Look into hands-free lubing 

by Drew D. Troyer 

Single-point lubricators are an increasingly common sight in plants and factories.

A single-point lubricator is a storage device designed to slowly dispense lubricant (usually grease) into the bearing over a period of time. Such devices are usually mounted in the port that a Zerk fitting occupies. They may be driven mechanically, electrically, pneumatically or by a chemical reaction process. Typically, the user sets the dispense rate to meet the requirements of the bearing based upon its size, type, speed, orientation, etc.

Suppliers offer tables or formulas to estimate the dispense rate. Some even provide simple-to-use software. In a few cases, single-point lubricators are designed to feed lubricant to several bearings in parallel, so the single-point lubricator actually functions like a simple and small-scale centralized lubrication system. Some lubricators are refillable, others are disposable. You have a wide variety of choices.

When selected and used properly, single-point lubricators can be real plant problem-solvers. This column outlines four instances (applications and motivations) where single-point lubricators might be advisable.

Hard-to-reach bearings: Most plants have motors, pillow-block bearings or other lubricated components that you can’t easily or safely reach during operation. The interval between relubrication is often very long in these applications. This results in lubricant starvation and/or caking of expired lubricant thickener, which robs equipment life and undermines the plant’s reliability efforts.

Frequent relubrication applications: Sometimes, application and/or environmental conditions dictate more frequent relubrication. High dirt contamination levels, frequent equipment washdowns, high operating speed, vertical shaft position and high operating temperature are among the factors you must consider when determining the regrease interval. In these instances, it’s simply not practical to manually relubricate.

Increase reliability: Manual lubrication results in a sinusoidal cycle between under-lubrication and over-lubrication. Just after regreasing, the bearings are over-lubricated. Toward the end of the preventive maintenance interval, they may run dry. This cycle adversely affects bearing reliability. Likewise, manual grease guns can develop as much as 15,000 pounds per square inch of pressure. Used improperly, a grease gun is a “reliability assault weapon.”

Over-greasing forces grease into motor windings, causing overheating; damages shaft seals; and can push bearing shields into the bearing. Single-point lubricators don’t develop the pressure of a manual grease gun and they level the flow of volume into the bearing.

Reduce PMs: Most plants are “blessed” with more work than they can say grace over. Single-point lubricators, if selected and used properly, can reduce workload and free up the lubricant technicians’ time for other activities.

Like all devices and strategies, single-point lubricators aren’t perfect, nor are they suitable for all applications. One major drawback of these systems is that they aren’t typically equipped with a relay to shut down the lubricator when the machine stops. In fact, some of them can’t be shut down. So, while the machine may not work weekends, the single-point lubricator does, which can result in over-lubrication, or at the very least, a big mess.

The devices can also clog or become blocked if the bearing is caked up. It’s a good idea to inspect the lubricators to ensure that they are working and that the grease is actually dispensing. In some cases, the feed rate is a function of environmental conditions. The limitations vary by product type and activation mechanism. Be sure to carefully evaluate the options.

For some machines, the lube technicians’ monthly, bi-monthly or quarterly visit may be the only inspection it gets. Don’t allow single-point lubricators to lull you into a false sense of security. Nothing replaces a well-designed and timely machine inspection by a skilled technician.

Drew Troyer is the senior editor of Machinery Lubrication Magazine. If you have a lubrication or oil analysis question, contact Coach Troyer at 800-597-5460 or e-mail dtroyer@noria.com. 

This article appeared in the August/September 2003 issue of MRO Today magazine. Copyright 2003.

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