Locking screw link

J

Jim

Location
Baltimore, MD.
I ordered a couple of Petzl OK locking screw-type carabiners and was a bit suprised when I got them. They have a red marking on the male side of the threads and according to the instructions, when the red is not visible the carabindr is locked.

When given a good twist, the 'biner does have resistance to unscrewing, but it's not what I consider a 'locking' carabiner.

Is this safe, or even ANSI approved, for use in a climbing system. I wanted to use them as connection points on both ends of an SRT setup (similar to Tom Dunlap's) with a microcender on end and a rocker on the other. They're rated to 31 Kn, but I'm uncomfortable with the 'lock'

Thanks,
Jim
 
ANSI Z133.1-2000: A carabiner has to have 2 seperate motions before opening the gate and has to be self closing & automatic locking. Minimum strength requirement 23kN. All screw gate biners do NOT meet the standard.
 
Screw links exist in a foggy area of Z133 interpretation. The really aren't auto locking. It does take many turns to unlock them. Much different than screwgate biners.

But most people will allow them as long as the breaking strength can be determined. My parameters are that they not be from the Pacific Rim. I've seen tests of PR screwlinks breaking at a very wide load. Using ones from marine manufacturers or Maillon Rapide is a sure bet on quality.
 
Thanks, Tom. Do you think the Petzl OKs at 31 Kn would be usable, or should I get something else, like the Maillon Rapide you suggested?

Thanks again,
Jim
 
Jim,

You'd be better served using a screwlink.

The threads on screwgate biners are cut so that they spin easily. The clearances and radiuses are designed to have very little friction. I don't know how the final bit locks, but there always seems to be a little more friction in the last turn or so. The issue is that our systems have lots of moving parts. If something were to bump the screwgate sleeve then jiggling can allow the sleeve to open.

The threads on screwlinks are cut with less slop. If there is a machinist in the Treebuzz Cafe they'll give us the correct term for tolerances in threads. It escapes me now. Also, the threads are much finer. It takes many more turns to open the sleeve on a screwlink. They're cheap, super durable and can stand larger cross loads than biners. The main thing that screwlinks have against them is a low CF rating. What's CF? Coolness Factor :)

In all of the years of using screwlinks the most that the sleeve has ever opened up is about four flats. Not even a full turn. Count the number of turns needed to get the sleeve clear of the threads. It would take a lot of jiggling to have it come open. In most cases I take a wrench and give the sleeve just the tiniest turn. You don't want, or need, to tighten very much. Just a twitch beyond finger tight.
 
i appreciate your help, Tom, I think I'll stay on the safe side and go with a carabiner. I see that's what you use in your system.

Thanks again,
Jim
 
I've never used them, nor even seen them except on the recent Petzl website, but the "spinball" carabiners look to be screws with a locking ball like in their "ball lock" devices.

The ball would preclude vibrational unscrewing, but I doubt they're self-closing, so that factor still remains.

They look like they've got a high "CF" though!

Glen
 
i've opened and closed a lot of spin carabiners and shackles (for cranes)by drawing length of hand 'blade' firmly down the spinning lock once. Ya need more than that i think!
 
Glen, TreeSpyder, thanks. I'm definitely going with a self-locking, non-screw type carabiner. The Petzl OKs were not what I expected. I didn't realize 'locking' meant 'sticky'.

Jim
 
In reference to the red marking on the screwgate, I have a similar line of red stitching on my rock saddle when the buckle isn't doubled back. Somebody described it as "red equals dead." Made sense to me.
 
Hé Zac,

Happy /forum/images/graemlins/dancing2.gif /forum/images/graemlins/beerchug.gif /forum/images/graemlins/friday.gif /forum/images/graemlins/hoos.gif /forum/images/graemlins/icon315.gif birthday

Wolter
 
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