Preparation and planning

Planning a lift with concrete elements? Use this page as a guide for how to prepare safely.

Risks

Working with concrete elements can include the following risks:

• incompatible components
• incorrect rigging
• incorrect orientation of connection (the tail away from hook).

Always take up the load slowly, controlled and while checking alignment.

Twisted chains

Twisted chains or slings can cause problems with vertical lifts.

During the lift, conventional clutches can turn from:

• safe: tail up, to
• unsafe: tail down

If the chains are twisted, torsion develops in the chains when the load is applied. The torsion exerts a rotational force to the clutch handle. This means it makes the clutch handle rotate.

The twisting forces between the curve of the handle loop and the interior curve of the sphere causes the sphere to turn around the anchor head.

Finally, the handle “flips” around, the sphere turns into the “tail-down” position and the tail rotates up, seen in the image below:

Twisted chain

The image above shows:

1. Clutch connected in “apparently safe” tail up position
2. Twisted chains cause the handle to turn and the sphere to rotate
3. The sphere may continue through the horizontal position as the handle rotates
4. The handle flips over, the sphere turns to the unsafe “tail-down position” and rotates up.

Attaching conventional clutches “tail-up” does not guarantee safety.

Supervision is needed at all times during the lift.

Tail up connection can lead to:

• clutch rotation
• anchor or clutch side-wall failure.

Depending on the twist in the chains or if it relaxes, the sphere can drop into the unsafe horizontal position.

Unsafe horizontal position