SS Power-bolt Loosening in Corbin Sandstone

We have had some problems with the 1/2" x 4 3/4" SS power-bolt loosening in the Red.   I have spoken with a couple of engineers at Powers about it and they have recommended torquing up to 34 lbs-ft.  Also, recommended re-torquing after 24 hrs due to the bolt "relaxing" and reducing tension by up to 50%.  

I have recall that a group in Colorado went to a 13 mm bit to reduce spinners, but not sure if that would help with loosening at all.   I have heard it recommended put on graphite to act as lubricant to reduce thread friction.  I am also considering putting on Vibra-Tite VC3 Anti-Vibration Thread Locker.  

Any expert suggestions?  I am looking at doing our annual spring purchase and would sure like to get away from this problem.  Some developers have chosen to go back to plated on steep for this reason (glue ins on less steep).  

TIA

Ian

Has your experience been that wave bolts aren’t workable for steep routes? I haven’t placed any, just curious because I know they advertise them as staying in with the interference fit before the glue has hardened.

Maximilian Tagher wrote: Has your experience been that wave bolts aren’t workable for steep routes? I haven’t placed any, just curious because I know they advertise them as staying in with the interference fit before the glue has hardened.

Everything is workable, even in steep sandstone.  However, it requires more time and effort, and possible equipment.   Placing temporary intermediate bolts or RB's helps.  However, to be honest, many developers aren't willing to take the time.   Plus if you get the bolt placement wrong, it is a harder fix.   We buy 100's of waves and subsidize them substantially to encourage developers to use them. 

I think you are on the right track with higher torque and thread lock....But, the thread lock only adds a bit versus the forces in a fall if there is twisting action.

Power Bolt = Sleeve, correct?

Have you tried wedge anchors? Dual wedge?

Plated is only getting you somewhere in that it is rusting in the hole to bind it....but you know about the rest of the can of worms they are...

Harumpfster Boondoggle wrote: I think you are on the right track with higher torque and thread lock....But, the thread lock only adds a bit versus the forces in a fall if there is twisting action.

Power Bolt = Sleeve, correct?

Have you tried wedge anchors?

Plated is only getting you somewhere in that it is rusting in the hole to bind it....but you know about the rest of the can of worms they are...

Yes, it's a sleeve anchor. 

Wedge anchors can't be used in corbin sandstone.  It's too soft.

Plated power bolts are spec'd to to torque to 45 lbs, plus they don't exhibit the same relaxation properties and seem to bind better.  It's not just rust that keep them from loosening, although that helps with time.

climb2core wrote:

Yes, it's a sleeve anchor. 

Wedge anchors can't be used in corbin sandstone.  It's too soft.

Plated power bolts are spec'd to to torque to 45 lbs, plus they don't exhibit the same relaxation properties and seem to bind better.  It's not just rust that keep them from loosening, although the helps with time.

Gotcha.

Check in with Jim Titt (Bolt Products supplier. He posts here regularly). He seems to be of the opinion that wedge are fine in softer rock, iirc. You might also try dual wedge.

Also, the roundness of the hole is a factor, you may try the "4" cutting edge bits to get more round holes.

Were the hole's prepped well? The most common cause I've seen for looseness is that the rock isn't very flush with the hanger which makes it harder to correctly tighten down as well as providing a constant push outward on the hanger. I will often take the hammer to the rock to flatten it out as much as is practical to avoid this. 

eli poss wrote: Were the hole's prepped well? The most common cause I've seen for looseness is that the rock isn't very flush with the hanger which makes it harder to correctly tighten down as well as providing a constant push outward on the hanger. I will often take the hammer to the rock to flatten it out as much as is practical to avoid this. 

Yes, it has happened to multiple developers with decades of experience bolting in sandstone.   Holes well prepped.  Brush, blow x 2.  I do agree though that the soft sandstone can be crushed somewhat behind the hanger.  I too often will take a hammer to it prior to placing the bolt to get rid of small irregularities. 

Thx

So you're talking about spinning hangers, or spinning bolts?

First thing: use long glue-ins instead.

The re-torquing after 24 hours is a good first step, probably even better would be to "notch" the rock surface so that the hanger can't easily rotate. No matter how well placed the bolt is, if the rock breaks out from behind the hanger then you can get a spinning hanger.

Never heard of 13mm bits, are they even available in Europe?

Are the holes drilled extra deep? In soft sandstone you can scrape quite a bit of rock off the sides of the hole as you pound the 4.75" length bolts in, enough to fill up some of the back of the hole. If the bolt is not drilled deep enough, then the bolt could snug up tight, but not quite as tightly against the rock surface as you think...still that's talking a millimeter or so at the most difference.

I had problems with 1/2 inch powers 5 piece bolts in very soft sandstone.  I could feel the sandstone giving while torquing the bolt.  I switch to glue-ins.  Crap bolts are no good for anyone even if it is quicker and easier.

In another soft sandstone I replaced several 5 piece and wedge bolts that were coming out with glue ins.