Mill Upgrades Boiler Plant

by | Jun 5, 2024 | 2024, May/June 2024, New Technology, Sawmill, TimberWest Magazine

CAMPBELLSVILLE, KENTUCKY –  Steam production is a big deal for Cox Interior, which makes interior and exterior building products. The company has extensive lumber drying operations that require steam, and it also uses steam to heat its facilities and to produce electricity.

The company recently turned to Hurst Boiler & Welding Co. to make significant improvements to its aging boiler plant. The investment and upgrades are paying off in a number of ways.

Cox Interior manufactures interior and exterior home building supplies, including molding, solid hardwood doors, stair systems, and custom trim and millwork. The company’s sawmill and manufacturing facilities are located in Campbellsville, Kentucky, and it has warehouses and sales representatives in six states. Cox Interior has about 500 employees, including less than 400 who work in Campbellsville. Sales average more than $4 million per month.

The sawmill cuts all hardwoods. It can saw about 100,000 board feet of lumber each week. The company also buys some specialty lumber, such as mahogany.

Cox Interior also has 11 lumber kilns with a combined capacity of 1 million board feet to produce kiln-dried lumber products. It dries lumber for its own products and also dries material for a nearby cooperage that makes barrels for bourbon distillers.

It sells direct to contractors and homeowners – not to ‘big box’ home improvement stores or independent lumber yards. Marketing is achieved through the Internet, word of mouth, and the company’s sales force, with a sales office at each warehouse.

Using the mill residual wastes, the boiler plant provides steam to generate power, to heat company buildings, and to heat the lumber dry kilns. The company generates 71 percent of the power it needs in warm months and 50 percent in the winter months, when more steam is allocated for heat and lumber drying.

Cox Interior purchased two boilers in used condition from Armstrong Rubber Co. in 1992. Hurst Boiler provided controls and peripheral technology when the boilers were installed at Cox Interior. The boilers performed “pretty decently” since then, noted Shane Turner, manager of Cox Waste To Energy, a subsidiary. Turner manages the boiler and steam production operations. His duties extend to the lumber dry kilns as well as to the grinding equipment and operations.

Mill residuals provide about 60 percent of the wood fiber used to fuel the boilers; the company obtains more from other sources. “A lot of the mix is pallets hauled in from other companies,” said Turner. The company has two trailer-mounted horizontal grinders to reduce the scrap wood, a Morbark 4600XL and a Peterson 4700.

Turner had discussions with Hurst Boiler personnel and proposed the improvements to Cox Interior ownership. Owners and management considered the project as well as investing in a new boiler plant, evaluating and weighing the options for about two years before reaching a final decision. One of the biggest factors in the decision-making process was the cost differential between a new boiler plant and making improvements to the existing plant.

“It was an overdue improvement for the system, for sure,” said Turner. The old controls were outdated and obsolete.

Georgia-based Hurst Boiler & Welding Company has been designing, engineering, and servicing a complete line of solid fuel, solid waste, biomass, gas, coal, and oil-fired steam and hot water boilers since 1967. It is a custom manufacturer of engineered packaged boilers and boiler systems, biomass boiler systems, and integrated PLC-based boiler controls and accessories. The company also offers major repairs as well as service and preventative maintenance. (For more information, visit

Hurst Boiler provided upgrades to the furnace, controls, emissions equipment, and ash handling systems. The company also replaced a few fans as well as the insulating refractories throughout the entire boilers.

New desktop monitors at Cox Interior with boiler operational data. Behind them are the boiler plant’s old control panels. Hurst Boiler also can remotely monitor, adjust, and control the system.

“The control system fully integrates the operations of both boilers, deaerator, fuel storage, emissions and control valves, controlling loops downstream of the steam turbine,” said Cliff Hurst, domestic solid fuel sales manager for Hurst Boiler. “The induced draft fan, multi-cyclone collectors, refractory furnace liner, main ash drag chain, and dry ash conveyance systems also received updates as part of the upgrades.”

One of the previous induced draft fans, one of the most critical parts of a boiler, failed while the Hurst Boiler team was on-site, making the improvements. “That’s just one example that shows why the upgrades were needed,” observed Hurst.

One of the key improvements of the control system was a complete human-machine interface that is easy to learn and operate. “All essential data of the system is available from a few desktop monitors,” said Hurst. “Alarms, setpoints, adjustments, troubleshooting – all can be done from one location. We also have the ability to remotely monitor, adjust and control the system. This aids in troubleshooting issues with professional programmers and engineers available to support Cox Interior in real time.”

Hurst Boiler also built and installed an integrated control system modular control room that houses the equipment control panels and PLCs. These are displayed via an ethernet cable to the new desktop monitors within the existing control room. This enables Cox Interior to display the control screens without needing to accommodate the control panels in the general production area. This approach enabled Cox Interior to maintain ongoing operations on one of their two boilers for the duration of the plant upgrade.

“The control room was positioned so that it was a real challenge to incorporate the multi-cyclone collectors in a close proximity,” noted Hurst. “This approach ended up being a really nice solution.”

Hurst Boiler installed new air handling equipment: fly ash collectors, induced draft fans and exhaust stacks.

The upgrades improve the efficiency of the boiler plant. Better control of fuel and air mixtures in the boilers enable cleaner, more efficient combustion. Finally, the improvements also reduced power consumption because electrical motors operate on variable frequency drives at a set point rather than with on/off type controls.

The project took about six weeks. The upgrades, completed in December last year, cost about $2.5 million, according to Turner.

“They’ve worked out great so far,” said Turner.

Since the fuel burns cleaner and more efficiently, less is required – about 15 percent less. That translates into savings of about $15,000 per month.




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