Thanks for the detailed reply Chris. That must have kept you out of trouble for a while.
I'll try to explain myself some more:
100kg is the standard load test used in industrial testing. Anything else is meaning less because this is the benchmark for other items in the safety system (EN standards). The MBS of the karabiners was 22kN. This is how the 22:1 safety factor is derived. For those that don't know, 6kN is the limit of force to be experienced in a work at height system in EU.
The karabiners were failing at their rated strengths, because the prusiks and knots used in a DdRT system were holdng out so well (phenomenally well).
Accounting for more than 8kN in real life (absolute max) is fairly futile, as the body is long beyond its 'best before load limit', and rapidly approaching its 'expirey load limit'!
Therefore, the 15kN you mention, has a built in safety factor to account for safety over time (material degradation) and rescue. This is more important for textiles than hardware. Normally, Karabiners will not weaken with time for this to be an issue.
As in rigging, safe systems consider cycles to failure and the weakest link. In a typical DdRT climbing system, this is extremely unlikely to be a properly aligned karabiner, but very likely to be the climber. I won't go into the issues of 'Sporty' climbing encouraging 8kN loads.
With regard to the hitch cords, the burns I have witnessed on my own ropes were from long descents - a hot spot develops over time. It can also easily happen with 'sporty' climbing.
The prusik research and my climbing style is based on seperate, properly aligned karabiners for hitch and terminating the lifeline. This is the same as the hitch climber, only obviously clipping to the same attachment ring, rather than the hitch climber/mickey mouse. This gives many advantages similar to the hitch climber, and some more.
Clipping all life support into 1 karabiner that isn't an HMS, creates high loads on the nose. I'm sick of pointing out to climbers that a klettersteig krab is not an HMS and is the worst of the lot in this situation (and not exactly getting thanked for it
). It still wouldn't reduce the load to 8kN though (i.e the human body will be at huge risk).
The real issues are:
1) Climbers obsessed with speed and style, abusing slack management in their systems, climbing above an anchor point, jumping around when tied to a small anchor point, creating situations that can easily generate forces sufficient to seriously damage their health for the rest of their life should they get it wrong and the equipment doesn't fail.
2) A blatant disregard for the above, as long as they look 'Cool'.
3) Lack of knowledge on the work site of what a safe system of work is (reliance on Breaking Strength without understanding limitations and configurations).
I expect you'll agree with some of that. Which again shows how far we have to go as an industry before we see competence in professionally managed risks on the work site (i.e. skilled and knowledgeable supervision).
FWIW, My points are:
1) A hitch climber can help reduce weakening forces on karabiners, but other systems do just as well.
2) The karabiner reduction in strength is still sufficient compared to the 6kN that our systems are designed for, let alone what the body can withstand (i.e. karabiners are not the weakest link)
3)Climbing 'sporty' (recklessly?) in a 'work positioning' sysem, is much more of an issue to health & safety than either of the above (capable of creating 'fall arrest' system forces).
As for presentations around the world, i feel there are much more cost effective and environmentally friendly ways of presenting important information to the everyday arborists that need it.