Rope Thickness for In-Situ Rope

[Mr Mike]

We are goign to be installing a 25m in-situ rope down a mine. Do people have any thoughts on rope thickness to use? Is 10mm fine or do you do a bit of belt and braces and use something thicker? We have left in place 10mm before, but now wondering.

 

[cavemanmike]

10 or10.5 should be fine.just make sure it is inspected every time it’s used

 

[pwhole]

I guess it depends if it's likely to get dirty or very wet - some of the in-situ ropes we've left in have become very grubby from exiting after digging, and without regular cleaning the mud gets forced into the sheath weave, making it more difficult to get toothed cams to engage. Similarly on descent it makes the ropes much stiffer and harder to fit into a descender. So a thick rope could become a bit stressful after a few months of use. If it's likely to stay clean, it may not be so much of an issue, but I hate thick rope personally so always try to stay low if possible - though appreciate if it'll be used regularly and unsupervised, damage may be an issue - or some heart-stoppers if it's less experienced users and there's a rebelay or similar? I'm sure 10mm would be enough for most stuff.

 

[PeteHall]

Another consideration knowing the sorts of places you frequent @Mr Mike, is calcification.

I've left a couple of ropes in Weardale mines and come back a year later and had to crack the calcite off the get down them, which will become more of an issue if it's a thick inflexible rope to start with. I has a similar rapid build-up of calcite on some pull-through anchors in Nent...

I'm not sure if the calcification is limited to the surface of the rope, or if it grows inside and could damage the fibres? Maybe need to pull one back out and get it tested...

 

[pwhole]

The bottoms of ours are also beginning to pick up a bit of calcification, though two have been in there about three years now - though the water is mostly percolation/surface run-off rather than cave-derived, so it's not too bad. The ropes at the very bottom of Oxlow/Maskhill are so encrusted they're like steel cable now.

 

[Mr Mike]

Thanks for your thoughts - calcite, not an issue in this case. It's in a relatively clean rise with a bit of drippy water, only grit will be getting onto the pitch top and anything that is dragged onto it.

 

[Bob Mehew]

The other point is potential for rub points due to rope movement. Though this is usually associated with people using the rope, there has also been some significant wear caused by water flow moving the bottom of the rope when dipped in the stream causing rubbing higher up the rope. But what is scary is that one sample of 10mm rope I received back in 2011 as BCA's Rope Test Officer, had suffered severe rubbing all the way through the sheath and into the cords with just 12 uses (both ascent and descent) of the rope (in a mine). The rope failed on the second dynamic drop test. So if you must leave a SRT rope in, then I would recommend going as thick as you can.

But frankly I would not recommend leaving SRT ropes in situ. I am not sure how to cope if it is an ascending pitch apart from a "pull around" loop, so one can inspect the whole length and then clip off one side of the loop at the base of the pitch to secure the other side which is used to SRT.

Even hand lines wear, though more slowly. In both cases an inspection program is required to reduce the legal liability (but it won't eliminate it).

 

[Mr Mike]

One of our group who also does caving mentioned the pull around loop, but we where thinking that not all mine explorers would be familiar with it. I feel mine explorer skills in rope work are somewhat more basic when compared to cavers.

 

[Wayland Smith]

A direct question to one of the groups that regularly install ropes into mines might get you first-hand information.
Possibly Shropshire or Derbyshire would know. (The people with the knowledge might not be on this forum.)

 

[Cantclimbtom]

If you are OK with 10.5 I've found that Southern Ropes (manufacturer in South Africa famous for its specialist marine ropes) 10.5 LSK "low stretch kern" is a decent enough budget rope for SRT, conforming to CE (that's actual CE not "China Export") and comes in at about £1 a metre on ebay new, for example https://www.ebay.co.uk/str/surplusropes

 

[Loki]

Consider not using 7mm maillons- go bigger so the rope doesn’t flatten around the bar and damage it.