Discussion in 'Tips, tricks and tutorials' started by Bill Fowler, May 4, 2018.
What if any are the dangers of leaving an airgun filling tank in the back of a hot car.
It will get stolen.
The pressure will increase according approximately to
p2 = p1 * T2/T1
where tempetature T is in degrees kelvin
20 deg C is 293 deg K
50 deg C is 323 deg K
So a fully filled tank at room temp in a hot car at 50 deg C could reach
232 * 323/293 or 255 bar. High but within test limit.
CO2 on the other hand follows a potentially exponential pressure increase. V dangerous.
Very good to know, I would never have thought about it! Thanks!
And even after filling it is highly unlikely you will have 232 bar in a 232 bar cylinder(or 300 in a 300bar cylinder), if filled directly from a compressor it will probably have a auto cutoff so it can be filled without the shop guy looking after it, it will be set for 232 bar as the shop will not "overfill", the compressed gas will be warm and therefore after shut off, it will cool and your "232" bar fill will drop. Large shops will probably decant from a big bank of cylinders, however your bottle will still warm a bit depending on fill rate as they decant into it. This warming is why they generally fill diving cylinders in a tank of water, however our bottles with surface pressure gauges (which is why we get the 5 year test cycle) cant be put in water.
One shop I go to overfills, another puts them in water (just not up to the gauge).
Used two dive shops - both put the bottles in water, just not up to the gauge.
maybe I should have said "should not overfill" and "should not be put in water"
I've sold my carbon bottle recently ,but I had it tested a couple of months earlier than its 5yr anniversary so I know it will be fine.
I was having a chat with the chap who did the test about not always getting the fill pressure you want.
I mentioned about putting the cylinders into water , he replied that doing that only cools the surface and can actually cause condensation in the cylinder.
He defiantly doesn't recommend putting any bottle into water to cool it.
He has the contract for West Yorkshire fire brigade so knows his onions .
He s tested and refilled mine for £35 ,
Acadamy Divers in Soweby Bridge, West Yorkshire
Oh! and he makes a good mug of Yorkshire Tea
Surely you can only get condensation if moisture is present/the air coming in is "damp" which it shouldn't be if proper diving air.
I'm just reĺaying what he said , I don't know enough about the workings of HP air other than connect fill n shoot .
Over filling ?
A 300 bar dive cylinder rated for a 300 bar fill but is hydrostatically tested to 460 bar every five years, At manufacture they test it even higher, The 300 bar rating is to make sure it is used well within the safety margins ,
Some fill stations fill in a water tank, some don't, Some overfill slightly so when it cools it will have the correct fill pressure , some allow the tank to cool and then top it up, Whatever the method you have paid for a 300 bar fill and that is what you should get!, A fill station giving the cylinder cooling down as an excuse for a low fill pressure is taking the proverbial
Thank you for a great reply
The rules of bottle filling well expelianed