Merged topic - Spit and BP bolt removal/replacement

[Simon Wilson]

Andrew,
Yes, that's the sort of core drill but I think you will need to get one with a 12mm bore. You will need a water bottle to wet it. Please have ago and let us know how you go on.

I'm hoping my puller will pull out a DMM in a few minutes.

 

[Bob Mehew]

I speak without practical experience but my memory is grinding heads off was considered to be dangerous given you almost certainly were hanging from a single rope which is likely to be located in the work area.  Would I be right in suggesting industrial rope access techniques require a number of anchors so as to organise several ropes to the work location in order to get them out of the way of the grinder?  One could use a hacksaw but that would take a fair amount of effort (and probably spare blades).

Extracting the Eco or BP anchor either requires one weakens the resin by drilling into it so as to enable the anchor to be pulled out with a much lower force or else one removes the head and drill in to remove the whole lot.  BP anchors are know to crack the surrounding surface rock on extraction without prior weakening.  I don't think anyone has tried weakening the resin before pulling them.  Eco usually came out cleanly with (or without) prior weakening the resin.

The only challenge I foresee with a core drill is build up of swarf / rock & resin dust. 

 

[nickwilliams]

A battery angle grinder was tried for removal of some of the Peco anchors, IIRC, but the resin quickly gets heated by the metal work and the resulting fumes in the confined space of a cave were found to be intolerable. Mind you, I don't know if this was using ultra thin discs.

Achieving the kind of pull forces required to simply extract an anchor with anything less beefy than the puller used for the test programme will not be easy. The forces involved are significant: for example I tried a straight pull with a 10t hollow hydraulic cylinder and this bent the eye on the puller and easily sheared the M12 8.8 bar I was using as the pull rod (the biggest that would fit through the hollow cylinder). Obviously stronger materials are available but this rapidly becomes a custom made solution requiring considerable effort and expense.

 

[Simon Wilson]

If cutting the heads off resin anchors or bending them over became acceptable we would end up with bolt rash. We should not install any anchor which can't sustainably be removed.

In the case of Spits, diamond core drills will only drill rock. The dust is removed with water.

 

[Simon Wilson]

Achieving the kind of pull forces required to simply extract an anchor with anything less beefy than the puller used for the test programme will not be easy.

I'll let you know how I go on.

 

[cavermark]

It would be impossible to drill the anchor enough the get it out.

To clarify - I was suggesting that, in the case of Peco anchors, if the "Bolt"head is drilled off, the hanger would be removed. The shaft of the anchor would still be in the rock, but flush with the surface - the same outcome as grinding or hacksawing the head off.  Not ideal but much less noticeable than the resin splodge solution perhaps?

Bob - Rope access for tasks such as grinding would involve 2 ropes (as standard) with "hard links" such as steel strops, between you and your descender and back up device. You would also carefully position yourself and your ropes before starting the work so that any kick back or follow through would not be a problem. The position of the new P-bolts in the CNCC photos look like they could be useful for positioning too.

 

[andrew]

We really should not be discussing this. It is ever cavers moral duty to conserve caves to the best standards, while still enjoying access. Anchors should removed and the placement reused. This should be as an important factor, possibly more important than the strength. After all a 40 year life is very short, we are privileged to be towards the start of caving and have a duty to leave the environment in the best condition possible.

 

[Maj]

Thinking outside the box.
What happens if you heat the anchor up with a blow lamp first. Would this have a detrimental effect on the resin and hence provide the weakening required before pulling.
I'm assuming the thermal conductivity of the anchor would be greater than that of the resin, and so the heat will transmit down the anchor heating the boundary between anchor and resin.
:-\ :-\
If it might work, I appreciate there are other factors to consider, for example:-
Affect on the surrounding rock.
Is there a risk of fumes from the resin?
Perhaps an aluminium plate to protect the surrounding rock and resin from direct heat, might resolve some potential issues.
:-\ :-\

Maj.

 

[Maj]

I didn't spot this second related thread before I posted. So I'll repost it here.

What happens if you heat the anchor up with a blow lamp first? Would this have a detrimental effect on the resin and hence provide the weakening required before pulling?
I'm assuming the thermal conductivity of the anchor would be greater than that of the resin, and so the heat will transmit down the anchor heating the boundary between anchor and resin.
:-\ :-\
If it might work, I appreciate there are other factors to consider, for example:-
Affect on the surrounding rock.
Is there a risk of fumes from the resin?
Perhaps an aluminium plate to protect the surrounding rock and resin from direct heat, might resolve some potential issues.
:-\ :-\

Maj.

 

[Roger W]

You might expand the bolt enough to loosen it when it cools. 

You might get it hot enough to degrade the resin (but watch out for fumes).

You might get the limestone hot enough to convert it to calcium oxide... (825 degrees or so).

Sounds like a suitable case for "try it and see" - preferably somewhere where there's plenty of ventilation and no danger of setting your rope on fire.

 

[Bob Mehew]

Anchors should removed and the placement reused.

We don't start from a clean sheet situation but have a range of different types of anchors which already foul up placements.  So I suggest we do not need to stop all placements of BP anchors whilst we determine if we an extract a BP anchor without fouling the placement location.  Perhaps we can make a stab at seeing if we can remove some resin from a BP anchor and then pull it using the BCA anchor puller.

I am free on Sunday 23rd Nov and currently have the BCA anchor puller.  If someone wishes to place an anchor in a convenient flatish surface location (concrete will do) I am prepared to drive where ever to pull it (I am in South Wales Saturday 22nd evening).  I don't have a battery drill to hand so someone will have to do the resin removal bit for me. 

The puller is booked for weekends of 29 & 30 Nov and also 6 & 7 Dec for use in South Wales.  I am a bit reluctant to offer to do it within that work as the existing plan is to pull 64 anchors which is challenging enoug!  The puller is then scheduled to go onto North Wales.

If we can get this underway, then people may wish to suspend placement of BP anchors, as few weeks delay is surely neither here nor there? 

Or can someone work on it with another puller?

What happens if you heat the anchor up with a blow lamp first? Would this have a detrimental effect on the resin and hence provide the weakening required before pulling?

Interesting thought.  As Roger says, trying it is probably the only answer.  Given the expected low heat conduction of resin, I don't expect the rock to get warm.  But heating the metal anchor would only damage the metal / resin bond.  For BP anchors the challenge is to extract the anchor without spalling the surface of the rock.  I am not sure if destroying the metal / resin bond will help that as one then has to remove the few centimeters of resin between the surface and the start of the BP anchor twist.  Another point to consider is the possible build up of CO2 if one is doing several anchors.  Being techi, I would want to place a thermocouple at the base of the anchor but that need not be done for the first suck and see.

 

[andrew]

If you are in Wales, Mendip is not that far, and it is jrat evening on Saturday. I have al, the kit, just need to find a flat piece of rock, big enough, but we should be able to do that.

 

[SamT]

What happens if you heat the anchor up with a blow lamp first? Would this have a detrimental effect on the resin and hence provide the

http://www.bolt-products.com/SustainableBolting.htm

see the section on "melting out"

I think fumes would be a real problem.

I did wonder if you could warm the metal up using electricity -  Some sort of welder type setup.  I was thinking surface though. Not underground 

 

[SamT]

Can I just say that before anyone gets too hung up (sic) on the subject of the removal, that if placed well in good rock, the BP bolts should NEVER need replacing (well - in theory)

The old DMMs on garlands in giants are probably the most frequently used bolts in the country and after ~20 years, are showing no signs of wear.

The only time we've had to drill out and replace bolts are where numbskulls have been lowering cavers down pitches directly off bolts causing them to wear thin.

I grant you the fact that having a bolt that is relatively easy to remove and replace is preferable.

 

[martinm]

I grant you the fact that having a bolt that is relatively easy to remove and replace is preferable.

I agree wholeheartedly Sam.  That's why I've been using Excalibur Screwbolts for years in the Manifold. There are a couple in Darfar Pot that are under water for much of the  year which I need to replace next year because of corrosion, but I can just unscrew them and screw new ones in using the same hole.

See:- http://www.excaliburscrewbolts.com/

Also, Excalibur are producing new Screwbolts now with corrosion protection that is apparently comparable to stainless steel... Will be trying them next year for the replacements I think.

Not covered by the BCA insurance scheme of course, but got fed up of waiting for DCA installers to install p-bolts. They get light usage too, of course...

I should also add that those eyebolts which will need replacing have been in there for 8 years and are still sort of OK, but I want to make sure they are safe. not that many people go down there. I may replace them with m12s as well instead of the current m10s, again just cos they'll last longer. The one above river level have hardly corroded at all and are all fine...

 

[Simon Wilson]

... got fed up of waiting for DCA installers to install p-bolts.

The full extent to which people got fed up of waiting and decided to install anchors outside the BCA anchor scheme is yet to come out.

 

[cavermark]

I agree wholeheartedly Sam.  That's why I've been using Excalibur Screwbolts for years in the Manifold. There are a couple in Darfar Pot that are under water for much of the  year which I need to replace next year because of corrosion, but I can just unscrew them and screw new ones in using the same hole.

See:- http://www.excaliburscrewbolts.com/

Also, Excalibur are producing new Screwbolts now with corrosion protection that is apparently comparable to stainless steel... Will be trying them next year for the replacements I think.

Could be something to consider - I bet some git would just pinch them if using them as "fixed anchors" in popular caves though...

 

[Pete K]

... got fed up of waiting for DCA installers to install p-bolts.

The full extent to which people got fed up of waiting and decided to install anchors outside the BCA anchor scheme is yet to come out.

I suspect that the various regional councils can only operate as fast as the volunteers who install the bolts do. Most of whom have jobs and lives to fit dragging drills and batteries into the deepest parts of the uk around. I don't think it is a failing of the BCA, more volunteers are required surely?
The volunteers who bolt for the DCA seem to get thinks done quickly.

 

[Grizzlybear]

Maybe before erasing all traces of previous exploration methods, including the repair of rock grooved by lifeline and wire tether. We could  reflect on Gibbons his account of Rome should be enough for most people ,however we still enjoy finding and preserving  Roman artifacts. To move on. I am sure most modern anchorage placers will consider the placement position of old spits ect. would be totally unsuitable for modern rope techniques These may often have been placed in a position for short term gratification rather than any long term considerations

 

[martinm]

... got fed up of waiting for DCA installers to install p-bolts.

The full extent to which people got fed up of waiting and decided to install anchors outside the BCA anchor scheme is yet to come out.

True, but in my case the current anchors can be removed in minutes, the existing hole reamed out to the required size and a resin bolt installed in it's place. They have been placed in sound rock in good positions. Under the river bed level however it would be interesting to see how quickly they corrode as they would be submerged in acidic water for many months of the year. Down there I'd rather have anchors I could replace easily in minutes rather than having to go through all the faff that has been discussed in this thread. (Drilling out bolts and resin, etc.) Different situation to most caves in the country. about 25ft. below highest flood level.