Overhead Cranes - Double Girder and Single Girder

Overview:

• <10 tons means single girder
• >15 tons means double girder
• Space considerations between Top of Rail and ceiling may change your configuration.

There are two ways of determining if your new overhead crane should be a single girder or double girder. The first is capacity-related, and is fairly absolute. The second is dimensionally-related, and requires a balancing test of cost versus dimensional suitability. Typically a jib crane will always be a single-girder crane. Gantry cranes have similar girder determining factors as bridge cranes. With a single girder crane, the hoist almost always runs along the top of the bottom flange of the mill-rolled I-beam or fabricated box girder. With a double girder crane, the hoist will mostly run on a railroad rail or steel bar mounted on top of the girder.

Most overhead cranes over ten tons will be double-girder. Almost all overhead cranes over twenty tons will be double-girder. The exception is a torsion-girder crane, where a hoist/trolley unit rides on top of the single girder and the lifting chains or wire rope is run down the side of the girder. This is a complex and rare overhead crane. When dimensional factors such as a lack of height above the crane come into play, the overhead crane builder can suggest the best configuration based on a balancing test of cost versus space needed. It’s best to plan on a top-of-rail to ceiling of three to four feet. Note that if you have lights, ducts, or sprinklers, the three-four feet must be between TOR and the hanging obstructions.

When filling out the “request for competitive proposal” we have on our site, it’s best to include as much detail as possible before submitting it, as lots of money can be saved when the most information is provided.