Return Rolls

Return rolls are similar to hearth rolls in that tube dimensions and trunnion selection are the same. However, return rolls have an added supporting tube that contacts the belt.

Return rolls can be produced in two different ways. The first way has less upfront costs and consists of using two short tubes with tube supports at each end to support the center support roll. The second method uses a two-piece design where there is one center tube, which supports the larger supporting tube. The benefit of the two-piece design, while somewhat more expensive to produce initially, is that if either tube should be damaged (i.e. broken trunnion or distorted contact tube), the unit can be repaired at less expense than replacing the entire roll.

Return rolls should be used on any cast link belt in excess of forty eight inches wide and, of course, some forty eight inch belts are also returned on return rolls instead of skid tiles.

It is most preferable to synchronize return rolls with the hearth rolls so as to prevent excessive stress on the belt.

Synchronized Rolls
In the late 1990's a design of cast-link furnace was placed into service. This 54” wide furnace, in the following years, would prove to be the best of this type of equipment yet produced. The unique feature of this furnace was that the rolls, along with the drive drum, were synchronized to turn at the same rate (ft/min). This uniform velocity meant that the belt floated over the rolls; thus, any stress on the pins and links was at an absolute minimum.

The result of this engineering was a furnace that was able to heat-treat 225 million pounds with very little maintenance. When the first belt was removed from service, it was due to alloy attrition, not from excessive stretching or loss of pitch. Not only was belt life dramatically increased, but also the ability to control belt tracking was increased.

Many existing furnaces can be retro-fitted with synchronized rolls for the hearth and, in most cases, return rolls can be added in place of skid tiles or rails. The increase in belt life and lower operational maintenance of these upgraded furnaces more than warrant the costs of the rework.

Accuracy is critical in a synchronization project. Hearth and return rolls should be machined so as to maintain plus-or-minus ten thousandths of an inch total variation with each other. This is necessary to minimize any out-of-synch condition because any error will be multiplied by a factor of three. Thus, if tubes are used in “as-cast” condition with tolerance of one-sixteenth then the roll circumferences through out the hearth could vary by three sixteenths. Over a great number of furnace cycles, this is enough to substantially reduce belt life.

Sound complex?  It is to some degree. However, Omega will do this engineering for you at no cost when you purchase your belt and rolls from us.

Contact Us today with your heat resistant, high temperature, cast alloy return roll and furnace part needs. We have the staff to help you select the correct standard parts, or to engineer and then fully cast the high quality alloy parts for your specific application.

Omega Castings, Inc.
301 Fritz Keiper Blvd.
Battle Creek, MI 49037
Phone: 269-968-8105
Fax: 269-968-1661



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