The most common energy systems used by Industry are Electric, Hydraulic, and Pneumatic. Of these, the Pneumatic or compressed air system has the most readily available medium – air.
Compressed Air is a clean, safe, reliable and versatile source of power which is simple and economical to use and can be harnessed in numerous ways to make light work of many industrial operations. You can overload compressed air equipment, even to stall, without damaging the motor or actuator.
There are no sparks or electric shocks with compressed air systems so they are more suitable for use in inflammable environments.
Generally compressed air equipment is smaller, simpler in operation, and more robust than equivalent electrically powered equipment. With fewer moving parts, wear and tear is less and maintenance costs are lower. For these reasons compressed air is widely used in the Manufacturing, Process and Service Industries as well as in Construction and Mining.
You can use Compressed Air for drilling, screwdriving, bolt tightening, nut running, grinding, sanding, polishing, chipping, deburring, wire brushing, descaling, deslagging, scabbling, compacting, cutting, sawing, pumping, paint spraying, blast cleaning, pressure lubricating, lifting and more.
The following advantages of Air Tools will help to improve productivity and product quality:
Compressed Air stores energy which if released accidentally is capable of causing serious injury or even death to persons in the area of the incident.
When using compressed air and compressed air equipment the following precautions must be taken:
Always exercise caution when using large air drills. Place yourself in a position where you have ample and safe footing.
Large drills should always be equipped with safety, self releasing throttles which shut off the air supply to the drill as soon as the handle is released.
The following points should be remembered when using twist drills, taps or reamers:
Put on eye protection before using a drill. Beware of chips lodged in drill bit flutes that can easily become embedded in your eyes. Never wear loose clothing when operating a drill. Clothing is easily caught by the drill bit or the chuck. Where necessary, use barriers behind the work to prevent people from being injured as the drill breaks through the other side of the work.
Accidents with grinders can be fatal. The greatest hazard when using grinders is wheel breakage. Attention is drawn to Australian Standard 1788.1 – 1987 Abrasive Wheels – Design, Construction and Safeguarding and Australian Standard 1788.2 – 1987 Abrasive Wheels – Selection, Care and Use.
Accidents can be minimized by observing the following rules:
Suitable racks, bins or drawers should be provided for wheels and tools. Stored wheels must not be subject to extremes of temperature and humidity. Wheels should be stored according to type, size and speed with all bins clearly marked. Particular care should be exercised, when handling wheels, to avoid dropping and bumping. The finest crack can cause some wheels to explode in use.
Portable grinders should have the Manufacturer’s nameplate attached, indicating the rated speed and rated air pressure of the tool. The label on the grinding wheel should show the Maximum Safe Operating Speed (MOS).
Always use a wheel with a Maximum Safe Operating Speed that is equal to or greater than the rated speed of the grinder. Never use a wheel with a missing label. Straight wheels, cupped wheels and depressed centre wheels must be used with protective guards. Always use the guard supplied with the grinder. If the type of wheel being used is changed, obtain a suitable guard from the tool manufacturer.
Personal Protective Equipment should be selected in accordance with SAA HB9 – 1994 Occupational Personal Protection and subsequent related Australian Standards. In general, with respect to grinding:
When mounting straight, unthreaded wheels always use heat treated inner and outer wheel flanges with equal outside diameters and matched recesses in accordance with AS 1788.1 – 1987. These flanges are supplied with the tool by the tool manufacturer. Never substitute soft washers which spread when tightened.
Always observe the following points:
Wheel breakage can also occur when:
When using straight cutting off wheels the tool being used must meet the following requirements:
Points for basic cutting procedure:
Most cup wheels that are mounted on vertical grinders have threaded steel bushings moulded into the wheel. These wheels are simply screwed on to the end of the threaded tool spindle, which is usually 5/8” (16mm) in diameter. The back flange for such wheels should be flat and unrelieved. Never use a recessed flange with a cup wheel as this has the tendency to pull the bushing out of the wheel when it is tightened down on the shaft. See AS 1788.1 – 1987 for the correct way to mount cup wheels.
Cone and plug wheels have blind threaded bushings which screw on to the spindles of straight grinders. In this case the grinder spindle must be shorter than the depth of the hole in the bushing. When the spindle is longer than the hole in the bushing it pushes on the bottom of the hole and tends to crack the top off the cone or plug.
If the spindle is too long, use a properly machined flat spacer to give the required thread clearance and to support the back of the threaded bush. Never use relieved flanges or spacers as these will pull the bushing out of the wheel. Never use a spacer that makes the engagement of the threaded spindle too short. When this is done it is almost certain that the bushing will break and pull out of the wheel.
Because of their shape and usage Type 27 & 28 wheels require specially designed backing flanges and locking nuts as described in AS 1788.1 – 1987.
For type 27 & 28 wheels the locking nut fits within the depressed centre of the wheel to prevent interference when side grinding, and serves to drive the wheel by clamping it against the depressed portion of the backing flange.
Mounts which are fixed to the wheel by the manufacturer should not be re-used as back-up flanges for un-mounted wheels.
Type 27 & 28 wheels must only be used with a safety guard mounted on the tool between the wheel and the operator.
The variation in flange diameters, the fact that the locking nut is less than one third of the wheel diameter and the exertion of side pressure during the grinding process limits the construction of depressed centre wheels to reinforced organic bonded types.
When using reinforced depressed centre grinding wheels the minimum recommended angle between the wheel and the work is 15 degrees.
The Maximum Safe Operating Speed for mounted wheels is determined by the following factors:
The Maximum Operating Speeds for medium and high strength mounted wheels having 2.4mm, 3.2mm, 4.8mm or 6.4mm diameter mandrels operating with various overhangs from 12mm to 125mm are given in AS 1788.1 – 1987. The wheel manufacturer’s specifications must be checked to see whether the wheels are low, medium or high strength. If the specification indicates a low strength wheel, the Maximum Operating Speed recommended by the wheel manufacturer must not be exceeded.
When using mounted wheels always observe the following points:
The recommended cutting speeds for Tungsten Carbide Burs vary with the material being machined and the desired finish. The bur manufacturer’s operating instructions should be consulted with respect to these factors in order to determine the correct bur speed for a particular job and therefore the correct tool to be used.
When using carbide burs always observe the following points:
Check grinder speeds regularly with a tachometer. If the grinder exceeds the speed on the name plate, or body of the tool, have it serviced immediately. An increase in the sound output of a tool is an indication that its operating speed may have increased. Speed changes can be caused by dirty compressed air fouling the speed governor inside the tool. Always use filters and lubricators on air lines.
Always prefer a lock-off throttle if this is an available option. This should especially be the case on larger, more powerful grinders. Lock-off throttles prevent accidental start-up as the operator must unlock the throttle before starting the tool. The throttle automatically returns to the locked-off position when released.
When mounting a new grinding wheel onto a tool remember the following points:
Even properly mounted and guarded grinding wheels can be fractured by misuse. Wheels should make smooth contact with the work without any bumping action. Forced grinding which slows down the air motor should also be avoided. Never grind against the side of a straight wheel.
Safety goggles or face shields are a must when sanding and grinding. Safety aprons, and properly fitted protective clothing should be used in prolonged grinding. Never wear loose clothing.
Protective barriers should be used to prevent grinding operations from causing damage or injury to others.
When grinding, the following points should also be remembered:
Apart from being a nuisance, noise can also cause permanent hearing damage. Even when a grinding tool has been designed to minimize its sound output, the combined sound level of the grinder plus the work noise could still be damaging to the operator’s ears and ear protection should always be worn. Where an operator is exposed to high sound levels, the time of exposure may also have to be limited.
When installing or removing large bolts and nuts, the use of hand wrenches with extensions can cause accidents. It is usually safer to use an impact wrench.
Impact wrenches have little reaction or kick. They deliver a large amount of torque for their size and weight. A 100kg man on the end of a 1.5 metre bar cannot deliver as much torque as an impact wrench weighing 11.5kg.
Impact grade sockets should always be used with impact wrenches.
When winding out a bolt or nut in a confined space make sure your hand does not get jammed as the tool moves back.