Deviations

A deviation redirects the path of the ropes from the anchor points to either:

• Avoid a hazard or abrasion of the ropes (and other potential causes of damage), or
• Provide more accurate access for the operative.

Deviation anchors should be full-strength slings or rope anchored to the structure.

Single deviation

A single deviation is used to position the technician — where the consequence of anchor failure would be a small swing which has no potential for injury or rigging damage.

Double-anchor deviation

Used to deviate the ropes by a greater angle and distance than a single anchor deviation, and/or to protect against more serious hazards such as a sharp edge, hot pipe, or a large swing into a structure.

A double-anchor deviation uses a double rated anchor system — two suitably rated anchors and connection components — to provide protection against failure of any one item.

Rigging a deviation

A deviation may be a sling, strop or rope attached to the deviation anchor, then attached to the ropes via carabiners pulling them to one side. Single deviations should not pull the ropes such a distance that, in the event of failure of the single deviation anchor point, a swing likely to cause personal injury, damage to property or abrasion could occur.

Effect of angle on loading

Drag the slider to see how the force on the deviation anchor changes with the deflection angle. The rope colour and recommendation track the IRATA hierarchy — single, double-anchor, or step up to a re-anchor.

Numeric reference table▾

Deflection from vertical	Anchor load (with 100 kg load)
0°	minimal
20°	34 kg
45°	70 kg
60°	100 kg
75°	122 kg
90°	141 kg

The formula

Anchor force = 2 × L × sin(½ θ)

Where L is the suspended load and θ is the total deflection angle between the rope above and below the deviation. Both rope segments carry tension L; the anchor takes the vector sum.