Roller hearth furnaces are specifically designed for long product such as pipe, tube, and bar. Product is placed on the rolls in many fashions; tubes, pipes, and bars incorporate laydown tables and lift-and-carry mechanisms, while basket-loaded product is lifted onto base trays. Rolls are supported and driven externally to the furnace chamber, with roll-to-roll drive systems and roll bearing air cooling for reliable, long-term operation. Special run-in and run-out clutching minimizes gaps in loading when running long product, with sensors that allow gaps to be closed once the incoming load reaches a designated point in the furnace. Surface Combustion has references over 300 feet long and with widths up to 10 feet wide.

Furnaces can be provided in electric, direct-fired, and indirect gas-fired configurations to meet specific processing requirements. For products requiring an internal atmosphere, only indirect gas firing and electric heating may be used. Controlled atmospheres supported include RX® endothermic gas, DX® exothermic gas, Nitrogen, and Nitrogen-Methanol. Heating options include the Trident® radiant tube heating system, the Surface Electric Radiant Tube (ERT)® system, and the Prolectric®. Variable speed capability accommodates varying production and process requirements.

Higher temperature furnaces operate in a typical range of 1400°F to 2000°F using radiant/conduction heat transfer to the load. Lower temperature styles for tempering or stress relieving operate at 350°F to 1400°F and typically incorporate convection fans. Designs are available up to 2,200°F.

Charge and discharge vestibules with fast in/out functions, along with charge and discharge throats, minimize atmosphere and heat loss. Entry and exit vestibules and separation curtains, combined with techniques to individually adjust the vestibule height for the specific product, further reduce atmosphere usage. Atmosphere flow balance is engineered into the system design. Slow cooling zones use a combination of insulated and water-cooled walls and rolls to extract heat and minimize distortion. Static cool sections are available for bright work. A variety of cooling options can be provided based on processing requirements.

The furnace design can be configured with lengths and layouts to meet the customer’s needs. Typical widths are 3 to 6 feet, with up to 10-foot effective work width designs available. Production rates range from 4,000 to 33,000 lbs/hr for tube annealing and bright normalizing applications. Furnaces are provided at any overall length required.