Toolbox Talk - Single Point of Failure or Backed Up

So, lets dive into the world of “Single Point of Failure” Or “Backed up”

A Single Point of Failure or SPOF is a point in a system (in our case, a rope system), that if it fails, the whole system fails. The idea of Single Points of Failure is the basic concept in understanding the application of backup in rope work.

If we were to look at the pictures above of a hauling system on the left, (into a replicated stretcher bridle) you can see the twin lines enter the pulley and back to the hauling system a simple 2:1 MA – but the double pulley only has a single axel and if it failed would be or could be catastrophic and its onto a single point on the Kong rigging plate (let’s not start on double rigging plates)

Whereas the one on the right has a quickdraw to back up the SPOF which would capture the twin ropes and a second point of attachment on the plate

Here we have a twin line deviation with the tree as the new anchor, the left picture has a single sling around the tree and into the double pulley but think what would happen to the critical load if a SPOF happened? (double pulleys in any MA don’t need backing up as not critical to the load if the axel failed)

But the one on the right now has two slings and the double pulley is now backed up with a quickdraw in case of a SPOF

The angle of the lines is 90º roughly so its less load on the anchor remembering that the critical angle is 120º as the load is now equal on the anchor, past 120º the load increases massively.