Sea cliff bolt failure

[mikem]

Not cave related but looks like it is in limestone - Diamond Handline North Wales
[Alex Rhodes] dropped into the Diamond on the falling tide this afternoon. The hand line is compromised on the green slab, just as you start to lose height down to the boulders.
The glue-in bolt has cracked on its underside rendering both maillons at risk of detaching completely and either handline before/after coming free. If someone was fully weighting either cable via their lanyards, that wouldn’t be a nice outcome.
There’s a second glue-in next to it linked by some tat, but this doesn’t back up the hand lines as the maillons aren’t incorporated.
I’ve stuck a bail biner linking the two maillons for now – worst case if the bolt blows completely, the two wires are still connected by something. Still would be a nasty shock for someone not expecting it!

BMC rep and NW Bolt Fund notified

Link to post: https://www.facebook.com/share/p/bGGtR3WvRT1a3iVw/

 

[mikem]

From the comments: "the bolts aren't 316, they're 1.4462 duplex stainless steel from bolt products 'seawater series'. Info here: http://www.bolt-products.com/SeaWaterSeries_000.htm "

 

[Steve Clark]

That's an alarming failure.

I don't know the overall layout of the handlines, but it appears to be sideways and eccentrically loaded by a very static (steel cable) line with a very high load angle, almost like a catenary. You could get a very large load like this if someone fell on it without anything dynamic in the system. Climbers clipped in with slings? The load at the bolt could be 5-10x that experienced by the climber.

Or fatigue, if the multiplier effect is making the repeated pulling on the handlines is repeatedly twisting the bolt close to yield? Not that many cycles required if the load is high.

 

[Steve Clark]

Actually, reading the facebook comments it looks like someone moved the left hand mailion from the correctly orientated left hand bolt and put it on the right hand bolt.

 

[Bob Mehew]

If you look closely at the two photos attached by mikem, you can see in the second photo that the other anchor is possibly coated by the green slime present on the cliff. Also the first photo appears to show a surface crack to the right of the exposed crack surface. I wonder if the green slime provides a means by which chloride ion concentrations can escalate upwards thanks to evaporation of sea water thus shifting the environment into the zone for Chloride Stress Corrosion Cracking for the steel. (I was sensitised to evaporation mechanisms after reading a paper reporting a small pool of water above Malham Tarn with sea water chloride levels.) I recall years ago the BCA Equipment & Techniques Committee decided to not go for these sea water anchors because of concerns over such mechanisms but looked at titanium anchors instead.

 

[Chocolate fireguard]

If the bolt had been completely overwhelmed by a force big enough to break it (100kN I think) I would expect it to have undergone a lot of plastic deformation both before and after it broke.

 

[Cantclimbtom]

Although the temperature and forces are lower than say hot pressurised pipes where you might expect it more, chloride stress corrosion cracking in austenitic steels (e.g. 304, 316 stainless) is a definite issue.

Some climbing environments like Thailand (OK not quite the same location as Diamond ) 316 stainless may corrode faster than galvanised. Partly the marine environment and partly other salts in the rocks drainage.

If the bolts get replaced, with hindsight maybe stainless isn't the right choice. https://www.titanclimbing.com/ (Sheffield based) can supply more suitable replacements.

No armchair critic tone is intended in this post. Respect to the volunteers who spent their time and money to equip and maintain this!

Edit: be very interesting to read Jim Titt's analysis (as THE expert ) does he frequent these parts?

 

[Cantclimbtom]

Mods... Actually, please edit/redact the post above to simply say

I've contacted Jim Titt to see if he has any advice or comments he can share, since he will be THE expert on this issue. he replies

 

[Bob Mehew]

If you wish to read some back ground on the topic, then try the documents listed here and also the minutes for the BCA E&T discussion on it which if I recall correctly lasted from 2011 to 2015.

And by the way, titanium may not be the answer.

 

[Stuart France]

The attached paste-up shows one of the photos from above with a P-hanger of similar genre. It appears there had been some plastic deformation (downwards pull) of the fitted hanger's shape prior to fracture. If so, it would only serve to increase existing stress at the sharp lower bend in the anchor arising from its manufacture which is near where it broke. The gap then widened due to some outward pull from the wire rope.

The nature of a multi-point traverse line supported by a mid-point twisted rod style of hanger is to apply torsional (twisting) stress to both shafts of that hanger as people pass along it, greater in the lower shaft which is where it broke. Whether chloride stress corrosion played a part in weakening the shaft is unclear, but the physical stresses are convincing. The lower shaft will have been stressed the most by creating its sharp bend at the factory, then stressed even more later due to ongoing usage in the particular circumstances here prior to it breaking at the point of maximum stress: a scenario that appears insufficiently considered.

The knotted rope had been placed under the incorrrect assumption that only the resin part could fail when it was the metal part that failed. The other assumption is that the traverse line, wire rope bends and attachment rings for maillons etc could not fail either, in and of themselves during normal use, or their age, or as a consequence of extraordinary forces following an anchor failure. There are lessons for us all in this.

 

[mikem]

Another failure on a sea cliff, from BMC incident and near misses, Sept 2023:

"A climber was lowering off from the top of the route which was equipped with Ram Horn Anchors attached by glue bolts. The climber was cleaning the route of quickdraws but was only lowering from one of the bolts with the rope through the ram horn. The bolt sheered off. He fell but was stopped half way down the route by the remaining quick draws.
Nearly a ground fall from considerable height.
Obviously he should have been lowering off both ram horns creating redundancy however this is a critical fail of the glue bolt which snapped cleanly off. The ram horn didn’t break.
No obvious rust on the glue bolt that snapped and climbers weight looked below 70kg."

"The persons who were involved in the incident will also be submitting information and have retained the bolt so pictures or inspection can be carried out if needed."

BMC Report 05/09/2023 Battleship Back Cliff (Dorset) Sport rock climbing

A climber was lowering off from the top of the route which was equipped with Ram Horn Anchors attached by glue bolts. The climber was cleaning the route of quickdraws but was only lowering from one of the bolts with the rope through the ram horn. The bolt sheered off. He fell but was stopped...

www.incidents.thebmc.co.uk

 

[wiggle]

Not cave related but looks like it is in limestone - Diamond Handline North Wales
[Alex Rhodes] dropped into the Diamond on the falling tide this afternoon. The hand line is compromised on the green slab, just as you start to lose height down to the boulders.
The glue-in bolt has cracked on its underside rendering both maillons at risk of detaching completely and either handline before/after coming free. If someone was fully weighting either cable via their lanyards, that wouldn’t be a nice outcome.
There’s a second glue-in next to it linked by some tat, but this doesn’t back up the hand lines as the maillons aren’t incorporated.
I’ve stuck a bail biner linking the two maillons for now – worst case if the bolt blows completely, the two wires are still connected by something. Still would be a nasty shock for someone not expecting it!

BMC rep and NW Bolt Fund notified

Link to post: https://www.facebook.com/share/p/bGGtR3WvRT1a3iVw/

I would replace with titanium bolts I know how not 2 have done bits of testing and have talked about how in a bolting project in crabby Thailand. Hope this at Least helps.