There are many constructions that might be considered acceptable anchors by ice climbers, aid climbers, alpinists, cavers, SWAT personnel, lobstermen, and even rock climbers which do not meet the standards for institutional climbing. Anchors for most climbers are evaluated on the basis of their strength. Whereas strength is certainly important for the institutional anchor, a host of other factors must also be considered. The institutional anchor must be secure against failure by abrasion or dislodgment through heavy, repeated use; easily set up by relatively unskilled instructors; constructed so as to minimize improper use by unskilled instructors; secure against tampering by curious bystanders or participants; generally consistent; free of specialized material use; positioned as to afford a high level of safety for set up and breakdown by instructors who do little personal climbing; easy to deal with in an emergency situation; etc..
Institutional simplicity and overall safety is best achieved by insisting on uniform basic minimum standards for anchors.
S.R.E.N.E.
Secure, Redundant, Equalized, Non Extending.
Every anchor should conform to the rules named in this acronym.
SECURE:
Once the correct use of proper institutional equipment, anchor set ups and properly tied knots is assured, security depends upon the points to which that equipment is ultimately attached. Those points can include trees, rock thread throughs, huge boulders, bolts, pitons, and climbing protection pieces. Anchor points should not incorporate grappling hooks, bushes, cars, fence posts, railing posts, etc..
TREES:
In general, any healthy tree that is too large for an adult to put their arms all the way around can be used as an anchor. But of course, even the largest tree might be long dead and easily toppled. Exercise judgment. Trees with less than a six inch diameter should be avoided. Trees should be slung at the bottom for maximum strength.
Trees are more fragile than they might appear. Whereas a large tree can survive centuries of the heavy weather, it only takes a few years of heavy traffic to kill it. The heavy traffic compacts the soil around a tree's base and compromises the function of the fine but essential surface hair roots. Most aging, heavily used areas have receding tree lines. Because of the rock substrate, the soil on top of and around cliff areas is often thin. The fact that water collects and runs off of the rock with great force also contributes to the delicacy of cliff areas. If the flow pattern is disturbed by unnatural erosion, the run off can be extremely destructive. Minimize foot traffic on soil. Restrict students to "sacrifice" areas or keep them on rocky surfaces.
ROCK THREAD THROUGHS
These are fully enclosed passages through rock that are formed by fracturing, erosion or the way in which huge rocks in formations or breakdown sit on top of each other. Their strength depends on the rock and the size of the rock portion that will bear the load.
A horn of rock may be perfectly adequate for many non-institutional applications if the direction of pull is consistent. The closed thread through guarantees that the anchor sling will stay in place.
Be wary of sharp edges inside of thread throughs. Pad sharp edges to prevent the slicing of anchor slings. Padding can also prevent a sling from being permanently pinched into a narrow seam in a thread through. Pull, push and jump on all of the rock in and around a thread through or other natural rock anchor--even huge rocks formations can be weak, unstable anchors if they are precariously balanced.
SLINGING GREAT BOULDERS
The bigger the better. The same precautions apply as for thread throughs. Regardless of size, a boulder may be an unsafe anchor if it is unstable or if it is shaped in a manner that will allow slings to slip off. Given the heavy exposure to the jostling that can be expected during a day of climbing on a set of anchors, a sling can slip up and off of a boulder that lacks a sizable indentation.
BOLTS
The simplicity of bolt use makes them a boon to institutional climbing. However, bolts are an eye sore and an unnecessary infringement of technology on wilderness areas. In their favor, bolts on the rock face can help to reduce the traffic on vegetated areas. Bolts can make it possible for an institution to avoid the more convenient, heavily used areas with tree lined ledges, and so reduce the impact on those areas.
Installing bolts for the purpose of an institutional climbing program is an option that should be considered thoroughly before implementation. Review local ethics and regulations. Staff must be competent to carry out the safe installation and maintenance of bolts. Prior experience is mandatory.
If the decision is made to use bolts in an institutional program, study the latest methods and technologies. The contents of this manual are an overview, intended to serve as a guide for research, not a replacement. Once a bolt is in place, it is difficult to judge its strength, and people will assume that it is reliable, so place the most reliable bolts possible. Use a power, rotary percussion drill, to make the holes if such tools are permitted in your area. A machine places more consistent, higher quality holes than a hand drill. At a minimum, place 3/8 inch diameter bolts of the longest practical length. Preferably, use extremely durable hardware such as half inch diameter stainless steel bolts or the special Petzl long life bolts.
Best of all, place glue in (epoxy) anchors. Petzl produces an excellent glue in anchor. The glue in bolts are less subject to corrosion and weather deterioration than standard mechanical expansion bolts. The mechanical expansion bolt will never completely fill the hole that is drilled for it. Into the spaces between the shaft and the hole, water drips or forms through condensation. This water freezes and thaws and causes the slow destruction of the rock around the bolt. Many regions suffer frequent freeze and thaw cycles. The epoxy of the glue in bolt fills the space in the hole and moisture is permanently excluded.
If mechanical bolts are used, the holes should be sealed with silicone or a similar substance. Such sealant must be replaced every two to four years, depending on the rock and the environment. Check with local climbers and climbing stores about the recommended bolting practices are for your area. Practices vary. In soft sandstone, for example, bolting is often accomplished by hammering small angle pitons into bolt holes.
The first bolt below is a Petzl Glue in anchor. The hole is, a capsule of epoxy is placed in the hole and the bolt is inserted, breaking the capsule.
The second illustration is of a common expansion bolt. (Illustrated before expansion) The hole is drilled, the bolt is hammered in and then the nut is tightened down. As the nut is tightened, the conical end is pulled back into the sleeve which expands around the cone and wedges the bolt into place. If this bolt is over-tightened, the sleeve will pull over the cone, resulting in a very weak anchor.
The third illustration below is of a Star Drive bolt. These were placed in great numbers during the seventies and early eighties. Many are sound. The sleeve doubles as the bit on this short, stubby bolt. Once the hole has been hand drilled, the cone is placed in the sleeve and pushed up against the end of the hole. The sleeve is then hammered down over the cone, expanding it against the sides of the hole.
A record should be kept of the date and type of every bolt placed. Eventually, every bolt must be pulled and replaced.
INSPECT ALL BOLTS
Check the shaft for excessive protrusion from the rock which may indicate a shallow hole in the case of the older hand drilled, star drive type bolt. The hanger should not be resting on the threads of the bolt, as this reduces the strength of the bolt, but many mechanically placed bolts are set up this way because most are purchased in hardware stores instead of from climbing manufacturers. The shaft of a hardware store expansion bolt is usually threaded differently than a climbing specific bolt. Any evidence of battering may represent damage due to previous attempts to remove the bolt. Check for looseness. Differentiate between a loose hangar and a loose shaft. A loose shaft is extremely dangerous. A loose hanger might be remedied by tightening the nut. Some hangers on relatively sound bolts are permanently loose because of the thread configuration on the bolt or the shape of the surrounding rock. Check the angle of the shaft. Anything other than perpendicular to the surface is a sign of poor placement and a compromised bolt. The hanger should be examined for hairline fractures, disfigurement, or looseness. Use no bolts with ¼ inch shafts for institutional purposes.
Although most modern bolts test out to four thousand pounds or more in both sheer and pull out strength, they are unpredictable and subject to flaws of manufacturing or placement. NEVER USE A SINGLE BOLT AS AN ANCHOR.
BOLT HANGARS
Use only modern climbing specific hangars. Most bolt hangars are directional, they are intended to support a pull in a limited range of direction. Except for specialized large diameter hangars, ropes and webbing must be attached to the hangar with an intermittent carabiner or quick link.
PITONS
Pitons can be used as fixed protection in some areas. Their use should be learned through experience.
CLIMBING CHOCKS:
Chocks are attractive in that they can be conveniently placed and removed in a variety of areas where there is a lack of natural anchors and bolting is unacceptable. They do have numerous drawbacks. Competency with chocks comes from leading routes requiring natural protection and setting up hundreds of anchors. If the number of individuals in a program who posses this competency is limited, regular training exercises must be held.
Even if solid placements are identified and their exact use prescribed, staff are more likely to make mistakes with chock placements than with slings around trees and rock thread throughs.
If climbing chocks are used for anchors:
A) Always form an anchor out of three or more pieces. Two may be sufficiently strong, but as such protection is subject to poor placement and dislodgment, insist upon a minimum of three pieces in every such anchor. Four would be better.
B) Use only the most solid pieces. Prohibit the use of tiny stoppers, super lightweight cams, and sliding nuts in institutional anchors. Use only large stoppers, hex's or camming units that are at least as large as a number one friend. Tri-cams and other passive units can also provide solid protection.
REDUNDANT
The anchor must not posses any single component the failure of which would result in the failure of the anchor. Most organizations use a single rope and belaying device, but these are not part of the load bearing anchor. (I know of one organization that pursues redundancy to the point of actually securing every participant with two harnesses, two ropes, and two belays.)
In the case of the tree that an adult can not put their arms around, redundancy is insured by the numerous roots extending from the trunk. However, if the big tree is used as a sling-shotting anchor, there should be two wholly distinct sling systems coming off of the tree and two locking carabiners at the ends of these slings, through which the rope will pass.
In the case of using two smaller trees for a sling-shotting anchor, a single sling can come off of each tree, but the anchor must terminate over the edge with two locking carabiners through which the rope will pass:
Note: It is often preferable to bring the slings together at a point above the edge, clip them into two carabiners, run two more two slings-slings over the edge, and clip the rope into two more carabiners at the end of those slings. This results in a unified bundle, going over the edge, which is easier to protect form abrasion. It is also easier to keep the load equally distributed
Minimal doubling insures that the anchor will not fail if one knot is tied incorrectly, if one anchor point fails, or if one sling is cut all the way through by abrasion. Nonetheless, anchors should be checked regularly while sling-shotting to be sure that the slings are not being affected by abrasion or other damage. Abrasion can be minimized by placing a sheath over the anchor slings or rope at the points most subject to abrasion .
When two or more points are used to form an anchor, the angle formed at the lower anchor point should be as small as possible. A large angle increases the load on both anchor points. Keep the angle in anchors below ninety degrees. This load increasing phenomenon must be minimized when estimating the loads generated by high lines, safety lines, and other systems. Even a sling around a tree or a rock which is too tight will break unde This load increasing phenomenon can be easily demonstrated with a pair of small fish scales and a small weight r a lesser load than a sling which is long enough to make a small angle at the load point. .
The set up on the left is incorrect, generating too much force on the anchor points.
EQUALIZED
The load should be distributed among the different components of the anchor as equally as possible. If two trees are used as an anchor, the slings should be adjusted so that they terminate at the same point, where the two locking carabiners will be placed.
Equalized is not the same as self equalizing, a configuration which will adjust to an equalized position even if the direction of pull should change. Most anchors do not need to be self equalizing. The direction of pull is usually consistent. If required, a simple method of self equalizing two points can be achieved with a single twisted sling. This common "magic X" configuration (illustrated below) prevents the carabiners which hold the rope from sliding off of the sling if one anchor point should fail. But the single self equalizing sling is neither redundant nor free from extension. If it is cut by abrasion, the anchor will fail. In order to achieve redundancy with this system, a second and identical sling would have to be added to the anchor. (illustrated below) But the doubled self equalizing sling is still subject to extension. If one point should fail, the other will be loaded dynamically, generating a force that is even greater than that which caused the first point to fail. If the self equalizing slings had distributed half of the load to each anchor point and then one of those points fails, the shock is going to place a load on the remaining point which is more than twice that which caused the first point to fail. If the initial failure was caused by an anomalous flaw in a bolt or a gear placement, the shock load would be unlikely to break the second bolt. However, if the initial failure were of a bolt due to a previously undetected weakness in the entirety of the rock (perhaps a softer rock substrate or a layered fracture in the rock) or corrosion weakened bolts, than the greater force of the shock loading could easily cause the failure of the second bolt. The double X method is only acceptable when working with solid rock, short slings and excellent protection.
There are several possible ways to create anchors that are both equalized and free from extension. The simplest is to equalize two independent slings to a fixed point and prevent shifting of the anchor which would unequally load the anchor points. However, it can be very time consuming to adjust the slings.
The one on the left is a single equalized sling. As described, if one anchor point fails, the slide will shock load and, perhaps, cause the other point to fail. The use of a single sling is also undesirable in the institutional setting because of the possibility of the sling wearing through and causing the anchor to fail. The second setup is a double of the first which obviates the second problem but not the first. The third set up obviates both problems, but can be a pain to set up.
Especially handy is the following method of equalization: First, tie an overhand loosely into a fairly long sling. Second, clip each of the ends of the sling into a carabiner. Third, adjust the overhand to the desired position of equalization and tighten it. Fourth, place the anchor carabiner(s) through each of the two side loops, being careful to position the overhand knot so that it is not on the rock and does not interfere with the carabiners. This setup is free from extension and it is much less time consuming than retying slings to achieve equalization, but it has a point of non-redundancy: the overhand knot which, if abraded through, will cause the failure of the anchor. This anchor can be used regularly in places where you will be present to monitor possible abrasion problems. One solution to the abrasion risk is to add a second sling of equal length to the system that is tied in the same manner as the first.
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It is possible to start with a self equalizing sling and then add a sling with an overhand knot as below. This set up achieves self equalization, redundancy and non-extension, but it is a little cumbersome and requires two different length slings. I do not recommend its use.
One of the simplest methods of using a pair of bolts for a slingshot anchor is to fix large chains to each of two bolts with either steel carabiners or quick links and run the rope directly through the chains. This method is currently in use by certain institutions which employ a large number of staff who possess little climbing experience. A light cord can even be left through the chains to facilitate set up. Chains eliminate a whole area of concern about mistakes in daily use.
NON EXTENDING
The reasons for avoiding anchors which have the potential for extension and shock loading is explained in the previous section.
ABRASION
Damage by abrasion can be a serious problem. Some rock is harder on webbing and rope than others.
As illustrated above, slings bent over an edge can be protected from abrasion with a sheath. Old denim pants legs work fine. Fire hose and plastic tubing are tougher, but they are heavy to carry around and sometimes more difficult to work with.
When a knot rubs against the rock under load, a great deal of force is concentrated onto a small point and destructive abrasion can occur quickly.
In the case of a domed, sloping rock face, protecting the anchor slings or rope from abrasion is problematic. The knot will often be the contact and abrasion point. One solution is to place a pants leg that extends out over the knot and carabiners. But this is sloppy and it is possible that the material could bind in between the carabiners and rope.
A much cleaner solution is to form such anchors with lengths of 11 mm static line, over which have been slid lengths of older one inch tubular webbing. A figure eight on a bight can be tied right into the portion of the rope which is covered by the webbing. This will protect the knot from abrasion.
When using the sheathed rope as a component of a sling-shotting anchor, it must be backed up, despite the more than adequate strength of the static line. A reasonable solution is to back up every such length of static line with a slightly looser length of webbing. By making the webbing a little longer, the load will rest on the sheathed static line rather than the unprotected webbing.
-webbing back up (a single strand with an overhand on a bight on each end)
Familiarity with the rock and its sharpness at different points is useful knowledge in the fight against abrasion. If a participant takes a swinging, pendulum fall across a protruding edge, the climbing rope can be damaged or even cut. Try to prevent such falls and check the rope whenever a potentially rope damaging fall occurs.