Types of Carabiners and What kN Ratings Mean

by September 30, 2009 09/30/09
Carbiners

Carabiners 01Today we offer a post to try to clear up some of the confusion surrounding carabiners, and what that kN thing means.

Carabiners come in many shapes and sizes and are purpose built for many different climbing applications.

We’ve highlighted the main variations of climbing carabiners as well as what we feel the positives and negatives are.

The carabiners referenced below are specifically for climbing, and  if a type of carabiner is not listed here, then it’s probably not recommend it for climbing.

We’re specifically referring to oval carabiners, which are more for clipping gear to a harness, but not recommended for climbing due to where the rope sits.

Unlike the “D” or symmetrical shape carabiners, which shift the rope towards the spine and away from the gate, oval carabiners keep the rope dangerously close to the gate.

Snap Gate Carabiners

Carabiners 02

Snap gate carabiners are designed for leading a climbing route and offer fast clipping and simplicity when placing protection.  They are also typically used for clipping gear to a harness.

The  two main categories of snap gates are solid gate and wire gate, which come in two available configurations, straight and bent.

Solid Gate

Solid gate carabiners tend to weigh more, and are quickly being replaced by wire gates. Weight isn’t the only reason though, there’s an inherent design flaw to solid gate carabiners.

During a fall, vibrations run through your carabiners upon full-loading. This causes solid gate carabiners to open and close rapidly, due to the mass of the gate.

Here’s a test to prove it. Take a solid, snap gate carabiner and knock the spine against the palm of your hand. Hear that click? That was the solid gate opening and closing rapidly.

If that happened under load on a climb, it’s possible for the vibration to open it enough for something bad to happen. Especially in a cross-loading situation.

Wire Gate

First and foremost, a wire gate prevents the aforementioned problem with the solid gate carabiners opening and closing during full-loading.

Less mass in the gate and not being as prone to vibration are the factors in prevention. This also reduces weight which makes sense when your carrying multiple carabiners.

Another tremendous benefit to wire gate carabiners are that there are  no moving parts to break, get stuck, or freeze. Solid gates have an internal spring within the gate, which makes them prone to failure.

Wire gates retain their spring through the way the wire is placed in the carabiner when it’s built.

Straight Gate

Straight gates are the standard in carabiners, and for a good reason. It’s a trusted design and not prone to the dangers of bent gates, which we’ll explain below.

Most wire gates are also straight gates, but there are bent wire-gates manufactured (see photo below). Typically though, the bent gates you’ll see will be solid gates.

Bent Gate

BentWireGateThe bent gate design allows you to clip-in easier, making it better for hard to reach places. The dangers of using a bent gate carabiner, are that it could become undone  if another carabiner or object is pressed against it.

If you do use a bent gate, don’t clip them into the protection side of your system, use them on the rope side. This is just in case they become twisted or inverted by the rope.

Screw Gate Carabiners

Also referred to as locking carabiners, screw gate carabiners feature a sleeve that can be tightened to prevent accidental opening of the gate.

The two main categories of screw gates are symmetrical and asymmetrical, which come in two different configurations, manual or automatic locking gate.

Symmetrical

The design of a symmetrical or “D” shaped carabiner automatically aligns rope and attached runners to the spine of the carabiner. This is where the greatest strength lies in a carabiner, and is why it’s the most common design.

It’s also why we mentioned not to use oval carabiners, as they align rope and runners to the mid-point because there’s no spine.

Asymmetrical

You may have read in our rappelling articles that we refer to asymmetrical carabiners as “Lead” carabiners. This is because they have a  larger “pear shaped” gate opening, and a better angle to use when clipping in during top roping and lead climbing.

The downfall is that they have less space inside then symmetrical carabiners do.  Yes, looks can be deceiving. It looks as though they have more room, but when the larger gate is opened it takes up more space within the carabiner.

Manual Locking Gate

The most common screw gate carabiner features a rotating sleeve that is “screwed down so you don’t screw up!” How many of you remembered that tip from the rappelling articles?

That simply means that when using a screw gate carabiner, be sure to orient it so that the direction the sleeve travels is down. This will prevent the screw gate from further rotation by gravity if it should become loose.

Another tip is to not over-tighten the rotating sleeve, It can become stuck and difficult to loosen.

Automatic Locking Gate

The last style of screw gate carabiners feature an automatic locking gate, available in either single or dual stage.

Single stage is opened with a simple rotation of the gate to unlock it, and dual stage requires that button is depressed prior to rotating the gate to unlock.

Most climbers stay away from automatic locking gates, because more moving parts equals more parts to fail. This was a reason above that the wire gate carabiners are favored by some, as there’s no mechanical spring in the gate.

kN Rating

All carabiners come with a kN, or kiloNewton rating engraved into the spine. If you have carabiners without a kN rating DO NOT use them for climbing!

A kiloNewton is equal to about 225 lbs., which is a force of gravity rating, not static weight or mass. If you remember back to algebra class, force is equal to mass times acceleration.

Everything you use for climbing, rope, webbing, carabiners, anchors and protection is designed to absorb the force (or shock) that’s generated by a fall.

All this equipment has a certain rating of force it can withstand, and that rating is typically referred to as a kN rating.

That rating doesn’t take into account wear and tear on your gear, so always check everything before use, and replace anything with excessive wear.

Strength

We mentioned previously that the greatest strength of a carabiner is in its spine, and is why kN ratings typically offer two different strength ratings. One if the load is distributed along the spine, and another if the load somehow gets distributed across the gate.

Obviously, distributing a load on the gate of the carabiner isn’t good, and this is evident by the kN rating which will typically be 1/3 of what the spine rating is. For example, the manually locking carabiner in our photos is rated at kN 27 along the spine, and kN 8 to 9 across the gate.

If you really look at the construction of carabiners you’ll see why they’re rated less along this axis. All that’s holding the gate to the carabiner is a pin where the spring portion of the gate is located.

As you can imagine, an aluminum pin of that size can not offer a comparable load rating vs. the spine of the entire carabiner.

Don’t get us wrong, 8 to 9 kN is still almost 2000 lbs. of force that the pin can take, but wouldn’t you feel safer knowing you were protected by 27 kN (6000+ lbs.).

Here’s a simple calculator to convert kN to force pounds.

Notes

We’ve tried to hammer home the most important things to take away from carabiners and kN ratings, such as their inherent design flaws in some cases, as well as why kN ratings are important to take into consideration.

If there’s anything we didn’t mention, or any questions you have, ask away!


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Christian1969
Christian1969

This is a helpful article in general but being a novice I had trouble identifying differences between the types because none of the pictures were labeled nor was there an example of each. I had  to google each term to understand the difference. Still, thanks for the info.

Kurt
Kurt

@Rick De Leon Carabiners are not designed for continuous loads, using them in this fashion will cause micro fractures that will in turn cause it to break under significantly less weight. Id suggest using a screw pin safety shackle, they are cheaper and much safer to use for this application, as they allow for tri loading, which is not a good idea to use a carabiner as they are not designed for this either, and will cause them to break under much less force than normal. PS all carabiner that have been used under a continual load must never be used for climbing or safety afterwards as they are no longer safe and rated for the wll listed.

Rick De Leon
Rick De Leon

I work in the electrical utility industry. We make heavy lifts for electrical equipment installations. Some employees are using a "Pear Shape Kwiklock ANSI Hook (Z359.1 2007). Most of our lifts are straight up and down. I am trying to find out what the SWL or WLL of this carabiner is. Can you help. I might add that I am a training instructor for this company and don't want anyone to get hurt. Any information is really appreciated.

Is there a website that has capacity information for carabiners.

Thank you for your time.

Rick De Leon
Rick De Leon

I work in the electrical utility industry. We make heavy lifts for electrical equipment installations. Some employees are using a "Pear Shape Kwiklock ANSI Hook (Z359.1 2007). Most of our lifts are straight up and down. I am trying to find out what the SWL or WLL of this carabiner is. Can you help. I might add that I am a training instructor for this company and don't want anyone to get hurt. Any information is really appreciated. Is there a website that has capacity information for carabiners. Thank you for your time.

Kent
Kent

Great article! Very informative. Do you have any links to good places to buy quality carabiner?

Thanks,

Kent

Kent
Kent

Great article! Very informative. Do you have any links to good places to buy quality carabiner? Thanks, Kent

Art
Art

Hi,

Thank you for the article. What about industrial equipment ratings? The snap hook on my full body harness at work has 5M stamped on the hook and 3.6M on the gate. What do those mean?

Thanks in advance.

Art
Art

Hi, Thank you for the article. What about industrial equipment ratings? The snap hook on my full body harness at work has 5M stamped on the hook and 3.6M on the gate. What do those mean? Thanks in advance.

Simon
Simon

Thanks for the info on carabiners, I was looking for a describtion of the double action carabiner? Do you know what that is? Thanks

Phillip N.
Phillip N.

Hello to all and a big "thanks" to all the people who helped and contributed to the startup of this website as I find it both fun and useful. Bear with my rusty English please...

I want to stress a point that might be of some concern as it is related to safety issues. The issue/question mainly is: "Does the KN rating provided by a manufacturer of a carabiner, refer to static or dynamic loading?". To make myself clear... static loading is a load applied gradually... if possible in a infinite amount of time (e.g. geological pressure on a bedrock. While a dynamic load is applied in a very short period of time (e.g. on a seat-belt in a car accident). Since biners are meant to gold a person even -and especially- while he is falling (and that is a dynamic load), if a rating is indicative of a dynamic load then static load of that biner is greater (the dynamic factor is always greater than 1.00)!

Just my two cents... but I would appreciate an answer!

Phillip

Phillip N.
Phillip N.

Hello to all and a big "thanks" to all the people who helped and contributed to the startup of this website as I find it both fun and useful. Bear with my rusty English please... I want to stress a point that might be of some concern as it is related to safety issues. The issue/question mainly is: "Does the KN rating provided by a manufacturer of a carabiner, refer to static or dynamic loading?". To make myself clear... static loading is a load applied gradually... if possible in a infinite amount of time (e.g. geological pressure on a bedrock. While a dynamic load is applied in a very short period of time (e.g. on a seat-belt in a car accident). Since biners are meant to gold a person even -and especially- while he is falling (and that is a dynamic load), if a rating is indicative of a dynamic load then static load of that biner is greater (the dynamic factor is always greater than 1.00)! Just my two cents... but I would appreciate an answer! Phillip

NASA TOW
NASA TOW

You forgot to mention the auto locking solid gate variant, even though you have them pictured above, which do not suffer from the issues of the non-locking solid gate, and are far superior than the wire gate models for many applications. We use these exclusively for rigging much heavier load applications than simple human climbing.

Thank you for the KN rating explanations. It helps explain it to others that don't understand.

NASA TOW
NASA TOW

You forgot to mention the auto locking solid gate variant, even though you have them pictured above, which do not suffer from the issues of the non-locking solid gate, and are far superior than the wire gate models for many applications. We use these exclusively for rigging much heavier load applications than simple human climbing. Thank you for the KN rating explanations. It helps explain it to others that don't understand.

ITS Admin
ITS Admin

Storm,

Glad you liked the article, and thanks for the suggestion! We'd planned a kN rating article, but after your email we decided to make it more comprehensive.

Bryan

ITS Admin
ITS Admin

LOL, Doc that probably has a negative kN rating!

Thanks for the kind words, and glad you enjoyed the article!

Bryan

Storm1
Storm1

Thanks for the article, very informative!!

(I was one that requested this) answered all my questions..very nice!!

Storm1
Storm1

Thanks for the article, very informative!! (I was one that requested this) answered all my questions..very nice!!

"Doc"
"Doc"

So what your saying is I shouldn't rappel with the keyring Biner I bought at home depot? ;-)

Very informative, haven't heard this much knowledge on Carabiners since HRST Master class. Thanks for putting out the knowledge!

"Doc"
"Doc"

So what your saying is I shouldn't rappel with the keyring Biner I bought at home depot? ;-) Very informative, haven't heard this much knowledge on Carabiners since HRST Master class. Thanks for putting out the knowledge!

Kurt
Kurt

@Rick De Leon Carabiners are not designed for continuous loads, using them in this fashion will cause micro fractures that will in turn cause it to break under significantly less weight. Id suggest using a screw pin safety shackle, they are cheaper and much safer to use for this application, as they allow for tri loading, which is not a good idea to use a carabiner as they are not designed for this either, and will cause them to break under much less force than normal.

PS all carabiner that have been used under a continual load must never be used for climbing or safety afterwards as they are no longer safe and rated for the wll listed.  

Bryan Black
Bryan Black

Glad you found the info useful Simon, I'm not sure what a double action carabiner is referring to? Possible a double sided carabiner like the Nite Ize?

NASA TOW
NASA TOW

Oops. Missed it in the article.

ITS Admin
ITS Admin

Storm, Glad you liked the article, and thanks for the suggestion! We'd planned a kN rating article, but after your email we decided to make it more comprehensive. Bryan

ITS Admin
ITS Admin

LOL, Doc that probably has a negative kN rating! Thanks for the kind words, and glad you enjoyed the article! Bryan

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