A Texas-based power plant was suffering boiler erosion, HVTS cladding has helped reduce downtime and costs.
A Texas based 350MW capacity power plant based and customer of IGS had begun to have problems with two of its boilers. Built by a South Korean boiler manufacturer in 1990 and 1991, the boiler burn lignite fuel then use limestone injection to reduce nitrogen oxide and sulphur dioxide emissions.
Unfortunately, the parts of the boiler most under pressure, including the lower furnace zone refractory interface and the boiler corners, have eroded leading to tube metal thinning. The plant was originally using carbon steel weld build up on the tubes at the refractory interface as an annual maintenance practice but this led to hard surfacing creating irregular bumpy patterns that set up little locations for eddy currents within the boilers leading to gouging and rapid metal loss.
The solution
Each boiler is on a two-year maintenance cycle and critical and maintenance and repair specialists IGS first began adding HVTS alloy cladding to the units in 2003. Over the past few years IGS has raised the HVTS protection at the refractory interface on the east and west walls along with applying the cladding around the cyclone inlet.
This protection has helped reduce the need for constant mechanical work since the hardness of HVTS exceeds the hardness of the bed ash. As a result, the plant has been able to move to two-year outage cycles for the boilers, taking one down every other year.
Paul Strauss, a boiler maintenance expert at IGS said: “The plant is satisfied with our work since we get the job done on time, within budget and to a high standard. That we are able to match the cladding thickness with erosion rates has been key to our success. as we are able to make the cladding as thick as 50 mils in the worst areas of the boilers.”
Welding to HVTS
An extensive mechanical repair process during each outage was moved to a less labour-intensive thermal spray application.
Welding and pressure part replacement required heavy transportation to the site, extensive turn around and as many as five men per shift, as well as unpredictable wear rates compared with the HVTS system which is not heavy to transport, has a shorter turnaround time, does not require extensive manpower and has projected wear rates and predictable maintenance.
Execution
IGS delivered an engineering package as part of the project – this included the project plan, a method statement, an inspection test plan, a project safety analysis, a risk mitigation plan and the job specific safety data sheets.
