# Prusik safety concern



## Blucollartweekr (Oct 19, 2009)

Hi folks, I have a question regarding the intended use of a Bee Line Eye to Eye Prusik Lanyard. http://wesspur.com/Prusiks/prusik-loops.html (5th one down). I am currently involved in a debate over wether this device, when used with a tiny oval quick link style connector, http://wesspur.com/carabiners/clips-links.html (first on page) is suitable for carrying the full body weight of a climber. The oval link, I believe had 800lbs stamped on it. 
This to me does not seem like any setup I would want to trust my life with. I myself have little to no experience with tree climbing having only done a bit of recreational SRT. Having done a fair bit of rockclimbing though I understand that great forces are generated even in short falls. Please correct me if I'm wrong but I just can't see how a tiny oval link like that can be trusted to hold a climber. Please advise me as to the intended use of the eye to eye prusik lanyard. Thank you.


----------



## RacerX (Oct 19, 2009)

You're asking about these two devices?


----------



## Blucollartweekr (Oct 19, 2009)

Yes, those two devices. Thanks for posting the pics. Should have done that in my original post.


----------



## zopi (Oct 19, 2009)

The 3/8" stainless screw link appears, with it's 16000 lb tensile rating to be workable, however it would be ill advised...a screwgate 'biner is definitely the way to go in the life support link...as you know, sometimes getting off the lifeline expeditiously is a good thing..screwlinks can jam, and, I for one do not climb anything higher than a tractor with a crescent wrench...

Nothing wrong with the eye to eye, if you use a closed hitch..VT or distel or somesuch...

OTOH...some folks use snap hooks to tend the friction hitch rig, some use 
pulleys...I would conjecture that in absence of something more efficient, 
you could tend the hitch with a screw link...

K..now hopefully some of the gurus will come along and tell me where I went wrong...:greenchainsaw:


----------



## Plasmech (Oct 19, 2009)

I would think that one would want the rope to be the weakest link in any rigging situation, lifeline or not...


----------



## TreeW?rx (Oct 19, 2009)

According to the ANSI rules and regs, any part of the climbing system buts have a breaking strength of 5200 lbs. So no, the small one stamped 800 lbs is not sufficient.


----------



## Tree Pig (Oct 19, 2009)

the beeline is great stuff, as for connectors industry standard now is auto locking biners such as ball lock or tri locking devices. Reason being the auto locking is they close and lock on their own and are very hard to have come open accidentally. Screw locking biners are not recommended because they have been known to unscrew and open unintentionally causing a serious risk to the climber. These are not area to be frugal on spend the money and go with what is recommended.


----------



## TreeW?rx (Oct 19, 2009)

:agree2:


----------



## lego1970 (Oct 20, 2009)

I could be wrong but I thought screw gates were also not ANSI approved. I have a couple older screw gate carabiners and a fellow I worked for that seems to really know his stuff said screw gates were no longer allowed.


----------



## Tree Pig (Oct 20, 2009)

lego1970 said:


> I could be wrong but I thought screw gates were also not ANSI approved. I have a couple older screw gate carabiners and a fellow I worked for that seems to really know his stuff said screw gates were no longer allowed.



You are correct ANSI does require auto locking connectors.


----------



## outofmytree (Oct 20, 2009)

As much as I hate to pound my AS buddies.... 

*WRONG WRONG WRONG*!!!!!!!!!!!!!!!!!!!!

The device pictured is a maillon not a screwgate karabiner. It is designed to be locked by a wrench or spanner. Providing you use one whose SWL exceeds climbing requirements it is suitable to climb with. It's function is to join the ropegrab of a polebelt to your harness and is not suitable for applications which require regular opening and closing such as a karabiner on your principal lifeline.


----------



## Tree Pig (Oct 20, 2009)

outofmytree said:


> As much as I hate to pound my AS buddies....
> 
> *WRONG WRONG WRONG*!!!!!!!!!!!!!!!!!!!!
> 
> The device pictured is a maillon not a screwgate karabiner. It is designed to be locked by a wrench or spanner. Providing you use one whose SWL exceeds climbing requirements it is suitable to climb with. It's function is to join the ropegrab of a polebelt to your harness and is not suitable for applications which require regular opening and closing such as a karabiner on your principal lifeline.





Not to sure your on the right track here his question appears to be he wants to connect his eye to eye to his rope with a quick link. Which means by ANSI standards it has to be a auto locking biner or clip. Not to mention the fact that the one he was referring to was 800lb which means its short of the ANSI 5000lb minimum. We may be making some assumptions here on his intent but considering he is new his terminology may be less evolved so I side on the side of error for his benefit.


----------



## zopi (Oct 20, 2009)

Stihl-O-Matic said:


> Not to sure your on the right track here his question appears to be he wants to connect his eye to eye to his rope with a quick link. Which means by ANSI standards it has to be a auto locking biner or clip. Not to mention the fact that the one he was referring to was 800lb which means its short of the ANSI 5000lb minimum. We may be making some assumptions here on his intent but considering he is new his terminology may be less evolved so I side on the side of error for his benefit.



I knew someone would have something I didn't know...learn something every day.

I still wouldn't use a screw link in my rig, simply because I like a certain 
commonality in the equipment...ie, all the 'biners the same, so If I 
reach for it with some urgency, I don't have to guess how it works..does that make sense a all?

can see using them in some rigging applications....read "have" prefer clevises though, as the tool to open them when stuck is my rigging knife, or a little straight bar...


----------



## SINGLE-JACK (Oct 20, 2009)

Stihl-O-Matic said:


> *Not to sure your on the right track here *his question appears to be he wants to connect his eye to eye to his rope with a quick link. Which means by ANSI standards it has to be a auto locking biner or clip. Not to mention the fact that *the one he was referring to was 800lb* which means its short of the ANSI 5000lb minimum. We may be making some assumptions here on his intent but considering he is new his terminology may be less evolved so I side on the side of error for his benefit.


:agree2:

Screw links are designed as replaceable chain links. Normally a stamp on a screw link indicates the manufacturers *opinion* of the Save Working Load (SWL). It could be 1/5, or 1/10, or some other *unknown *percentage of the breaking strength. ANSI specifies minimum breaking strength. In short there are unknowable risks in using screw links as part of life support. Not recommended - even by some manufacturers! Besides they're a PITA - as *outofmytree *implies.

*Hopefully the following quote may clarify some of the OP quesitons:*
_"The 2006 revision (Z133.1) also addresses other aspects of climbing
systems:
• Climbing lines used in a split-tail system and split-tails shall be
terminated with an eye splice or a knot that interfaces appropriately
with the connecting link that it is attached to. The termination knot
selected shall remain secure under normal loading and unloading.
When using a carabiner without a captive eye, the knot or eye splice
shall cinch in place to prevent accidental opening and/or side-loading
of the carabiner.
• Prusik loops, split-tails, and work-positioning lanyards used in a
climbing system shall meet the minimum strength standards for
arborist climbing lines*(see below).
• Snap hooks (rope snaps) used in climbing shall be self-closing and
self-locking, with a minimum tensile strength of 5,000 pounds
(22.24 kilonewtons).
• Carabiners used in climbing shall be self-locking and self-closing
with a minimum tensile strength of 5,000 pounds (22.24 kilonewtons).
Carabiners shall be designed to release the load by requiring
at least two consecutive, deliberate actions to prepare the gate for
opening (for example, having to move the thimble up or down
before it can be rotated). Standard turn and twistlock carabiners
do not have a positive-locking mechanism and therefore
do not meet this requirement."_

From:
_Z133.1 Safety Standard,2006: Safety Standards for Chain-Saw Use, Climbing, Pruning, Rigging, and Removal_
By H. Dennis P. Ryan (Professor of Arboriculture and Urban Forestry - *Dr. Ryan is chair of the Z.133.1 committee*), and
Brian Kane (MAA Assistant Professor of commercial Arboriculture, Department of Natural Resources Conservation at the University of Massachusetts, Amherst)
http://www.isa-arbor.org/publications/arbNews/pdfs/zpart3.pdf

_*"Arborist climbing lines shall have a minimum diameter of 1/2 inch (12.7
millimeters) and be constructed of a synthetic fiber, with a minimum
nominal breaking strength of 5,400 pounds (24 kilonewtons) when new.
Maximum working elongation shall not exceed 7 percent at a load of 540
pounds (2.4 kilonewtons)."_


----------



## Blucollartweekr (Oct 20, 2009)

Wow, Thanks for the info guys. Stihl-O-Matic, you're quite right in saying my terminology is fair bit less evolved. lol Guess I just had to do some more research to discover the differences between the tensile strength and WLL of equipment. 

The function in question of this piece of gear is similar to what outofmytree said; whether or not it should be used to join the two ends of an eye to eye prusik lanyard and then connected to a locking carabiner, which may be used for an ascender backup, or any other sort of attachment that may need to support the weight of the climber.

After looking at it closer I see that the oval screw gate link has 'WLL 880lbs" stamped on it. If the manufacturer used a 10% or less safety factor this could mean at least 8800 pounds tensile strength. Which would fall within the requirements of 5000 lbs tensile for gear and 5400 lbs tensile for rope. I also noticed that the eye to eye Bee Line prusik has a tensile strength of 5400 lbs, making it suitable to support a climber. Please correct me if I am wrong. 

With that being said I am quite interested as to what SINGLE-JACK had to say about the unknowable risks. So my question remains. If you used this oval link with a stamped WLL of 880lbs to connect the ends of an eye to eye prusik, then clipped it into a locking carabiner, could it be used for a life support situation?
Thanks


----------



## Tree Pig (Oct 20, 2009)

I am not totally sure what you want to do. Have your eye to eye on the link then that snapped to the biner which is going to be connected to a lanyard as an adjustable lanyard or are you attaching the eye to eye as your friction hitch for climbing?


----------



## SINGLE-JACK (Oct 21, 2009)

Blucollartweekr said:


> Wow, Thanks for the info guys. Stihl-O-Matic, you're quite right in saying my terminology is fair bit less evolved. lol Guess I just had to do some more research to discover the differences between the tensile strength and WLL of equipment.
> 
> The function in question of this piece of gear is similar to what outofmytree said; whether or not it should be used to join the two ends of an eye to eye prusik lanyard and then connected to a locking carabiner, which may be used for an ascender backup, or any other sort of attachment that may need to support the weight of the climber.
> 
> ...



First, about *"WWL 880"*: As mentioned previoustly, Screw Links were originally designed as replaceable chain links for rigging purposes. It is common to rate the Working Load Limit (WLL) for such items at 20% of the average breaking strength. In fact in Sherrill's catalog (p3), they specify 1/5 (20%) for rating product WWL. With a *"WLL 880"* stamped on a product implies a breaking strength of 4400 pounds. SherrillTree is an extrodinarilly reliable company. However, it is knowable that 4400 lbs. is below ANSI standards.

Now for the *"unknowable risks"*: For Screw Links to maintain full rated strength, they should be tightened with a wrench, as indicated in Sherrill's catalog (p58). So then, how tight? If too tight, the link threads can be damaged. If too loose and cyclicly loaded, the link will work open. Either way there is a unknown risk the link will fail. Neither Screw Links nor Screw Gate Carabiners meet ANSI standards for life support. Two of the reasons are they can come loose and it's easy to forget to tighten them.

Next, *i2i + link + carabiner*: The old adage "a chain is only as strong as it's weakest link," is important to consider when setting up a climbing system. A minimum DdRT climbing rig is merely a series of links; saddle, carabiner, life line, friction hitch back to the carabiner. The fewer the links, the better. An i2i is perfectly capable to fastening directly to a carabiner. So, why add a Screw Link to the rig? It seems to only add another element of risk! Reduce risk by reducing gear - less to hook-up, less to maintain, less to monitor, and less to pack-up.

Don't get me wrong. I love Screw Links but I don't depend on them for life support.

If you have to use one anyway - use the stainless steel. They are stronger, there's no plating to wear way, and they are polished so there's no sharp edges to damage the rope.

*BE SAFE - LOW & SLOW!!!*
Jack


----------



## BlackenedTimber (Oct 21, 2009)

Couple of comments:

One, if you have an eye-to-eye, why dont you just slip the two eyes onto your biner, and remove the quick-link from the equation all together? less hardware and compliance to ANSI. Maybe I am missing something, if I am please let me know.

As for the quick-link, being used in the manner which you have clarified, it would become loaded in a life-support situation as a backu to an ascender, and therefore does not comply with ANSI as Singlejack and Stihl-O-Matic have made clear. I have used these, before I knew any better, and although they are cheap, even when closed with a wrench, they can work themselves back open. Not Good, especially when you are airborne. If your going to be using anything in your climbing, make sure it is made for climbing (the quicklink is not) and meets ANSI standards (the quick-link does not). Additionally the largers ones can weight alot more than a biner.

Any climbing application where a quick-link could be used, a biner will do fine, if not better. As someone mentioned earlier, quick-links are for repairing sections of chain, not for trusting your life to.

My Two Cents.

T


----------



## BlackenedTimber (Oct 21, 2009)

HA... apparently Stihl and Singlejack were posting at the same time as me, aso I am asking questions that have already been asked and saying things that have already been said...

Oh Well...


----------



## Blucollartweekr (Oct 22, 2009)

Excellent information guys. You have certainly clarified the intended use of a quick link and justified my concerns on using it for life support. It definately makes alot more sense to simply connect the eyes of the prusik loop directly to the carabiner. Like you said the system is oly as strong as it's weakest link. Thanks alot


----------

