Cave Rescuer: This is My Job

[L Roebuck]

Cave Rescuer: This is My Job
Joanna Borns, Popular Mechanics
Photograph by Gina Levay

There are nearly 15,000 caves in the central United States, and an estimated 4000 people who explore them each year. Anmar Mirza, who volunteers as coordinator for the National Cave Rescue Commission’s central region, makes sure they come out alive. The 38-year-old has performed 80 rescues since 1985, embarking on blind searches to locate lost or trapped cavers. When he’s not running a company that sells caving equipment, Mirza trains fellow rescuers to operate in tight spaces and total darkness. “It’s not about being brave,” he says. “It’s about being prepared.”

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[jopo]

Interesting job. We get a kick out of teaching confined space rescue techniques to industrial customers (only) and find it very satisfying.
Strange though that the site claims that radio's don't work through rock - magnetic induction radio's have been used in caves since the 70's The Heyphone is in use by most Brit cave rescue teams and the new digital Nicola 3 - due for production within this year I believe - is rumored to be the much better than the N2 - which is pretty good now!.

Also - rope is replaced every 10 years? We use 11mm static which has a manufacturers recc. to replace every 5/6 years - unused or not. We would love not having to replace rope for 10 years!

Jopo

[tncaveres]

Anmar was our pt for this last yrs mock rescue in Va.
I bought my cave pack from him acouple yrs ago too.

[Brad Tipton]

jopo said:

Interesting job. We get a kick out of teaching confined space rescue techniques to industrial customers (only) and find it very satisfying.
Strange though that the site claims that radio's don't work through rock - magnetic induction radio's have been used in caves since the 70's The Heyphone is in use by most Brit cave rescue teams and the new digital Nicola 3 - due for production within this year I believe - is rumored to be the much better than the N2 - which is pretty good now!.


Jopo

Underground low- frequency radios are quite reliable. Chattanooga-Hamilton County has a set that we use infrequently, but they work great on long rescues in a complex cave. It is far easier to set up the radio than to run miles of com wire in a cave.

We did find out just recently as last year that you cannot operate LED's near the unit. They interfere with the signal. That is rather disappointing considering cavers are trending toward LED.

[Brian Roebuck]

Hmmm, that must be an issue with the LED light's voltage regulation circuit broadcasting RF around near the radios (guessing anyhow). Perhaps some shielding in the LED lights would eliminate this.

[NZcaver]

jopo said:

Strange though that the site claims that radio's don't work through rock - magnetic induction radio's have been used in caves since the 70's The Heyphone is in use by most Brit cave rescue teams and the new digital Nicola 3 - due for production within this year I believe - is rumored to be the much better than the N2 - which is pretty good now!

Hi Jopo,

You're right - that remark about radios was probably just over-simplified for the benefit of the masses.

I'm guessing you know most "normal" commercial radios (Ham, CB, UHF FRS, UHF Fire/Rescue, etc) usually have a somewhat limited range transmitting through rock (although I have seem some impressive exceptions to this). The VLF MI transmitters you mentioned have propagation properties a little different to regular RF, which of course can help them to work rather well underground. A couple of specific areas (like Chattanooga-Hamilton) use VLF equipment to great effect, however the recommended basic equipment for most cave rescue communications in the US is still the good old rugged army field telephone system. Hence they show one of the TA-1 handsets in the picture.

Also - rope is replaced every 10 years? We use 11mm static which has a manufacturers recc. to replace every 5/6 years - unused or not. We would love not having to replace rope for 10 years!

I guess it all depends on the manufacturer, plus any applicable local etc standards for rescue agencies. Opinions vary greatly about this, and aren't always based on solid facts. Some of the "5 year" info may apply to the technology of 20 years ago, but not so much today. Incidentally DuPont Nylon T707 (used in some static caving ropes) should have an indefinite shelf life, unless exposed to chemicals, heat, or some other detrimental influences. Personally, I've often used several types of rope which are over 10 years old - and seen some of it destruction tested with minimal change to the factory MBS after 10+ years. Do you destruction test your old ropes before retiring them and throwing them away?

Straying a little off-topic here, but I thought I'd chime in. Nice shot of Anmar on rope, anyway.

PS Yes, the PWM regulating circuits in most LED lights wreak musical havoc with VLF receivers.

[jopo]

Hi

We have had some success with HB sets in straight lines. Very useful between 'front and back' of the rescuer chain. We also use a earth return simplex wire system ( ours is called a Francepone after the maker) We use thin high spec teflon coated twin wire (as a single) as we have a guy who has miles of the stuff. Very light and tough but can be difficult to join if just using teeth. We used to use a duplex twin wire system but balanced the weight of wire against using thin twin which is weaker and requires a bit more care in laying. The duplex sets had the advantage of power from the surface only whereas the earth return has 9v in each handset. Power consumption is very low. The hardwire has two distinct advantages. a) To be able to clip in anywhere and 2) A good guide wire to the cas.
One problem is the user remembering to earth the set. At a static point - with the earth wire provided - on the move with a hand on the rock. We did have a bit of a smile at a medic using the earth return - held in a rubber gloved hand with the other hand - also rubber clad - on the rock.
Where possible we do use the magnetic thru the earth as it uses less manpower and you can use non cavers on the surface with a standard HB back to base. We did some trials with led's near to through the rock and found not all do interfere but some most definitely do. Easy to tell as the set begins to howl with an offending led - usually the more sophisticated ones.


Rope lifespan.

Interesting to us as we were following the manufactures recommendation which - when we brought the rope - was 5 years.
I have just emailed some manufacturers and found Bluewater say (website) 5 even with no use. PMI (email) up to 10, Beal (website) up to 15. Edelrid (email) give up to 10 - which has doubled since our last purchase of the rope we use (11mm Superstatic in Red, Blue and White)
All manufacturers who have replied give a sliding scale of use and storage from trashed on the first use to Beals 15 years light use and good storage. For completeness they all indicate that the recommendations apply only to well treated and stored rope with no chemical or mechanical attack.
We do not do destruction tests on rope on the principle that the test is only good for the bit you have just destroyed but the BCA has a long running scheme for testing cavers ropes at the annual national bash, and the tests have shown that manufactures - on the whole - are a little conservative in their lifespan recommendations - but they do like to sell rope!

Jopo

[NZcaver]

jopo said:

We also use a earth return simplex wire system ( ours is called a Francepone after the maker)

Ah yes. A system virtually identical to the Michie ("mickey") Phone used in other parts of the world such as Australia, where Mr Michie developed his system decades ago. Not a bad concept at all. Assuming, as you say, users remember to ground themselves properly. The Teflon wire sounds like a nice thing to have.

On the subject of interference at VLF frequencies using the MI sets, how does the atmospheric noise level sound on the surface with a Heyphone or Nicola? In the past we've found the signal to noise ratio increases significantly the further below the surface you are. Although I suppose remoting the surface unit deeper underground and/or some good digital signal processing might improve things.

tests have shown that manufactures - on the whole - are a little conservative in their lifespan recommendations - but they do like to sell rope!

Isn't that the truth! Interesting info from the manufacturers there - thanks for taking the time to find out and post about it.

When I mentioned destruction testing earlier, what I really meant was taking your already-retired rope and testing sections along it's length as a post-mortem analysis. I didn't mean to suggest you just test a short piece chopped off the end, and then continue to use the remainder of the rope.

[jopo]

On the subject of interference at VLF frequencies using the MI sets, how does the atmospheric noise level sound on the surface with a Heyphone or Nicola?

We find in the UK that the noise from navigational beacons can be a problem. It manifests itself in a noise like galloping horses and is only a problem with the surface sets. Certain operators can seem to 'tune out' the noise but for others it masks the reception from the ug sets. At the limits we have found that the female voice seems to propagate better. I believe the Nicola is slightly better at filtering out surface interference, but thanks to the superb efforts of John Hey all UK teams could purchase Heyphones at less than £200 per end.
Some time ago it appeared that the beacons were going to be phased out but they are still very much in evidence. Digital sets will improve comms, ( I am told because my electronics skills stop just this side of the plug), and we look forward to their availability but suspect that they will be expensive.
In some areas the nature of the rock/mineralization affects the signal to a degree which makes through rock comms unusable. We are responsible for rescue from thousands of abandoned metalliferous mines (many used for 'sport') on our patch and tend to use hardwire.

The Teflon wire sounds like a nice thing to have.

Yes it is. We used to use a heavier wire - in fact the wire commonly used for overhead domestic telephone connections, because it was readily available and very cheap. One of our members was in the scrap wire trade and I suggest looking into this market you may find very high quality wire at very low prices. A 500m reel of the wire we use weighs about 0.5K. There are a couple of down sides. Connecting can be difficult because the particular wire we use has a nylon(?) sheath under the outer so you have to be careful to expose the wire when connecting and some of the wire is brown - not the best colour in a cave! Other is bright orange and is great! We tend to tie a overhand knot to take the load off the connection and simply cut it out when re-reeling. In crawls - and we have a lot in South Wales - laying has to be done with care and the team negotiating the crawl has to be careful, although the wire is very strong - the connections may be pulled apart. We are looking for a crimp type connector which would simplify connection.