FAQ >> Mobile Crane Clearance In Tight Quarters

Mobile Crane Clearance In Tight Quarters

It is remarkable how a mobile crane, by its very nature a huge appa ratus, is routinely shoehorned into snug urban or industrial settings. The means of getting the crane assembled and into a postage-stamp sized position is a subject unto itself. Once there and operating, clear ance for both the front end and the back end is often tight and needs verification.

A large front-end attachment such as a boom with a luffing jib has a correspondingly large minimum working radius. While the boom or jib might have clear space to swing from the pickup location to the load setting zone, the minimum radius prevents loads from being placed close to the crane. A luffing jib might be fitted with a mid fall hoist line to overcome this inadequacy.

The tail-swing radius may encroach over an active traffic lane or face interference from an obstruction. A large crane can have a rear projecting gantry, strut, backstays, or a live mast capable of fouling trees, buildings, or electric power lines. Placement of the crane is often close to the face of a building that prevents the tail end from swinging through a full circle. Tail-swing of a live mast or guy struts varies with the boom angle; the full working range of boom angles needs to be considered.

The front-end attachment, be it a straight boom, a boom-jib com bination, or another type, could also be prevented by buildings or other obstructions from swinging in a full circle. A crane that starts a project with a free swing might not have clear space by the time the erection work is completed. These limitations not only weigh on the operation but also need to be considered when the front-end attach ment is to be stowed during nonworking hours or the crane is to be secured in advance of a storm.

Interference is sometimes caused by a secondary element that might easily be missed unless the planner takes a second look. A cab, slack cable, or transition piece might easily be overlooked. The clearance dimensions of projecting or overhanging components are usually given in general dimension diagrams provided with the crane documentation.

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