chrsgrain
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| posted on 10/4/09 at 06:27 PM |
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OT - how to generate low pressure easily?
Right guys... I know the locostbuilders can answer anything, but this might be pushing it!
I need to generate 30cm of water (edit = 2.9kPa or 0.43 psi) air pressure into a tube which can then be split at least 6 ways to generate positive
pressure over some cells in culture (the idea is to mimic the constriction of cells in the airways when someone has an asthma attack).
The pressure has to be maintained for at least an hour, and ideally could be a switch on and forget system with an option for a control system to
deliver the pressure for varying amounts of time. Any ideas? Getting the pressure onto the cells is easy enough, once I've got the pressure in
a pipe - it has to be accurate in terms of pressure generated.
If anyone comes up with a good idea, I may have some cash to get something made up.....
Here's hoping!
Thanks
Chris
[Edited on 10/4/09 by chrsgrain]
Spoing! - the sound of an irony meter breaking...
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theconrodkid
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| posted on 10/4/09 at 06:32 PM |
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pressure release valve?,what sort of pressure is it in psi?
who cares who wins
pass the pork pies
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NS Dev
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| posted on 10/4/09 at 06:33 PM |
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Right, well what is the budget?
We use an extremely fine air control system at work for controlling air pressure inside hollow rubber and plastic extrusion as it is extruded and
cured.
It is accurate to 2mm water gauge so 30cm is very easy.
The systems I have been involved with were circa £1500 fully "productionised", and were made by a company called Aipex Engineering,
www.aipex-sussex.com.
They make air pressure regulators of various sorts among other things, several of which will do your job, and can be servo motor controlled via PLC
should the need arise.
I can get you the phone number of the guy you need to speak to there etc if you need. I have bought a bit from them so they do know me.
[Edited on 10/4/09 by NS Dev]
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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paulf
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| posted on 10/4/09 at 06:34 PM |
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I would imagine a conventional diaphram type pressure regulator would do it .You could feed it from a small compresssor or canister of air.To get a
consiten pressure it may be worth using 2 stages and making them fairly large bore regulators.
Other option may be BA equipment or scuba gear.
Paul.
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chrsgrain
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| posted on 10/4/09 at 06:38 PM |
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quote:
Right, well what is the budget?
I can get you the phone number of the guy you need to speak to there
The budget is as small as possible (!) but could probably stretch to a fair proportion of that if it just 'worked' and there was no
fiddling to do. The guys number would be great - I had googled, but couldn't find anything, obviously using the wrong terms...
There is a minor complicating factor, the air has to contain 5% CO2 (which we have in ample quantities) to keep the cells happy....
Chris
[Edited on 10/4/09 by chrsgrain]
Spoing! - the sound of an irony meter breaking...
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NS Dev
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| posted on 10/4/09 at 06:39 PM |
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PS meant to add, you want to look at Aipex's "APR" regulators, they mainly do blown film thickness guaging but do all sorts of cool
bespoke stuff including these really clever regulators. The guy there designed the first one in his shed!!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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NS Dev
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| posted on 10/4/09 at 06:43 PM |
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quote:
Originally posted by chrsgrain
quote:
Right, well what is the budget?
I can get you the phone number of the guy you need to speak to there
The budget is as small as possible (!) but could probably stretch to a fair proportion of that if it just 'worked' and there was no
fiddling to do. The guys number would be great - I had googled, but couldn't find anything, obviously using the wrong terms...
There is a minor complicating factor, the air has to contain 5% CO2 (which we have in ample quantities) to keep the cells happy....
Chris
[Edited on 10/4/09 by chrsgrain]
Ah, now that's tricky!!
To be honest, for an exact 5% CO2/Air mix, you might be best to speak to your gas supplier. Mixing accurately (and cheaply) is quite tricky!!
If you did buy it in premixed in bottles, you could then feed a bog std Aipex APR regulator with flow metering valve attached, via a normal 2 stage
bottle regulator. The APR regulator needs about 40 psi on its inlet or thereabouts.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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chrsgrain
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| posted on 10/4/09 at 06:45 PM |
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quote:
you want to look at Aipex's "APR" regulators ...... The guy there designed the first one in his shed!!
Just looked at them - seems ideal - and they aren't that far away from me, so could always go and see them.
Cool - see locostbuilders can answer anything!
Chris
Edit - we've got cylinders of 5%CO2 coming out of our ears, its standard in the stuff we do - and I don't have to pay for its, which makes
it easier! Would probably have to step the pressure down with an ordinary reg first.... is pretty close though. If could get some sort of control
system, that would then be perfect.
[Edited on 10/4/09 by chrsgrain]
Spoing! - the sound of an irony meter breaking...
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NS Dev
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| posted on 10/4/09 at 06:47 PM |
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Just remembered the guy's name, Barry Moore, tel. is as per the website, 01825 873600. Say Nat from Metzeler (now Schlegel) in Coalville passed
on the details.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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owelly
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| posted on 10/4/09 at 06:54 PM |
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When I first spotted the thread title, I was thinking along the lines of introducing an airflow which, as we know, causes an area of low pressure.
Then the other clever guys replied.
However, for a cheap means of creating a low pressure, it may well work. You could use a jet of air to create a venturi effect and by regulating a
bleed-off, it could be very accurate. You could also use a fan to blow the air but regulating the amount of air moved, by either bleeding off the
pressure or restricting the air in to the fan, as well as having a variable speed fan. The 5% gas could be injected into the stream and monitored via
a gas monitor. Once set up, it should stay the same.
Obviously, I'm no scientist. Just a tight Yorkshireman!
http://www.ppcmag.co.uk
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dmac
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| posted on 10/4/09 at 08:29 PM |
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Cheap way to reduce pressure would be a u-tube of mercury, measure the volume of trapped air/co2 over your cells and then lower the open end to reduce
pressure to the desired level, all you need to be accurate is a tape rule to measure the difference in fluid levels and a good head for maths. In fact
forget about measuring the volume, measure the ambient air pressure and then the difference in level will tell you the pressure in the closed end.
Duncan
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dmac
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| posted on 10/4/09 at 08:34 PM |
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Cheap way to reduce pressure would be a u-tube of mercury, measure the volume of trapped air/co2 over your cells and then lower the open end to reduce
pressure to the desired level, all you need to be accurate is a tape rule to measure the difference in fluid levels and a good head for maths. In fact
forget about measuring the volume, measure the ambient air pressure and then the difference in level will tell you the pressure in the closed end.
Duncan
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SteveWalker
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| posted on 10/4/09 at 09:18 PM |
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Are you talking psi a or psi g? If it's g and you've got access to a flow regulator (or even just a needle valve), just set a very low
flow and put the end of the open tube 30cm below the surface of a bucket of water and you'll have a constant pressure in the pipe, as any excess
just bubbles out. Basically it's the reverse of bubbler tube level measurement.
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