single
Well-Known Member
I'm thinking of using a pub nitrogen cylinder to inflate the dinghy. How many fills will I get per full cylinder?
Nitrogen cylinders.
- Thread starter single
- Start date
maby
Well-Known Member
Not that many, I suspect. I don't think the contents is liquidified, is it? If not, what pressure do they run at? 20 bar? 40 bar? I doubt it is more than that. If it's 40, then it could inflate forty times the volume of the cylinder to 1 atmosphere - I'm guessing that the two tubes plus an aerodeck of a medium sized dinghy comes to two or three times the volume of a cylinder - so you get what? Fifteen to twenty fills?
It's all guess work till someone tells us what pressure they are delivered at.
Update - the Air Products web site says that industrial cylinders are delivered at 200 bar, so perhaps you are looking at a hundred fills or more - isn;t the internet wonderful?
It's all guess work till someone tells us what pressure they are delivered at.
Update - the Air Products web site says that industrial cylinders are delivered at 200 bar, so perhaps you are looking at a hundred fills or more - isn;t the internet wonderful?
Last edited:
Chalker
Well-Known Member
Expanding gases get VERY cold and can cause the dinghy material to become brittle whilst frozen. Make sure you do not damage it.
maby
Well-Known Member
That is quite true. Also, a cylinder of that size is pretty heavy - the wall has to be quite thick to carry that sort of pressure. Personally, I would go for a good electric inflator - or better still, get some exercise!
vyv_cox
Well-Known Member
Having some spare time to kill while waiting for the present gale to die down, I calculated it. A 2.7 metre dinghy with 40 cm tubes has a capacity of 678 litres, roughly speaking without trying to allow for tapered ends, bow tube, etc.
Pub gas is either CO2 or a mixture of CO2 and nitrogen, depending on the product it is intended for, beer and soft drinks CO2, lager and guinness the mixture. The gas comes in bottles of 10 - 50 litres at 200 bar pressure. The smallest of these therefore contains 2000 litres at NTP.
Again, not allowing for what pressure you can get into the dinghy, you will just about get 3 inflations from a 10 litre bottle.
Pub gas is either CO2 or a mixture of CO2 and nitrogen, depending on the product it is intended for, beer and soft drinks CO2, lager and guinness the mixture. The gas comes in bottles of 10 - 50 litres at 200 bar pressure. The smallest of these therefore contains 2000 litres at NTP.
Again, not allowing for what pressure you can get into the dinghy, you will just about get 3 inflations from a 10 litre bottle.
single
Well-Known Member
That is quite true. Also, a cylinder of that size is pretty heavy - the wall has to be quite thick to carry that sort of pressure. Personally, I would go for a good electric inflator - or better still, get some exercise!
I have been looking at electric but which one? Ones I have used still require a manual pump to do the last bit.
Skylark
Well-Known Member
I did a similar calculation while eating my sandwich at work! Inflating the tubes to 1.3bar abs, I recon the gas required is closer to 1000 litres. A 10 litre diving cylinder filled to 200 bar will be a bit less than that once it's cooled down to room temperature. You'll be lucky to get two decent inflations.
The advantage of a foot pump is that you're ready for beer when the job is done.
Trundlebug
Well-Known Member
A few years ago we bought a Coleman cordless one like this
http://www.amazon.co.uk/Coleman-2000000834-Rechargeable-Quick-Pump/dp/B00005JD40
and it's absolutely superb.
Yes you have to manually pump about 3-4 pumps max with the footpump to get it really firm, but it makes such short work of the main inflation that's no hardship at all.
Inflates a 2.4m dinghy in less than 5 minutes - about 2 mins per side.
One charge lasts years. Bought ours about 3 years ago at a show for £20 (on offer) and I'm still on the first charge!
Can recharge from either mains or 12v. Can be used to fast deflate the dinghy as well. Cordless, no wires to trip on. Weighs about 1-2 kg - probably about 1/10 as much as a pub cylinder. What's not to like!?
duncan99210
Well-Known Member
And you'd need some sort of regulator to step down the pressure to about 2 - 3 bar. Just attaching a hose and cracking the valve would lead to an interesting dance with the end of the hose.
Nudge
Well-Known Member
I tried it 25 years ago. Did all the calculations and.... davidjackson has it spot on, I didn't quite get the second inflation completed. I was of course very young and the confidence of youth made me leave the pump in the car...
My mates were hugely amused by my final ministrations by mouth to the dinghy to get us to the pub. They were still laughing bythe 3rd pint.
Go electric....
My mates were hugely amused by my final ministrations by mouth to the dinghy to get us to the pub. They were still laughing bythe 3rd pint.
Go electric....
DipperToo
Well-Known Member
+1. The fact it is rechargeable means no cables or restrictions. Also very good value. The expensive (much more) ones also need quite a substantial power outlet and need up to 20A in some cases......
Again, just the last bit of pumping by regular pump.
Amazon link above is showing £54 but search their site and you can find it for £27
nigelmercier
RIP
- Joined
- 20 Jun 2007
- Messages
- 16,234
- Location
- Live in Kent, boat in Canary Islands
agurney
Well-Known Member
It's far simpler than that.
in my younger days if I was in a hurry, or just feeling lazy, I used to inflate our dinghy by cracking open the pillar valve on a diving tank a few inches away from the (Avon) dinghy valve.
The dinghy inflated in a few seconds, and the pressure was fine.
I'm pretty sure there was a venturi effect that helped it along, but it was pretty neat.
single
Well-Known Member
Are the Coleman 12v wired ones better?
davidpbo
Well-Known Member
Does the Coleman rechargeable inflator get the dinghy up to full pressure?
single
Well-Known Member
Apparently not but I ordered one so i'll tell you on Tuesday!
BlueChip
Well-Known Member
The inflator to buy is this one http://marinedirect.co.uk/bravo-btp12-manometer-p-466.html
It pumps even an air deck to high pressure and doesn't require any topping up. Once you have used one any other inflator is just junk.
Just dial in the pressure, sit back and wait for the pump to shut down. It's quick easy and in our case means we can blow our air deck up in about 5 minutes from scratch.
skyflyer
Well-Known Member
back to original point about using a cylinder.
The slide-rafts used on commercial airliners do not have sufficient 'bottle contents' to inflate them, they use the bottle pressure to power an integral inflator pump, that sort of 'draws in' extra air. This is because the size of bottle needed for a self-contained inflation would be enormous!
The slide-rafts used on commercial airliners do not have sufficient 'bottle contents' to inflate them, they use the bottle pressure to power an integral inflator pump, that sort of 'draws in' extra air. This is because the size of bottle needed for a self-contained inflation would be enormous!
nigelmercier
RIP
- Joined
- 20 Jun 2007
- Messages
- 16,234
- Location
- Live in Kent, boat in Canary Islands
Strange they call it a Manometer. It seems to have both turbine and a piston pumps, which is good for the last bit. I'd rather save nearly £100 and do the last few pumps by hand. However, I wonder if it could power a breathing tube 1m under the surface.
agurney
Well-Known Member
That sounds like the venturi effect to which I referred above
