Building an anchor system requires much practice and experience. When dealing with structures, chose anchor points which are part of the inherent structure of the building. This includes columns, beams, anchors for window cleaning equipment, and elevator housings. Avoid corroded metal, weathered stonework, and deteriorated mortar. Avoid using vents, flashing, gutters, and chimneys.
When using a vehicle for an anchor, remove the ignition key, set the brake and chock the wheels. Do not use the bumper. Connect directly to the vehicle frame using such items as the axle, cross member or tow hooks.
Often a desirable anchor is off to the side of a needed direction of pull. Ideally, they should be directly above and close to the fall line. When this is not possible (which seems to be more times than not) advanced anchor rigging skills come into play, namely, focusing the direction of the main anchor to a viable position.
Anchors are the foundation on which we build our rescue systems. Rescuers must quickly decide on an appropriate anchor system for a given rescue situation. Usually, anchors need to be in place before other aspects of the rescue can proceed. Determining where anchors should be built and beginning their construction early are critical steps in timely rescue operations. Here’s a quick review of anchors and related keywords we’ll cover throughout this course:
An Anchor is a general term for the combination of everything combined. Single connection point (e.g. tree, boulder, camming device, etc.).
An Anchor Point is a single object or component used either alone or in combination with others to create an anchor system capable of withstanding a significant force.
An Anchor System is one or more anchor points connected in order to provide a secure connection. Multiple anchor points rigged together creating a redundant system.
Redirects the natural fall line of the rope on the rock face. A deviation point may or may not to be subjected to the same force as the primary rig point.
Rigging technique to change the natural line of a rope with a carabiner or pulley attached to an alternative anchor.
A location, floating or fixed, where all rigging is directed for anchor points. This concept disciplines rescuers to construct rigging which joins together at an efficient point, rather than unwittingly resorting to wherever the knot that joins all anchor points ends up due to the length of material used; the latter can result in an awkward spot to manage rope handling tasks.
We will always try to engineer our anchor systems with housekeeping in mind. Though a single “bombproof” anchor may be strong enough to support an entire rescue system, including multiple load bearing lines, we may still build a second anchor for convenience and cleanliness and to allow more workspace for rescuers. Rescue systems are often more efficient and easier to operate with redundant load bearing lines rigged on separate anchors.
E – Equalized
In a system with multiple anchor points or multiple strands of anchor material, the various components of the anchor system should bear roughly equal parts of the load. Self-equalization is not required. Pre-equalize the anchor for the anticipated direction of pull.
R – Redundant
Failure of any one component of an anchor system should not lead to complete anchor failure. For example, construct the anchor system so that if one strand of software is severed, at least one additional strand capable of supporting the load will remain intact.
N – Non–Extending
Failure or shifting of one element in the anchor system should not cause significant movement of the load. This is why we fix and focus our multi-point anchor systems and why we generally avoid self-equalizing anchors. The location of anchor points relative to one another is also a factor in this stage of anchor system analysis. Failure of one anchor point should not result in excessive swinging of the load toward the remaining anchor point or points.
S – Solid
Choose the strongest available anchor point. If no single anchor point seems strong enough then combine multiple anchor points until you are confident your anchor system is strong enough. Build your anchor with materials at least as strong as the weakest point in your system.
T – Timely
Balance the need for strong anchors with the need to reach your patient as quickly as possible. Simpler is usually better.
Single Point Anchors
Within a Single Point Anchor, there are two types of connections:
Indirect for webbing, cord, and other such material.
Direct which uses the actual working or belay lines themselves.
Often, single point anchors are either non-existent or marginal, thus necessitating the need for multipoint anchor systems.
Rigging a backup or secondary connection to a separate anchor.
Available anchor points are not exactly where they need to be.
A directional shift is possible during the evolution
Four Types of Multipoint Anchor Systems:
Slack Anchors Systems: These are non-tensioned systems are more for backups.
Tensioned Anchor Systems: These utilize some form of tensioned mechanical advantage rope system between anchor points. PreTensioned back-ties, non-working 3:1 MAs, AZTEKS, Munter Mule are examples.
Load Sharing Anchor Systems.
Load Distributing Systems.
Shared & Distributive Anchors (Specified Multipoint Anchors)
Load Sharing Anchors (LSA) are theoretic in the distributive attributes. They’re clean and generally efficient. The point of disproportion happens at the point when a load shifts and the anchors won’t accomodate and safe transition between the two anchors. This could result in a slacked line, and this is not what this anchor system is intended for. So if there is ever concern where the load could shift, don’t use an LSA, but rather something more accomodating. That said LSAs are the preferred Multipoint Anchor. They cleaner, faster, non-extending, safer and have a greater operational application that LDAs.
Load Distributing Anchors (LDA) are similar to its Load Sharing cousin, but differ at three points:
A single piece of material to connect anchor points.
Will theoretically distribute the load when a shift does occur.
Should an anchor point fail, redistribution still remains.
Extensions, Back-Ties & Redirects
As with all anchor systems, making sure extension, back-ties, and redirects meet all the criteria of EARNEST.
What does this stand for? Equalize your anchors so they are always in tension. Angles are minimum. Redundant. Never Extending if failure occurs, and Strong. Timeliness is important but better correct than hastily done and wrong.
Theory of Anchors
Anchors are the most critical component of any rope rescue system. The entire rescue is in jeopardy if the anchors are not reliable. Anchor systems are made up of two major elements:
Choosing the best anchor (i.e. boulders, vehicles, trees, and bolts), and
Rigging the anchor
Peace on your days…