The term “carabiner”—derived from the German word “Karabinerhaken”—describes a type of snap hook that is wider at the top and more narrow towards the bottom. This type of tool is referenced as far back as 1616, by German military writer Johann Jakob von Wallhausen, and is originally believed to have been used by military men to attach equipment to a bandolier when it was too heavy to carry on a belt.
What Are Carabiners Used For?
Carabiners are used for a variety of things, including rock climbing, window cleaning, and construction work. They are effective in creating pulley systems when combined with rope and other equipment. Other applications might include rope rescue, tree maintenance, and industrial rope work.
Parts of a Carabiner
There are six main elements to a carabiner. Each one plays a role to make the carabiner more secure and effective.
1. The Nose
The tip at the start of the carabiner, designed thinner than the rest of the body for the gate to close over it.
2. The Large Bend
Also called the basket part of the frame, this is the area where rope is run through. Its wide curve can also help reduce wear on the rope and the frame.
3. The Spine
The straight length of frame connecting the large and small bends. This is the strongest part of the carabiner. For that reason, it’s typically where you’ll find strength ratings and certifications.
4. The Small Bend
This area is useful for carrying other essentials to assist in the task that you are trying to perform with the carabiner. In rock climbing, for example, a runner might be held here to anchor and reduce rope drag. Or an additional carabiner could be attached to hold more supplies.
5. The Gate
The part of the carabiner that is spring-loaded to snap closed over the nose. There are a few variations in how the gate is built, including some that come with locking sleeves to further secure the carabiner.
How Are Carabiners Made?
Depending on their use, most carabiners are formed out of a type of metal. Most commonly they are produced from aluminum alloy or galvanized steel. This metal is heated, mixed, and poured into a mold to dry. Once sealed, any metal edges are removed before the metal is heat-treated to solidify the shape.
The final shape is cooled in cold water and then sent through vibrating drums to remove any coarse edges that might affect its function. Carabiners may undergo a final, aging heat treatment and be ground or polished to remove any remaining coarseness. Finally, the gate is applied by hand before the carabiner is tested and stamped with certifications and codes.
How Are Carabiners Measured?
Carabiners are tested and certified to meet specific requirements. These requirements are established depending on how the carabiners will be used. The United States Department of Labor, under the Occupational Safety and Health Administration, states that carabiners must be capable of withstanding a minimum load of 3,600 pounds. These regulations are provided to assist with fall protection. Industries impacted by this include construction, marine terminals, shipyard employment, and general labor.
The force carabiners can withstand is measured in kiloNewtons (kN) with one kN equaling about 225 pounds. The strongest part of the carabiner, or the area that can hold the most weight, is located at the center of the large bend—also called the major axis. With the information provided by OSHA, that would mean that a carabiner must support a minimum breaking strength of at least 16 kN.
Carabiners can also be measured by the amount of pressure required to open the gate. Though it is not explicitly listed by the Department of Labor, the International Climbing and Mountaineering Federation (UIAA) sets a minimum requirement of 5 kN, while the University of Arkansas (UARK)—in regards to mountaineering activities—recommends somewhere between 5-15 kN.
Regardless of what carabiners are used for, they must pass three certification standards in the United States. These include a National Fire Protection Association (NFPA) certification, an American National Standard Institute certification and a CE marking that establishes safety, health, and environmental protection requirements.
Types of Carabiners
There are four basic carabiner shapes and four gate types. Asymmetrical D-shape carabiners have a large gate opening, but are more expensive and less strong than standard D-shapes. They resemble pear-shaped carabiners that also have a large opening, but are heavier. Regular D-shape carabiners are also heavier and have a smaller opening, but are stronger than both of the aforementioned. Oval-shaped carabiners are the least strong, but their uniform shape enables them to hold more gear. All of these carabiners can be completed with one of the following gates:
Snap Gate
One of the first gate types established, they have the advantage of being able to quickly snap open. Can be straight or bent, with a bent gate being more helpful in clipping rope. However, their ease of access can also result in accidental openings.
Wire Gate
Resemble snap gates, but are made of two lighter-weight stainless steel wires that are less likely to open by accident due to reduced inertia in shock loading.
Screw Gate
Developed to prevent any accidental openings by containing internal threading that screws over the threading of the gate, these gates are less prone to accidental opening but can become vulnerable in some situations due to vibrations caused by ropes or wind.
Twist Gate
This type of gate remains in a locked position through spring tension and is only temporarily released when twisted and pulled down. It’s less prone to user error or accident, but can still become dislodged under the right circumstance.
Learning what carabiners are and how they are measured is an effective way to practice workplace safety. And properly using carabiners with other fall protection equipment can prevent accidents from happening.
Product Compliance and Suitability
The product statements contained in this guide are intended for general informational purposes only. Such product statements do not constitute a product recommendation or representation as to the appropriateness, accuracy, completeness, correctness or currentness of the information provided. Information provided in this guide does not replace the use by you of any manufacturer instructions, technical product manual, or other professional resource or adviser available to you. Always read, understand and follow all manufacturer instructions.