Careers From Welding to Predictable CFB SMARTGard Boiler Maintenance since 2003
A power plant in Texas with 350MW capacity has two CFB boilers. The boilers were designed by a South Korean boiler manufacturer and have gone into service in 1990 and 1991. The boilers burn lignite fuel and the fluidized bed technology utilizes limestone injection to reduce nitrogen oxide and sulfur dioxide emissions.
The Challenge
Pressure parts, including the lower furnace zone refractory interface and the corners of the boiler suffered from erosion leading to tube metal thinning. The plant was using carbon steel weld buildup on their tubes at the refractory interface as an annual maintenance practice. Carbon steel buildup is a constant repair item as the bed ash is harder than the carbon steel weld buildup.
Weld Build Up
Hard surfacing also creates irregular bumpy patterns that set up little locations for eddy currents. These areas can experience gouging leading to severe rapid metal loss.
Problem
Tube metal erosion in the areas adjacent to the refractory. Repeated welding repairs led to unpredictable wear rates and the risks of tube leaks.
Solution
IGS’ SMARTGard® service applied HVTS alloy cladding on-site since 2003 to stop tube metal wastage and provide a predictable annual maintenance spend.
- Welding creates a bumpy surface
- Bumpy surface can cause gouging
- HVTS is smooth and wears uniformly and predictably
The plant is extremely satisfied with IGS as we get the job done on time and within budget with the highest quality. Our ability to match the cladding thickness with erosion rates has been a key factor to our success, as we are able to build the cladding up to 50 mils in the worst areas of the boilers.” The latest capacity factor for the plant is 98.7%.
– Paul Strauss, IGS Boiler Maintenance SME
Transition from Welding to SMARTGard HVTS
Large mechanical repair process during each outage can shift to a less labour-intensive thermal spray application.
| Welding and Pressure Part Replacement | HVTS |
|---|---|
| Design, welding approval and production time, heavy transportation to site | Light transportation to site |
| Potentially extended turnaround | Shortened turnaround |
| 5x men per shift | X men per shift |
| Bumpy surface (can cause gouging) | Smooth surface (uniform wear) |
| Unpredictable wear rates | Projected wear rates and predictable maintenance |
| Varied scope | Known scope |
| Boiler is the main driver for outage | Boiler is not the main driver for outage |
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