How Bad is it to Tie Directly Into Plate Hangers?
- Thread starter Hammy
- Start date
Simon Wilson
New member
Hammy said:
It is very bad and research has been done.
Research has shown that the radius over which a rope passes has an effect on the strength of the rope. http://personal.strath.ac.uk/andrew.mclaren/David%20Smith%20Technical%20Paper%202013.pdf
It is very bad to tie directly into plate hangers because it is against the manufacturers advice and you would therefore not be acting responsibly and would probably invalidate any insurance.
Manufacturers advice - scroll down and click on PDF Technical Notice: http://www.petzl.com/en/Professional/Anchors/COEUR?l=US#.VgjPr5cgmKJ
Simon Wilson
New member
topcat said:
In the thread title Hammy used the term 'plate hangers' and I assumed he meant bolt hangers of the type made out metal plate such as the one in the link or this one - http://www.petzl.com/en/Sport/Anchors/VRILLEE?l=INT#.Vglb5JcgmKI
You really would need to read the link and look at the diagrams on the Technical Notice.
I think 'plate hanger' is not a bad term for that family of bolt hangers and I don't think I have misunderstood what Hammy meant.
Here is a single point of data, fresh from the shed!
-8mm Mammut cord
-6 years old
-Tied with a figure 8 on a bight
-into an Edelrid Draco plate hanger at one end
-and directly into the Rock Exotica Enforcer
with a bowline...
The Draco hanger has nicely finished edges, and a plate thickness of 3mm.
Broke at the loaded point of entry into the bowline at max force of 11.0kN, with very minimal damage (basically negligible, ie can't see any core fibers) to the sheath of the rope at the point it was bearing on the hanger. Tactile inspection at the point of loading does not reveal any anomalies.
Pretty good I would say. In fact better than I expected, as I predicted the age of the rope and the bowline would lead to a failure below 10kN at the knot.
This is consistent with _Alpine_Caving_Techniques_, where they state that "it always breaks where it leaves the knot and never in the loop." Pg 211
-8mm Mammut cord
-6 years old
-Tied with a figure 8 on a bight
-into an Edelrid Draco plate hanger at one end
-and directly into the Rock Exotica Enforcer
with a bowline...
The Draco hanger has nicely finished edges, and a plate thickness of 3mm.
Broke at the loaded point of entry into the bowline at max force of 11.0kN, with very minimal damage (basically negligible, ie can't see any core fibers) to the sheath of the rope at the point it was bearing on the hanger. Tactile inspection at the point of loading does not reveal any anomalies.
Pretty good I would say. In fact better than I expected, as I predicted the age of the rope and the bowline would lead to a failure below 10kN at the knot.
This is consistent with _Alpine_Caving_Techniques_, where they state that "it always breaks where it leaves the knot and never in the loop." Pg 211
Pete K
Well-known member
Snoboy, I'm a recent acquirer of an Enforcer and looking for ideas of how to incorporate it into a pull test rig for this kind of investigation. I'd appreciate any tips or suggestions, especially if you have made something up yourself for it. PM might be better so I don't derail the thread.
I would tend to agree with snoboy, but also unfortunately accept that Simon's insurance point is probably all too valid as well.
The chances of the rope failing at the hanger rather than the knot must be pretty small ... so small in fact, I'm happy to tie in directly if I "need" to.
But equally, if I needed to be worried about insurance paying out, I guess I'd be helping the insurance company say no.
The chances of the rope failing at the hanger rather than the knot must be pretty small ... so small in fact, I'm happy to tie in directly if I "need" to.
But equally, if I needed to be worried about insurance paying out, I guess I'd be helping the insurance company say no.
nickwilliams
Well-known member
With regards to insurance, please refer to reply No. 28 in the thread linked here:
http://ukcaving.com/board/index.php?topic=17706.25
It isn't a factor in this thread. Please base the discussion on technical matters.
Nick Williams
BCA PL Scheme Manager.
http://ukcaving.com/board/index.php?topic=17706.25
It isn't a factor in this thread. Please base the discussion on technical matters.
Nick Williams
BCA PL Scheme Manager.
Bob Mehew
Well-known member
We have not tried dynamically testing knots over hangers, we usually use a round bar of at least 12mm diameter. But as I understand it, the reason for the rope usually breaking within the knot is because the bend causes stress across the rope, see http://iopscience.iop.org/article/10.1088/1367-2630/3/1/310/pdf (especially the videos of spaghetti breaking). I would therefore expect a rope to break bent over a thin plate than in the knot as Simon's reference found. But how thin does the plate have to be? I note Simon's reference used 0.5, 10. & 1.5mm thick plates. (Nor an I find any detail on how sharp the corners were.) EN 892 for Dynamic rope requires an 'edge' with a 5mm radius for the rope to run over (plus detail on surface roughness limits) as part of the drop test with the rope bent through an angle of 330 degrees (so the rope goes up to the edge and then come down vertically similar to a classic climber and life liner situation). I am uncertain how thick hangers are but I would guess around 3 or 4 mm.
In passing, I note Petzl Couer hanger specifically rules out directly tying a rope into the hanger, see
http://www.petzl.com/sfc/servlet.shepherd/version/download/068w0000001O2hLAAS . So I suspect you don't have a leg to stand on if you did.
In passing, I note Petzl Couer hanger specifically rules out directly tying a rope into the hanger, see
http://www.petzl.com/sfc/servlet.shepherd/version/download/068w0000001O2hLAAS . So I suspect you don't have a leg to stand on if you did.
Mark Wright
Active member
Petzl don't actually recommend against attaching ropes directly to the Couer hanger plate, they recommend against lowering directly through one but instead to use a carabiner. I think the main problem is the rough edges they have which is why it is not recommended to rig anything other than deviations in this manner. I did however only recently rig the final drop into East Chamber in Oxlow by poking a loop of rope through the 'P' bolt and tying an overhand stopper knot. I did check the hanger to make sure it was 100% smooth before I tied it though. I'd run out of Maillons.Bob Mehew said:
One of the acceptable loadings for the Clown hanger (upside down) has the rope passing over just one rough (non-radiused) edge as opposed to two rough edges for all the other types of hanger. Maybe Petzl considered this to be more acceptable. The Clown hanger hasn't been in the Petzl sport catalogue for some time. I've had one for years but never actually used it. My worry is how close the rope is to the rock where it passes over the bolt and plastic spacer. Much better to have the rope hanging further away from the rock by using a Maillon or carabiner.
Having ropes tied directly to the ring hangers at the top of every pitch will cause some problems if others need to use the same hangers, the cave rescue for instance. If someone was incapacitated on a rope, the loaded rope loops are unlikely to move along the hanger when additional carabiners are attached causing potential damage from trapping and deforming the rope.
Its generally accepted that 7mm is the smallest diameter a rope should pass over which is why most Maillons people have in their store are 7mm and why the old harness attachment rings, particularly on industrial harnesses were 7mm. The smallest Maillon rated as PPE is also 7mm. Most harness manufacturers have since moved over to much lighter alloys which have much larger round and smooth edges.
Some of my Petzl twist and spoon type hangers do show signs of slight damage (burring) due to 7mm Maillons being attached to them and a lot of people using the ropes. If using the hangers with Maillons or carabiners there is absolutely no danger of failure however tying a rope directly to them I wouldn't be too happy with. Having done a fair amount of rope and anchor testing I would expect the rope to fail at the anchor on many of my hangers and probably many of the ones in your own stores. This burring, also probably visible on the bottom attachment hole of your Croll or similar chest and upper ascenders, can be kept at bay with a plumbers de-burring tool.
There is certainly an argument for taking an item of equipment that has the potential to fail, e.g. a carabiner or Maillon, out of the anchor system if possible but I think for general rigging, attaching ropes directly to hangers that are not really designed for such use is not recommended. I think in this case it has the potential to cause more serious problems.
As most of our caves are 'P' bolted the situation is only really going to arise at the start of each new rope.
Back in the 80's I experimented with Dave Elliot's method of feeding all the required ring hangers for each length of rope onto the end of the rope and tying each knot directly over the hanger before attaching to the next red ringed bolt and nipping it up with a spanner. I quite liked the method but its not really possible to do it in these 'P' bolt times. Ring hangers, being round and made of steel are less likely to become damaged by Maillons or carabiners and therefore less likely to subsequently damage the rope. They are very expensive though and probably weigh the same as an alloy hanger and 7mm long Maillon so the technique doesn't offer any real benefits with regard to weight saving.
Mark
Simon Wilson
New member
In Petzl's Technical Notices it says:Mark Wright said:
Only some types of misuse and
forbidden uses currently known are represented
(shown in the crossed out diagrams). Many
other types of misuse exist, and it is impossible
to enumerate, or even imagine all of them.
Only the techniques shown in the diagrams
and not crossed out are authorised. All
other uses are excluded : danger of death.
There is no diagram of a rope passing through a plate hanger which is not crossed out - end of.
When a Clown is loaded correctly as shown in the diagram in the Petzl Technical Notice the edges over which the rope passes are radiused.Mark Wright said:
Mark Wright
Active member
You are correct Simon, there are no diagrams of ropes passing through a hanger plate that aren't crossed out. I was never suggesting it was acceptable, merely stating the text beside the crossed out diagram stating that lowering should be done through a carabiner. Lowering a load through a Petzl Couer hanger plate could cause the bolt to vibrate itself out of the hole.
With regard to the Clown, the two radiused edges either side of the bolt are only slightly radiused for when the hanger is loaded in its 'normal' configuration. When its placed upside down however the rope does pass over a slight edge and if the load were to swing then this could cause problems depending on the condition of the edge.
As I said, I've never actually used the one I have because of my concern of the rope being too close to the rock. I also have a Troll Bollard which I never use for the same reason.
Best to always use some type of connector when attaching ropes to fixed hangers.
Mark
With regard to the Clown, the two radiused edges either side of the bolt are only slightly radiused for when the hanger is loaded in its 'normal' configuration. When its placed upside down however the rope does pass over a slight edge and if the load were to swing then this could cause problems depending on the condition of the edge.
As I said, I've never actually used the one I have because of my concern of the rope being too close to the rock. I also have a Troll Bollard which I never use for the same reason.
Best to always use some type of connector when attaching ropes to fixed hangers.
Mark
Simon Wilson
New member
I've just measured the radius at either side of the bolt on a Clown and it's 5mm.
By 'normal' I assume you mean radial and by upside down I assume you mean axial. I think there is no 'normal'. In practice anchors rarely get loaded at 90 or 0 degrees to the axis but instead very often get loaded at angles around 85 or around 45 with a mean I guess to be around 60-70. It is in these angles of load that Clowns and Bollards are a good choice of hanger and apply the load to the bolt efficiently.
When I am forced to use spits or drop-ins I carry the full range of hangers including Bollards which I like for their very good weight and bulk saving. I have couple of Clowns but I'm not keen on them because they get damaged by bending and because the bolt isn't easily replaceable. Like all hangers you have to be careful how you use them and choose the most appropriate design of hanger for each particular situation. Bollards are really good hangers but don't load them at less than about 45 degrees.
Back on topic. The answer to Hammy's question is officially most emphatically do not put rope directly through a plate hanger under any circumstances whatsoever. If you do and I hear about it you might have to face my wrath and facing my wrath is something you would not want to do. Have I made that quite clear young Hammy my lad? :spank:
----- However-----, what you choose to do in the privacy of your own cave is up to you. Don't tell anybody but I might have been known to tie things into plate hangers occasionally when nobody was looking.
By 'normal' I assume you mean radial and by upside down I assume you mean axial. I think there is no 'normal'. In practice anchors rarely get loaded at 90 or 0 degrees to the axis but instead very often get loaded at angles around 85 or around 45 with a mean I guess to be around 60-70. It is in these angles of load that Clowns and Bollards are a good choice of hanger and apply the load to the bolt efficiently.
When I am forced to use spits or drop-ins I carry the full range of hangers including Bollards which I like for their very good weight and bulk saving. I have couple of Clowns but I'm not keen on them because they get damaged by bending and because the bolt isn't easily replaceable. Like all hangers you have to be careful how you use them and choose the most appropriate design of hanger for each particular situation. Bollards are really good hangers but don't load them at less than about 45 degrees.
Back on topic. The answer to Hammy's question is officially most emphatically do not put rope directly through a plate hanger under any circumstances whatsoever. If you do and I hear about it you might have to face my wrath and facing my wrath is something you would not want to do. Have I made that quite clear young Hammy my lad? :spank:
----- However-----, what you choose to do in the privacy of your own cave is up to you. Don't tell anybody but I might have been known to tie things into plate hangers occasionally when nobody was looking.
