Comparing & Contrasting Three Bridge Crane Designs

Welcome to the Hoist Guy’s Blog, where our resident hoist guy, Andrew T. Litecky, shares his experience and knowledge in the overhead material handling industry to compare and contrast the three main bridge crane designs.

Advantages & Disadvantages of Different Bridge Crane Designs

A customer who was planning to erect a new building called us to request a bridge crane quote with the following requirements:

• 15-ton capacity
• 54 foot span
• runway support steel at 25’ intervals

Which of the three main types of bridge cranes designs (Underhung, single girder; Top running, single girder; and Top running, double girder) best fit their application? Learn more about the advantages and disadvantages of each overhead bridge crane design here. As a general rule, this analysis applies to cranes with a capacity range of ½ to 20 tons and a span range of 20 to 60 feet.

First, let’s review.

What is a bridge crane?

An industrial bridge crane or overhead crane is a permanent material handling system built into a production space or warehouse and composed of a bridge beam, runways, and trolley hoist. This gives hook coverage in the X-Y-Z axis. The bridge beam forms the main framework of the system and supports the trolley hoist. The bridge is supported by the runway, which ties the crane to the structure of your facility. The trolley hoist lifts vertically and moves horizontally along the bridge beam. A bridge crane’s headroom is the distance from the lowest ceiling-based obstruction (such as an HVAC unit, sprinkler head or light fixture) to the highest point on the crane beam. Crane engineers work to find the system with the lowest amount of headroom to maximize a bridge crane’s lifting height.

There are three main designs of bridge cranes:

1. Underhung, single girder
2. Top running, single girder
3. Top running, double girder

What is the underhung, single girder bridge crane design?

This type of bridge crane uses an I-beam or patented track as the bridge beam. The hoist is monorail underhung or travels on a trolley suspended below the beam. Like the crane, the runway beams can be I-beams or patented track.

This design would work for the customer’s application in question, at 15 tons and 54’ of span. While the end trucks needed for this capacity on the I-beam are special, they can be obtained.

When using patented track, the crane’s pre-engineered design from the track manufacturer’s catalog is used extensively for foundries, airplane maintenance hangers, and manufacturing applications with high duty cycles.

How do you determine headroom for this design of bridge crane?

Special attention must be paid to the headroom on underhung, single girder bridge cranes. Starting from the top of the runways, the beam is connected to the support steel, in this case at 25’ intervals, to match building columns. The beam size is calculated by a structural engineer. The end trucks ride on the lower flange of the runway beams and the single girder underhung trolley hoist operates on the 54’ span bridge beam.

Headroom is calculated by totaling these four measurements:

1. the size of the runway beam
2. the end truck drop
3. the bridge beam section
4. the headroom of the hoist.

What are the advantages of an underhung single girder bridge crane?

The underhung crane allows the trolley hoist to move to the end of the crane beam, which has 2” OSHA side obstruction clearance. This end approach maximizes the hook coverage on underhung cranes.

What is the top running, single girder bridge crane design?

This type of bridge crane uses an I-beam for the runway with the crane operating on ASCE crane rail above the beam. The runway can be supported with either free-standing columns or on structural haunches from building columns with the loading of the crane designed into the building steel. For new construction, designing the crane loading into the building steel is both a cost savings and floor space savings. The single girder bridge beam is connected at each end to the top of the end truck.

For the customer’s application at 15 tons and a 54’ span, this is a standard capacity and configuration for a top running single girder bridge crane. Meanwhile, 25’ support centers are common, and the runway steel is sized for this spacing. Again, the runway beam size is calculated by a structural engineer. In new construction, the customer has the option to allow the steel building contractor to supply the runway beams or allow the crane builder to do so.

How do you calculate headroom and hook approach for this design of bridge crane?

Headroom can be determined by adding 3” from the lowest obstruction from the ceiling to the high point on the crane beam, the height of the crane beam and the headroom (typically the dimension from the bridge beam to the saddle of the hoist hook at its highest position) of the trolley hoist. Headroom on top running single girders cranes is typically far better than underhung single girder cranes, maximizing the lifting height of the system.

Hook approach dimensions will be limited by the approach of the trolley hoist to the end truck and runway on either side. The runway end approach of the hook will be determined by half the overall length of the end truck and the position of the end stops on the crane rail.

What are the advantages of a top running, single girder bridge crane design?

Of the three configurations, this one may be the most cost effective.

What is the top running, double-girder design?

Like the top running single girder bridge crane, the double girder bridge crane uses an I-beam for the runway with the crane operating on ASCE crane rail above the I-beam, but now with two bridge beams. The runway can be supported with either free-standing columns or on structural haunches from building columns with the loading of the crane designed into the building steel.

The double girder bridge beams are I-beams, connected at each end to a long wheelbase end truck. For the application under review, 15 tons and a 54’ span is a standard capacity and configuration for a top running double girder bridge crane. For 25’ support centers, the runway steel is sized for this spacing. The trolley hoist runs on crane rail above the double bridge girders. The distance between the crane rails, center to center, on the bridge is known as the trolley gauge. Because the top running trolley hoist runs above the end truck on either end, the hook approach at each end of the double girder bridge is maximized.

What are the advantages of the top running, double girder design?

This design offers the best headroom of the three configurations, and it’s determined by adding: 1)the height of the top-running trolley hoist running on crane rail and 2) the beam section which is based on the capacity and span. Frequently, the high hook of the trolley hoist will rise above the bottom of the bridge beams. The disadvantage of this bridge crane design is that it tends to be more expensive than a single girder crane.

Bridge Crane Experts

Since 1969, Shupper-Brickle Equipment has provided bridge cranes, hoists and overhead lifting equipment to the Mid-Atlantic States and worldwide. Our experienced crane engineering and sales teams offer consultations on all types of overhead lifting applications. Contact us for manufacturer-standard equipment as well as customized designs.