure to include: removal of failed cladding, repeat inspection to determine severity of tube damage, mechanical tube repair, install IGS cladding installation.
3. IGS completed removal of the failed cladding (by means of grit blasting).
4. IGS, Client, and the 3rd party expert completed detailed NDT, visual, inspections to document and determine correct mechanical repair process in each location.
5. Client’s mechanical contractor began tube repair process. IGS supported inspection efforts throughout to ensure tubes were repaired to agreed standards.
6. Following complete sign-off of all repairs, IGS installed new fit-for-purpose cladding system in all repaired areas.
Lessons Learned
When Thermal Spray Cladding Systems are not properly specified, installed, or quality controlled, the consequences extend beyond poor performance — they can introduce entirely new issues. In this case, the end user experienced near-total failure of a competitor’s cladding material, leading to extensive and severe tube damage. The result was significant unplanned spending on mechanical repairs and additional outage time to restore the system.
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