Conventional car-bottom furnaces loaded manually with overhead cranes and forklifts are still the norm in the heat-treating and forging industries. This article will examine a new, patent-pending, technologically advanced furnace that can be better integrated into plant systems.

While there has been a significant gain in energy efficiency, process controls and instrumentation over the last few decades, the way products are handled in and out of these types of furnaces has not changed. The benefits of this new furnace are fewer man hours/WIP, less floor space, increased work flow and plant layout flexibility, avoiding double handling, and increased safety and profitability.

Conventional Systems are Tied to Rails

Car-bottom or bogie-hearth furnaces are robust mainstays of most heat-treat and forging operations. These batch systems are used primarily because of their simplicity and load flexibility. The moving car allows manufacturers to load product of variable size, shape and weight into the furnace in a simple in-and-out motion along the car rails.It is this simplicity that can create restrictions.

Plant layouts revolve around accessibility to an overhead crane, long rail turning radii, complicated cross transfers and the space needed for forklift access. Multiple stations (staging, loading/unloading, quenching, cooling, etc.) are required to complete the processing cycle. The furnace cars, whether self-driven or pushed/pulled, are bound to steel rails with traditional flanged railcar wheel systems to keep them on their tracks.

Mobi-Hearth^™ Furnaces for Heat Treatment and Forge Heating

But what if it was the hearth that moved within the heat-treatment cell and beyond, not just station to station? A new approach to material handling can reduce the costly multiple handling of work in process. The Mobi-Hearth™ furnace system is comprised of three main components: the static furnace body; the Mobi-Hearth (steel skid with insulated top); and a manually or automatically controlled transporter car (AGV). The system can be seen in Figure 2.

The Mobi-Hearth has no wheels or moving parts and instead relies on the transporter for motion. The transporter is not “leashed” to any particular furnace or processing station. The system is designed in such a way that once the furnace loading operation is complete, the transporter can move on to its next routine. Thishas been developed to reject the convention of rail-bound cars and their travel being limited to the length and direction of the rail system installed in tandem with the furnace. The transporter also allows movement from bay to bay and building to building, making plant layouts much more flexible and avoiding multiple loading and unloading.

Proven technology has allowed the development of a furnace system where the manufacturing floor becomes an open area, allowing many different arrangements in layout and full 360 degrees of hearth movement. The AGV’s capability in a forward, sideways and diagonal motion and its ability to rotate about its center drastically enhances plant layout and future flexibility.

System Benefits

This new system can realize major cost benefits to the user because it is the simple Mobi-Hearth that moves in and out of the furnace rather than a more-complex, wheeled car. Capital material costs of the system are the same as traditional railcar systems where two or more furnaces are required, although there are operational savings due to reduced product handling. As the number of furnaces increases to three or more, the savings increase incrementally. One AGV replaces several furnace cars and a lateral transfer car.

Load staging is another way that heat-treat and forge shops can take further advantage of the cost savings over a traditional car-bottom furnace system. The product can be directly loaded onto the Mobi-Hearth in a staging area located nearby or in a more remote location. The transporter then moves these pre-loaded pallets directly into the furnace. Setup time and in-process handling are significantly reduced. Furnace optimization improves since one does not have to wait for a car to be unloaded before another load can be charged.

The system (Mobi-Hearth and transporter)provides flexibility in plant layouts and changes since no rails or dedicated car bottoms are used.The Mobi-Hearths are interchangeable and can be loaded into multiple furnaces. Since the transporter only requires a solid floor and a guidance system for its operation, multiple stations (loading, furnaces, quenches, cooling, etc.) can be serviced with a single transporter. This provides significant initial equipment savings and ongoing maintenance savings because it is not necessary to have a dedicated track and car system for each furnace.

Other benefits include the ability to integrate the furnace system into the space available. The “trackless” system broadens the opportunity to integrate a furnace system of this nature in areas where traditional car-bottom furnace placement is not possible. In an existing heat-treatment system, the Mobi-Hearths can be transferred to an existing quench tank and reached via overhead crane or dedicated transfer device integrated into the quench system.

Reduced Expansion Costs

Once the investment in the system has been made, furnaces can be added as required without the need for costly concrete work typically associated with traditional car-bottom-type furnace systems. Future capacity can be added in areas where space is available.

Flexibility, Consistency and Safety

The systems are flexible, and schemes exist to allow different furnace dimensions while still incorporating the same transporter system. Transfer times to quench are consistent and can be fully automated to ensure metallurgical properties from batch to batch are consistent and repeatable. The systems can be fully automated, which reduces tow-motor traffic within a plant. Since loading/unloading is no longer on a car in front of the furnace, one can utilize dedicated loading/unload areas with safety systems incorporated to guard against interference from auxiliary equipment.

Servicing

Maintenance of the Mobi-Hearths themselves is minimal. Servicing and lubrication of the transporter can be done in a remote location, thereby ensuring that the maintenance is performed away from tow-motor and overhead crane traffic.

Level II Automation

In many cases, the days of stand-alone furnace operating systems in a customer’s facility are a thing of the past. Increasingly, customers want Level II automation systems that have the capability for recipe control, part tracking, process history, scheduling, and alarm and maintenance notifications. In addition, many customers are asking for Level II automation systems to be interfaced with their plant-wide management systems. These systems in conjunction with the ability of the Mobi-Hearth to stage loads and automatically transfer them to the furnace allow the end-user to optimize their facility, which increases throughput and minimizes the time between heat-treat or forge-heating loads.

Conclusion

The Mobi-Hearth furnace system can be a solution to several very specific problems experienced in existing plant processes. A new approach to expansion projects incorporating this system will save time and money while offering the added benefit of employee safety. All of this is achieved without stepping too far away from the systems that have proven reliable for many years.

For more information:Contact Joe Saliba, sales manager, CAN-ENG Furnaces International Limited, 6800 Montrose Road, P.O. Box 628 Niagara Falls, Ontario Canada L2E 6V5; tel: 905-356-1327; fax: 905-356-1817; e-mail: jsaliba@can-eng.com; web: www.can-eng.com