Hilt HKD-S and HKD-SR (spit style) strength vs externally threaded bolt.

[francis]

We are having an ongoing discussion on the Norwegian caving forum about bolt strength (what is and isn't safe). The standard bolt in Norway seems to be externally threaded 10mm bolts. These are used together with the petzl coeur 10mm stainless hangers. These bolts are quite expensive so i am interested in the cheaper hilti HKD style bolts with a flange to stop them going into a slightly too deep hole. These are available both in galvanised and stainless models. The stainless model is about 4-5 times the price of the galvanised ones but are still cheaper (i think) than the externally threaded sort which are also available in both stainless and galvanised versions and different lengths.

My questions are: Are the hilti's strong enough for regular caving and with the posobility of having to be used for rescue purpose? Are non stainless anchors appropriate if greased when set and how long is the expected lifetime of such a bolt compared with a stainless one?

My theory is that as the hilti bolts are cheaper and require a much smaller hole, more bolts will be used for rigging and even tho they are weaker then the safety will actually increase. I have read about CUCC's testing of these bolts in Austria and i am pretty convinced that they are strong enough.

What are your veiws on the matter? What things do you take in to considoration when choosing bolt style?

Externally threaded bolt

Hilti HKD-S(SR) style bolt

This post ended up a bit messy, i hope you get what i'm trying to ask about.

Francis 

 

[nickwilliams]

I would not recommend using any female threaded anchors, stainless or not, as long term anchor placements in caves. This is particularly true of anchors where the ring or other hangar is carried into the cave and placed by individual cavers. Experience with self drilling threaded anchors in the UK is that they wear out in just a few years of use. I very much doubt that the fact that stainelss is used will make any significant difference. The key problem is that standard form machine threads are not suitable for repeated loosening and tightening cycles, particularly in conditions where grit or corrosion are a factor.

I think the argument that more of them will be placed is a specious. Apart from the conservation issue (before the NCA/BCA P-blt programme started dozens more bolts were placed in the UK than was strictly necessary) for the system to be safer if people have more bolts, they have to use them properly. In practice, more often than not, it will be the individual strength of a single anchor which provides protection for the user in any given set of circumstances.

In my opinion, HKD and self drilling anchors are suitable only for expedition style exploratory caving, not for locations which are the subject of repeated visits by different people over a period of years. For the latter application, anchors which do not require a thread to be repeatedly loosened and tightened are greatly preferable.

We had this disussion in the UK 15 years ago, and the result was that self drilling and similar anchrs have all-but died out in regularly visited caves.

Nick.

 

[francis]

So you would recomend an externally threaded bolt? I just found some stainless ones for about £2 each which is an OK price. Another alternative is P38's (longlife) but these are quite expensive and i don't really feel like the idea of leaving behind very expensive bolt's in mines that people probaly visit once every other year, if that.

Francis

 

[Bob Mehew]

My questions are: Are the hilti's strong enough for regular caving and with the posobility of having to be used for rescue purpose?

Are non stainless anchors appropriate if greased when set and how long is the expected lifetime of such a bolt compared with a stainless one?

What are your veiws on the matter? What things do you take in to considoration when choosing bolt style?

At the risk of being obvious, how safe do you want them to be (in terms of maximum impact force and direction)?  I presume you have read the P Bolt thread and followed up the references to the standards mentioned within my response. 

You might like to ask around your caving community to see if you have any rope access workers who have their "own" anchor tester, see http://www.hydrajaws.co.uk/ for what I am referring to.  These testers can work up to 20 kN in the "pull out" mode which is beyond the Mountaineering standard requirement of 15 kN and are sufficiently small and light so can be used underground.  You can then test them yourselves.     

Bob

 

[nickwilliams]

The externally threaded anchor is what is called a 'throughbolt' in the UK. Hilti sell them under the HST or HSA part numbers so I'll use this designation in an attempt to avoid confusion.

Personally, I'd prefer to use HST or HSA anchors rather than HKD's. However, in ether case, if I was expecting them to get used more than once and I wanted to maximise the safety of the system, I would leave the hangar in place once it has first been fitted. It is the repeated fastening and loosening of the nut which is the primary cause of failure of this sort of anchor. I'd also choose long ones rather than short ones.

At least with the HST or HSA anchors there is a reasonable chance of being able to inspect the thread before trusting your life to it.

Nick.

 

[francis]

Thanks a lot for your time and help! I think i'll be getting some throughbolts in the near future

Francis 

 

[Bob Mehew]

Sorry, I omitted my comment on grease and bolt style from my previous posting.

Re grease, it can only be considered to be a temporary measure against corrosion.

Re styles, for me the first question is strength (in pull out, shear and also torque modes).  The second is corrosion (general & stress in particular - see http://www.uiaa.ch/web.test/visual/Safety/SafComdownloads/Bolt%20failures%20on%20sea%20cliffs.pdf ).  Although I have no evidence, I would also be worried if your mine water carried corrosive chemicals leached from the ore.  The third would ease of threading your rope or getting a crab on the anchor.  Last would be the thread as it could wear (both internal or external) or worse get plugged with dirt (internal) {which is why the UK moved to resin anchor systems}.

Bob

 

[MatthiasM]

[...]I have read about CUCC's testing of these bolts in Austria and i am pretty convinced that they are strong enough.

I know these HKD bolts during a week in Austria (Krippenstein with Andy Bigler), and personally I would prefer the HKDs to the SPITs, but I'm afraid I may need some more technical arguments pro these nice tiny HKDs to convince some old guys. Can someone point me to a web link or a contact person for these test made by CUCC or to a specific publication (hopefully on the web available) where I can read more?
Thanks a lot

Matthias

 

[francis]

Happy reading.

Francis

 

[francis]

I posted the wrong link before and now I can't edit. It's a bolt test but I assume the bolts tested are spits as the test dates back to 1983.

This is the right one

Francis

 

[whitelackington]

where did u locate the stainless bolts?

 

[MatthiasM]

whitelackington,

if you mean where I found them for purchase, Dieter Sulzbacher from Wiener/Niederösterreicher Höhlenverein purchased currently for me 200 pcs as they get much better conditions at their Hilti office than I will ever get as private person at my Hilti office (I doubt my club would purchase some at least now with no own experiences - we are still on spits for quick'n'dirty rigging or HST like stuff for important belays).

If you mean where I located them in caves - I attended Andy Biglers Krippenstein week last year and learned how to use this stuff instead of spits; with the Petzl Rockpecker and a Hilti SDS drill they are a perfect spit replacement especially for manual rigging.

francis,

Thanks for the link to the CUCC article. On Krippenstein I found the same fact that in hard limestone I weren't able to set the HKD fully according the instructions, it remains this gap as mentioned in the article. But the pull tests from CUCC seem to show that the bolts do their job.

Matthias

 

[francis]

I got some of these bolts when I was in Sweden over xmas. They are pretty much exactly the same as the ones made by hilti (same breaking strength) but they cost less.

Here are some pics. I took the cone out of one to find out how far the driver has to go in before it's all the way in.

Francis

 

[PhilipSargent]

Update to all this. CUCC in Austria are now using Raumer M8 Hang Fix anchors: M8 HANG FIX inox M8L (ØM8x78)
see

CUCC Expo Rigging Handbook: Drilling holes

expo.survex.com

 

[Ian Ball]

Interesting, thank you.