Fans and tubing for forced ventialtion of digs

biffa

biffa

New member
I've been wondering about forced ventilation of digs for removal of bad air or fumes.  I've seen some plastic tubing (8" diameter) cheap on ebay, that is like thick plastic bag.  Fan wise I'd like something that runs at 12 or 24v.

My question is whether anyone knows what drop of in air flow I can expect trying to force air down the tubing.  e.g. a small computer fan may be rated at 24cfm, but if I have six of them blowing down the pipe (that may be 50m long) I will not get 6x24cfm out of the end of the pipe.  Has anyone tried this?  I know that some people have played with much bigger fans.

Obviously one way is just to try it but if someone has established it doesn't work I'd rather not waste my time.
 
SamT

SamT

Moderator
a bit of background might be useful.
What fumes are you trying to remove - CO2 from physical excertion - Bang fumes - permanant "bad air".

also - whats the nature of the passage - bottom of a deep vertical shaft - or end of a horizotal dig.

check out
http://ukcaving.com/board/index.php/topic,2839.0.html
for more ideas
It might be more profitable to suck fumes out that force air in which is where a chimeny may come in.

Stupot - did you ever try this??
 
paul

paul

Moderator
There's still an old vacuum cleaner in the Orpheus hut marked "Dig  Ventilation Unit" and was actually used for this purpose...
 
Cave_Troll

Cave_Troll

Active member
i like the idea of the Chimney method but have not hada  chance to try it.
I have some SamT hosepipe that you can use if you want to try it Bif
 
D

Dave H

Guest
Blowing is a problem in that you have to overcome the Resistance of the static air in the pipe.
The types of fans used in PC's are not the right sort for this job.
However, you may find that placing them at the exit (expelling end) of the pipe might work
 
gus horsley

gus horsley

New member
It was fairly common practice for mines to be ventilated by lighting a fire at the entrance and constructing an airtight channel along the floor but there are obvious disadvantages when attempting to apply it to a caving situation.
 
AndyF

AndyF

New member
We have done ventilation in Rubble Rift in Stoney...

First, suck the air out, dont try to blow it down a pipe...

We used 2" Waste pipe from B&Q and push on fittings.....dirt cheap, it was fine over 30ft+

For the blower unit we got an ammo box with a couple of 240 volt fans in (like the ones on PC power supplies)...you can easily get 24v ones similar.... we glued a fitting through a hole at the end and used a puch fit to stick it to the pipe...

We found you didnt need much flow at all to keep things fresh. This was for CO2 build up not bang fumes though...



 
Bob Smith

Bob Smith

Member
BEC regularly use vacuum cleaners to remove bad air from digs, using relatively small diameter pipes (<1") This is very effective. Extraction is certainly our preferred method of use, but the situation usually dictates what systems is best. Will have to look through my mines ventilation coursework stuff to elaborate.
 
biffa

biffa

New member
SamT said:
What fumes are you trying to remove - CO2 from physical excertion - Bang fumes - permanant "bad air".
Click to expand...

Mainly CO2.  The place I am thinking of specifically is the downstream mud choke in Water Icicle Close Mine.  This used to suffer from a build up of bad air when I dug there a couple of years ago.  For those not familiar with WICM there is a 30m entrance shaft then ~100m of horizontal walking passage until a choke is met.  The air was only ever bad in the last 5m, probably due to a too tight aven that carried a slight draught ventilating up to that point.

AndyF said:
First, suck the air out, dont try to blow it down a pipe...
Click to expand...

What about if there is a natural outwards draught.  Will sucking increase the natural flow of air or just cause the airflow to travel in the pipe instead of the passage?

Sounds like some fixed pipe with a 24v fan sucking air out of the dig is the way to go.  I've already started to go off the idea of going back there in the three hours I've had to think about it mind......
 
shotlighter

shotlighter

Active member
If you are going to blow, use a centrifugal (snail) blower as an axiial fan is not so good with the back pressure the tube introduces. Seem to remember Bob Mackie discribing use of unformed plastic carrier bag as cheap vent bagging. Hucklow digging supplies had some suitable blowers & I think Nick had some involvment with the "carrier bag" episode - worth an ask. With the blower on the bank & baggin' down the shaft you should be able to purge the place in no time. Mind you, you won't be able to use that little shaft for access once the baggin's inflated!
 
biffa

biffa

New member
I don't think that WICM needs that much airflow.  I was aware of the plastic bag as a conduit experiment done which was how my original line of thought came about.

 
shotlighter

shotlighter

Active member
biffa said:
I don't think that WICM needs that much airflow.  I was aware of the plastic bag as a conduit experiment done which was how my original line of thought came about.
Click to expand...
Fairy Nuff - good luck with it, always thought that place rather a fascinating conundrum.
 
paul

paul

Moderator
shotlighter said:
biffa said:
I don't think that WICM needs that much airflow.  I was aware of the plastic bag as a conduit experiment done which was how my original line of thought came about.
Click to expand...
Fairy Nuff - good luck with it, always thought that place rather a fascinating conundrum.
Click to expand...

... and watch out for the  ghosts!  :)
 
Leclused

Leclused

Active member
At the moment we (SC avalon) have a ventilation system installed in one of our explorations (Chantoir de Fagnoules). At the end of an almost completely filled gallery, which is going in the good direction to bypass the next siphon, we encountered 2% co2 before the dig starts. So after 30 minutes everybody is having problems there.  So we've installed a 30m long tube with at the end an old 12v car-fan connected to external batteries. With each battery we can work around 1 hour and per day we use 3 batteries. After that even the fresh air becomes bad

the tube is a ribbed tube 10cm (4") diameter 

Dagobert

www.scavalon.be
 
C

cave junky

New member
The BALLS digging team have used ventilation systems in the digs. The most up to date was very effective. It used the fan from a photo booth, like you find in supermarkets. This was enclosed in a box with a connection for the hose on 2 sides enabling is to blow or suck depending on what was needed. A piece of ridged pipe was used for the entrance shaft and at the bottom is was connected to a plastic hose with a wire spiral inside which kept it open. This comes packed very small which makes transporting it easier. We did run this off a generator which isn't what you are looking for but worked really well.
Ally
 
C

cucc Paul

Guest
you can get bouncy castle blowers (electric) that would surly do the job for you, high volumes and a fair bit of pressure. I believe the ones in maplins and argos have 12volt options nowa days if not use an inverter and a car battery would probably give you 30 mins of intensive blowing. If its not rigid pipe you will need to blow and not suck
 
shotlighter

shotlighter

Active member
cucc Paul said:
you can get bouncy castle blowers (electric) that would surly do the job for you, high volumes and a fair bit of pressure. I believe the ones in maplins and argos have 12volt options nowa days if not use an inverter and a car battery would probably give you 30 mins of intensive blowing. If its not rigid pipe you will need to blow and not suck
Click to expand...
Not just me then who eyes bouncy castles covetously - I'm waiting for my niece to knacker the castle bit so I can have the blower 8)
 
C

cucc Paul

Guest
You need an adults only bbq and lots of alcohol and conveniently leave the castle blown up, nature will take its course.
 
paul

paul

Moderator
shotlighter said:
cucc Paul said:
you can get bouncy castle blowers (electric) that would surly do the job for you, high volumes and a fair bit of pressure. I believe the ones in maplins and argos have 12volt options nowa days if not use an inverter and a car battery would probably give you 30 mins of intensive blowing. If its not rigid pipe you will need to blow and not suck
Click to expand...
Not just me then who eyes bouncy castles covetously - I'm waiting for my niece to knacker the castle bit so I can have the blower 8)
Click to expand...

Get her a set of crampons!
 
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