Below is a brief instruction that is applicable to all project sites where heavy-duty tyres are in use.
Repairing and replacing heavy-duty wheel assemblies presents a safety hazard because of the size and varying types of rubber tyred equipment. This Instruction outlines the safe methods to be followed in mounting heavy-duty tyres and rims.
Project manager is overall responsible for the implementation of this standard vehicle servicing procedure.
Tyre Mounting Procedure – General Precautions
a) Inspect tyres, rims and lock rings frequently while in service. Any suspect part should be checked.
b) Inflation pressure should be released from the tyre by removal of the valve core before any attempt is made to remove the wheel from the machine.
Note: All dual wheel assemblies require the deflation of both wheels before removal of any retaining hardware from either assembly.
c) Before work on any type is attempted on large tyres, every precaution should be taken to see that the surrounding area is free of water, oil, grease, mud, pebbles, or any other material that would present a footing hazard.
d) No work should be performed on tyres unless there is sufficient space to permit a person to stand clear if the tyre should fall over.
e) No attempt should ever be made to roll or guide a large tyre from a vertical position to a horizontal position on its side. If a tyre is small enough to be moved safely by rolling, the person should stand behind the tyre and roll it ahead.
A person should not assume any position where a falling hazard is present. Large tyres should never be rolled. It must be handled by proper lifting devices.
f) Do not place hands or arms inside the restraining device (tyre cage) while a tyre being inflated. Use a long extension piece of inflating pump at least 2m. This will keep hands out of danger zone and a clip on valve.
g) Do not place hands or arms between mounted dual tyres during inflation.
h) Stand away from the restraining device and out of the expected trajectory of flying rim parts in the event of a failure during inflation. The control valve should be located some distance away from the tyre.
i) Ensure the Rim is secured to side of tyre cage using the securing mechanism.
j) Use pressure limiting gauges or valves that automatically shut off the air at the desired pressure and prevent over inflation.
k) Never reinflate a tyre that has been run flat because the lock-ring may have come loose.
l) Never inflate a hot tyre. Specifically, a tyre which is under suspicion of potentially being a tyre fire.
m) Valve cores should not be removed unless air pressure is below 5 psi in either the tyre or tube and body should be positioned outside the line of trajectory. Caution should be taken on all order tubes/tyres and tyres with ballast. The interior material and small pieces of rubber tend to block the valve stem and can blow out at anytime if the core is removed under pressure.
n) Never handle medium or large tyres without the use of a truck boom, overhead crane or forklift. If a forklift is used, ensure that all personnel are clear with removing the tyre, and secure the tyre immediately after removal from equipment. Never attempt to remove a tyre/rim combination by pulling with a forklift or other piece of equipment.
o) Always wear safety glasses when handling, removing, mounting or installing tyres.
p) Inspect tyre gauges at least once per month for proper calibration.
Inflating & Deflating Tyres
Tyres should be inflated only in a restraining device (tyre cage), which will contain flying parts incase a blow off occurs.
Eye protection is essential during tyre inflation.
The following is the inflation procedure:
i. Make a final inspection for proper seating and locking of rims, looking for signs of deformation or damage. Replace any component that may be suspect to any abnormalities.
ii. Make sure there is enough room in the restraining device to allow for the tyre’s expansion.
iii. Inflate the tyre slowly and carefully while inspecting for proper seating using at least 2m extension on pump and as clip on valve. Secure tyre in tyre cage.
iv. If the ring is not flush with the rim or (on some wheels) if there is space between the ends of the ring, the ring is not properly seated.
v. If adjustment are necessary deflate the tyre by removing the valve core (only if less than 5 psi) before making changes. Do not remove the tyre from the restraining device and do not try to knock a detective or out of position rim into place with a hammer.
vi. Inflate the tyre to the manufactures recommended air pressure. Any tyre undergoing an inflation must never be left unattended.
vii. After any tubeless tyre is inflated, it should be rechecked when inflated up to its working pressure.
Even though a tyre appears to be flat, it may still contain enough air or gas to be dangerous. For this reason, before a heavy-duty tyre is removed from a rim, the valve core must be removed from the valve stem. Once the valve is removed and the air or gas escapes, a wire should be run completely through the valve stem into the tyre cavity to be sure that it is not plugged at the base of the stem. Persons doing this work must wear eye or face protection and
be positioned out of the direct line of escaping air.
Where loose ballast is in the tyre, the initial blast of escaping air may bring a blinding burst of granulated fines. A safety coupler should be installed prior to tyre deflation to permit safe seepage of granulated fines into a ballast depository.
Changing Heavy Duty Tyres
a) In preparation for tyres that must be change on the roadway, all machines should be supplied with wheel chocks.
b) If the operator of equipment has a flat tyre while operating, he should park the vehicle, turn off the engine and set the park brake and lock-out.
c) In cases where large vehicle are inoperative and cannot be removed from steep inclines, another large vehicle may have to be positioned against the inoperative vehicle to keep it from rolling.
d) Lug nuts or bolts should be loosened before the machine is raised. Lug threads should be wiped clean or brushed clean prior to loosening.
e) Jacks used to raise the machine must be perpendicular to a level surface. Also, all jacks operated by compressed air should have their hoses and attachment tested and serviced at least once a month. Only jacks rated and designed for the equipment should be used to raise equipment.
f) If a hydraulic hoist on field tyre repair trucks is to remove the wheel, the truck must be positioned for most effective lifting. The employee who directs the positioning must stay within sight of the tyre truck driver and should not take a position between the tyre truck and the wheel to be replaced while he is directing. A cradle should be placed around the defective wheel, and the hoist should be hooked to the cradle.
g) The operator should use the controls on the side of the truck away from the wheel pulling action. All employees should stay clear of any possible hoist boom movement, whip lash, or swinging of the removed wheel.
h) On the initial pull, the wheel may bind. Rather than pound it free, relocate the hoist attachment and make a light pull to free the bind. When the defective wheel is free, it can be loaded onto the tyre truck bed.
i) Some wheels are secured to the hubs with heavy steel wedges held in place by lug bolts. To avoid foot and leg injuries from falling of the wedges, loosen the nuts that hold the wedges, but leave at least one half of the nut on the stud. The nut will prevent the wedge from flying when tapping the wedge loose. When tapping the wedges loose take a safe position to the side.
j) When the good wheel is picked up and placed on the wheel hub, all employees must keep clear of the path between the oncoming wheel and the hub. It is recommended that a lifting hook or a probe be used to help position the dangling tyre.
k) Install dual wheels so that the valve on the inside wheel can be easily reached for inflation and checking. Also, the nuts on the inside wheels should be checked to see that they are securely tightened before the outside wheels are mounted.
l) Lug holes should be inspected for any deterioration or elongation. Report any deformed damaged lugs to your supervisor and have replaced immediately.
m) Without exception, whenever one or both tyres and rim assemblies are to be removed from a single position on any dual wheel assembly, both tyres must be deflated to 5 PSI.
n) Routine inspection of all restraining devices should be made on a frequent basis.
Removing Wheels in the Shop
Block the vehicle to be retyred securely. Loosen the lug nuts and jack up the vehicle.
All tyres for removal must be deflated.
Remove the defective tyre and wheel with the forklift clamp, and carry it well clear of the truck or vehicle.
Pick up the good tyre assembly and place it on the wheel hub. Employees must stay clear of the space between the oncoming wheel and the wheel hub.
Avoid all sudden movement with the hands to grasp the tyre for positioning.
If a traveling or overhead crane is used to raise a truck for tyre installation, suitable wooden blocking or well designed stand must be positioned to prevent the truck from falling because of cable or cable attachment failure.
Handling Tyres in the Shop
After removal, tyres and rims must be disassembled for repair. When lock rings are removed, care should be taken not to damage bend, or spring them out of shape.
Before assembly, rings and rims should be cleaned with a wire brush of buffer and the following defects should looked for:
i. Distorted rims
ii. Distorted and twisted rings
iii. Rim or ring bent out of round
iv. Bent rim or ring beads
Defective parts, even those showing only small cracks, should be discarded, Rings or other parts only from different wheels should not be interchanged except according to the manufacture’s recommendation.
Before installing a tube, the tyre casing should be checked for cracks, cuts or foreign particles. Dusting the tube with talcum powder or dipping in a soap solution will facilitate insertion. Also the tube should be inflated slightly. The lubricant and slight inflation will tend to reduce pinching and chafing during final stages of inflation.
Excessive pressure should not be exerted nor unnecessary hammering done when tyres or lock-rings are being placed on rims. Excessive pressure or hammering tends to bend or spring rims and rings out of shape and proper fit becomes impossible.
If wheels are to be stored after assembly, rather than used immediately, they should not be fully inflated.
Unmounted tyres should be in a standing and leaning position, and in rows. For the purpose of expediting work, tyres must be stored in a standing position, provided that each tyre is leaning against the next and a chock is blocking the outside tyre. Tyres being transported upright on forklifts must be chained to the forklift frame.
Never, under any circumstances, attempt to rework, weld, braze or heat rim components. If in doubt as to the correct action to take, check with your supervisor.