Monday, August 9, 2010

Runway Alignment

One of the crane system components that often get overlooked is the runway. Often cranes will have wheel problems and the wheels get changed out not thinking of the actual runway being a potential reason for the original wheel wear. If your crane travels down the runway and is very loud, and you hear lots of cracking, and racking of the crane, you probably have a runway issue. Sometimes the crane runs silently down the runway and you still could have potential crane rail issues.

CMAA specification No. 70-2004 1.4 gives some good guidelines for your runway. It is a must that the runway be “straight, parallel, level and at the same elevation”. If any one of these factors is out of skew it can affect the performance of the crane or cause premature wear. The span of the runway is also a important dimension that if is not within tolerance will cause premature wear as well, and also cause racking of the crane. If your span is less than 50’ as most cranes are, you are only allowed a overall tolerance of 3/16 “. From 50’ to 100’ you are allowed ¼” of tolerance, and if it is over 100’ span than you have up to 3/8”. If you think about that is such a small tolerance over such a distance. You are allowed a ¼” rate of change maximum for every 20’ of runway. When your rail is no straight it is extremely hard on your wheels and brakes when it constantly racks. Your runway elevation should be within 3/8” on each side of runway, and same as crane span when it is compared to each other. Meaning your rail to rail elevation on a crane less than 50’ can only be out by 3/16”, between 50’ and 100’ you’re allowed ¼”, and same with a 100’ you’re allowed 3/8” with a maximum rate of change of ¼” on 20’.

Another important dimension to keep in mind is the space between the rails. The CMAA standards are 1/16”. However the larger the rail and the larger the wheel the greater dimension you will be allowed to get away with. CMAA does not deviate from that dimension. I have seen the dimension larger than this and it has not created any issue with wheel wear or noise during travel because the rail was 160# rail and the wheel had a diameter large enough that it was not affected by the gap.

Konecranes has designed a new and efficient way to perform a runway analysis called Rail Q. From their website page I have learnt several things that would be beneficial for any company with a rail concern to look into Rail Q. Rail Q is much more accurate than previous ways to perform runway analysis. It is also quicker. This would minimize the downtime of your crane during the analysis, and reduced cost of the analysis. Results from such a precise analyisis offer the customer a more cost effective means of repairs to get the runway within tolerance.

Below is an introductory video of the Rail Q survey. Please take a look.

Rail Q Survey

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