Lubrication Checkup: Single-Point Lubricators

By Ken Bannister, Contributing Editor

Symptom:  

“We’ve begun using a variety of single-point lubricators for remote plant bearings on HVAC rooftop units, cranes, conveyor drives, etc. While our bearing failure rate has decreased drastically, we still experience failures. Is that normal for this type of automated lubricator?”

Diagnosis: 

Automatic single-point lubrication (SPL) devices are relatively inexpensive, compact and easy to operate when engineered and set up correctly. They can continuously deliver full-film lubrication to single or multiple bearing points for up to two years on one lubricant charge. There are four major SPL types:

1. Mechanical: Grease-gun-filled and reusable, spring-actuated; relies on atmospheric and system backpressure to slow lubricant release.

2. Chemical: Pre-filled single-use; employs a chemical reaction to generate expandable gas acting on a flexible diaphragm to push the lubricant into the bearing; once invoked, can’t be stopped or influenced until all lubricant is discharged. 

3. Electro-Chemical: Pre-filled single-use; employs a battery-operated programmable timer that sends an electrical charge into an electrolyte to produce an inert expandable gas that acts against an expandable bellows to push out lubricant.

4.Electro-Mechanical: Battery-operated, motor-driven device attached to a small positive-displacement piston pump; fully controllable and refillable; higher discharge pressure allows coupling to “splitter” devices and lubrication of numerous points simultaneously with one pump.

Each type demands different set-up and maintenance procedures. Their success relies on the user understanding exactly how to install and operate the chosen type, compensating for ambient condition factors and performing regular preventive checks while the SPL is in operation. Lack of discipline in this area can easily lead to incorrect use and bearing failure.

A second reason for bearing failure can be attributed to use of the wrong grease. Many SPLs come pre-filled with a specified lubricant that can easily be mixed and/or mismatched when units are taken from inventory. Be careful.

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Prescription: 

Keep your approach toward SPLs simple and consistent: Choose a design that best suits the application and use only that type of lubricator. Closely read and follow the OEM’s instructions for setting up, operating and maintaining the unit. Then train all staff on its use. Good luck! MT

Lube questions? Ask Dr. Lube, aka Ken Bannister, author of the book Lubrication for Industry and the Lubrication section of the 28th edition Machinery’s Handbook. He’s also a Contributing Editor for Maintenance Technology and Lubrication Management & Technology. E-mail: doctorlube@atpnetwork.com.