Food processing plants are brutal on bearings. Caustic foamers, hot water, chlorinated cleaners, steam. A greased bushing does not survive that routine for long, and worse, its grease can become a hiding place for bacteria. That is why design engineers keep turning to PTFE-lined composite bearings for conveyor drives, packaging lines, and filling machinery.

The regulatory backbone for this application is 21 CFR 177.1550, the FDA rule for perfluorocarbon resins. It covers PTFE homopolymers and copolymers used as articles or components of articles that contact food. The rule sets extractives limits: total extractives no more than 3.1 milligrams per square decimeter and fluoride extractives no more than 0.46 milligram per square decimeter. The USDA, which oversees meat and poultry processing, accepts PTFE resins that comply with this regulation for direct food contact. Dairy equipment adds another layer: 3-A Sanitary Standards and HACCP plans govern cleanability, while European plants look to EHEDG guidelines.

Self-lubricating construction solves a sanitation problem that greased bearings create. External lubricant collects dust, food fines, and process debris, and that mixture becomes an abrasive paste that grinds both the shaft and the bushing. A PTFE composite liner, by contrast, forms a microscopic transfer film on the shaft during the run-in phase. Friction then occurs between PTFE film and metal, not metal on metal. With no grease to trap soil, washdown cycles remove contaminants instead of spreading them. One-piece liners also eliminate the grooves and crevices where residue lodges and bacteria multiply.

The DU-style bearing in this series is a three-layer composite. A steel backing carries the load and gives the bushing press-fit rigidity. A sintered bronze interlayer conducts heat and anchors the overlay. The sliding surface is a PTFE and MoS2 composite that runs dry, with no lubrication program at all. Published ratings: static load capacity 140 N/mm2, dynamic load 60 N/mm2, and a PV limit of 3.6 N/mm2.m/s. The temperature window spans -195 to +280 degrees C, which comfortably covers hot-fill lines and freezer tunnels. Thin walls keep the design compact, and the low coefficient of friction prevents stick-slip on indexing conveyors.

Shaft finish matters more than most engineers expect. Industry guidance calls for a moderate finish in the 8 to 16 RMS range; mirror-polished and very rough surfaces both hurt film formation. In washdown areas, pair the bushing with 300-series stainless shafting, 316 grade where chloride-based caustics are used. Bearings with stainless or ceramic-coated shells offer FDA/USDA compliant options that weigh about one quarter of solid stainless assemblies. Keep housings aligned, because misalignment causes edge loading that concentrates pressure and accelerates liner wear. Allow for the higher thermal expansion of the PTFE layer in interference fits, and verify the specific compound, including any fillers, against the applicable regulation using the supplier declaration and migration test data.

Compliance is not automatic. The FDA does not approve finished bearing assemblies; it sets material standards, and the equipment designer carries the responsibility. Ask your bearing supplier for the grade certificate, the 21 CFR reference, and documented test results before you commit the part to a food line. Done properly, a DU PTFE bushing delivers years of maintenance-free service through thousands of washdown cycles.