Shot blasting cylinders

[Fiona]

Not a happy bunny

I took my cylinders in for O2 cleaning on Thursday and I have just received a voice message to say that thy need shot blasting because they have - been continually drained.

These are Euros and were bought April 08 have only ever been filled at Divelife and have NEVER been drained, they even had 20 bar in when left at the shop.

How on earth have they got rust in.

[steveharriss]

There's no possible way to say cylinders have been continually drained IMO. They can say they have rust which means at some point water has got in but in my case it was a compressor that had not been maintained to specification. If the filters are allowed to exceed their recommended operating hours then there's a possibility that water will get into the system, and then into your cylinder.

If you've never drained them and they've always been filled at one operators site then it's clear where the blame lies.

[Fiona]

Just rememberd they had to be drained when I took them to be filled in Poole because some shops don't seem to be able to fill without emptying them first.

Also these have probably been filed no more than a dozen times since I bought them.

I now face a larger than expected bill which I wasn't anticipating.

[Ali]

Last time I took my 15 Ltr in to Divers Warehouse it needed shot blasting. I've only filled it at DW and all the time with 40%. It never went in for a fill with less than 30 bar in it (no need DW have a Haskle pump) I know the air is well clean at DW it goes through loads of filters.
But the tank went went elsewhere for the Hydro/Vis forget which how about yours.
It's another £12 for shot blast isn't it? times a lot of tanks is a lot of money!

[Dyson Diver]

fraid they only need to be empty once , and have the ambient air in them , go from a warm to cold environment , or weather change suddendly , and thats it . condensation. sorry , but thats it really.

[copperband]

I took mine to Aqualogistics in Stockport for an o2 clean, they also found rust in the cylinders but still charged me the quoted £52. Nice one Geoff.

Can emptying the cylinders too quickly, thus cooling the cylinder(s) allow moisture to form on the inside if the valve isn't closed once empty?

And this bit might cause a ruck but shutting down the valve during a shutdown drill, then breathing the reg down, allow for the possibility of small amounts to make their way back into the cylinders? I can't see it, so just asking.

edit: Just seen Dysons reply about the moisture thing as well.

[Dyson Diver]

i think that draining them down totally to do a partial pressure fill of nitrox if its done too quickly isnt a good thing , we allways try to leave a few lbs of gas in , and as such keep an eye on them while draining , if gas is coming out of the valve ,,,, none is getting in. but as mentioned else where it dosnt take much to start rust ,,, a damp end on a filling whip , dropped into the water bath and not blown through ,,, rain or worse sea water in the pillar valve ,, not blown out , if theres no pressure in the tank , opening the valve to start a fill wont blow anything out of the top part of the valve before the compressor starts to blow in whatever is there ,, all just worthy of remembering. if you drain tanks down tape the pillar valve once its clean and dry , beware of the frost that forms if you drain them too fast .

[Leg Of Salmon]

Why would dropping the pressure quickly allown frost to form on the inside of the tank? Isn't the air in there dry to begin with?

[don]

Am I the only person who takes the tank valve off to have a quick look myself before sending them in for an inspection?

I'm not suggesting for a moment that a shop might find non existant rust but it only takes a minute to undo the valve and have a look for yourself.

[Fiona]

Just to be clear the set has never been emptied except for once in Poole at the end of April, my LDS don't need to empty them to refill, they have rarely had less than 100bar in them.