I'm certainly no pro-arborist but I would say that there are two reasons for not using screw_link_s in climbing systems: 1) a rope moving through the screw_link_ could cause the gate to turn with it, undoing the gate...

I've found when using screw_link_s for non-personal-safety fixings (I've used Maillon Rapide _link_s) the _link_s can be very hard to undo, particularly with wet/cold hands and if they've been done up too tight.



A friendly observation - As I read the comments from the many pros an ams on the board something struck me...Aren't the above statements contradictory?

The NFPA,(National Fire Protection Agency)who regulate ALL safety and operations concerned with high angle rescue, require screwgate biners. Until recently, they required those biners to also be steel.

IMO, if a screwgate is closed properly, it should never come open, and even if it does, think about the strength rating on your biners. I'm sure someone has mentioned this on this forum before, but...
1 kN is equal to approx 224.8 foot pounds of force. I don't have a biner rated less than 25 kN. or 5,620 lbf.(closed) The same biner is rated 11kN or 2,023.2 lbf with the gate open - not unscrewed, but wide open.

It's all relative! A screwgate done up tightly might be hard to undo with cold hands (particularly with my circulation) but could it still be moved by a rope with a person's weight on it?. However I did use a couple of them in mountains of Scotland after posting the original message. They were holding my snow shovel onto my rucksack. As the wind chill was about -20°C I had to keep my mountain mitts on and found that the gates undid smoothly, depite my being hampered by the mitts.

I've found on my Maillon Rapides that the tightness of the screwthreads varies so I'm still not sure that a rope sliding over it wouldn't turn the gate on some _link_s. The main concern then wouldn't be the loss of strength in the _link_, but the possibility of the rope coming out of the gate.

I'm sure the NFPA use equipment which is totally safe for their applications, but perhaps their use differs somewhat from tree climbing techniques?

Sorry, you're right there. I wasn't thinking about the rope slipping out, only the strength issue.

I now realize that the same tool (biner) can be used by 2 different professions in different ways. I encountered this with rock climbing, and rescue as well. Why not 3?

I learned something else. While discussing this very subject, an arborist/rock climber friend reminded me that if I were to use a munter hitch to rappel(with a screw gate pear)it is possible to tie the hitch in such a way that if the rope does come in contact with the gate, it can actually tighten it.

As I said in an earlier post I DO like my BD posi-locker biners, and will use them when/wherever I can.

Time for me to sit back and read some more from those who have been doing this a lot longer than me - at least the tree part. I've been rock climbing and doing rescue work for 20+ years, but have just gotten into the trees and I love it!

I've also done both rock climbing and tree climbing for many years and I have to say that I prefer climbing trees - the canopy is a beautiful place to be and I actually feel like I've left the ground! (I don't when I'm hanging off a wall of rock).

If one is so concern about an unlocking biner, then I suggest what the French are using::: A combonation biner.
As French climbers( Rock climbers and cavers) descend and unhook to take a look around; someone would still their biners that they used as tie offs. It got to such a hugh problem that the police where doing investigations. Finally, a life rated biner with a combonation lock was created.

I do not think a tree or treebranch could unlock that one.

Website _link_s to combo-biner:

http://www.ocscoutshop.org/cg0369.html

http://www.asia.ru/ProductInfo/1427009.html

I am still trying to locate the one from France that is life rated.