General Updates

Results from testing some of the fixed ropes in Rhiwbach

nwmines

A few months ago I sent the rope we’ve been using to manage the short traverse to the start of the tyrolean in Rhiwbach to the BCA for testing. The rope had been in place for a little over 2 years. As well as the used rope I also retained a unused length of the rope so we could compare the used and unused rope.

Here’s the results…

Hi

 You sent me three ropes.  I have put the BCA hand line experiment rope to one side awaiting other ropes from that experiment to test.  I took your other two samples and have just tested them.  I took the unused length and cut it into two samples labelled AB and BC.  I took the used sample  and cut it into 3 samples labelled DE, EF and FG, see photos.  So end G was by the broken sheath in the used rope.

 

Sample Drops Survived
AB 15
BC 12
DE 11
EF 10
FG 15

 

All samples broke on the following drop.  FG was subject to a delay during testing (my winch line almost broke and needed replacing) which might go towards explaining its higher number of drops survived.  But I do not think the results justifying claiming there is a difference between the ropes.

I define ‘broke’ as the rope not arresting the test mass’s movement.  I use this definition because the ropes did show a peculiarity in behaviour which I have seen a few times in large diameter rope.

For sample AB, I noticed damage in the sheath as it came out of the knot after drop 12.  In drop 14, the sheath parted exposing the core.  (I did not think to count the number of intact cords.)  After drop 15 I counted 10 intact cords (out of 16).  It broke on drop 16.

 For sample BC I noticed damage in the sheath as it came out of both knots after drop 9.  In drop 12, the sheath parted exposing the core and I counted 12 intact cords (out of 16) after the drop.  It broke on drop 13.

 For sample DE the sheath broke on drop 10 and I counted all 16 cords intact after the drop.  After drop 11, I counted 14 cords intact.  It broke on drop 12.

 For sample EF I noticed damage to the sheath after drop 8.  The sheath broke during drop 10 and after the drop I counted 13 cords intact.  It broke on drop 11.

 For sample FG, I noticed damage to the sheath as it came out of both knots after drop 12.  More damage to the sheath was observed at the bottom knot following drop 14.  During drop 15 the sheath broke and after the drop I counted 9 cords intact.  All bar 2 cords broke in drop 16.  Although these two cords remain connected to both sides of the sample, the length is such that I think they must be broken somewhere within the intact sheath. 

 I have to admit I do not usually look for damage at the point where the sheath on the active rope exits the knot so I can’t say if the above observations were timely or comprehensive.  But I do recall seeing this before on 11mm ropes.  Perhaps I should do it as a routine.  From memory, separate sheath breakage is unusual for smaller diameter ropes.  Usually and certainly for thinner ropes, the sheath and cords break simultaneously.  I hesitate to suggest but possibly one might examine the knots on installed ropes to check for such damage before use as a possible indicator of prior abuse.  I think I would have to do a wide range of tests to build up confidence to say that such damage always occurs well before break.  And I also think it is only a feature of large diameter rope which is in good condition.  As it happened I also tested two samples of supposedly 12mm rope in the past few days which broke as normal (having survived 3 and 6 drops) with no sheath breakage.

 I did not bother to take photos of the damage; instead I thought I would send the rope back to you.  It is currently drying and with a bit of luck I will post it on Monday.

 I should add the tests was conducted using a wet 0.8m overall length sample and used a Fall Factor 1.0 drop each time.  

 BS EN 1891:1998 requires that a Type A SRT rope can survive at least 5 drops using a 2m long sample.  However this test is done on a specially conditioned dry rope.  As wetting the rope will reduce the number of drops survived by around a factor of two, I conduct tests using a rope which has been immersed in water for at least two hours.  But the reduced length of the samples I use to test do not impart the same impact on the rope.  Some work suggests this over estimates the drop survivability of the rope.  

 BCA is not able to offer advice on the implications of these results, but if you want clarification do ask.

 Regards

 Bob

GT rope a

GT rope b

Inspection week, 7-10th April

nwmines

The mines are getting inspected next week so if there’s anything significant you’ve noticed please get in touch (we’re aware of the rockfall in Wrysgan). 

The programme for the week is as follows: 

  • Monday: Rhiwbach & Bwlch y Plwm
  • Tuesday: Cwmorthin & Wrysgan
  • Wednesday: Cwm Bychan & Gaewern
  • Thursday: Henddol & Penrhyngwyn

If you’d like to accompany Les on any of the inspection please do get in touch. 

Gethin

Mine Inspection Updates (Nov 2013)

nwmines

Following last weeks inspection Les has prepared his reports which I’ve now added to each users Google Docs folder. Rhiwbach still requires monitoring however the boating chamber has been cleared for use.

The report also includes inspection of the adits/trials at Geironydd.

Possible movement within the boating chamber, Rhiwbach

nwmines

Hi All,

I’ve just heard that there may have been some movement within the boating chamber of Rhiwbach, the painted cracks still remain however there may have been some movement on the side wall, and some new cracks in the brow itself. I’ve not seen it myself.

I’d suggest it prudent to avoid the rafting pool until further notice.

Possible rockfall (small) in Rhiwbach

nwmines

During a trip in Rhiwbach yesterday we noticed some small fresh rockfall just on the pool and hand-line side of where some scaling down was completed during the 2006 inspection (noted on the inspection mine plan), floor 1.

Although not significant is size there does appear to be some loose rock at head height in that section of the mine, I’d suggest we continue to monitor that area and ensure our groups move swiftly through without pulling on bits of the roof!

Gethin

 

Should we remove the fixed aids (metal rungs) in the airshaft, Rhiwbach?

nwmines
Poll removed
Dear fellow users of Rhiwbach Slate Quarry
I am writing to hopefully gather your vote on the current use of the airshaft exit from the mine at the top of the hill (the alternative exit to the more commonly used daylight chamber).
You might be aware that the airshaft has not been part of the blue route in the mine until fairly recently. We (Go Below) asked to bring into use as it looked like a more fun and challenging way to finish a trip.
Given that the shaft as it was fell beyond the abilities of most participants to climb, we put a line of holds all the way up. These were small blocks of slate bolted to the face (like those used further down the mine). We also installed a gate at the top, and have more recently placed some meshing over all the loose rubble at the top (following a near miss with a rock sliding down the shaft).
The slate-block holds were particularly nice as they were easy to use and blended in nicely. However, over last winter, many of them fractured and became dangerous due to the water running behind them, and freezing overnight. The blocks were breaking in peoples hands, or when stood on, and falling down the shaft. This was obviously a serious hazard for any others who might be below. (the slate blocks further within the mine obviously do not have this problem, as there is no water and it does not freeze).
We opted, as a bit of a rush decision, to swap the blocks for metal holds, very much like the ones used in the Alps for Via Feratta. They don’t look as nice, and have taken a bit of the challenge away, but they are unaffected by freeze-thaw and therefore much safer. The other disadvantage to these holds is that should you want to abseil down the shaft, rather than climb up it, they are awkward to step over.
The change in the type of hold has received mixed feedback, some positive, some negative. I am therefore putting it out to vote so all users of Rhiwbach can vote whether they should stay or go. Reverting back to the slate blocks isn’t a viable option given the hazard.
Option One: Keep the steel steps, nothing changes. Go Below will continue to maintain them.
Option Two: Remove the steel steps, and leave the airshaft bare.
If you use the airshaft, and wish to cast a vote, please email me [edit] or vote here [edit] and I will tally it up. If the vote is to remove the steel steps, we will do so when we get a couple of free days and will post notice when the work is complete.
I’ll give it a week or so for votes to come in.
With many thanks indeed
Miles Moulding