The Secret to Smooth-Running Pneumatic Tools
Air tools, also known as pneumatic tools, are a class of power tools driven by compressed air supplied by an air compressor. These versatile tools come in a wide variety of shapes and sizes — from small hand-held devices to jackhammers (paving breakers) and large, rig-mounted equipment used in mining and quarrying.
In the tooling industry, general-grade air tools are relatively inexpensive, have shorter lifespans, and are often viewed as “disposable.” In contrast, industrial-grade pneumatic tools are among the toughest and most durable power tools available. Yet, even these can experience premature failure. To understand why, it’s important to first consider how pneumatic tools operate.
How Pneumatic Tools Work
An air compressor forms the heart of any pneumatic system, converting ordinary air into compressed air. This compressed air travels through a flexible hose to the actuator at the business end of the system. The actuator then converts this potential energy back into kinetic energy, producing useful mechanical work.
Actuators either move back and forth (reciprocating action) or rotate. For example:
• Percussion tools like jackhammers use piston-type actuators.
• Rotary tools such as air drills and grinders use geared or turbine motors.
What Causes Air Tool Failure?
Despite their rugged construction, many pneumatic tools fail before their time due to poor maintenance and operating conditions. The two primary culprits are dirty air and moisture:
• Contaminants like grinding dust can infiltrate the actuator and cause abrasive wear.
• Moisture promotes rust within the tool, especially if wet air is introduced into the system.
To combat this, it’s crucial to fit an airline filter and water trap between the compressor and the tool. This removes impurities and most of the moisture from the air supply — although achieving completely dry air isn’t always practical.
The Role of Lubrication
Just like engines, the moving parts inside pneumatic tools require consistent lubrication to prevent wear and ensure smooth operation. However, air tools lack a built-in oil sump, so lubrication must be delivered via the compressed air.
This is where airline lubricators come in. These devices inject a fine oil mist into the airstream, lubricating valves, cylinders, and motors, helping the tool operate efficiently and extending its service life.
Correct positioning of the lubricator is important, as is the oil quantity:
• Too little oil leads to excessive wear and early failure.
• Too much oil is wasteful and can contaminate the workspace, carried out with the tool’s exhaust air.
How Airline Lubricators Work
A typical airline lubricator features an oil reservoir that feeds lubricant into the moving airstream. As compressed air flows through a venturi inside the lubricator, it draws oil from the reservoir through a capillary tube, dispersing it as a fine mist into the air supply.
The system includes:
• An adjusting valve to control the oil flow rate.
• A sight glass for monitoring output.
• A filler plug for convenient in-place refilling.
Lubricators are usually specified based on pipe connection size, oil reservoir capacity, acceptable pressure drop, and flow rate. Most manufacturers also recommend a minimum air flow rate for the lubricator to function correctly.
Challenges in Pneumatic Tool Lubrication
Pneumatic tools are precision-built with close-tolerance components, often operating under demanding conditions. During use, internal temperatures can vary dramatically, especially in reciprocating tools. The combination of heat, high loads, and moisture makes adequate lubrication absolutely essential.
Lubricants for air tools must:
• Control wear.
• Protect against rust and corrosion.
• Resist foaming and water wash-off.
• Prevent sludge and deposit formation.
• Minimise fogging (especially important in mines and enclosed areas).
Protecting Seals and ‘O’ Rings
The most vulnerable parts of pneumatic tools are the internal rubber seals, typically ‘O’ rings. While lubrication is vital, the wrong type of oil can degrade these seals. It’s therefore essential to use a lubricant specifically formulated for pneumatic tools, typically blended with:
• Highly refined mineral oils.
• Anti-wear and tackiness agents.
• Emulsifiers, rust inhibitors, anti-foam and anti-fogging additives.
Selecting the Right Oil Viscosity
The oil viscosity affects how much lubricant is picked up by the airline lubricator — and this varies with temperature. Equipment manufacturers’ recommendations should always be followed, but in their absence, the following ambient temperature guidelines can help:
• Small hand-held tools: ISO VG 32
• Larger industrial tools:
o ISO VG 100 (below 20˚C)
o ISO VG 150 (20˚C to 25˚C)
o ISO VG 220 (25˚C to 30˚C)
o ISO VG 320 (30˚C to 35˚C)
o ISO VG 460 (above 35˚C)
When operator health and safety is a priority — such as in underground mines — greases or emulsions are often a preferred alternative for large tools like rock drills.
Conclusion
Pneumatic tools are designed for tough environments, but they rely on proper lubrication to perform well and last long. A well-maintained lubrication system, using the correct oil type and viscosity, not only protects your investment but also ensures a safer, cleaner, and more efficient working environment.
Blue Chip Lubricants (Pty) Ltd offers a full range of air tool lubricants for diverse operating conditions. To find out more, contact us at info@bcl.co.za — we’d be happy to assist.