Pneumatic tools are to aircraft technicians as scalpels are to surgeons. Yet despite this fact, some technicians either neglect or mishandle their air tools. It can be something as small as using the same compressed air supply to drive paint guns and air impact wrenches; risking lubricating oil leaching into the paint and ruining the next 737 refinishing job. Or it can be as big as tossing precision pneumatic tools around like baseballs, with the concrete shop floor serving as backstop.
Whether in drive units, open-loop or closed-loop control systems, engineers can get quite a lot out of thin air. Acting on cylinders, air pressure and suction can shift, lift or reshift work pieces and
tools, start, stop, and direct machinery as well as control the flow and pressure of media. Small wonder pneumatics are very much at home in the fields of industrial handling and automation
engineering. Pneumatic cylinders and valves take up little space and are not only very robust but overload-proof as well. This is due to their high functional reliability and long service life; both are subject to the problem-free operation of seals being in contact with mostly metal pistons and cylinders. Because friction and wear must be minimized, lubricants that are suitable for a wide variety of operating conditions are of vital importance. Factors such as ambient temperatures, sliding speeds and normal forces must be taken into account by the manufacturers of the highly complex tribological systems that are pneumatic drives. It’s a good thing the manufacturers of seals and lubricants cooperate closely to develop optimized solutions for pneumatic applications.
Renowned manufacturers of pneumatic components and university research centers also participate in this cooperative venture, and the special combinations of sealing materials and lubricants is beneficial to pneumatic tool manufacturers and consumers. These solutions allow the
optimized operation of pneumatic systems in all kinds of applications.
Friction conditions
The sliding speed of the friction bodies is one of the many factors that cause different friction conditions. A Stribeck curve will show you the friction force as a function of speed, which leads to
the following friction conditions.
Boundary friction
When an attempt is made to move the friction bodies relative to one another, adhesive friction builds up due to micro-interlocking. Internal friction also acts as a force resisting relative motion of the interlocked surfaces. No relative motion of the friction bodies occurs in this state.
Mixed friction
There is relative motion between the friction bodies; however, it meets with resistance from micro-interlocking and adhesive friction as well as internal friction. The total friction force is normally lower than that of static friction, as the interlocking portion of the asperities is much smaller and the lubricant becomes effective. The higher the speed, the less asperities can interlock, which results in reduced friction.
Fluid friction
If the sliding speed is high enough, the viscosity of the lubricants leads to pressure building up between the friction bodies, which separates the contact surfaces (grease planning). The degree of friction depends on operating parameters (pressure, temperature and speed) and the element
of internal friction within the lubricant.
Surface finish
If a surface is too “smooth”, it has only very small pockets in which to retain the lubricant. The lubricant is wiped off the seal lip because there is not enough texture to keep the lubricant in place, which results in insufficient lubricating film and increased wear of the seal lip and its opposing body.
A surface that is too rough, on the other hand, has a direct negative impact on the surface of the seal lips, which is worse when subjected to reciprocating motion. Both types of surface – too rough or too smooth – lead to shorter service life (leakage) and higher friction (wear). What is also important is the surface’s topography: large asperities scattered at a wide spacing have a negative
effect, while small ones close together are beneficial. Therefore, the loadbearing area of the surface needs special attention. Pneumatic systems are made up of working elements (cylinders
and motors) and control elements (valves), and the systems (mechanical elements) they form can be especially reliable and long-lived. To ensure this, utmost cleanliness is mandatory prior to greasing the system and putting it into operation, i.e. all machining residues, used grease and other particles must be carefully removed. Once this has been achieved, the seals as well as the
opposing body can be greased. This ensures even wetting of the friction bodies.
Hints for the greasing of running surfaces in cylinders
Use suitable round brushes or automatic greasing pistons. Upon installation, the working piston should be moved up and down its whole stroke path several times. This makes for even distribution of the lubricant and ensures seals are sufficiently wetted when applying the lubricant
to the cylinder walls only.
Hints for the greasing of valves
Valves can be greased in a similar fashion as cylinders. Depending on the valve’s size, excess lubrication of the piston seals will also lead to even lubrication of the friction bodies after a certain number of piston strokes.
Care & Maintenance of Pneumatic Tools
Pneumatic Tools generally operate at a maximum pressure of 90 psi. Consult manufacture specifications for correct operating pressures. Controlled air consumption with combined regulator/oil/water separator unit, which with proper maintenance will ensure a constant supply of dry air and lubricating oil at all times. Always check machine operating pressure before use. Water in the compressor tank will cause serious corrosion to your air tools and should be drained daily to avoid excessive water in your air supply. Dirty wet air rapidly shortens the life of your air tool. If you are using an air tool on a hose over 25ft. long, increase the hose to the next larger size available [ie. 1/4″ increases 3/8″]. This will ensure adequate pressure and volume of air to power the machine.
Recommended air supply operation
Some air tools have built-in regulators which can be used to control speed/torque performance, on machines without built-in regulators this can be done by varying the pressure on your air supply regulator.
Maintenance
Here are some tips that will keep your air tools humming along for years to come. Every day, before use, remove the tool from the air line, use an oil can and pour the equivalent of a tablespoon of suitable oil into the machine (through the air intake). Operate at low speed to ensure lubrication of all moving parts. If machine is in constant use or, is to be used for long periods of time, install a combination filter/lubricator. Always use an inline air filter. Always use suitable oil, labeled for use in pneumatic tools. Do not use engine oil or other general lubricants.
Failure to perform general maintenance will lower the life of your air tool.
Safety rules for air tool products
- Always wear safety goggles or glasses.
- Always ensure tool is switched off before connecting to air supply.
- Disconnect tool from the air supply before changing blades or discs, and before servicing.
- Always keep your air tool clean and lubricated. Daily lubrication is essential to avoid internal corrosion and possible failure.
- Use only lightweight coil hoses from a tool to the wall or compressor coupling.
- Do not use quick-change couplings, as vibration can cause the coupling to fail.
- Do not overload the machine. Allow the tool to operate at its optimum speed for maximum efficiency.
- Do not increase the air pressure above the manufacturers recommended level, as excessive overload can cause the tool casing to split, this also creates excessive wear on moving parts and possible failure.
- In the interests of safety and possible damage to the machine/operator, always ensure that the machine has stopped before putting it down after use.
- Always ensure that the work piece is firmly secured leaving both hands free to control the machine.
- Always ensure that the accessories such as blades, discs, sockets, etc. are rated/designed for use with the tool and securely fastened before connecting the tool to the air supply.
Handle with Respect
1. Pneumatic tools are meant to be used repeatedly in harsh environments. This is why pneumatic tool manufacturers build their products out of hardened metals, with enough resilience and toughness to keep working day in, day out.
- This said, even the toughest air tool has its breaking point. Sometimes breakage occurs because a tool is being asked to do too much. Other times, a properly used tool will fail due to years of wear and tear.
- The most common things that break or get damaged on ratchets and impact wrenches are anvils. Anvils often wear out and simply need to be replaced when they break. They’re always under heavy torque, which leads to steel fatigue.
- Gears get damaged on tools like drills, grinders, and ratchets when the user puts too much load on the tool. Pressing too hard on a grinder or hand tightening a fastener with a ratchet after the ratchet torque has maxed out puts a lot of stress on the gears.
- To make pneumatic tools last, the rule of thumb is to always use the right tool with the job. Don’t try to make smaller impact wrenches do the work of larger models. Otherwise, they will break sooner simply due to repeated overstressing.
- In the same vein, respect that each tool has its wear limits. Take note of the manufacturers’ hour ratings for a given tool, and keep track of its actual usage. This does not mean that you have to note every time a tool is used, but you should record when a tool enters service, and forecast when it will need to be checked for servicing and/or overhaul.
Handle with care
In a perfect world, air tools and concrete floors would never meet. In the real world they often do, either by being dropped or tossed by careless technicians. That’s not all: Tools have been run over by cars or forklifts on shop floors, it is not uncommon.
Any time a pneumatic tool suffers this kind of shock, its internal mechanisms can become misaligned and/or broken. The result can be wrenches that don’t turn, or compressor lines that leak. Whatever the damage, once it has happened, it has happened. Sometimes a pneumatic tool’s workings can be repaired, but sometimes they can’t.
The rule of thumb: Always have a safe resting place for pneumatic tools handy to the job site. By having this, technicians can put down the tools as needed, without dropping them on a concrete floor. If need be, put some kind of shock-absorbing padding around the resting place, to protect any tool that may slip off by accident.
On a larger scale, never toss pneumatic tools. It doesn’t matter if you were a star Little Leaguer or if you could have attended Notre Dame on a football scholarship. Don’t toss those tools!
The importance of oiling
It may seem like a no-brainer, but pneumatic tools require regular oiling and lubrication. Without this degree of care, the parts inside will start to grind against each other. Eventually, the tool will erode into uselessness.
Amazingly, we’ve seen many tools that have never been oiled. This actually happens, even though almost all air tools on retail shop racks say ‘oil daily’ right on the housing. All technicians know the need for grease and oil in automotive applications, yet a few of them don’t see the need in their air tools!
For all air tools, a lack of grease and oil probably accounts for most damage. The other common factor that consistently causes damage to pneumatic tools is water in the air line.
When you do oil your air tools, be sure to use the lubricant recommended for the job. Additionally, be sure that the oil doesn’t get all over the tool, seeping onto rubber and other components that need to stay oil-free. Whatever you do, don’t get oil in the air line!
Oil tools daily at the end of the day. The inner components of air tools are often made of steel and will rust easily. By oiling the tool at the end of the day, then running it for a few seconds, the oil will stay in the tool overnight protecting it from moisture. For your use of company-owned assembly air tools, we recommend a few drops of air tool oil daily, and a tear down, inspection, and cleaning quarterly.
Keep them clean
Like oiling, being told to keep pneumatic tools clean seems obvious. Yet tool manufacturers often see pneumatic tools that have failed due to dirt buildup and water-caused corrosion.
In many cases, cleaning is a simple matter of wiping grime and moisture off the tool as needed. However, if an air wrench falls into a puddle, don’t just wipe it off and keep working. Instead, take steps to ensure that the inside is properly dried and relubricated, as directed by the tool’s service manual. In the same vein, make sure that pneumatic tools are regularly stored in clean, dry cases. Protect them from moisture and shop floor dirt, especially when not in use.
Problems, Possible Causes & Remedies
Tool runs at normal speed but loses speed or power under load.
Possible cause, motor parts worn
Cam clutch worn or sticking due to lack of lubricant.
Lubricate clutch housing. Check for excess clutch oil. Clutch cases need only be half full. Overfilling can cause drag on high speed clutch parts, ie. A typical oiled/lubricated wrench requires 1/2 ounce of oil.
Heat usually indicates insufficient grease in chamber. Severe operating conditions may require more frequent lubrication.
Tool runs slowly. Air flows slightly from exhaust; Motor parts jammed with dirt particles; Power regulator in closed position; Air flow blocked by dirt.
Check air inlet filter for blockage. Pour air tool lubricating oil into air inlet as per instructions. Operate tool in short bursts quickly reversing rotation back and forth where applicable. Repeat as needed. If this fails return to manufacturer’s service center.
Tools will not run and air flows freely from exhaust
One or more motor vanes stuck due to material build up. Pour air tool lubricating oil into air inlet. Operate tool in short bursts of forward and/or reverse rotation where applicable. Tap motor housing gently with a plastic mallet. Disconnect supply. Free motor by rotating drive shank manually where applicable. If tool remains jammed return to service center.
Tool will not shut off
‘O’ rings throttle valve dislodged from seat inlet valve. Replace ‘O’ ring or return to service center. Note: Repairs should be performed by a qualified person or service center.
The Bottom Line
Take care of your air tools, and they will take care of business for you. Whether you are a shop floor technician, a foreman, or a general manager, this is the most important truth about the proper care and feeding of pneumatic tools.
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Safety:
Longer lubrication intervals reduce the frequency of maintenance work and the need for your staff to work in danger zones. Lubrication systems can therefore considerably reduce occupational safety risks in work areas that are difficult to access.
Reliability:
GG Friction Antidote treated lubricants ensure reliable, clean and precise lubrication around the clock. Plant availability is ensured by continuous friction reduction of the application. Lubrication with GG Friction Antidote treated lubricants help to prevent significant rolling bearing failures.
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INSTANT ROI FOR OPTIMIZING YOUR LUBRICATION REGIMEN
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The information in this literature is intended to provide education and knowledge to a reader with technical experience for the possible application of GG Friction Antidote. It constitutes neither an assurance of your vehicle/machinery optimization nor does it release the user from the obligation of performing preliminary tests with GG Friction Antidote. We recommend contacting our technical consulting staff to discuss your specific application. We can offer you services and solutions for your heavy machinery and equipment.
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