Help Inert Gas Volume

[James28if]

Victor Flow Meter arived today. its got setting for Argon, CO2, Helium. theres no N2 flow setting. is there a conversion i can use?

 

[TiredHorse]

I use the argon scale straight across on my Harbor Freight model. Not very scientific, but I'm not doing precision welding, and a 15LPM flow rate is pretty forgiving. Maybe someone will chime in with a conversion factor?

 

[color_me_gone]

Flow rate conversion factors:
https://engineering.dartmouth.edu/microeng/equipment/RTA/gas.calibration.html
The table compares nitrogen to various gasses, so use the reciprocal of the argon value to arrive at nitrogen flow rate.

 

[Hush Sweet Charlotte]

I was wondering the same as my flowmeter is for argon. My maths skills are utterly lame, so how do you work out what the nitrogen flow rate should be? I saw this conversion table before but was sadly none the wiser.

I know argon is denser, so if you want 20 lpm does that mean you should put it a little higher, like 25 lpm?

 

[color_me_gone]

@Hush Sweet Charlotte :
liters/minute:
Argon___actual
scale:___nitrogen flow:
21_______14.6
22_______15.2
23_______15.9
24_______16.6
25_______17.3
26_______17.0
27_______18.7
28_______19.4
29_______20.1

 

[Hush Sweet Charlotte]

Good grief, thanks so much for that color me gone. That's much more of a difference than I thought it was. In Five Last Acts it says an argon flow meter is fine to use for nitrogen, but if you set it at 15lpm you would not have the recommended flow to push out the CO2. Curse the devil-may-care attitude of these books. You're a lifesaver (not literally:).

Do you think that may have had a role in your failures Tired Horse, or did you set the flow a bit higher to compensate? Sorry to pry, just wondering.

 

[color_me_gone]

Sorry to pry, just wondering.

I was actually surprised at the big difference myself.
And I too, wondered about @TiredHorse
The flow rates between helium and argon are almost identical, but BIG difference between them and nitrogen.

 

[Hush Sweet Charlotte]

If the flow rate is too low it probably wouldn't cause a hypercapnic alarm response as that seems to take longer to trigger, but it might not flush all the air out as fully or quickly as needed - which could slow down the time to unconsciousness.

 

[color_me_gone]

What is interesting is the flow rate must not be related to the density of the gas, because argon is the heaviest, and helium the lightest, yet they have nearly identical flow rates. Nitrogen falls between them, yet has a major flow rate difference. Wonder why?

 

[Hush Sweet Charlotte]

I was actually surprised at the big difference myself.
And I too, wondered about @TiredHorse
The flow rates between helium and argon are almost identical, but BIG difference between them and nitrogen.

That doesn't make sense as helium is so much lighter than argon. How could the flow rate be the same for helium and argon? I'm wondering about how accurate this dartmouth page is.

 

[color_me_gone]

Ok, so I found this:
https://www.physicsforums.com/threads/finding-flow-rates-for-different-gases.684183/
which basically states that a person found different formulas for different flow meters.
He questioned why, but his question was never answered.

 

[Hush Sweet Charlotte]

Gahhhh! I thought I'd seen a conversion table before where the difference in flow between helium and the other gases was sizeable. Mine is a finger type one with a floating ball. I asked the company BOC what the conversion rate was before but they never got back to me. Either they didn't know or I was arousing suspicion by asking.

 

[color_me_gone]

@Hush Sweet Charlotte
So unless you know what the conversion rate is for your particular flow meter, and if your meter is not marked for nitrogen, seems like you are pretty much hosed. From that question thread I gave above, those rates were all over the place. Definitely not a vote of confidence.

 

[James28if]

Color Me Gone... should we use the Argon flow scale btw 23 to 29 to equal 15 to 20 for N2?

 

[color_me_gone]

should we use

Nop, seems it is specific to the flowmeter.
If you look at the physicsforums link I provided, a guy was questioning the fact that 4 different companies gave four different sets of conversion factors, which, in some cases, varied widely between them.
So it remains a mystery.
I would NOT assume those values I gave to work for just any meter.
The answer would be, either buy a flow meter designed specifically for the gas you are using,
or use a conversion factor given specifically by the manufacturer of the flow meter you are using.

Sorry, it just sucks!

 

[TiredHorse]

Do you think that may have had a role in your failures Tired Horse, or did you set the flow a bit higher to compensate? Sorry to pry, just wondering.

WHEW! That's a much greater difference than I would have expected! I think I set the flow a bit higher, just to err on the side of caution, but not as high as 22 LPM. Maybe 17 or 18?

However, I'm not sure that flow difference was what stymied me. I say that because I had done a couple dry runs with the bag over my head, no gas flowing, just breathing from the air trapped in the bag (bag not balloon-inflated, just pulled down over my head), waiting for the air to run out and hypercapnic alarm to set in. It took much longer for hypercapnic alarm to set in with a static-volume air-only bag than it took for me to freak out with a steady (if lower than ideal)(maybe?) flow of N2 inflating the bag.

With even the reduced flow of N2 flushing away a portion of the identical tidal volume of CO2, and the flow of N2 being adequate to keep the bag inflated away from my face (the dry runs did not have this volume), I would expect hypercapnic alarm to be significantly delayed compared to the static-volume dry run.

It also felt different from hypercapnic alarm. I wish I could describe the differences for you all, but I can't find the words.

Additionally, I did get greying out around the edges of my vision, which implies to me that I was on the edge of blacking out. The N2 was taking effect, but not fast enough to outpace my survival instinct. I suspect my delayed onset of unconsciousness was much more a factor of my very shallow stress-breathing than of inadequate gas flow.

However... Thank you, @color_me_gone, for an excellent bit of research, and a very appropriate caution that flow rates are unlikely to be the same, N2 vs. Ar --and that your regulator/flowmeter will be what makes the difference (ain't that a damned nuisance!). Kudos to you!

 

[James28if]

Harris® Model 335-2N2/Air-580 Heavy Duty Air Or Nitrogen Calibration Single Stage Flowmeter Regulator, CGA-580
Airgas Part #:HCL3100207

Harris Calorific

Manufacturer #:3100207

Log in to get your price
$214.23 /Each


N2 flow meters are hard to come by with the 580 connection. i'm sending my Victor back and going to get this Harris 335-2N2

 

[color_me_gone]

N2 flow meters are hard to come by with the 580 connection. i'm sending my Victor back and going to get this Harris 335-2N2

I think that is a wise choice, considering the ambiguity of it all.
Nothing better than buying something that absolutely fits the application,
especially considering the criticality of this application.

 

[James28if]

if there's a better N2 Flow Meter then the Harris 335 please LMK

I think that is a wise choice, considering the ambiguity of it all.
Nothing better than buying something that absolutely fits the application,
especially considering the criticality of this application.

thanks Color Me Gone

 

[TiredHorse]

N2 flow meters are hard to come by with the 580 connection. i'm sending my Victor back and going to get this Harris 335-2N2

I know it's a lot of cash to keep tied up, but it might be interesting to keep the Victor for the moment, order the Harris, and when it arrives hook the Victor and the Harris in line and see how they differ.

I suspect that when the time comes I'll just tweak my flowmeter's setting up a couple LPM, but it would undoubtedly be better to get a dedicated N2 regulator.

Or maybe this is the sign I'm waiting for that I should stop waffling and use a gun...

 

[James28if]

TiredHorse... please use the N2 method. guns are too violent and i hope you do it peacefully which you deserve for all the help you give.

 

[TiredHorse]

TiredHorse... please use the N2 method. guns are too violent and i hope you do it peacefully which you deserve for all the help you give.

You're very kind. I haven't decided even if I'm heading back to the bus stop, let alone what method I'll use once I get there. I'm very uncertain, very tired, very unhappy; recovery is an uphill slog, at best. Each method has a lot going for it, and I suspect which I use will be a matter to decide on when the moment is upon me --but I will bear your words in mind.

 

[color_me_gone]

stop waffling and use a gun

A gun does have its advantages.
If I were to do it in an old car far away from home, as I plan to do with gas,
the car would contain the mess, and sold for scrap after, without cleanup.
Sawed off shotgun with 00 buck leave little to worry about aiming for brainstem.

 

[Hush Sweet Charlotte]

Additionally, I did get greying out around the edges of my vision, which implies to me that I was on the edge of blacking out. The N2 was taking effect, but not fast enough to outpace my survival instinct. I suspect my delayed onset of unconsciousness was much more a factor of my very shallow stress-breathing than of inadequate gas flow.

Although the gas flow wouldn't have been low enough to trigger a hypercapnic response, the gas still needs to flush out residual air from the bag. Scrunching it up won't get quite all the air out, then there's some air that's bound to get in when pulling the bag down over your head. Also the gas needs to quickly fill the space taken up by the upper part of your head before you pull the bag down. I'm just wondering if your time to unconsciousness might have been delayed by having a little too much residual oxygen in the bag due to a slightly low gas flow, creating more time to experience panic and alarm. Although given you experienced the sound of the gas as surprisingly loud, it can't have been that low - so maybe not!

Nop, seems it is specific to the flowmeter.
If you look at the physicsforums link I provided, a guy was questioning the fact that 4 different companies gave four different sets of conversion factors, which, in some cases, varied widely between them.
So it remains a mystery.
I would NOT assume those values I gave to work for just any meter.
The answer would be, either buy a flow meter designed specifically for the gas you are using,
or use a conversion factor given specifically by the manufacturer of the flow meter you are using.

Sorry, it just sucks!

Thanks so much for finding this out and totally solving the mystery of the random numbers. This is just in the nick of time as I was paying someone to come out today to fit my regulator, involving a very flimsy excuse for why I have a sizeable gas cylinder in my poky flat. I've cancelled and will order the only regulator I can see in the UK that is made for N2 (unless you go for the Max Dog one of course). It seems lots of folk in the UK will have argon flow meters if they're following Five Last Acts. I'm sure they're fine if you know to set them a bit higher (for the gravity ball type at least - it's anyone's guess for the other types), but nobody in Five Last Acts mentions this, though they mention setting a slightly higher 15-20 lpm flow rate without explaining why. Not really the best time for withholding detail. Anyway, although the argon one is probably fine the N2 one will put my mind at rest more. Thanks.

 

[James28if]

Purchasing N2.... my experience in buying the N2 was to read a quick article on winemaking and N2.... tell the clerks your learning the homemade wine process etc. it works really well. ask if they have any other wine making customers in casual conversation etc. these guys tell me they have some beer customers but no amateur wine makers. i was able to buy N2 from 2 different sources. i'll practice the art and when its time for the bus i'm going to try and get Beverage grade N2 if i can...

 

[ArtVandelay]

Purchasing N2.... my experience in buying the N2 was to read a quick article on winemaking and N2.... tell the clerks your learning the homemade wine process etc. it works really well. ask if they have any other wine making customers in casual conversation etc. these guys tell me they have some beer customers but no amateur wine makers. i was able to buy N2 from 2 different sources. i'll practice the art and when its time for the bus i'm going to try and get Beverage grade N2 if i can...

Is that necessary? There are no laws against the sale of it in the US as far as I know. If they ask I'll just tell them it's for welding and call it a day. There are multiple stores near me so if they give me any trouble I can easily just take my business elsewhere. Or pay a bit more to order it from Cyberweld.

 

[TiredHorse]

Yes, it's legal and unrestricted, but I've found it's always good to have a cover story prepared because as often as not some bored salesman behind the counter asks, "So what's the project?" Most of the time my uses for inert gas have been innocuous --welding, paint shop, pantry-- but of course I got the question when I went in for my 40cf CTB supply.

Excellent cover story, @James28if.

 

[ArtVandelay]

That's a good point. Maybe I'll use James's wine making story. As a cop out I could always say a family member asked me to pick it up for them, so I'm not familiar with the specifics.

 

[Hush Sweet Charlotte]

I went for the wine-making too. Now I know what sparging is. Am teetotal :)

 

[James28if]

i talked to a Mom and pop welding supplies/ gas dealer today about beverage grade N2 compared to industrial grade for amateur winemaking. beverage grade is harder to get hold of and the swapping of cylinders at Air Gas leaves those rental tanks contaminated and he would never use them for wine making. for this place to get beverage grade its to much of a hassle for them, they don't bother. i touched base with TireHorse before on this issue of contamination. to CTB is industrial grade N2 ok? i'd like to cop some beverage grade. i'm going to start looking for that Monday. any thoughts on these issues good folks? I'm thinking most people who've been successful at CTB weren't using beverage grade N2.