A major North American agricultural equipment manufacturer was looking for a better bearing solution for a fertilizer spreader shaft exposed to continuous rotation, abrasive granules, chemical attack, and regular washdown. The existing bronze sleeve bearing depended on grease, but in the field, lubrication was being washed away or contaminated. TriStar recommended a self-lubricating Rulon LR sleeve bearing to help reduce galling, eliminate the relube requirement, and extend service life in a tough rotating application.
When Bronze Depends on Grease
The application involved a spinner shaft driven by the tractor’s power take-off, or PTO, turning continuously at roughly 540 RPM while handling intermittent shock as material dropped onto the disc. The original bearing was an SAE 660 / C932 bearing-bronze sleeve, grease-lubricated on an approximately 50-hour relube interval.
That maintenance schedule was difficult to maintain during planting season. High-pressure washdown, fertilizer dust, and abrasive granules stripped and contaminated the grease film, allowing grit to grind between the shaft and bronze sleeve and accelerate galling and wear. As the bronze sleeve galled and wore, the shaft no longer ran true. Clearance increased from a design value near 0.003" toward 0.020" and beyond, leading to shaft runout, disc imbalance, and reduced reliability.
Why Rulon® LR Made Sense
Rulon LR was a strong fit because it is a chemically resistant, self-lubricating filled-PTFE material designed for sleeve bearing service in rotating applications. Rated up to 10,000 PV, and higher in intermittent duty, it provided ample headroom for the spinner shaft’s pressure-times-surface-speed demands.
Because Rulon LR carries its own lubrication, there is no grease film to wash out and no grease to trap grit. It also helps reduce startup stick-slip, and its coefficient of friction drops as load and speed increase. Against a hardened steel shaft, Rulon wear decreases as mating-surface hardness increases, with Rc 35+ considered ideal.
Built for Fertilizer, Washdown, and Grit
The material was also a strong fit for the surrounding environment. Rulon LR offers chemical resistance to common fertilizer materials such as ammonium nitrate, urea, and potash, along with exposure to wash water. It also maintains dimensional stability across a wide temperature range, from cryogenic conditions up to approximately +500°F.
For this manufacturer, the bearing solution did not require a redesign. TriStar matched the existing SAE 660 sleeve envelope, allowing a press-fit Rulon LR bushing to drop into the current housing without changes to the shaft, bore, or assembly.
A Practical Path for New Builds and Refurbs
As the exclusive North American distributor for Saint-Gobain’s Rulon line, TriStar supplied genuine, lot-traceable Rulon LR material from inventory to help keep the build schedule on track. The same drop-in approach can also support aftermarket replacement and refurbishment programs, not just new equipment production.
The result was a self-lubricating Rulon® LR sleeve bearing that eliminated the relube interval, held bore clearance through a full season of washdown and grit, and is projected to turn a per-season wear part into a multi-season component.
A Broader Fix for Dirty Rotating Applications
This same engineering approach can be applied to rotary metering valves, sprayer rotary unions, agitator shafts, and other rotating equipment exposed to contamination, chemicals, or difficult maintenance schedules. If you have an application where self-lubricating bearing materials could make a difference, reach out to our experts to start the conversation.
Agriculture: An Industry Overview
