There are a few preventive measures that can be taken to increase the life of your wheel and rail. While many factors can contribute to extensive wheel and rail wear, some simple measures can be taken to avoid this from happening.
Changing drive wheels in pairs is often a best practice that is neglected. Many times spare wheels are kept in the store room and when a wheel goes bad due to wear, it is swapped out with the spare. If the opposite driver wheel is not showing excessive wear, it often is assumed to be all right to use without double checking the diameters. The matching drive wheel needs to be within .001 per inch in diameter with a maximum of .01 inches. If the difference in diameter is greater than allowable tolerance, per CMAA Standards, it is deemed not safe. A symptom of mismatched diameters includes crane skew, which over time will result in excessive flange and rail wear.
A simpler way to think about this scenario is taking a car tire into consideration. If tires for example, have 50% of thread left and a nail makes its way into the tire making it go flat, replacement is needed. Owner decides to save money and replace only the flat tire with a brand new tire that will have 100% of tread on it. The diameter of the newer tire will be slightly bigger than the old tire on the opposite side. When driving the vehicle, even though the tires are making the same amount of revolutions, the new tire will travel further due to its larger diameter. This will cause your car to steer towards the side where the old tire is. It is recommended that the driver wheels always be replaced in pairs to avoid the crane skew.
Another preventive measure that can be taken is to watch for signs of flange wear. When a wheel is subject to flange wear, the float will be greater than allowable per manufacturing standards. Float is the distance between rail and flange. Per CMAA Standards, this should be around 3/4” to one inch total. When float greater than one inch is present, the crane will have more room to skew. When the crane goes into deep skew, the lateral forces exposed to the flanges will increase, causing the flange to dig into the rail. The result is rail and flange wear and could potentially lead to a catastrophic failure where the flanges break off. Without extra safety features in place, the crane could run off the runway. There have also been scenarios with the flange digging into the rail, then lifting the rail and breaking the rail clips, causing additional expense and down time.
Lastly, with the first signs of flange wear, it is important to check on the condition of the rail. A Crane Rail Survey is an excellent preventive measure to assure the crane will not be exposed to flange and rail wear. When the rail span is outside the allowable tolerance or there are elevation issues, flanges will rub against the rail. There are a few simple things to look for to identify this issue. First are flakes next to the rail from either the wheel or the rail. Second are loud noises coming from the wheel area when the crane is in motion. If the crane is equipped with flange lubricators, it is good to periodically remove the lubricators and run the crane up and down the runway a few times to see if any noise is coming from the flanges. If the Crane Rail Survey comes back with results that are not concerning, a CraneQ Crane Geometric Survey is recommended and will check for crane squares as the end trucks must be parallel to each other to ensure the crane is tracking properly.
It is recommended these steps be taken into account to prolong your wheel and rail life, saving you money and time in the long run. For more info on crane wheels, please contact your Konecranes representative today.