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Finless: You couldn't invent him...
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Christmas is coming, so am I (to the point that is) and I am doing Trimix after Christmas.

I am hoping Santa will bring me an O2 analyser - should I be greedy and ask for an O2/He analyser?

Is it necessary to analyse He?

Fast replies would be much appreciated as I am waiting to throw my letter to Santa up the chimney.
 

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<font color='#8D38C9'>i know a couple of people who have he analysers, there expensive but good. Always worth analysing everything. Diveshops make mistakes. I dont own one but wouldnt get a mix off a shop who doesnt have one.
 

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He analysers are really bloody expensive & I have to say I don't feel it's necessary to blow all that dosh.
As long you put a known quantity of all the relevant gases in an empty bottle- if the O2 analysis measures up to your calculations, the He will be correct also.  It gets a bit trickier if you're doing subsequent tops but tables do exist to let you calculate what the projected He component will be after, say, an air,O2 and He top.
The thing with He is a few percent either way is not necessarily as much of a problem as it would be with O2 - you'll be slightly more or less narked depending on the error, but I wouldn't let an error of up to 5% make any difference to my deco obligations for example.
A fresh Heliar/Trimix fill can be calculated to within 1 percent even using a whip if you've got a decent enough guage on it.

I suppose if you thought your LDS was pulling a fast one with your fills it might be handy ..
 

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I personally wouldn't remix a trimix fill more than once or possibly twice if I was fairly sure what it was. The errors are cumulative.
I use heliair rather than trimix for this reason as you can top off ad infinitum with nothing more than an O2 analyser.
 

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You're right, I should have mentioned that. Maximum 2 tops on a trimix fill.  What %  Heliar do you make your first mix though?
 

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It doesn't matter. you can analyse any helium/air mix and do anything you want afterwards to it and still get an accurate mix with an O2 analyser. It is a fixed relationship rather than trimix where you are introducing a third variable.
 

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Finless: You couldn't invent him...
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[b said:
Quote[/b] (Rob Evans @ Nov. 12 2003,14:03)]You're right, I should have mentioned that. Maximum 2 tops on a trimix fill.  What %  Heliar do you make your first mix though?
I don't - I haven't done the course yet!!  


'choo doin scannin the forum -  shouldn you be workin!!!  

I think, on that basis, I will make do with the O2 anlyser.

Rgds
Bryan
 

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[b said:
Quote[/b] ]It doesn't matter. you can analyse any helium/air mix and do anything you want afterwards to it and still get an accurate mix with an O2 analyser. It is a fixed relationship rather than trimix where you are introducing a third variable.
That much is obvious - just wondering what your typical startoff heliar mix is.  I'm thinking it'd have to be a pretty strong (& hypoxic) mix to make it worth doing an air top the second time round and still get the benefit of a bit of He. Presumably for two deeper dives in a row you'd do a fresh mix for each one? Or put a squirt of He in the depleted original heliar & top with air?
 

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[b said:
Quote[/b] (Ben @ Nov. 12 2003,13:22)]I dont own one but wouldnt get a mix off a shop who doesnt have one.
<font color='#0000FF'>Any shop which sells you a nitrox mix should have an analyser for you to use to check the mix was as requested.  If they haven't got one they shouldn't be selling it.

FB
 

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<font color='#8D38C9'>talking more about trimix, I know quite a few big shops that sell it without an analyzer. They just get you to sign something saying you buy without analisying. Helium analysers are fairly new arent they?
 

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Thing is though, He analysers are £625 +.  If I went to a shop for my He I'd rather they didn't spend that sort of money on a not-strictly-necessary bit of kit and pass on the saving to my back pocket in the form of reduced  cost on what is already an expensive gas.
My blending goes on in the garage. The £625+ I've saved on the analyser will pay for lots of He & dives.
 

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The centre where I did my normoxic course had an He analyser, a booster pump and loads of storage tanks. The instructor would analyse the mixes as we went along and squirted in more of each gas as required for the next dive and charged us only for the helium we actually breathed - quite a saving for us.
 

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Finless: You couldn't invent him...
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[b said:
Quote[/b] (Rob Evans @ Nov. 12 2003,14:44)]Thing is though, He analysers are £625 +.
FFS - an O2 analyser it is then. Not even Mummy Santa Clause would buy that for me.
 

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Now that's a nice touch.  Wouldn't have been Deep Blue down in Plymouth would it?
The question is - is this centre (or whoever you used) the exception or the rule? Can you expect this sort of treatment at other He-supplying LDSs?

EDIT:
Actually, tell a lie.  Oxycheq are doing He analysers for around £530 (plus whatever taxes). The combi O2/He set is £625
 

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It was actually a British chap calles Don Shirley who has based himself in South Africa at Komati Springs - a flooded mine with a large open pit section to it. Very good instructor and course was very well priced.
 

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[b said:
Quote[/b] ]just take a breath and guess. Donald duck principle.
Now you're talking! You could hook up a mic to your PC, take a swig of the mix, speak into the mic and have voice-analysis software analyse your He content.  Donald Duck- medium mix. Mickey Mouse-strong mix.
I really must get some bloody work done....
 

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A short fat well off crap cave diver. Likes wrecks
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All my mix fills area garrage fills and my garage man has an He analisor. Surley if he can do it the shop can.

He aparently caught a cirtain shop in Weymouth charging for 16/35 fills that were more like 16/25 fills and was not amused. Neither was the shop owner when he marched in an set up his analiser. Over the 12 twin sets it would have been an overcharge of about £120.00

Aparently this year the frills were spot on  


ATB

Mark Chase
 

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has anyone got a contact tel no for He analysers, having it explained by my gas blender up in scapa this year that top ups are O.k (he still checked HE and O2) if done once and analysing the O2 only,  as the HE deco is not critical to a few percent,im not convinced but thats probably cause i.m new at Trimix , some divers in queensferry only dive heliair toavoid the possible errors
 

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[b said:
Quote[/b] (ianbaker @ Nov. 12 2003,21:39)]has anyone got a contact tel no for He analysers, having it explained by my gas blender up in scapa this year that top ups are O.k (he still checked HE and O2) if done once and analysing the O2 only,  as the HE deco is not critical to a few percent,im not convinced but thats probably cause i.m new at Trimix , some divers in queensferry only dive heliair toavoid the possible errors
Hope these links help...

Helium Analyser

Another link
 
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