Selection of SRT kit and risk assessment etc.

[Marc]

The reason I'm asking about rope selection is that should a ground anchor be used we have a potential for twice the 'normal' load on the rope. Potentially if then used in this configuration for rescue it becomes four times the 'normal' load. One of my climbers said he had read an article about the working loads tree climbing ropes are designed for and that some of the lower specification ropes are not strong enough to have an acceptable redundancy for all SRT applications.. I will try and track down the article.

 

 

 

 

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Mike has covered this well, but also consider this - the rope is only doubled its not 2 ropes, when the rope goes through a pulley/rings its essentially a single rope at that point on a bend! There is some thought that when ropes are tied off at the top either with a stopper knot/bowline/alpine the increased number of turns/bends when subject to a dynamic load this will absorb the energy.

 

I would like to see the article, as currently in the UK we do not climb on tree climbing ropes rather ropes to the standards laid out in EN1891 which is single rope for industrial rope access.

 

What he may be referring to is this the EN1891 type a and b

European Norm 1891 from A-to-B

Edited March 27, 2017 by Marc

[Wooden Hand]

I'm writing a risk assessment and method statement to support the use of SRT. I am not aware of any national (FISA/AFAG type) guidelines for this. If there are any please point me in that direction.

 

Non CE marked equipment eg the rope runner causes me some concern. As its not CE marked it can't be supplied/sold for the work we do in Europe. I am interested to know how others are managing the risk assessment and method statement in this and similar situations?

 

Also

 

I understand that not all tree climbing ropes are suitable for SRT. Is this the case and if so what makes a rope appropriate and another one inappropriate and how are people managing this particularly with sub contract climbers providing their own kit

 

Thanks David

 

Hello David,

It is nice to see your considered approach to taking stationary rope system(s) into the professional work environment. You are right about mechanicals not being certified and while this may stop you from going deep into the work practices right away, it is only a matter of time before a certified device comes into the market. It is sensible to do some homework regarding the myriad differences in risk awareness and anchoring strategies inherent to stationary systems. This way you may iron out some close-calls before they appear at your work site. And find ways to manipulate the systems to best suit your work environment.

From my own experience of running dismantling crews along railway lines I have set up some protocols.

1. No Big Shots as the rebound can be uncontrollable.

2. Very specific throwing risk assessment which ensures the safe capture of the uppermost point in the tree when setting a floating (trunk anchored) line. Blind bounce testing is not how we do it, logical and systematic steps and multiple person and angle checking is key for us.

3. We work off trunk anchors around 1-2% of the time and so we developed ways to self release the trunk anchor in order to set top anchors. This is a huge subject. I expect you will need to differentiate between work off a top anchor or work off a floating anchor and then apply known techniques to deal with each. There is no question that for simple tasks simple trunk anchored systems are hard to beat but it is also true that they pose a far greater risk when cutting and rigging. I have watched novice climbers bounce there non running chainsaws along the anchor leg when accessing, it does't take much to cut a taught line.

4. Set retrieve lines after the work has been done as they are simply a hindrance.

5. Use false anchors to save damage to the tree and rope. You can use stationary systems within DdRT anchoring ideas. In fact, this is a mighty good way to make the transition from dynamic to stationary.

6. Understand the difference between load sharing and non-load sharing re-directs.

7. Relearn basic movement patterns so as not to rag the hell out of elbows and shoulders.

 

I have just finished writing a test for an association over here and decided to fail systems if they did not have the implicit rigging potential to retrieve as and when the climber needs to. Single stationary systems, wether top anchored or floated fail in this. It may not be a crucial point for you but I thought I would mention it all the same.

 

Good luck and please throw any questions back to me.

[Wooden Hand]

 

A single rope (even without the added semi-active rope of a base anchor) may absorb much more force in a fall than a doubled one as the force isn't halved/ strand so it can elongate more, absorbing the impact.

 

Hey Mikey,

I wanted to write this into an exam recently but was asked to remove it because I couldn't back it up with any facts. Do you know of any testing done on this? Perhaps we could do something together in the autumn?

[Wooden Hand]

The reason I'm asking about rope selection is that should a ground anchor be used we have a potential for twice the 'normal' load on the rope. Potentially if then used in this configuration for rescue it becomes four times the 'normal' load. One of my climbers said he had read an article about the working loads tree climbing ropes are designed for and that some of the lower specification ropes are not strong enough to have an acceptable redundancy for all SRT applications.. I will try and track down the article.

 

 

 

 

Sent from my D6603 using Arbtalk mobile app

 

With an 11.5mm double braid, tied and knot blocked against a ring you have around 15-20kN ABS. That gives a 100kg climber a 15-20:1 safety factor, a rescue scenario potentially halves this. Is this adequate?

Testing for the ART Twin Line got 22kN with an Alpine Butterfly blocked directly to the side plates of the Cocoon 5 pulley, their user instructions ask for a natural anchor to withstand at least 12kN.

It comes down to what you desire, what you feel is safe and fit for your company. You should see some of the anchors that the gardeners tie into over here, completely hair-raising, I suspect that they average a safety factor of 2:1 at most.....with gear averaging ten times that !