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third-party service provider. A crane service provider can survey your crane rails and runway systems to identify and correct any issues before they become bigger problems. A crane service provider can make sure that your overhead crane system is in compliance with the allowable tolerances specified by the Crane Manufacturers Association of America (CMAA) for the design of the runway system.
• CMAA Specification #70 – 1.4.2: “Rails shall be straight, parallel, level, at the same elevation and at the specified center to center distance, within the tolerances given…”
> Crane Span Tolerance: • Less than 50 feet: ± 3/16” • 51-100 feet: ± 1/4” • Greater than 100 feet: ± 3/8”
> Straightness Tolerance: ± 3/8” > Elevation Tolerance: ± 3/8” > Rail-to-Rail Elevation Tolerance: • Less than 50 feet: ± 3/16” • 50-100 feet: ± 1/4” • Greater than 100 feet: ± 3/8”
• CMAA Specification #70 – 1.4.5: “Rail joint misalignment can be a significant factor in wheel, axle, and bearing failures. It is recommended that horizontal rail separation at joints not exceed 1/16”. Vertical and horizontal alignment at joints should be maintained as closely as possible. Rail joints should be ground flush as necessary to provide a smooth transition from each rail segment to the next.”
3. EXCESSIVE WEAR TO END TRUCK WHEELS
End truck wheels are components of overhead cranes that can require frequent maintenance, replacement, or adjustment. Troughout the course of a crane’s life, the wheels will naturally wear down due to normal use of the crane and will need to be replaced. Wheels can be made of a variety of materials, including
polyurethane for gantry cranes, alloys, low-carbon steel, or medium-carbon steel. Te more carbon in the steel, the harder the wheel will be. Tere are also methods of heat-treating that can be used to increase the hardness of a wheel—increasing the service life and load capacity of the wheels. If the wheels, wheel bearings, or wheel flanges begin to
wear or break down prematurely, it can be an indication that the crane is skewing and not properly tracking down the runway system. Skewing of the crane can cause excessive wear and stress on the wheels, but also on the runway beams and support structures as well.
Tere are a number of different issues related to an overhead crane’s electrification system that may require service or future maintenance.
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Wheels tend to wear out faster on a crane that was installed using an existing rail system as opposed to a new installation. Unless the runway has been properly surveyed prior to installation, the runways may be misaligned or the rails may be out of tolerance. To avoid premature wear on the wheels and end trucks,
your overhead crane runway system should be designed, tested, and regularly inspected by a reputable overhead crane manufacturer. Any signs of premature wear will indicate the possibility of a larger problem that should be addressed and corrected before the problem compounds itself. Make sure wheels were made specifically for the rail they’re running on. Hardness must match hardness of rail.
4. ISSUES WITH THE ELECTRIFICATION SYSTEM
Improper runway alignment can cause premature wear to end trucks and wheels.
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