Rated? What does it mean

I agree with what you're saying, Sergio- some peoples perception of risk in regard to wear can be iffy, to say the very least.
As to regulation for ITCC & breaking strains, the rules are pretty clear, in 8.2.3 is stated: "All personal equipment shall at minimum satisfy OSHA and ANSI standards or the local equivalent from the contestant's chapter of qualification".
So maybe that's the explanation for the 22 kN biners being OK-ed.

Tom Dunlap

Here from the beginning

As Todd observed, the 22kN was applied inconsistently in Seattle. Most of the time that is really not an issue. But...what if
someone decides that they want to file a complaint at a TCC because they find that someone is climbing on a 22kN biner or gear
that doesn't meet ANSI standards but was approved by one of the gear inspectors? Now there will be an issue.

To take Todd's point a step further, what about my favorite saddle, the Butterfly? It hasn't been submitted for ANSI testing. What
about when someone uses a piece of gear that's labeled for 13mm rope and they use half inch rope? Half inch equals 12.7 mm
and we all know that there are very few American arbo ropes that are truly half inch ropes no matter what they are sold as. I'd
like to have the time and funding to put a working load on some ropes and then put my micrometer on the rope to see what the
actual diameter measures.

Here are some other ratings on pieces of gear that are accepted routinely:

Petzl Ascension, handled ascenders: Lower carbiner attachment point rated at 4,496 lbf/20kN

The Ropeman is supposed to be used only on 10-11mm rope

The double handled Kong ascenders are rated for 12mm rope in the 2000 catalog but now they are rated for 13mm rope, huh?

sorry... trying to be too brief & to the point- apart from unarguable inconsistencies, my point really was that the 22 kN gear conforms to CE requirements, so according to the rules as a competitor from europe my 22 kN biner should be passed at gear-check.
Tom, I'd like to know your personal opinion on the matter. Do you think that the equipment you mentioned should be allowed or not?
As for consistency, it doesn't seem to me such a big problem to solve. It would be enough either to have a single judge inspecting the gear or a head inspector that decides all controversial issues.

Most hardware can safely be used with a 5:1 safety factor and have an indefinte service life, depending upon wear. Such a safety factor will easily cover heavier persons (over 100Kg) because it is designed to cover 200Kg in exceptional circumstances. I think anyone much over 120Kg is going to struggle to climb a tree often enough to put a question over wear, but if they do (and no doubt one of you will know someone weighing 200Kg on a daily basis!)they just ought to replace their gear sooner.

These latest comments illustrate my concerns with where the comp is heading.

If the comp is not to reflect industry best practice, and take the role of an X game type event, then much, much lighter weight equipment could be used with narrow safety margins for just that one event and then disposed of. For example, a typical Karabiner can stand a proof load of 16kN, but it is unclear for how many cyclic tests. But after one test the Krab is not mis-shaped and still functions perfectly.

The same goes for rope; light weight kernmantle ropes could be sourced for safety during a comp, but should never be used for industry.

Developing such gear would cost a fortune without an industry to use it. And industry wouldn't allow it, because of insufficient safety factors to account for our abrasive conditions at work.

I think the idea that an extreme angle of the TCC would be fanatastic - like formula 1 to the car industry. But are sponsors going to give the cash to develop the gear the same way - what would be in it for them? What as an industry would be gained?

I feel the TCC's belong to professional arborists, and an X games event would be great for extreme innovation that could be developed for daily tree work.

As for the conversion of kilonewtons to pounds, it doesn't work. A kilonewton is a measurement of dynamic force. That could mean a 50Kg weight being caught while falling and exerting 100Kg of force. Consequently, 22kN equals roughly 2200Kg of force. That is a higher rating than just 2200Kg in a static lift. By that reasoning, I would argue that a piece of gear rated at 22kN would out perform a static rating of 5000lbs.
It is still plenty strong enough for what we require either way.
As a nation, we Americans have resisted Metrification vigorously.It would be nice(and reasonable) if ANSI would update the Z to reflect the KN rating system. A simple phrase such as "rated at 5000 lbs OR 22 Kn" would solve things. The fact that 22Kn does not equal 5000 lbs isn't really relevant. The issue is safety and rated gear. A little clarification about prusik loops would'nt hurt either. Bottom line in the real world of work is "will it work safely". Fortunately, ANSI sets standards but we do get to make our own choices in the field. As faras competition goes- I suppose saying "eqipment meeting any recognized standard" might create more problems than it solves.("I'm goin' by Uru Buru's standard-they say 'You want to climb trees? It's up to you crazy man'." Still it would be nice if things were standardized to reflect the gist of U.S. and common European Standards.


Well-Known Member
"The fact that 22kN is more like 4800lbs"

i'm with Tom here
! i round a kn to 225# of force or 4950#force = 22kn; that is fairly close and quick for most things. i beleive legal is 224.8# force= 1kn, or .2#error per kn; or our guestimate of 4950#force=22kn is really 4.4#too much confi-dance (ie. less than 1% error). Working with SWLs of 8/1 to 25/1, should allow some to wink at the diffrence, some might even say with a SWL of 10x on up, it is okay to call'em 5k.

Not sure what to say about a 250# climber safe on a 5000#force accesory, while a 125# climber is unsafe on a 4945.6#force accesory. Did ya think of that lil (guy) view Big Baaad John?? Bet you think like JP that one size fits sm-all too huh?
But there need to be standards, evenly applied, with recognized gear.

Also, IMAO i might feel safer with a conservatively rated CMI (or BlueWater) 22kn accesory, than a hardware store 5k piece (for rigging), or lesser known or reputable (climbing) competitor's 5k climbing accesory on m-eye sight.

But insamuch that competittion sets new standards of style, speed, public awareness etc.; equally judged; so they tend to set equipment standards too; and strictly maintain them at their sites as example, evolution, equal standard, minimum acceptable level for pro standing, testing and liability reduction. i think you will find the same pair-allel circumstances in saw championships, auto racing, football etc. Some might say that is snobbery, some professional status.

Part of the problem might be an accepted standard of ours in our terms of measurement with equipment made by manufacturers using a diffrent system that by luck of the draw on one step of the ladder happens to be less at a favoriate position of their's.

Everything might evolve universally to one standard, but it hasn't in every other arena, some of which have been seriously pushing and leading upper tech echelon longer than tree climbing science; which i hope is in its infancy as if has just sstarted leading more than borrowing from its sibling's disciplines in the last few years.

Another lil'twist in terms; a pound is a measure of weight, a kn is a measure of force as is foot pounds. The diffrence is that 50# dropping 4' has ~250 foot pounds of force, but still only weighs 50pounds.
Somehow I get a feeling that while many of you (from the U.S.) find it hard to accept a only CE approved gear, if the situation was reversed would be outraged if a piece of equipment wasn't accepted in Europe because it had only a ANSI rating.
As Tom said, you should decide whether to have a INTERNATIONAL TCC or keep it as a U.S. event. Honestly speaking, we in Europe couldn't care less about ANSI ratings...


[ August 21, 2002: Message edited by: Ghivelder ]
Thanks Joe - very interesting web sites!

My crude explanation was used to high light the difference between stopping a falling mass with the effects of gravity and supporting a static mass.

However, I didn't find a helpful explanation of the terms so this is the UK definition that we use to train inspectors of equipment:

One Newton is the force that would have to be exerted on a 1 kilogram mass to make it accelerate at a rate of 1 metre per second.

Force = mass X acceleration. Thereby, 1 Newton is equal to the force exerted by stopping 1Kg which is accelerating at 1 metre/second/second.

Acceleration due to gravity is 9.8m/s squared. Therefore the force required to stop 1Kg falling due to gravity would be 1Kg X 9.8m/second squared. i.e. 9.8 Newtons. Where larger forces are involved, the Kilo Newton (kN) is used, i.e. 1000 Newtons.

25kN = 25000 N or 2551 Kg of force (kgf).

For ease of conversion, 1kN roughly equates to 100Kg. In my previous posting I stated equal to 100Kgf - which should have read 100Kg. The differences can be seen from above.

Our standard used to be 2500Kg for a karabiner. That has now changed to 22kN to allow for the new unit of force and amended test procedures(kN), and to fall into line with European standards.

It would save alot of confusion if the USA had adopted the metric system as rigorously as they opposed it! Either we allow the 5000lbs and 22kN rulings, or the USA could have their TCC, Europe theirs and never the twain should meet.

I wouldn't want to see that, and little would be gained for anyone!

As for prusik loops, I have a few opinions on this under the 'prusik cords' forum.

Also, just so as I'm not mis-interpreted, the 'Hardware' I was refering to was pulleys, karabiners and shackles; metals, not textiles such as rope and slings, which require higher saftey factors!

[ August 21, 2002: Message edited by: MrPez ]

Tom Dunlap

Here from the beginning
This thread started out by talking about what ratings mean. Could be, who's rules do we follow? In the US we are supposed to
follow ANSI. Personally, I think the CE and UIAA rating/testing system is a better one.

Check this out:
http://www.bacou-dalloz.com/us/fall.lasso?where=products Notice that the same group that owns Miller in the US owns
Komet. I wonder why Miller doesn't get involved in getting the Butterfly ANSI approved.



Well-Known Member
"Most hardware can safely be used with a 5:1 safety factor and have an indefinte service life"

Does that go for aluminum? i have seen test specs (somewheres) that bear out that steel has an indefinite service life at that rating; but 10k aluminum with a 2k load, no shock or weathering; will fail after so long (can't remember that specific part) from just a static hang.

So i have always kept that in mind along with the other tempermental properties of aluminum (less shock worthy, rigging with device and dropping on hard surface). ie. it is my understanding that in trade for lightness aluminum needs extra care shockwise and still early retirement.

Tom Dunlap

Here from the beginning
As far as aluminum's durability is considered, all we need to do is go look at how big wall/rock climbers use their gear. From what I gather, hardware breakage isn't a big consideration. Now, using al for rigging tree work, that's completely different. Not even a fair comparison.

The alloys used for al biners is tough! It's made to take abuse and still stay strong. There has been lots of research done on the breaking of biners. Not only the manufacturers but engineering grad students too. A while ago I found a link about an engineering curriculum in outdoor sports equipement. there were some interesting projects being worked on.

Spydy, working with common hardware store grades of aluminium will tend to make a person except the idea that aluminium is easily fatigued.(Low grade steel alloys aren't much better) However consider aircraft aluminium alloys. There have been lots of Air tanker crashes this year-because they have aircraft in service that are past retirement age. Consider though how many TRILLION times did that wing flex before failure? Some aluminium alloys are amazing. Trust your biners.


Active Member
Mr. Pez;

These 2 pages confirm what you are explaining about the newton as a unit of force.

The 1st page listed one needs to access force.

This 2nd page and the contents in the rest of the site reflects the reasoning I use my reply for the rest of this post.

It's to my understanding force is a unit describing mass under some type of influence, like that of gravity.
A static mass is still influenced by
gravity, whether it's in motion or not. The static mass under the influence of gravity is described as weight. Since we're discussing equipment ratings and the differences in how our cultures interpret freefall, a dynamic mass to me is a mass under the influence of gravity that is experiencing an acceleration, whether that acceleration is speeding the mass up, or slowing it down. When a mass is accelerating, it moves through a distance, but it's weight is unchanged. Because the weight moves through a distance when accelerating, other concepts are used to describe its motion, such as work and momentum.
There are several ways to express the units describing mass, weight, and motion. The more popular method being the S I unit of measure. The S I unit of measure is merely a reflection of the culture which uses it. The pound force, known as the pound to me, is a unit of force which reflects the culture in which I live. Both systems of measure describe the same everyday phenomena we experience.

For those of us who are accustomed to some of the language of introductory physics, using newtons(N) or pounds(lbs.) is a matter of convention and can easily be converted from 1 unit to the other so we can better relate our experiences with each other.



Well-Known Member
O i hear ya on the aluminum, i have no hardware store models. i have used aluminum mostly in personal support, where that was 1 of the identifying characteristics betwixt rigging and life support gear for years.

Now as i have built up a collection (Kong, Bluewater, HB Wales, Black Diamond etc.) and werking on lightning my belt some ( i go for 'knotless' rigging or sling and 'biner on everything lowered virtually; then clipped to eye of riggingline.) i am using the aluminum for lighter stuff.

The refrences i made to the info on failure; was from a special on aircraft aluminum failure. The gentleman they cut to; was speaking sounded very expert and broadly covered all aluminum as a whole, without exception. The words about steel, aluminum, even the exact numbers of 2k load on a 10k piece of aluminum and its failure where all his. That coupled with, shocking giving internal damage, i think is worthy of consideration, and perhaps shelf life.

i am very interested in how our (higher developed?) roping cousins handle this gear, that they have years jump on us in! i have long looked to them in my own evolution, and advocate thinking and acting like you're on a ledge 5000' on the side of a mountain when making tie in decisions (or something like that). My copy of "On Rope" by Padgett and Smith (#16201) is rather worn. Nothing else gave me such a deep understanding of handling line, life, friction, connections etc. Perhaps, it was because of the ez reading, completeness, but i think also that depth of understanding from studying 2 similar, intense pir-allel subjects, and drawing to-gather there commonalities as a wide base. Then being so lucky to be able to practice it every day!

i use 'biners all of the time! Really respect the aluminum, i know its strong, but it ain't steel!

Am i erring to much on the side of caution? Perhaps.

P.S. 2 very, very good linx there Joe, easier to digest than most on such topics (to me), common language guys!!
i hit some of these other things at a lil diffrent angle in the last post on first page, jsut found out someone missed it; guess that is ez to do!

[ August 22, 2002: Message edited by: TheTreeSpyder ]

[ August 22, 2002: Message edited by: TheTreeSpyder ]
Alloy Karabiners - absolutely nothing to worry about!.

UK tree climbers, and probably most Europeans, have been climbing on karabiners as a standard clip in for decades. From talks with a certain US salesman a few years ago, they expressed concerns with how karabiners were being used inappropriately by some USA climbers, because they were used to steel snaps.

My experience & knowledge of Karabiners comes from using them for the past 15 years, and a working relationship with a prominent krab manufacturer. He has manufactured between 9 & 10 million of 'em!

The alloy used in his krabs is of the highest quality. If used with a safety factor of 5 from the minimum breaking strength, he counts on a minimum of 30,000 cycles before failure. However, this is academic. Some trainees have put forward krabs that he made 20 years ago (and they have climbed on every day since!)for destruction testing. All of the karabiners failed above their rated minimum breaking strength. If a krab that has a certificate of conformity fails, it must have been mis-used due to the rigorous batch testing procedures used for the certificate of conformity. For example, an offset 'D' krab used with a 1" sling, can exert enough leverage against the gate to make it fail at half of its rated strength. Also, stress cracks in alloy krabs is a myth, and something he gets quite angry about! If a krab has a crack, it must have occurred at the manufacturing stage, and this is eliminated because of the batch testing. Stress cracks forming from dropping on a hard surface in alloy krabs is a myth! The problem comes with external burring, which can cut rope and webbing under load.

Alloy krabs do not have as much resistance to side loading the minor axis or bending as steel, and the barrels are not as strong as steel (when subjected to a nose punch). It is for these reasons (plus the fact that typically a steel krab is twice the strength of an alloy, type for type)that alloy krabs should only be used for climbing, and be loaded properly. Steel krabs should be used for rigging, but NEVER for shock loading, because of the ease of loading the minor axis and punching the nose through the barrel on impact with the tree.

If slings are to be used for rigging, Use HMS type krabs - they may be rated lower than 'D' types, but are designed to be loaded away from the spine, making the rating more reliable.

If your krabs can rotate in your D rings, there is a real danger of loading the minor axis. The best way to use krabs is to tie off the line with half a double fishermans. This chokes against the krab, preventing it from spinning round.

If you ever visit a reputable krab manufacturers factory, and see what is involved in making and breaking them, you'll never worry about quality krabs again. A real bargain for the price! If the locking mechanism works properly and is regularly lubricated, a krab has an indefinite service life.

Check out the DMM 'Onja'lock krabs. The steel ones seem particularly bomb proof!

Sorry Tom, it's called 'OVALOCK'.

It is aimed at the industrial market - us! The promotional material I was sent states it was designed for their 12mm steel krabs and garauntees a 5000lb or 22kN rating with the load applied in any direction or at any point!!

I've got one and its the biz! It is available as double locking or triple locking. I have the gate on an HMS style for rigging slings. It is ideal for us as the barrel resists an external force pushing the nose through and causing failure. This can easily happen when swinging branches into the trunk.

Drop them a line and ask for USA dealers - it is marketed at the ANSI Z359.1 ( standard.

web page


DMM, ISC and HB are about 30 minutes from me - handy for good info and tours on training courses!