Safe Main Line Loads on a Single Karabiner Load Sharing Connection

by Alan Sheehan B.E.

This information is provided for experienced Vertical Rescuers, abseilers, cavers and climbers to help them understand the behaviour of loads applied to a karabiner used in a load sharing anchor (or similar). As technical rope work requires skill (and experience) the author can accept no responsibility for the use or abuse of this information or the consequences of such use. If you use more conservative rigging methods, by all means continue to do so.

The following data assumes a karabiner with axial strength of 2000kgf, a strength across the krab of 600kgf, and the main axis (spine) of the karabiner aligned with the main line (rope).

The following diagram (from Vector Analysis for Vertical Rescuers) illustrates the rig this paper is concerned with.

WARNING! These safe loads do not apply if the karabiner is not oriented correctly to the rope! (ie karabiner spine approximately parallel to the mainline.)

The angles along the top and left of the table are measured in degrees from the line of the rope projected between the slings. The angles along the right and bottom of the table are measured from the rope itself.

Angle | Loads in Kilograms Force Safety Factor = 7 Angle
of |  from
this | Angle of the Other Sling -----> Rope to
Sling V 0 10 20 30 40 45 50 60 70 80 90 100 110 120 Sling
 0 286 286 286 286 286 286 286 286 286  286 286 286 286 286 180
 10 286 286 286 286 286 286 286 286 286 286 286 286 286 170
 20 286 286 286 286 286 286 286 285 267 251 235 220 160
 30 286 286 286 286 251 234 220 198 180 164 148  150
 40 286 286 286 251 204 188 174 152 133 117 140
 45 286 286 286 234 188 171 158 135 117 101 135
 50 286 286 286 220 174 158 144 121 103  130
 60 286 286 285 198 152 135 121 99 120
 70 286 286 267 180 133 117 103 110
 80 286 286 251 164 117 101 DO NOT USE SLING 100
 90 286 286 235 148 ANGLE COMBINATIONS 90
 100 286 286 220 IN THIS AREA OF CHART 80
 110 286 286 70
 120 286 60
 Angle from Rope to Other Sling ----->
 180 170 160 150 140 135 130 120 110 100 90 80 70 60

Where circumstances and equipment dictate that a karabiner must be used in a load share situation, the following simple rule may be useful. Where the angle between the two slings (ie opposite the mainline) is less than 60 degrees, the karabiner will not fail due to cross loading, and so is safe to the full SWL due to axial loading (eg 286 kgf). If the angle is between 60 degrees and 90 degrees, the krab is safe for up to 200 kgf, and for an angle between 90 and 120 degrees it is safe for only 100 kilograms maximum!

It is recommended that Maillon Rapides of 2000kgf minimum strength be used where possible in these situation. Alternatively, the karabiner can be backed up with another one the same size. This MUST happen if the main load is greater than the safe load listed in the table above. Alternatively the anchor could be re-rigged using an Alpine Butterfly knot to eliminate the need to cross load the karabiner.

SWL's for Cross Loaded Krabs / Alan Sheehan / mailto:als@mail.ix.net.com.au / revised July 29, 1998