Mining & Minerals

Industrial Access performed partial gunite liner replacement on a steel boiler stack. The existing liner was in poor condition with severe spalling and interior plate exposed to flue gas. Industrial Access provided deteriorated liner demolition and new refractory installation services utilizing custom-engineered access methods to fit the client’s needs and maximize the structure’s longevity.

A mining facility in the Upper Midwest was in need of interior repair services for their 238’ tall steel boiler stack. The top half of the stack interior liner was in poor condition with severe spalling and deterioration of the refractory. Failed, crumbling gunite rendered the steel plates exposed, and some areas were hollow when sounded. The interior of steel smokestacks such as boilers are continuously exposed to the acidic, corrosive flue gas, which makes regular protective liner refractory inspection and maintenance incredibly important.

Industrial Access (IA) team designed and built a custom motorized work platform to provide technicians with the full-height boiler interior wall access. A temporary steel framing was assembled at grade and installed at the top of the stack to support the platform as well as other work machinery. Two access doors—one at the base and one in the middle section of the stack—were installed to facilitate the access strategy as well as efficient debris removal.

To start off the repair process, the two necessary access doors were cut out and installed with reinforcement while existing access ports were opened. Some accumulated debris was already present at the bottom of the stack, so IA cleared it out. In order to enable the access steel framing installation on top of the stack, the top cone section had to be temporarily removed. Once the access system was established, liner replacement could begin.

It had been decided that the liner above 90’ el. would be replaced entirely due to its severe degradation (the rest of the liner was still in relatively fair condition). First, the existing degraded gunite refractory was demolished across the majority of stack interior. IA used innovative tools and machinery to accomplish efficient gunite removal. Once the liner was demolished, the steel plate surface was thoroughly cleaned by removing present oxidation and the existing anchors were prepped for new refractory installation. Then, the chemical-resistant castable gunite layer was applied in 2”-4” thickness.

The top cone underwent liner replacement process as well. Existing refractory was removed, new steel horn anchors were installed, and a fresh gunite liner was applied. Before the gunite application, the cone was reinstalled back on top of the boiler. To complete IA’s work on this site, all temporary rigging was removed, the debris was cleaned out, and temporary access door at base as well as open access ports were sealed off with plates.

The installation of the new refractory system was completed successfully and on time. This repair will help ensure the longevity of the structure and maximize its operational efficiency. It is important to protect the steel plate of smokestacks from their harsh interior environment in order to preserve their structural integrity and safety. Performing regular inspections and timely maintenance on steel stacks and their liners will help identify signs of deterioration early and take preventive measures before extensive damage occurs.