Ceramic Fiber Heaters Improve Glass Annealing Conveyor Furnaces


Annealing stress out of glass light bulbs. A large furnace OEM had to develop a special glass-part annealing furnace. The part to be annealed was the small piece of glass tubing inside the base of the common household light bulb. A long, yet compact furnace chamber was needed to process thousands of these parts per hour. A special high watt density conveyor furnace was their recommendation to their customer.


The design and manufacturing flexibility, and the high temperature and excellent insulating properties of the standard ceramic fiber heater product line provided the answer to these requirements. To assist the furnace OEM in designing and sizing his system, Watlow engineering personnel conducted in-plant testing of different prototype configurations and power levels. The final design solution employed the standard embedded sinuated element configuration, but with an interesting and customized "twist." The single wide pass of the high watt density sinuated element was bent into the shallow "Vee." The element thus conformed to the grooves that the customer needed for good thermal uniformity and clearance around the glass part.

The OEM and his customer immediately put the new furnace into production-line service. The success of the furnace is evidenced by improved product quality and throughput.