Frequency of bolt/hanger failures

I'm curious how many people have experienced a bolt and/or hanger failure while climbing? Is this something that happens with any appreciable frequency? My gut feeling is no.

If you have witnessed a bolt and/or hanger failure personally, did you expect it? I mean to say, did you climb up to that manky-looking 1/4" with SMC hanger and think, "yeah, that looks sketchy but I'll clip it anyway." only to fall and have it fail on you?

Also, if you have experienced a bolt and/or hanger failure, what type of hardware was it (3/8" wedge bolt, 3/8" sleeve bolt, etc) and what kind of rock was it in?

Thanks.

From a force perspective...Here ya go.

youtube.com/user/pulltesting

Be suspect of anything BUT titanium glue-ins at seaside crags.

At Index last summer two bolts failed (in a row!) due to different metals being used in the hanger. Different metals placed together causes corrosion. I think that was the analysis...

Bolt failure is exceedingly rare, but it does happen. There's a lot of time bombs out there!

Edit: gotta scroll down for the bolt failure videos.

i was rope soloing a slab route in the south platte, winter of 03/04 i think, and clipped a buttonhead that promptly broke. i have the leeper hanger somewhere at home. the bolt broke off about 1/8 of an inch below the rock surface. judging by the rust pattern, it was probably cracked about 90% of the way through. that was a moment i won't forget.

Ian G. wrote:At Index last summer two bolts failed (in a row!) due to different metals being used in the hanger. Different metals placed together causes corrosion. I think that was the analysis...

Hadn't heard that. Was an aluminum hanger that'd been out in the wet for 20 years. Probably standard corrosion.

You have a reference? Please let me know.

-Brian in SLC

Brian in SLC wrote: You have a reference?

Kong-Bonatti plated carbon steel hangers, rc.com discussion and pictures here.

Cascade climbers discussion here.

There was speculation from Phil Box on rc.com that corrosion might have been caused by galvanic corrosion if bolts were stainless (which wasn't determined, as far as I know). There isn't a lot of information on stainless steel/carbon steel galvanic coupling available on the web, but this paper indicates it isn't a problem for concrete reinforcement. However, galvanic potential tables for metals in seawater indicate that zinc (i.e., plating) will corrode preferentially to stainless steel. Of course, with fresh water, who knows?

Perin Blanchard wrote:Kong-Bonatti plated carbon steel hangers, rc.com discussion and pictures

I still think they're aluminum.

So did a guy who looked at them and may have tested them with a magnet.

From the CC thread:

"I have had ther opportunity to view the failed hanger in question, and strongly believe it is aluminum alloy with an anodized clear coat. The product appears to be non-magnetic, very lightweight compared to steel or ss, and has exfoliating corrosion between layers that looks similar to some old Eiger biners that were part of an ancient belay rig on the diamond some years ago. Aluminum is very sacrificial to the steel bolt in the presence of water. I'll return the hanger to D this week."

Really looks like exfoliation corrosion and/or just standard aluminum corrosion.

Almost no iron oxide in the pictures. If they were carbon steel, there would be reddish rust all over them.

Cheers.

rickd wrote:quite strong in fact.

It is wrong to generalize from the test of a single example to the entire population.

A single test tells us the strength of that particular example. That's all.

The only meaningful number is the standard deviation of a representative sample.

You'd have to test, say, 500 hangers, then look at the bell curve of the results. If 97% of them failed at 4500 pounds (or 2500 or whatever), then you can say they're strong enough.

Similarly, anecdotes of failures in the field can also be misleading.

I had a bolt fail on Head Full of Lead in Rifle 10 or so years ago. The bolt pulled completely out of the rock when the second was pulling back in to clip for top roping. I'm pretty sure whoever placed it didn't know what they were doing, or they forgot to actually put the wrench to the bolt. As I recall it was a wedge bolt. In many types of limestone one can encounter subsurface pockets or pockets of entrained salt or dust that can affect the quality of bolt placements. I was glad not to have fallen on lead..........

Larry wrote: You'd have to test, say, 500 hangers, then look at the bell curve of the results. If 97% of them failed at 4500 pounds (or 2500 or whatever), then you can say they're strong enough. Similarly, anecdotes of failures in the field can also be misleading.

I've pulled close to that many Leepers and never had one break on me. I would say that here in Colorado they are very bomber hangers. Of course they usually have a crappy bolt that can be pulled with a few tugs of a funkness device.

Old SMC hangers (the gold ones) and any aluminum hanger should be very suspect. I have broken several with a single funk.

I broke off a 1/4 inch rawl split shank bolt when I wiggled it with my bare hand last week on a sunny/dry West-facing vertical granite climb done around 1980. The rock is small crystaled and solid. There were no water streaks near this placement. This is the same hardware and time placed in rock as the bolts in Tres Piedras, NM. These all have the "old style thin SMC hangers with the stamp horizontal. The bolt sheared just below the threads and was very rusted and corroded. The nut and threads fell to the ground. I pulled the next bolt up with one yank on a hammer, came out like a nail in rotten wood. This rock was larger crystals but still good quality. I placed a bolt back in the same spot after re-drilling the hole to 3/8s. These were the only protection for about 50 ft.
I assume the bolts were both the same. The one I pulled intact is a split shaft 1-1/2 inches long and feels and looks OK.

We had 2 dynabolt gold 3/8 sleeve bolts fail during placement and we went back and replaced any we had used. The heads sheared while tightening, prior to any cranking down occured.

I have not seen a 3/8 or 1/2 bolt (Rawl, Powers, Red Head, Fixe or Hilti) fail. Nor have I seen a hanger fail.
safeclimbing.org/education/…

The usual suspects

Thanks for the replies, guys.