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Mine Exploration Forum

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Author Disused Mine Ventilation natural and forced.
stuey

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Disused Mine Ventilation natural and forced.
Posted: 09/06/2009 23:34:23
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Bad air is a topic I'm quite interested in, not really nasties floating around, but oxygen deficiency. I've had a few dallies with it including abseiling into 17% (with gas meter) and going well below that in walk ins. Quite a few mines I'm interested in have air issues and I'd be interested in the factors influencing air quality.

Obviously, we have wood and oxidisable minerals as well as bacteria in some cases. It would be nice to digress into the science behind ventilation and see if we can agree some terms.

'Around here' is a mine which is hugely interesting but doesn't seem to breathe much. The gas detector lowered about 100ft down the shaft reads 17%. I would have thought this to be disturbed by atmosphere, diffusion and temperature. This flies in the face of what I would expect.

Pressure:

If there is any through ventilation, a pressure system would cause air to follow the gradient. A variation between an average high and low pressure is about 10% difference. I would expect the mine to breathe slightly and diffusion to dilute the stale air.

Temperature:

I pretty much gather that most normal mines are in the order of 10 deg C. Surely, as cold air is more dense and we see "vapour rising on cold days" should it not be the case that cold air tumbles into the shaft and despite local turbulance, a transfer of air should be pretty significant.

Porous Stuff breathing:

..... during an area of low pressure, would it be right that bad air seeps out of oxidisable deads. The contrary being true also.....

That's pretty much how I understand it. I think that if there is no through ventilation, there is very little diffusion, air replacement and some places pose a proper hazard.

Which leads me onto this:

What ways are there of forcing ventilation into poor workings without buying thousands of pounds worth of kit. Perhaps a few hundred.....

Fire away chaps......
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Wormster

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Joined: 15/08/2006
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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 00:10:35
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You could use a low tech solution, used by the diggers in Caine Hill on Mendip:

Get a couple of vaccum cleaners and then use one to suck the bad air out (at the bottom of the shaft) and the other one to blow air into the shaft (this is done by using the exhaust (construct a collection box around the exhaust vents). All you need then is enough 2" hose (similar to the normal bendy hose on a vaccum) to reach a suitable distance down your shaft. One sucks the air out at the bottom, 'tother pumps fresh air in.

Or take B/A - Diving kit with you Crying

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stuey

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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 00:22:18
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The chaps digging a local mine have got a syphon set up which works like a venturi vac pump. A flow of water causes a tube to suck.....both water and eventually air. Gradually the air quality improves. It is a very gradual process though. The bonus is that it works underground with only a small water head.

I gather in the old days, falling water in a tube was used to move air and a separation "bong" made the air flow along a pipe without water. This is another good idea. Rather than drawing bad air out, a fresh air in approach makes more sense.

IP: 87.115.149.189 Edited: 10/06/2009 00:23:21 by stuey
Knocker

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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 00:38:14
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If there are to shafts one old method was to set a fire at the bottom of one, which woul pull air down one shaft and exhust the other, just hope you get the right way IP: 90.221.39.44
derrickman

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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 06:33:26
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the fact is that when a lot of these mines were worked, ventilation levels were accepted which were at times, plain dangerous.

there are a whole range of reasons why disused workings don't 'breathe'. Sulphide ores can take the oxygen out of the air, a contemporary of mine at CSM was suffocated having skived off to hunt for specimens in a bratticed-off section, at his summer job in a well-known Cornish mine....


have to say, some of the things diggers do make me cringe, because I can't help looking at it professionally Sad
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stuey

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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 07:22:27
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If we managed to open the other shaft to this mine, I imagine the lady (who is allready highly strung) seeing smoke at the bottom of her garden would have an orgasm!

It would make sense though. I'd have big reservations about having a fire in a shaft, even if it was textbook.
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derrickman

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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 07:50:51
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depending on what equipment you have for digging with, there are really only three ways of ventilating effectively;

1) an open shaft or adit connection at a different elevation to the entry point, which will usually provide a sufficient through flow, especially if there is running water

2) a small 110v ( not 240v in underground conditions )electric axial-flow fan of the sort you can get at Machine Mart or somewhere like that. 6" collapsible ( the spring-wound type, not layflat as used for pumps ) dusting, and you are away

3) best of all, a venturi-type air mover if you have a compressor, although I am assuming you don't.

anything else is just tinkering with the fringes of a real problem with the potential to cause fatalities. Some mines simpl aren't accessible for this reason, and that's all there is to it.
IP: 149.254.49.88 Edited: 10/06/2009 07:52:49 by derrickman
Boy Engineer

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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 12:30:38
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stuey wrote:

If we managed to open the other shaft to this mine, I imagine the lady (who is allready highly strung) seeing smoke at the bottom of her garden would have an orgasm!


Two points: Is this a bad thing? And secondly, can it be more generally be achieved with the use of smoke?
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derrickman

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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 13:13:17
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Boy Engineer wrote:

stuey wrote:

If we managed to open the other shaft to this mine, I imagine the lady (who is allready highly strung) seeing smoke at the bottom of her garden would have an orgasm!


Two points: Is this a bad thing? And secondly, can it be more generally be achieved with the use of smoke?


wouldn't it be more usual to smoke AFTERWARDS? Blink
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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 13:26:31
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Let me be clear, I wasn't suggesting it as something to be attempted! Fires underground are not something I fancy playing with! IP: 90.221.39.44
derrickman

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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 13:30:47
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as evidence the recent fatality involving setting a campfire in a cave.. IP: 149.254.56.116
Knocker

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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 13:46:10
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That ones a little more bizzare, as the cause of death appears to be crush from collapse caused by drying of the sandstone by the fire! Pretty unfortunate really. IP: 90.221.39.44
stuey

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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 16:16:19
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derrickman wrote:



anything else is just tinkering with the fringes of a real problem with the potential to cause fatalities. Some mines simpl aren't accessible for this reason, and that's all there is to it.
#

Yep, aware of that. The levels aren't low enough to kill, but low enough to probably hinder a roped ascent. The current thinking is to unblock a shaft about 200m away and leave it for ages to be vented by passing weather systems. The next step is to force vent it with a blower and ducting.... although this is pricey. Venting the shaft would probably be enough to enable a safe climb out.

I wonder what forms of cheap pipe I can get my hands on...
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JR

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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 17:09:53
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As long as precautions are taken to ensure that the air is drawn out of the mine rather than from the side you could set a fire at the top of an upcast shaft to draw air through. Not as efficient as a fire at the bottom of said shaft, but a tad safer I imagine.
I've never seen it done but I've read about venting mines this way and Ironbridge Gorge Museum have one (admittedly a mock up) at the Blist's Hill site.

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stuey

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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 17:17:13
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I think the danger may be in the duration/proximity of your fire and residual heat.

Since cold weather doen't really seem to add a great deal to venting due to sinking air, I assume the wall temp of the shaft, as well as the difficulty in establishing a proper current, I imagine that a fire could quite easily cause recirculation and mixing in the shaft, rather than an updraft. The resulting CO conc's could make entry very dangerous indeed. Also what happens to the fire as it burns down could allow a bit of recirculation. I'd say it was a great idea but had a fair chance of being bloody dangerous.....twofold with the "firesetting".

I think forming a club and all chipping in for a km or so of ducting is a good idea Smile
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Brakeman

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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 17:23:22
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JR wrote:

As long as precautions are taken to ensure that the air is drawn out of the mine rather than from the side you could set a fire at the top of an upcast shaft to draw air through. Not as efficient as a fire at the bottom of said shaft, but a tad safer I imagine.
I've never seen it done but I've read about venting mines this way and Ironbridge Gorge Museum have one (admittedly a mock up) at the Blist's Hill site.


Interestingly this was done at the Alderley Edge copper mines in the West mine, this stempled shaft had a brazier in situ on a small platform near the top, to draw the air from the working chambers & flats at this far point of the mine away from the main haulage level. The timbers are still in good order & can be climbed carefully. Presumably when the mine was being worked it was someones job to climb up & light the fire, the brazier was not at the very top.



(click image to open full size image in new window)



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RPJ

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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 18:51:59
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For furnace ventilation, although it was usual to locate the furnace at the bottom of the upcast shaft, there were instances of a furnace at shaft top being used, with a short stack (circa 30 feet) to ensure draught. Not as efficient as a furnace at shaft bottom but it clearly worked.

But a furnace or powered ventialtion can be dispensed with if only a low volume of air requires to be exchanged and if you have patience. Around 1930 a cousin sank a shaft 100 feet and, as anticipated, broke into old coal workings. He tested the air by lowering a candle in a bucket down the shaft and, as expected, it was extinguished (old shallow workings rarely have methane, only excess Co2 and/or O2 deficiency). He lowered a pipe (6 or 8 inch diameter) down the shaft and let it project around ten feet above shaft collar. In a week or so, the difference in atmospheric pressure plus the wind cleared the old workings. He then applied to the mineral owner for permission to work the coal but was refused. Such a non-furnace, non-powered ventilation technique might possibly have application in the present case?

Have very great caution - there are inumerable instances of well sinkers, miners, and mine explorers descending into O2 deficient or other poor atmospheres and being unable to ladder or prussick out and dying as a result - and not infrequently rescuers going the same way.

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agricola

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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 19:08:12
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On the subject of smoke underground, beware, remember what happened at Maggpie Mine, Derbyshire Wink

IMO I would prefer to force ventilate inwards, due to the reasoning that it is fresh air and results in pushing the bad air out. Exhausting air could have the effect of drawing bad air in and could result in higher levels of bad air.

If bad air is suspected the use of some form of safety device flame safety lamp etc etc would be a good idea. The human nose is not that good at detecting the presence of ordourless gases some of which will be harmful to health.
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sbt

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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 20:42:46
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RPJ wrote:


Have very great caution - there are inumerable instances of well sinkers, miners, and mine explorers descending into O2 deficient or other poor atmospheres and being unable to ladder or prussick out and dying as a result - and not infrequently rescuers going the same way.



One of the things peripheral to my job is reading Maritime Accident Reports. Not that long ago there was an instructive case where Person X collapsed at the base of a ladder due to low O2 levels. Being aboard ship BA was available and it was sent for. However Person X's mate, Person Y, couldn't wait and attempted a rescue without BA and joined X as a casualty When the BA team arrived Y was still breathing, X wasn't, so they prioritised the rescue of Y as having more chance of success. Y survived, X didn't.

The moral of the tale is contained in the Accident Report. It pointed out that had the only casualty been X there was a reasonable chance, even though he wasn't breathing, that he could have been saved - people can recover from some surprising things. But only one person could be extracted at a time and by the time Y was out X's fate had been sealed. In attempting a rescue without BA not only did Y nearly die he ensured that his friend did.

BTW the accident occurred in a ballast tank – rust had consumed the Oxygen, something for investigators of metal structures, or confined spaces containing them, to consider.

Rick
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Mr.C

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Disused Mine Ventilation natural and forced.
Posted: 10/06/2009 20:56:12
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derrickman wrote:




2) a small 110v ( not 240v in underground conditions )electric axial-flow fan of the sort you can get at Machine Mart or somewhere like that. 6" collapsible ( the spring-wound type, not layflat as used for pumps ) dusting, and you are away

.
Centrifugal fans (ex air con or computer room for instance) work better against any back pressure & used with a roll of lay flat poly tube (the raw stuff to make poly bags from before it's heat sealed/cut), the blower will unroll the tube for you!
You should have attended this years BCRC Stuey. We did a full day on foul air & how to identify & deal with it.
Including a demo of the above clearing bad air from a shaft & a very impressive film of the scaled up system used by Yorkshire CRO in Wet Earth Colliery & some typical N Pennine lead levels.

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If things dunner change - the'll stop as the' are.
IP: 91.110.118.39 Edited: 10/06/2009 20:58:28 by Mr.C
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