Force of a 250mm fall

[ANK]

Wots the reasoning behind it being banned ? Do you know P  ?  K

We do a lot of commercial work for big construction firms and councils so all climbing systems have to be CE certified and fit for purpose.

It’s a very professional and well run company which is great but they have to be really careful to adhere to any HSE guidelines or legislation.

So what wouldn’t be a problem for many climbers can be for us.

I just don’t believe using the ASAP to be inherently “dangerous” and there doesn’t seem to be any clear legislation one ways or the other as to if it can be used in tree work.

[openspaceman]

25 minutes ago, ANK said:

 

Exactly that! I’m asking because Petzl mentioned that the ASAP could potentially be used in tree work but that when deployed with a shock absorber it can easily generate 4 to 5kn of force.

So I’m wondering if our anchor points that we select can withstand 4 to 5kn of force? And how much force a 500mm fall generates.

If it absorbs shock on the body it also  reduces shock on the anchor. The point of the simple ones is they  rip stitching and in doing so slow down the body as the breaking the stitches absorbs some of the kinetic energy of the falling mass, they spread the smaller force due to deceleration over a greater distance. As tension in the rope is the same throughout this force is also reduced at the anchor.

[Paddy1000111]

59 minutes ago, ANK said:

 

Exactly that! I’m asking because Petzl mentioned that the ASAP could potentially be used in tree work but that when deployed with a shock absorber it can easily generate 4 to 5kn of force.

So I’m wondering if our anchor points that we select can withstand 4 to 5kn of force? And how much force a 500mm fall generates.

If I can tick all the boxes that Petzl stipulate then I can argue my case to the company I work for.

 

That seems a bit silly if that's what they are worried about. The force generated during a fall is going to be the same be it a petzl asap, grigri or a hitch.

 

Or are they saying that the asap creates more force as it drops a little bit before it locks in? Which would be deminished by the shock absorber system?

 

I take it somewhere in the asap manual it says that the anchor point must be rated to 5kn and that's the issue? 

[daltontrees]

8 hours ago, Justme said:

Or this one for static rope

 

Fall Factor Calculator

FERFORGE.TRIPOD.COM

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how to fall

 

You can't compare rock climbing to tree work. Rock climnbing ropes are for fall arrest, tree work ropes are for work positioning. The former have to elongate to absorb the fall, the latter have to be almost non-elastic so that you can climb the rope and then be stationary while cutting etc.

[daltontrees]

6 hours ago, ANK said:

 

Exactly that! I’m asking because Petzl mentioned that the ASAP could potentially be used in tree work but that when deployed with a shock absorber it can easily generate 4 to 5kn of force.

So I’m wondering if our anchor points that we select can withstand 4 to 5kn of force? And how much force a 500mm fall generates.

If I can tick all the boxes that Petzl stipulate then I can argue my case to the company I work for.

4kN to 5kN force on an anchor point is the same as hanging a 400-500kg weight off it. When selecting an anchor one should maybe try and imagine if you could hoist 1/2 a tonne up on it slowly.

[daltontrees]

I imagine the effect on your intetrnal organs of a straight vertical drop and sudden stop in a harness would be something like being in a car crash at 30mph wearing a seatbelt. i.e survivable but not good for you and with little margin for error. And as with car crashes, falls and sudden stops could cause disastrous skeletal damage, and then there's ligaments, tendons, cartilage... brain damage.

It's nothing like jumping off a sofa. Paratroopers can arrest falls on landing becasue they're ready for it and trained to absorb the energy in ways that doesn't cause damage to them. Not the same as taking it all through your pelvis and base of spine in a fraction of a second, unprepared, sideways.

The limit of 500mm might seem silly, but it's probably only half of what would certainly **************** you right up, and there can't be many people around who would vouch for it being silly, after having experienced it.

[Justme]

3 hours ago, daltontrees said:

You can't compare rock climbing to tree work. Rock climnbing ropes are for fall arrest, tree work ropes are for work positioning. The former have to elongate to absorb the fall, the latter have to be almost non-elastic so that you can climb the rope and then be stationary while cutting etc.

Did you not see the word static? 

That calc works for you.

Using static over dynamic doubles the impact force.

[openspaceman]

4 hours ago, daltontrees said:

I imagine the effect on your intetrnal organs of a straight vertical drop and sudden stop in a harness would be something like being in a car crash at 30mph wearing a seatbelt. i.e survivable but not good for you and with little margin for error. And as with car crashes, falls and sudden stops could cause disastrous skeletal damage, and then there's ligaments, tendons, cartilage... brain damage.

Quite and I'm unsure what shock loading the body can survive, of course the body will deform  to some extent and thus absorb energy and reduce damage elsewhere. In this case the OP is concerned with the shock loading on the anchor point.

 

When I was a child  fatality from minor car accidents were common so ROSPA, IIRC, attended local shows with a demonstrator to encourage the use of seat belts. It was a car seat and belt on a tilted rail such that the seat came to a sudden stop after accelerating down the short ramp and reaching around 5mph. The shock loading was hard enough even at that speed that a normal person would have had difficulty in not being thrown out of the seat without a belt on.

 

Of course in most accidents the vehicle deforms somewhat and absorbs energy but a static climbing line...

[Dbikeguy]

Only issue you may have with the Asap is it’s designed to be used with a shock absorbing tether, they rip on force falls, that would drop you further and potentially into stuff below you.
They are also a locking device so to release you have to lift the casualty up to take load off the asap to then be able to descend.
That may show up a problem to your employer in that we as 38 ticket holders are not specifically trained to deal with that problem. It requires more kit and ideally a pulley and ascender to make life easier. of course you could attach them to your harness in the usual way then cut away their asap rope but it’s not ideal as they will jerk when you do this.

If going down that route it would be worth practicing with your usual crew on how to unload it.

[Paddy1000111]

5 minutes ago, Dbikeguy said:

Only issue you may have with the Asap is it’s designed to be used with a shock absorbing tether, they rip on force falls, that would drop you further and potentially into stuff below you.
They are also a locking device so to release you have to lift the casualty up to take load off the asap to then be able to descend.
That may show up a problem to your employer in that we as 38 ticket holders are not specifically trained to deal with that problem. It requires more kit and ideally a pulley and ascender to make life easier. of course you could attach them to your harness in the usual way then cut away their asap rope but it’s not ideal as they will jerk when you do this.

If going down that route it would be worth practicing with your usual crew on how to unload it.

Whilst I agree with the rescue issue, when doing the cs38 rescue portion the training was (at least in my case) based on the climbers gear being cut/unsafe so you would transition the casualty into your gear by a bridge to bridge and tying an alpine butterfly into the static side of your ddrt or using a prussic to do the same then clipping them into that so you can take the casualty weight up on your gear  and disconnecting the casualty from their kit completely or in reality cut it away so it shouldn't make too much difference?