Bolt techies: Do these bolts need replacing?

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I have been prospecting for new routes in a quarry that contains five existing old sport routes that are totally neglected and dirty. The quarry isn't in any guidebooks or on UKC so the neglect is not surprising. Today I checked out one of the existing routes. It was in need of a big clean up but the key thing I wondered about was whether the through bolts would need replacing. They didn't seem to be stainless steel. They looked like the (galvanised?) steel ones that have a greenish-yellow sheen. The visible parts of the bolts and the hangers all looked clean and uncorroded but all the washers were rusty. The last time I encountered something similar to this (in this case badly corroded hangers on clean bolts), the bolts actually seemed to be in excellent condition when cut. I put it down to the corroded hangers behaving as sacrificial anodes. In the present case I wondered if the corroded washers were doing the same thing and protecting the bolts. My questions are;

1) Are the bolts likely to be OK now as a result of cathodic protection.

2) Would this protection be likely to last as long as would 316 stainless steel bolts so I can leave them as they are or

3) Would it be better to replace them now with 316 stainless?

 ChrisClark1 20 May 2019
In reply to harold walmsley:

Sorry if irrelevant and not bolt-related but is this a Cheshire/Mersey Sandstone addition out of curiosity?

 cambromo 20 May 2019
In reply to harold walmsley:

This sounds like Taylor Park, is it? I asked about this once and was told they were bomber but I'm not sure I've never seen them.

 spenser 20 May 2019
In reply to harold walmsley:

I suspect that Dan Middleton will be able to provide some help on this subject having recently prepared the BMC's bolting guidance (focusing mostly on the technical side of things rather than ethical issues). He posts on here as danm, or you can find his email address on the BMC staff list.

 jimtitt 20 May 2019
In reply to harold walmsley:

Without seeing them, knowing what they are and testing them anyone is just going to be guessing. Washers often corrode first as they generally appear to have less plating than the bolts, won´t be doing anything to protect the bit of the bolt in the hole.

 tonyg9241 20 May 2019
In reply to harold walmsley:

only one way to be sure and that is to pull test them see link  youtube.com/watch?v=_Ggfp-CAQc0& 

 danm 20 May 2019
In reply to harold walmsley:

Galvanised steel bolts are no longer considered acceptable for outdoor use. That said, if the bolts are still sound, no point in replacing them until you need to. Only way to decide that is by either pull testing one and assuming the others are similar, or making a decision based on the visual appearance, a bit of load testing, and some educated guesswork. You can do a quick and dirty test on top rope, clip in to a bolt with a long draw and push outwards with your legs to see if there is any movement etc. The other thing to consider is if the bolts are appropriate for the rock type, as you might want to consider replacing them whatever their condition corrosion wise if they are expansion bolts in soft rock. PM me if you want to chat more about anything specific.

In reply to harold walmsley:

Without having any technical knowledge to offer, I would suggest that if you're worried about them, replace them.

4
 jimtitt 20 May 2019
In reply to harold walmsley:

Remove the nut and make sure the threads are clean and lightly lubricated and replace the nut and hanger + new washer, if you can torque them to 30Nm for a 10mm bolt they should be good to go.

 Steve Clegg 20 May 2019

In reply:

clip into a bolt with a long draw and push outwards with your legs to see if there is any movement ...

A cricket box might help prevent collateral damage!

In reply to ChrisClark1:

No, Clwyd Limestone

In reply to jimtitt:

>Remove the nut and make sure the threads are clean and lightly lubricated and replace the nut and hanger + new washer, if you can torque them to 30Nm for a 10mm bolt they should be good to go.

That sounds like a good suggestion. I'll try that tomorrow.

Post edited at 20:35
In reply to jimtitt:

I followed your suggestion. All the bolts seemed fine although they were 12 mm bolts and I still used 30  Nm. I hope that is still reasonably OK? I gave a couple an extra nip and they still were fine at the higher, but un-measured, torque.

In reply to jimtitt:

The Petzl Coeur bolts should be torqued to 50Nm. At least that's what Petzl say in their instructions iirc.

Admittedly that is in concrete so could be different in different materials

Post edited at 08:04
 danm 24 May 2019
In reply to Wide_Mouth_Frog:

50 Nm for 12mm, 25 Nm for 10mm. One of the reasons you have to be very careful not to over-torque when placing 10mm's if you aren't using a torque spanner, as it's more easily done.

If you can't achieve the stated torque, then the bolt isn't the correct choice for the material you're placing it in, or you've hit a piece of poor rock and the placement isn't up to scratch. When I finally finish writing my manual it'll have all this kind of knowledge in it!

Edit: i'm referring specifically to Petzl bolts above, other manufacturer's specs may vary.

Post edited at 15:02
In reply to Wide_Mouth_Frog:

The data I can see from bolt manufacturers websites (e.g. Fischer but also others) indicates, for maximum performance, a fixing torque of 30 Nm for 10 mm bolts and 50 Nm for 12 mm bolts. I now see that to fully test the 12 mm bolts I should have used 50 Nm but I also saw that, for each bolt diameter, multiple fixing torques are given with different holding powers and, if I interpret this correctly, when torqued to 30 Nm, 12 mm bolts would match the performance of 10 mm bolts. As 10 mm bolts are considered acceptable I therefore think that, although not optimal, the testing I have done should be sufficient to establish that the existing bolts are, for now, acceptably safe. I would welcome comments if I have misunderstood this.

 jimtitt 24 May 2019
In reply to harold walmsley:

The torque figures are a bit confusing (well they aren´t really )

For our 10mm wedge bolts the recommended torque is 30 or 40Nm depending on whether it´s cracked or uncracked concrete as this type of bolt are torque controlled, that is you torque them to the given value which guarantees they will hold the rated pull-out value multiplied by whatever factor is being used, normally 4 x.

The maximum torque values given for stainless bolts are nowhere near the failure point, they are actually where the pressure on an unlubricated bolt will start to gall, for a 10mm bolt the actual failure torque is around 92Nm which one is unlikely to achieve, the better designs actually prevent this by making the small engagement ears on the clip so they shear off first and the whole bolt spins instead.

A lot depends for the extraction force on whether the threads are lubricated (stainless wedge bolts come already treated as a rule with anti-galling compound but of course you might have dropped them in the dirt), approximate values for the clamping force (the pull-out force) are 70 x torque for lubricated and 50 x for unlubricated so your 30Nm gave either 21kN or 15kN.

For 12mm bolts the diameter and the pitch are different so 56x lubricated and 42x dry, for galvanised bolts more or less in the middle of the two values.


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