Lifting methods

Working with concrete elements? Here's a guide on lifting with clutches.

Lifting with clutches

Do not lift with a lifting clutch connected side-ways.

When lifting with lifting clutches, always make sure that the clutch is connected with the tail of the clutch in line with the load.

It should never be connected at right angles and when lifting vertically. It should never be horizontal. With the clutch tail horizontal, a long lever arm develops between the load and the anchor.

Tail of the clutch in line with the load

Never horizontal

Lifting with the sphere horizontal causes the anchor to bend. It becomes trapped by its head between the slot lips of the sphere. The lips bare hard against the top of the anchor and the underside of its head.

Depending on the size of the load and the direction of lift, there may be two severe outcomes:

• repeated loading can cause the clutch lips themselves to bend out and break
• the anchor head may be “chopped off” from the shaft by the clutch lips.

Anchor head chopped off

Note: the sphere of the Locking Klaw (LK) may also rotate, but has reinforced side walls which resist bending. The LK sphere always remains in the safe position with the anchor locked in the rear of the slot.

Locking Klaw

Anchor recess

Lubricate the anchor and recess when using lifting clutch systems for “in-plane” rotation of concrete elements.

Some elements may need to be turned either after casting, or from their transported position before placement. Typical examples are:

• box culverts
• pipes
• piles.

Best results come from the anchors being installed with (round or articulated) steel recess formers. These formers provide a smooth surface and constant rotation path for the spherical head of the clutch.

When turning elements such as box culverts or pipes through 90 degrees, the anchors are normally placed in opposite faces in line with the centre of gravity. This is to ensure element stability during rotation.

Side elevation

Section A

Section B

In some situations (for example, piles) anchors are placed near one end and the element rotated about the other end. This is shown in the images below:

Rotating element

Rotating element

The sphere and concrete recess

During lifting, the force in the slings causes the spherical head of the clutch to roll over and press against the inside surface of the concrete recess.

The bearing force develops a high friction resistance between the sphere and the concrete recess. This is shown in red in the diagram below. This resistance can prevent the sphere from turning freely when elements are rotated.

This can be common with the conventional lifting clutch design where the tail must be in the “up” position for safe lifting. Be aware that this results in an asymmetric friction surface extending from under the tail down into the recess.

High friction resistance between the sphere and the concrete recess

High friction resistance between the sphere and the concrete recess

If the sphere jams, it may suddenly release when the friction force is overcome and then catch again. This causes juddering and impact loading.

In severe cases, if the sphere becomes completely jammed, the rotation of the handle causes sideways loading. This results in damage and possible failure of either the anchor, clutch or both.

Smooth rotation

Smooth, safe rotation is achieved by lubricating the inside surface of the recess with grease. This prevents the sphere from sticking.

Lubricate the recess for smooth, safe rotation

Install anchors with steel recess formers and lubricate the recess for smooth, safe rotation.