Which Crane should you choose – Single Girder or Double Girder?

Hii..this post is about which crane should you choose either Single Girder or Double Girder?

A common misconception is that double girder cranes are more durable! Per the industry standards (CMMA/DIN/FEM), both single and double girder cranes are equally rigid, strong and durable. This is because single girder cranes use much stronger girders than double girder cranes. The difference between single and double girder cranes is the effective lifting height.

Generally, double girder cranes provide better lifting height. Single girder cranes cost less in many ways, only one cross girder is required, trolley is simpler, installation is quicker and runway beams cost less due to the lighter crane dead weight. The building costs are also lower. However, not every crane can be a single girder crane. Generally, if the crane is more than 15 ton or the span is more than 30m, a double girder crane is a better solution.

The advantages and limitations of Single / double girder cranes are as follows:

Single Girder Cranes

o Single girder bridge cranes generally have a maximum span between 20 and 50 feet with a
maximum lift of 15-50 feet.
o They can handle 1-15 tonnes with bridge speeds approaching a maximum of 200 feet per minute (fpm), trolley speeds of approximately 100 fpm, and hoist speeds ranging from 10-60 fpm.
o They are candidates for light to moderate service and are cost effective for use as a standby (infrequently used) crane.
o Single girder cranes reduce the total crane cost on crane components, runway structure and building.

Double Girder Cranes

o Double girder cranes are faster, with maximum bridge speeds, trolley speeds and hoist speeds approaching 350 fpm, 150 fpm, and 60 fpm, respectively.
o They are useful cranes for a variety of usage levels ranging from infrequent, intermittent use to continuous severe service. They can lift up to 100 tons.
o These can be utilized at any capacity where extremely high hook lift is required because the hook can be pulled up between the girders.
o They are also highly suitable where the crane needs to be fitted with walkways, crane lights, cabs, magnet cable reels or other special equipment.

TYPES OF ELECTRIC OVERHEAD CRANES - Part 2

Hii...we continued the last post that talk about overhead crane generally or basically..

There are various types of overhead cranes with many being highly specialized, but the great majority of installations fall into one of three categories:

a) Top running single girder bridge cranes,
b) Top running double girder bridge cranes and
c) Under-running single girder bridge cranes.

Electric Overhead Traveling (EOT) Cranes come in various types:

1) Single girder cranes - The crane consists of a single bridge girder supported on two end trucks. It has a trolley hoist mechanism that runs on the bottom flange of the bridge girder.

2) Double Girder Bridge Cranes - The crane consists of two bridge girders supported on two end trucks. The trolley runs on rails on the top of the bridge girders.

3) Gantry Cranes - These cranes are essentially the same as the regular overhead cranes except that the bridge for carrying the trolley or trolleys is rigidly supported on two or more legs running on fixed rails or other runway. These “legs” eliminate the supporting runway and column system and connect to end trucks which run on a rail either embedded in, or laid on top of, the floor.

4) Monorail - For some applications such as production assembly line or service line, only a trolley hoist is required. The hoisting mechanism is similar to a single girder crane with a difference that the crane doesn’t have a movable bridge and the hoistingtrolley runs on a fixed girder. Monorail beams are usually I-beams (tapered beam flanges).

Ortie, see u next post..thanks.