What Are Spreader Bars?
Spreader bars, often called spreader beams or lifting beams, are horizontal structural members that are used to provide expanded versatility while hoisting loads.
Figure A below is a sketch of a typical spreader bar.
How Are Spreader Bars Used?
Spreader bars are used in several different ways. The basic arrangement is that shown in Figure A. This allows for two attachment points on the load. This is safer than a single pick point because the stress is divided between the two hoisting ropes. By providing a direct upward hoist, often times this lifting arrangement avoids the need for an angled pull. An opposite configuration is that shown in Figure B which is simply the basic arrangement flipped vertically. Not commonly used, the Figure B arrangement might be appropriate in a situation where two cranes are being used to lift a common load.
Figure C below shows a specialized spreader bar being used to lift an irregularly shaped load. Figure D shows a spreader bar being used to create multiple pick points for a load that might be extremely flexible. These examples illustrate the usefulness of spreader bars.
How Are Spreader Bars Fabricated?
Aside from the already mentioned steel beam sections, the horizontal beam itself can be fabricated from hollow structural shapes, or even from pipe. Figure E below shows these other cross sections.