· IRATA Training Manual

Mechanical & chemical anchor bolts

Rope access bolt anchors must comply with EN 795, and the substrate must be proven to withstand a 12 kN force applied to a sample area of 0.6 m² over a period of 3 minutes in the direction it would be applied in service.

Installation should be in accordance with BS EN 7883.

Minimum anchor strength

BS 7985 requires anchorages to have a minimum strength of 15 kN.

For eyebolts or other types of temporary anchors, this minimum may be obtained by linking and equally loading two EN 795 anchors with suitable knots (e.g. a Y-hang).

For aid climbing bolt anchors, a suitably competent person should ensure that the structure is engineered to be able to withstand a force of 15 kN in the direction it would be loaded in normal use.

Types

Three main fixing types exist — selection depends on the substrate:

  • Mechanical (expansion).
  • Chemical (resin).
  • Bolt-through.

A resin anchor should be used if it was considered the expanding action of a mechanical anchor might fracture the host material.

Reusable holes

A sleeve-type resin or expansion anchor can be left in the hole, the hanger plate removed and the hole capped. The anchor can then be subsequently re-used on return visits by uncapping the hole, replacing the hanger plate and re-testing to the required load.

Good-practice installation rules

  • Anchor bolts for rope access must always be used in pairs.
  • The host substrate should be carefully checked for cracks and other weaknesses.
  • The correct anchor type must be selected for the substrate material.
  • Pairs of bolts should be aligned correctly in relation to the intended load direction.
  • Holes should be drilled at 90° to the surface and to the correct depth using the depth gauge on the drill.
  • Hole diameter is dependent on bolt diameter and fixing type.
  • The minimum distance between 12 mm bolts should be 150 mm if full strength is to be retained. (Some manufacturers allow closer placement under strict criteria.)
  • Clean holes with a suitable hole brush and blow out — especially important for chemical anchors.
  • Expansion bolts should be torqued to the value specified by the manufacturer.
  • Resin anchors should be given time to cure — which may be temperature-sensitive.
  • The bolt head or hanger should sit flush with the surface.