Graphite Alloy Bearing in Restaurant Oven

• reduces maintenance
• eliminates expensive food-grade lubricants

Restaurant warming ovens designed to keep chickens warm can require frequent maintenance. These ovens are produced specially by Julien Industries for a large Canadian restaurant chain. The oven is not designed for cooking the chickens, but rather keeping them warm prior to serving while displaying them in an attractive manner to the restaurant patrons. The oven is about 5 ft wide by 6 ft high by 3 ft deep and has a single spit, with branches to hold the chickens, driven by a sprocket attached by a chain to an electric motor. Appearance is critical as the oven is designed to function as a point-of-purchase display. This makes it critical to hide the bearings and other aspects of the mechanism. This requirement introduces complexities that make it difficult to relocate them to a cooler area in the oven. The ball bearings that were originally specified for this application needed to be lubricated every two weeks because the 450°F temperatures broke down the lubricants.

Failure to lubricate traditional bearings can cause bearing failures and calls to the service department. Additionally, one of the challenging aspects of this application is that its sanitary food environment precludes the use of normal greases — instead, it requires an expensive, vegetable-oil-based lubricant that is hard to find and difficult to apply. The obstacles encountered in obtaining and applying the right lubricant — not to mention the annoyance of performing regular maintenance in a busy restaurant — means that these tasks are often neglected. The result is that a significant number of bearings fail in the field. Julien service engineers promptly replace bearings when this happens to avoid a disruption of service to the restaurant’s customers. This situation in turn creates a burden on the field service team, which has spent considerable time on this single issue.

Pierre Olivier Roy, research and development engineer for Julien, investigated high temperature greases, but was unable to find any that would meet the company’s performance requirements while still satisfying food service specifications. He also tried redesigning the oven to reduce the heat on the bearings; he found that even a major redesign that relocated the bearings outside the heated portion of the oven even yet produced too much heat transfer via the driving shaft. And the redesign could not be retrofitted into existing ovens.

Internet research yielded a high temperature graphite-metal alloy bearing material from Graphite Metallizing corp. Graphalloy is graphite filled with a metal impregnant to enhance the chemical, mechanical and tribological properties of the material.

By replacing the bearings on new and existing ovens with Graphalloy 845 series insert bearings, Roy’s team eliminated the need for maintenance. Based on experience to date, Julien expects that the new bearings will last about 10 years —approximately 20 times the life of the previous ball bearings.