NAI Solutions
North American Industries is pleased to bring you the fourth issue of our quarterly customer e-newsletter designed to keep our customers informed and answer your crane questions.

Volume 2, Issue 4 800-847-8470
February 2008

Under-running Cranes

What are they? When are they appropriate?

Underhung and Under-running cranes are two ways to refer to the same type of crane. With underhung cranes, the end trucks ride on the bottom flange of the runway beam rather than on top like other types of overhead cranes. With an underhung crane, the runway beam is often suspended from the roof, which eliminates the need for extra floor columns to support the runway. This can be advantageous if floor space and the need to reduce obstructions is a major issue in the factory or warehouse. An underhung crane may even be appropriate with sloped ceilings or multiple crane systems.

Underhung cranes can be either single girder or double girder. Double girder underhung cranes are often suitable for longer spans or higher capacities.

However, underhung or under-running cranes are typically limited to lighter capacities (usually about 10 tons maximum).

Does Your Crane Need Parts or Inspection?

What crane parts may wear faster in your industry? A Recommended Spare Parts List can be created specifically for your crane’s duty cycle and application. Be proactive - not reactive. If you're prepared, you can avoid downtime and reduce costs. Consider spare parts, preventative maintenance, and regular inspections. It's the smart choice.

No matter who the original crane manufacturer was, North American Industries can supply parts that are compatible. 800-847-8470 ext. 104.


Crane Project Highlight

A multibillion dollar worldwide construction company required a gantry crane to move materials needed to rebuild a section of the I-95 highway, including a 1,000m bridge over Turtle River in Georgia. This was part of a $199M contract between Georgia’s DOT and the construction company.

Tuttle River Gantry Crane

The construction company and its subsidiaries operate in more than 30 countries with annual sales over $18 billion. Areas of operation comprise construction, residential and commercial development, and infrastructure development.

25 ton double girder double leg gantry crane

Solution: North American Industries built a customized 25 ton double girder double leg gantry crane with lights to allow nighttime work on the bridge. The system includes:

  • NEMA 4 weatherproofing
  • Cold weather protection
  • Trolley designed for maximum cross slope of 1%
  • End trucks designed for maximum longitudinal slope of 3%
  • Generator mounting platform on one end truck
  • Emergency brakes that will stop the crane in 12’ and act as a hold down (brake sufficient for a 50 MPH wind velocity)
  • Quick disconnect electrical fittings
  • Completely bolted construction to facilitate erection as well as disassembly for easy relocation
  • Radio remote controls & full length catwalk


Get on Board with Safety

Problem: The customer had numerous cranes in multiple locations throughout the United States. With the cranes aging, senior management was committed to having all cranes at all locations inspected for structure & safety. This customer, headquartered in Europe, has operations throughout the world and annual sales over $37.7 billion.

Solution: North American Industries was awarded the job to complete crane structural surveys of twenty seven bridge cranes and associated runways at 10 locations across the United States. Crane inspections and related services from North American Industries will help keep the plants running efficiently and help ensure the safety of over 298,000 employees of the customer company.

After the inspections were completed, some of the older cranes were found to be in need of repair. North American Industries has recently been entrusted with the job of repairing these cranes.

Pick Our CraneBrain with Q&A

What importance does the class rating of the crane have? (Class "C" versus Class "D")

The Crane Manufacturers Association of America (CMAA) has issued over 150 pages of specifications
detailing how to design and build cranes of differing classifications. An extensive list of more than 50
components (wheels, bearings, motors, axles, contactors, etc.) are upsized for each successive crane class, which means that parts on a Class “D” crane are physically bigger and stronger than parts on a Class “C” crane. Crane designs are strictly regulated by the CMAA and must be documented by engineering calculations.

Compared to a Class “C” crane of equal lifting capacity, CMAA specifications dictate that a Class “D” crane is designed to:

  • Make twice as many lifts over its lifetime
  • Lift the maximum rated load with 30%
    greater frequency.

If you have a question that you would like answered in a future publication, please send to

Discuss your crane needs with North American Industries. We spend the time to understand your particular application. To submit a new inquiry or speak with a sales engineer, call 800 847-8470 ext.117 or use our web form

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North American Industries, Inc.
80 Holton Street, Woburn, MA 01801
phone: 781-897-4100 / toll-free: 800-847-8470
fax: 781-729-3343 /