Info Supplied by CNCC Technical Group
The Anchor – DMM Eco
The Eco anchor is produced by DMM, in 8mm diameter 316 stainless steel, (which is also used for marine applications). It is then formed into a double ‘P’ shape, which requires a drilled hole of 18mm x l00mm deep.
Wear & Tear on the Anchor
Being made from 316 stainless steel there should be very little wear even on anchors placed on popular pull through routes. Anchors placed in Swinstow Hole Yorkshire, show very little signs of wear on their inner curvatures. Should an anchor fail the annual test, then it should be deemed unsafe and a regional official should be informed. The regional anchor officer/co-ordinator shall ensure that the anchor is checked, and if necessary, another anchor will be installed into the hole. Although the Eco anchor has considerable strength, basic rigging practices should still be observed i.e. back ups & ‘Y’ hangs etc.
The Chemical Anchor Mortar – Resifix 3 Plus
The resin that shall be used to secure the Eco anchor shall be RESIFIX 3 PLUS chemical anchor mortar. This can be used in dry or wet conditions. A limitation is that it cannot be used when the temperature on the day of application is below -5’C. The resin is contained in a large tube, this large tube contains the polyester resin and a smaller tube, the smaller tube contains the activator. Both are expelled simultaneously and mixing occurs in the nozzle. As the resin and activator pass through the nozzle and mix, a colour change takes place. When the colour is consistent (no streaks), the mortar is correctly mixed, and can then be injected into the hole.
If an open tube is not used for some time, or curing has taken place between pitches, remove the nozzle, then remove any hardened mortar from the two apertures in the end of the tube. Screw on a new nozzle and expel the chemical mortar until a consistent colour is achieved.
Avoid breathing the vapours and skin contact, wear gloves and goggles when injecting the resin, ensure that you read & understand the precautions supplied which each tube of chemical anchor mortar.
Curing time, this varies with temperature, underground at +10’C. Curing is complete within 80 minutes, this however may be longer or even shorter. Therefore, a minimum of 6 hours must elapse before the anchor is loaded.
It is recommended that TWO people, experienced in rigging, discuss the following points before fixing the anchors:
- Anchor sites to be suitable for SRT, laddering or pull through trips.
- TWO resin anchors for:
- Main belays for abseil and S.R.T
- Re-belays if more than 10 metres from the pitch bottom, or next re-belay.
- Anchors should give a free hang, check for rope rub by holding krab or maillon just clear of the wall with rope attached. Consider methods of linking anchors; see Figs. 4 & 5.
- Anchors need to be reasonably high; this allows the main belay knot, shared anchors, traverse lines, and attachment for belay device or pulley to be shoulder high. This will decrease fall factors for any one fastened on, facilitate SRT rescue and access to and from the head of the pitch.
- Resin anchors need to be at least 20cm (8 inches) apart to, avoid overlapping stress cones in the rock. The anchors should be angled towards the proposed direction of loading figs. 3,4,5 & 6.
- Pull through routes, two anchors should be available for pitches in excess of 4 metres. The hangers can either share the load or be super-imposed; either method is acceptable fig. 6. If using the super-imposed siting, fig 6b, then careful alignment and angle of anchors will ensure a trouble free rope run, for retrieval after abseil.
- Existing 8mm S.D. anchors can be left in if they do not compromise the optimum siting and are not to close to the resin anchors. If the old 8mm S.D. anchors are within 150mm (6 inches) of a resin anchor they are best removed, the hole can be enlarged to take the resin anchor.
Although Eco anchor placements have considerable strength, basic rigging practices i.e. backups, shared loading ‘Y’ hangs, deviations etc. should still be used. Eco anchors are not an excuse for bad rigging techniques. All the precautions used to gain a safe descent and ascent of pitches and negotiate exposed areas, still apply when using these anchors.
When using SRT, the rope can be tied directly to the first anchor by using a figure of eight knot. Maillons or karabiners are then used for the attachment of the rope to further Eco anchors to the head of the pitch, where two anchors, normally on opposite walls, provide a ‘Y’ hang. It is good practice to try and keep the rope taut, this ensures that each anchor placement is backed up to the previous anchor.
All anchor placements at pitch heads have been placed to give a free hang as far as a re-belay or deviation, as required. It is still important to check that a rub point has not been caused by too short, or too long a loop in the ‘Y’ hang. Occasionally 2 maillons or karabiners may be required to avoid a rub point close to the anchor placement.
DO NOT tie the rope to the first anchor and then pass it through all the other anchors to the head of the pitch, the rope must be secured to each individual anchor placement.
Due to the shape of the Eco anchor, more than one rope can be rigged from each anchor point. This practice may lead to some tangling of the ropes, but this is far safer than using other (non Eco) anchor points, where security and strength of placement cannot be guaranteed.
Pull through trips
A number of caves are descended as ‘pull through’ trips. When descending a cave and pulling through, the rope should be always be threaded through two anchors. There are a number of safe ways to approach the head of the pitch.
If the Eco anchors are more than a cows tail width apart, tie a butterfly or figure of eight knot in the rigging rope so that you can reach the next anchor.
A separate short length of rope can be taken to rig each traverse, (long enough for the longest traverse), this is derigged by the last person to descend, during the traverse and finally unfastening the last anchor point from a safe position or while the descender is locked off on the main descent rope. Take care to ensure that the short end of rope is knotted to prevent anyone descending the wrong rope. When a single rope descender is being used, a Butterfly or Figure of Eight knot with a karabiner (maillion is better) can be used to strangle the anchor, care is required to ensure that inexperienced cavers descend the correct rope. The pitch can be rigged with a single rope until the last person, or the spare end pulled up to avoid confusion.
When clipping directly to an anchor, it is possible that under certain circumstances during movement, the anchor can open the gate of snap gate karabiners.
Ladder and Lifeline techniques
Use at least three anchor points for pitches rigged using ladder and lifeline. The belay device is best attached to two shared anchors. Cows tails used in conjunction with traverse lines will provide safety when negotiating exposed areas. Always use a pulley or karabiner for double lifelines, under no circumstances should the rope be pulled through an Eco anchor when loaded. This action will damage the rope and cause premature wear on the inner curvature of the Eco anchor.
Twist the anchor using the fingers, while observing any movement. Slight flexing or rotational movement (+/-1mm) of the anchor is acceptable.
The following points should be checked before using or loading the anchors:
- Looseness or fractures of the rock in which the anchor is placed.
- Grooves or abrasion inside the curvature of the anchor. i.e. the inside contact area of the anchor.
- Obvious damage to the anchor or placement from rock fall.
- Excessive rotation of the resin within the drilled hole.
- Rotation of the anchor within the resin. · Fracturing of the rock within 20cm of the anchor placement.
- Egress of the anchor from the resin or the resin from the drilled hole.
Should any of the above defects be noticed, you should contact the anchor co-ordinator via the regional caving council secretary, any defect reported will be checked out ASAP.
The following information is required when reporting suspected defective anchors:
- Name of cave.
- Route on which defective anchor is.
- Traverse or pitch number/name.
- Anchor number, counting from the start of that group of anchors.
Note: Due to the cost of installing Eco anchors (£5 per placement) and the amount of good useable limestone at pitch heads, the anchors have been installed so that all cave users, whether SRT, ladder and lifeline or pull through can use them. Attempts have been made to avoid over rigging and to encourage the use of available natural belays where possible. In areas where there appears to be excessive numbers of Eco anchors, they have been installed in addition for ladder and lifeline techniques or to facilitate rescues. When Eco anchors are used for ladder and lifeline it is essential that pulleys are used, the rope must not be pulled when loaded through the anchor as this will cause premature wear on the contact area.
The Eco anchor has been approved by the British Caving Association as a fixed anchor to ensure the safe descent and ascent of caves and potholes. All enquiries regarding fixed anchors should be addressed to the regional secretary
A number of the popular caves have pieces of old rope and slings ‘tat’ left in them by previous parties. DO NOT be tempted to use them even if they look safe. Take and use your own, then remove them after the trip.