The squeaky wheel gets the oil. We know this means giving someone what he or she wants just to keep them quiet and stop their complaints. In manufacturing circles, the squeaky wheel is saying something too: take care of me, please. Maintain me, and I’ll do my job.
Last month, we talked about why it’s important to shut a system down before beginning any maintenance work. This month, we’ll take a look at maintenance for the compressor drive and motor. Proper upkeep and attention can keep the machine operating efficiently and effectively.
There are three basic types of drives for air compressors: V-belt, direct and gear (a fourth type is a combination of any of the above with a variable speed motor). Their basic characteristics are:
- V-belt drives allow a smaller footprint for the enclosure, the alignment is not critical and maintenance is relatively simple.
- Direct drives have alignment built-in; belt and gear maintenance are eliminated, and the footprint may be larger but the machine typically is quieter.
- Gear-driven elements eliminate alignment problems and are usually best suited for higher horsepower uses. As with V-belts, compressor speed can be different from motor speed.
- Variable-speed drives (VSD) usually alter the frequency of the incoming motor power; this approach is a simple way to vary compressor output and can be efficient when the element has a wide efficiency range or a flat efficiency curve over a wide speed range.
A compressor drive is only as good as the motor that powers it. A poorly maintained electric motor uses more energy and also won’t last as long as those that are properly maintained. The two most important aspects of motor maintenance are lubrication and cleaning.
Lubrication – Too much lubrication can be just as harmful as too little lubrication; both situations can contribute to premature motor failure. Motors should always be lubricated according to the manufacturer’s specifications. Depending on annual hours of operation and motor speed, this is usually around every two to 18 months. For motors with bearing grease fittings, the first step in lubrication is to clean the grease fitting and remove the drain plug. High-quality, new grease should be added, and the motor should be run for about an hour before the drain plug is replaced. This allows excess grease to be purged from the motor without dripping on the windings, which can damage them.
Cleaning – Since motors need to dispel heat, it is important to keep all of the air passages clean and free from any obstructions. For enclosed motors, it’s critical that cooling fins are kept free of debris. Their clean surface area is how the motor disperses the heat from friction and operation. Poor motor cooling will increase temperatures and create winding resistance, which shortens motor life while increasing energy consumption.
Belts – Motor belt drives also require periodic maintenance. Just like lubrication, there’s a line between too much and not enough. Tight belts can lead to excessive bearing wear; loose belts can slip and waste energy. Belts will stretch and wear with normal operation. A periodic inspection and adjustment will ensure tension remains in that sweet spot. A good rule-of-thumb is to examine and adjust belts after every 400 hours of operation.
Making time for regular review and your machine’s will reward you with long-lasting and efficient performance. Don’t get overwhelmed or intimidated. All it takes is following instructions and recommendations provided by the manufacturer and regular reminders to review performance, monitoring for consistency or dramatic changes.
5 min
