Breaking strength ratings, misc. life support hardware

[Burnham]

I don't have any rub with the dicotomy of 5,000 lb. vs. 22kN specs...we have written that exception to the Z into the FS climbing regs. Those two numbers are so close as to be materially identical.

Where I'm in real conflict is how to manage language in the FS Treeclimbing Guide to allow use of these ubiquitous items that have BS ratings that fall far short of this.

SRT systems really are popular in tree crown research activities, and I've been teaching several different styles of SRT ascent for many years. I have known that the handled ascenders themselves don't come up to the stated USFS (and ANSI) standard, but have for the most part kept my mouth shut, though as you well know, I seldom do that .

I think the straw that broke the camel's back for me is the growing popularity of the Tree Frog SRT system. I looked up the BS of the Croll on Petzl's website recently, and see that it's rated BS is 4.2kN to 6.5kN, depending on the diameter of the rope it's mounted on.
http://en.petzl.com/ProduitsServices/B16_CROLL_B165000J.pdf
That is pretty darn low for the component in the system that supposedly performs the final backup...unless you follow Petzl's diagram and use a second "safety" line towing some sort of rope grab (I for one have no idea what the specs of a type A or type B rope grab is) attached to a dorsal point on a fall arrest harness :roll:. We all know that is not going to be viable in tree work.

Then I started looking at the ropegrab style lanyard/flipline adjusters, and woe is me...

Somehow we (the tech. advisory group) need to come up with a way to allow use of these things in the USFS program, either within the general requirements of OSHA and ANSI, or by exclusion language that is defensible.

Any suggestions? Please??

 

[Stumper]

I suggest writing a subset of rules for ascent systems only. Include the general rules for system back-ups and redundancies and write in an exception to the Breaking Strength rules for ascent sytems ONLY. If a hybrid system is to be employed where a DdRt sytem will be used off of the SRT ascent line then it must be secured in defined ways (For our local chapter TCCs we are requiring either a prusik type knot with a knot in the rope below it or a loop knot such as an Alpine butterfly from which the DdRT system is suspended. We made those rules acknowedging that mechanical Ascenders are useful and viable rope work tools adequate for their designed purpose of ascending ropes with relatively static loads of human body weight but almost ALL of them have issues of inherent strength or rope shearing tendencies when shockloaded at levels including "survivable falls".

 

[Burnham]

Now we're getting somewhere. Thanks very much, Justin.

Any bright ideas about the lanyard adjusters?

 

[sotc]

An addendum to Justins idea by adding in "work positioning" lanyards. Kinda leaves you hanging as far as chunking down a stem unless you required a (decent line climbing line) long enough to reach the ground...

 

[SkwerI]

When I started climbing the 'three point stance' rule was still in effect. You could legally unclip to reposition your rope if you maintained your 3 point contact.

 

[emr]

Two years ago at our annual arb. conference I asked two speakers that same question about ascenders not being rated. The response that I was given made sense to me. They said that since the ascenders are made for humans to ascend a line, so as long as you are using the ascender as it was intended to be used, you will be fine in OSHA's eyes. The speakers are very well known and respected arborists and one of them is very very involved with ANSI, so I trust what they say.

 

[Stumper]

Burnham, Sorry I failed to check back in on this thread. I have a rope grab for a lanyard adjuster for use on conifers but I almost always use a friction hitch adjusted lanyard-I tend to not think about them much. Off the top of my head it would seem that a 2500 lb mbs rating on a lanyard adjuster would be reasonable-lanyards should never take long falls and by nature of application the load is shared between two legs. If a stopper of some sort is located on the end then running through the device is precluded. I think most of the lanyard preferred rope grabs can meet that since they are more solid in construction than handled ascenders. Since the cams are usually smooth and they don't shear rope as readily they aren't as tricky as other ascenders on the whole safety issue...but they are definitely living in sort of a gray area.

 

[Burnham]

Some meet 5,000 lbs. and some don't, Justin. The Petzl Macrograb is 6,000, but the Micro is 3,500. There are 3 different versions of the Gibbs, only one exceeds 5,000.

The Positioner, Trango Cinch, and the Ushba don't meet 5,000...best as I can ascertain.

CMI Ropewalker does exceed...7,500 lbs.

So it's a case where more don't than do pass muster.

I hear you about the two legs thing for lanyards...but how about the odd time when I take a turn around the tree with the snaphook end and clip back to the lanyard, then I'm on one leg only.

 

[pantheraba]

...but how about the odd time when I take a turn around the tree with the snaphook end and clip back to the lanyard, then I'm on one leg only.

I have used a round turn on a small trunk before to get a cinched up lanyard to help with positioning...but I don't think I have ever gone around the trunk and snapped the lanyard back onto itself...that means if you fell just that one D-link would be holding you, right?

When would you use that? Maybe when you are twisted around precariously and can't get to the far "D"?

 

[Stumper]

Burnham, I've done that also but at the back of my mind there is the little voice saying that if forces exceed 2500 lbs the body is failing anyway so why worry about the ratings(?).

Gary, brings up another point about single side D attachment. The New Tribe saddles which all 3 of us prefer come equipped with standard side D's that are only rated at 2500lbs force each... I realize that some models have the bigger Ds standard and they are available for all the New Tribes but the small Ds are "enough".(see rationale above)

 

[sotc]

Gary, I do occasionally use that method, but I i will move my attachment point back to the center d

 

[pantheraba]

Gary, I do occasionally use that method, but I i will move my attachment point back to the center d

I sometimes go around the tree and snap back into my center D, especially when I have to hang from the lanyard rather than stand with it.

But I have not snapped back into the lanyard itself.

I don't know why there is a square around the pict...best I could do in a hurry.

 

[pete mctree]

That method is only recomended for work positioning, to supliment a primary anchor point. The reason being that the lateral loading on the snap(or krab) firstly has the potential to sever the line if a fall was occour, due to the acute bending radius of the line, compounded by the crushing motion against the stem. Secondly the hardware is not designed for lateral loading at the tip. The research below (incompete sorry but all I could find) illustrates this. (page 40)

http://www.treemagineers.com/downloads/Karabiners_and_Connectors.pdf





There are ways to avoid this. You cound tie an alpine butterfly or a small sling on the line to clip back too.

 

[Burnham]

I have used a round turn on a small trunk before to get a cinched up lanyard to help with positioning...but I don't think I have ever gone around the trunk and snapped the lanyard back onto itself...that means if you fell just that one D-link would be holding you, right?

When would you use that? Maybe when you are twisted around precariously and can't get to the far "D"?

Gary, I might use this when I want to counter the pull of the lifeline...say my tie in is above and off to the left and I want to cut on my left. If I can cinch the lanyard to a limb off to the right, exerting pull on my right D ring, I keep from having to fight the lifeline's pull on me towards the place I want to cut...and don't have to fight to balance that pull as I would if I had clipped into both D rings. Also, the lanyard is not crossing in front of me, where the lifeline already is complicating reaching to the cut. I can lean way out to the left to cut, often extending my body laterally using my legs out to the right to counterbalance my upper body out to the left, without fighting to keep position.

 

[Burnham]

Burnham, I've done that also but at the back of my mind there is the little voice saying that if forces exceed 2500 lbs the body is failing anyway so why worry about the ratings(?).

Gary, brings up another point about single side D attachment. The New Tribe saddles which all 3 of us prefer come equipped with standard side D's that are only rated at 2500lbs force each... I realize that some models have the bigger Ds standard and they are available for all the New Tribes but the small Ds are "enough".(see rationale above)

Agreed, Justin.

Again, I'm really not concerned about these devices, or D rings either, being safe. I am looking for a way to address their lower than OSHA requirement breaking strengths in language I can defend.

 

[pantheraba]

Gary, I might use this when I want to counter the pull of the lifeline...say my tie in is above and off to the left and I want to cut on my left. If I can cinch the lanyard to a limb off to the right, exerting pull on my right D ring, I keep from having to fight the lifeline's pull on me towards the place I want to cut...

Got it...work positioning. I do similarly but have always snapped back into the same side D, not the lanyard. I'll let that idea ramble around in the background next time I'm in that kind of situation.

Thanks.

 

[Burnham]

What you just described works just as well, so long as you have enough lanyard, Gary.

 

[pantheraba]

What you just described works just as well, so long as you have enough lanyard, Gary.

Yep, I am running a lanyard of 16 feet so I often use it to belay myself back towards my anchor point (or below it, really) to control the pendulum effect.

 

[CurSedVoyce]

Hey Burnam... You see the rating on this one?

http://www.baileysonline.com/itemdetail.asp?item=FP7208&catID=

Has anyone tried the AMP ascender ? Just askin....

 

[Burnham]

That's a new one to me, Stephen...never heard of the company either. Doesn't say what diameter rope it's designed for...

Wonder if the quick release pin can be replaced with a bolt?

Pretty inexpensive compared to most of the competition.

 

[CurSedVoyce]

I might just order it to find out..

 

[Burnham]

I might just order it to find out..

Quick phone call might be a cheaper way...

 

[CurSedVoyce]

Why talk about it when you can own it..... HAHAHA
Just call me the equipment junkie

 

[Burnham]

 

[CurSedVoyce]

Might have to add some wedges to that order too