Lifting beam

If a long load is slung from the crane hook with two inclined legs, two things happen. The force in each leg rises with the angle: for two symmetrical legs F = G / (2 · cos β), where β is the angle to the vertical. At 60 degrees each leg already carries the full weight of the load. And the horizontal components of the leg forces compress the load.

The beam replaces the inclined legs with vertical ones. The lifting points are loaded upwards only, long or flexible parts stay straight, and the hook height needed is lower than with a long sling at a small angle.

A lifting beam hangs from one point at its centre and carries the load at its ends; the beam is loaded in bending. It is low in height and is the usual form on handling devices and in halls with limited hook height.

A spreader beam hangs from an inclined sling at its ends, with the load below at the same points. The beam then mainly takes compression and can be built lighter – but the arrangement needs more height. For four lifting points there are H-beams and cross beams.

What has to be verified is bending and deflection of the beam, stability against lateral buckling, the suspension and the lifting points. Adjustable lifting points allow different load lengths; capacity may then depend on the position and has to be stated for each position.

The dead weight of the beam comes off the capacity of the hoist, its height off the lifting height. Both belong in the planning at an early stage.

A beam hangs level only if the centre of gravity of the load is vertically below the suspension. With asymmetrical loads, the suspension or a lifting point is shifted. If that is not done, the load hangs at an angle, and the lifting point on the heavy side carries more than half – possibly more than it is rated for.

Lifting beams are lifting accessories with their own declaration of conformity under EU machinery law; EN 13155 is the relevant standard. Working load limit and dead weight are marked on the beam. Like any lifting accessory, the beam is inspected periodically by a competent person – above all for deformation, cracks at welds and wear at the suspension and lifting points.