MRO Today - Air line lubrication

Air line lubrication
Correct oil usage maximizes the performance and life of your pneumatic tools

Pneumatic tools, hoists and motors are used every day in a wide variety of applications and industries. Keeping these tools running at peak performance requires attention to lubrication in the airline.

The primary cause for repair of pneumatic tools is improper airline lubrication. Pneumatic tools require clean, dry, lubricated air at the right compression. Failure to provide these basic needs for your tools can result in:
— Reduced performance (speed, torque)
— Shorter blade life
— Excessive wear on the gear package
— Inconsistent torque output
— More frequent tool service
— Shorter motor life

Compressed air fed into a pneumatic tool pushes the blades, causing the rotor to rotate and generate torque output. Lubrication in the air helps the blades rotate easily by reducing friction. It creates a seal within the motor chamber to maximize efficiency.

Lubrication also performs a cooling function, which is very important when you consider most pneumatic motor vanes or blades are made of composite materials that are susceptible to heat damage.

Airline lubrication is often the most overlooked area in a plant’s tool maintenance program. Ironically, it can be one of the most important.

Airline filter-lubricators are a necessity for long life and maximum performance from hand tools, hoists and motors.

Oil injected in the tool and reconnected to the airline lasts three to 10 minutes while the tool is running. The higher the tool’s speed, the faster the blades heat, evaporate the oil and run dry.

Some blades travel up to a mile a minute (more than 88 feet per second). Centrifugal force gives even a small blade a weight equal to five or six pounds.

The heat generated in a substandard oil environment causes blades to dry out, become brittle and chip. The chips and blade dust can clog the muffler, or break blades and cause motor failure.

Type and weight of lubricant
When considering lubrication maintenance programs, give special attention to the type, weight and amount of oil.

Motor oil, 3-in-1 oil and other penetrating oils are not acceptable substitutions for an airline lubricant approved and recommended by the tool manufacturer. Airline lubricant is designed to lubricate and cool tools, and blow through without creating buildup.

Inappropriate oil leaves deposits inside the tool — on the blades, cylinder or end plates. These deposits accumulate over time and drag on the blades, causing the tool to work harder, produce less torque and run at a lower rpm. The buildup eventually gums up the motor and burns up the blades.

Repairing this problem takes the tool off the line and out of service. To avoid downtime, emphasize proper use of an airline lubricant that is recommended and approved for your specific tools.

For a specialized application, consult the tool manufacturer for assistance in selecting the proper lubricant. Some hoists used in the food processing industry use oil approved by the USDA as a lubricant.

Amount of lubricant
Excessive lubricant blows through the tool as exhaust. If the lubricant is the correct weight, too much lubricant won’t hurt the tool or its performance, but it is still inappropriate.

Too little lubricant burns up blades and causes the blades to become brittle and chip. Dry blades can heat, stick, and break or wear out in 20 hours of operation or less. Properly lubricated blades can withstand more than 2,000 hours of operation.

Most manufacturers suggest four drops of lubricant per minute of continuous use. Tool manufacturers provide specifications for exact requirements.

One of the best ways to test for sufficient lubrication is to hold a piece of hard-finish white paper at the exhaust for one minute. Lubrication is not sufficient if there is an absence of oil marks on the paper. Airline lubricant is excessive if oil drips and runs off the paper.

Other important considerations
There are alternatives to traditional tools that require airline lubricants. Some manufacturers offer tools with lower lubricant requirements. Some offer an “oil-free” line of tools, requiring only one drop of lubricant per minute. Such manufacturers also offer an oil-free line of pulse tools that require no airline lubricant.

Standard airline filters do not remove all water from an airline. When water is visible in the filter at the individual tool, consider a dryer at the compressor to protect the tool, motor or hoist from rust and early failure. Types of dryers include refrigeration, coalescing or desiccant.

Always keep the air supply dry and clean. Blow out hoses, drain moisture sumps, and install and maintain airline filters and lubricators.

While lubrication is a crucial consideration for any pneumatic tool, hoist or motor, the problems discussed in this article are compounded in tools that run at high speeds with no governor.

Simple routine maintenance on airlines ensures longer tool life, more time between routine services, less tool breakdown and more consistent tool performance. That translates into less downtime and increased productivity for the user.

Article provided by Cooper Power Tools.

This article appeared in the June/July 1999 issue of MRO Today magazine. Copyright, 1999.