Ben Lawrence Posted January 15, 2015 Report Share Posted January 15, 2015 When I take my bottle to be filled at Kent diving centre they always put the bottle in a tank of water while filling to keep cool. Speaking to my father in law to day he told me he took his to be filled somewhere an they didn't have a water tank an that the bottle was hot afterwards. Will this do any damage to the bottle or is it even safe filling this way??? Quote Link to comment Share on other sites More sharing options...
R33SY Posted January 15, 2015 Report Share Posted January 15, 2015 When you compress air it heats up and expands it is how a jet engine works By keeping it cool in a tank of water you can actually fill to the required pressure with the full amount R33SY Quote Link to comment Share on other sites More sharing options...
bruno22rf Posted January 15, 2015 Report Share Posted January 15, 2015 Normally a bottle is filled then allowed to cool for a while then topped up again-sounds like your guys are simply doing it quicker by cooling as it fills. Quote Link to comment Share on other sites More sharing options...
secretagentmole Posted January 15, 2015 Report Share Posted January 15, 2015 Bruno is right. To cool the contents of the bottle down some places immerse the bottles in water. It will not damage the bottle if it is not immersed, however if they do not allow it to cool right down and then top it up you are losing at least 10% of the fill due to heat expansion! Quote Link to comment Share on other sites More sharing options...
Ben Lawrence Posted January 15, 2015 Author Report Share Posted January 15, 2015 Thanks for your replies guys, that's good to know it won't damage the bottle. Forgot to say the bloke filled it to 330 an said once it's cooled it would go down to 300 Quote Link to comment Share on other sites More sharing options...
robbiep Posted January 15, 2015 Report Share Posted January 15, 2015 Thanks for your replies guys, that's good to know it won't damage the bottle. Forgot to say the bloke filled it to 330 an said once it's cooled it would go down to 300 That would come in under 'bad practice' Quote Link to comment Share on other sites More sharing options...
secretagentmole Posted January 16, 2015 Report Share Posted January 16, 2015 Not really Robbiep! The test pressure on the cylinder is 450 bar (that is what it is filled too and when a 5 year Hydro test is done). So filling to 330 and letting it cool down by air won't do any harm as the gas inside will contract and it will drop down by 10% or so! Quote Link to comment Share on other sites More sharing options...
robbiep Posted January 16, 2015 Report Share Posted January 16, 2015 My wife is a cylinder tester, also certified to do divers trimix fills, etc. Her viewpoint was that it is bad practice, which I then typed in. Why is it bad practice ? Her reply : When cylinders are tested, a 'go/no go' gauge is used on the threads that the valve screws into. If you regularly overfill a cylinder, then the threads are likely to expand/deform a little over time, making a fail on the gauge more likely. Meaning that your cylinder is more likely to end up as scrap whgen your test comes around. She sees this with particular dive groups/clubs which have their own filling gear. Members of one club in particular had a LOT of test failures of this type a couple of years ago, and the only thing they were doing differently was filling to 330 (for 300s) or 250 (for 232s) and allowing to cool. They've now gone back to filling to 300/232, allowing to cool, and then topping up. Out of interest, the shop where she works at they also fill using a cold water bath. Quote Link to comment Share on other sites More sharing options...
Junkyard Dog Posted January 16, 2015 Report Share Posted January 16, 2015 Most shops dont use a bath any more, due to good old HSE lifting rules and regs. I have been in the dive industry for over 20 years, main users of water baths are abroad where it needs to be in a cooling bath as they are filling huge quantities at once from storage banks, so they can blast the air in. If you are filling straight from the compressor, it is not necessary to do this, unless you are filling a 3 litre from a 25cfm+ compressor. Best option is fill, and top off if required, Seen plenty of cylinders that have fractured whilst filling, this is down to rust, which can be caused by hot air going into an immersed steel cylinder and condensing, its fine with allly tanks, so just slowly does it, and stay within the pressure of the tanks. Quote Link to comment Share on other sites More sharing options...
Ben Lawrence Posted January 16, 2015 Author Report Share Posted January 16, 2015 Thanks for the info guys, il tell the father in law to go else where an make sure they let the bottle cool down an top up Quote Link to comment Share on other sites More sharing options...
Lord Geordie Posted January 17, 2015 Report Share Posted January 17, 2015 (edited) Would I be correct in assuming, that is the bottle were to fail in the water bath! It would act as a retardant, and take some of the force out of the resulting explosion? Reading up on the effect of firing a bullet into water, I wondered if the same physics weren't applied? Or is it SOLELY for cooling purposes? Edited January 17, 2015 by Lord Geordie Quote Link to comment Share on other sites More sharing options...
secretagentmole Posted January 17, 2015 Report Share Posted January 17, 2015 The place I use fills to 300 bar. Cools the cylinder in water if you are waiting for a fill. Allows them to cool whilst filling other cylinders if you are taking advantage of his collect and deliver service. Tops up. Allows to cool and then check fills again! Oh and Lord Geordie, the water would act as a shock absorber.A Hydro test chamber is filled with water before they whack 1.5 x the working pressure in. Quote Link to comment Share on other sites More sharing options...
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