Least Resistance Training Concepts (LRTC) Volunteers Training for Emergencies

LRTC Emergency Response Team INFORMATION SHEET Basic Rope Rescue Systems Part Four This feature is a continuation of Part One which explains the concepts for this discussion.   Carabiner Key Points Whether lowering or raising a person or dragging a downed animal, carabiners are among the most common devices we use. When used properly, they are extremely safe and reliable. But as with any tool, it's important to understand their strengths and weaknesses. One key point element involves carabiner axes. The major axis runs the length of the carabiner. The minor axis runs the width of the carabiner. Understanding the difference is important since how a carabiner is loaded can affect its strength. Note in the example below that the strength along the major axis is 24 kN (about 5,400 Lbs.) while the strength along the minor axis is only 7 kN (about 1,575 Lbs.) Improper loading can significantly impact the 15:1 safety ratio for life line loads and 5:1 ratio for large animal loads. A carabiner will perform to its load rating when it is loaded directly on its major axis. Such loading may not always be practical, so it's important to understand the effects that offset loading may have when carabiners are placed under critical loads. Best layout, directly along major axis. Less desirable with some loss at webbing connections. The following recommendations regarding carabiner loading appear in Confined Space Entry and Emergency Response. (This is a very useful reference text.) As a rule of thumb, the strength of most carabiners across their minor axes will be about one-third or less than the strength along their major axes. The following images have been provided by Petzl, the manufacturer of several of our carabiners. They illustrate common mistakes that could potentially produce carabiner failures. (You can view Petzl's complete feature on proper and dangerous carabiner loading practices here.) Additionally, whenever carabiners are being used, the following additional issues can be critical for mission safety: Always safety check to see that all carabiner gate screws are properly closed before placing a load on the system. When working in sandy or dusty areas, back off gate screws about 1/4 turn from fully tight to keep them from binding. (This allows you to "rock" gate screws back and forth if they get jammed with dust or sand.) Avoid allowing any objects (webbing, ground surface, equipment) from contacting any gate screw that could inadvertently cause the screw to turn. Never load a carabiner that is placed across a hard edge.   Useful Accessories There are several ways that anchors and loads can be customized to facilitate optimal loading on carabiners. We carry a couple of pieces of equipment can make balancing a load quick and easy. One device is a rigging plate. These plates come in various sizes. Larger rigging plates are often referred to as bear paws. We use both large and small rigging plates to accommodate multiple attachments while providing a consistent load rating of 30 kN (over 6,700 Lbs.) between any of the various points. While webbing can be directly attached to a rigging plate, connections via carabiners are generally preferred. We also carry delta links, also called "trilinks." Delta links are still weaker along their minor axes than major axes, but they are generally stronger overall for multi-point loading than are carabiners. Rigging plate. Balanced load. Gate screws away from ground. Preferred layout. Delta Link. Balanced load. Gate screws away from ground. Less desirable than a rigging plate, but workable. Continue to Alternative Anchor Points Return to Part Three Return to Part One Return to Information Sheets and Resource Guides Return to Sample Incident Responses Return to LRTC TLAR / EVAC Page The training information presented in these information sheets and guides is offered for illustrative and volunteer refresher purposes only. It is not a substitute for actual hands-on training. Press Back to return to the page which brought you here Return to LRTC Wild Horse Mentors Return to KBR Training Page Go To KBR Horse Net