# How long will this O2 tank last?



## Sassafras (Sep 26, 2010)

On long distance rn patient refused o2 at origin but stating low now. Put on NR because he does not like NC in nose and was able to get him to 10 per minute before he started complaining. Patient hospice dnr so he's very clear about what interventions he wants. However main o2 at 700 when we started trip. How long will it last before I need to switch to back up tanks of O2 if I have hi
e at 10 and how will I know if it's run out?


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## Shishkabob (Sep 26, 2010)

If only there was some sort of math equation they taught in EMT school to help with such a scenario...  



Multiply coefficient by current pressure in psi, then divide this product by litre/minute flowrate

The coefficinet for the the various tanks are:

D cylinder = 0.18
E cylinder = 0.21
M cylinder = 1.5

(stolen from another source as I suck at math...Then again I take the easy way out and use the main big tank on the truck, which I make sure is full at the start of a shift. )


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## Sassafras (Sep 26, 2010)

Since most of our transports are local we are supposed to drain the main before changing it.


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## Sassafras (Sep 26, 2010)

Well he refused to keep it on so I ended up not having to worry about it. We never got the formula in emt class but I knew there had to be one. I learned alot on this run and ended up with more questions. I will type up the scenerio after I get home to pick your brai s some more.


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## MSDeltaFlt (Sep 26, 2010)

Sassafras said:


> On long distance rn patient refused o2 at origin but stating low now. Put on NR because he does not like NC in nose and was able to get him to *10 per minute* before he started complaining. Patient hospice dnr so he's very clear about what interventions he wants. *However main o2 at 700 when we started trip*. How long will it last before I need to switch to back up tanks of O2 if I have hi
> e at 10 and how will I know if it's run out?


 
You multiply the tank factor times your psi and devide that by your liters per minute and you'll get how many minutes that tank will last.

1.56 x 700/10 = 109.2 minutes which equals out to be 1.82hrs.  That's a little less than 2 hrs to completely empty.



Linuss said:


> If only there was some sort of math equation they taught in EMT school to help with such a scenario...
> 
> 
> 
> ...


 
Not quite.

D cylinder = 0.16
E cylinder = 0.28
M cylinder = 1.56
H cylinder = 3.14



Sassafras said:


> *Since most of our transports are local we are supposed to drain the main before changing it*.


 
No you're not.  If a tank is bled dry, it will need to be static tested before it is refilled.  Most regulators have a red zone beginning around 500psi.  So basically you'll have a working psi of 500 less than you are showing.  So let's rework that above formula.

1.56 x 200/10 = 31.2  You have a little over a half an hour on that tank.


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## Sassafras (Sep 27, 2010)

Some one needs to explain that to the peeps that did my orientation then.


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## Sam Adams (Sep 27, 2010)

MSDeltaFlt said:


> Most regulators have a red zone beginning around 500psi.  So basically you'll have a working psi of 500 less than you are showing.  So let's rework that above formula.
> 
> 1.56 x 200/10 = 31.2  You have a little over a half an hour on that tank.



Also don't forget that tanks are considered empty at 200 psi. It's called the safe residual pressure. So even if you don't change the tank at 500 psi, you've only got 300 psi to work with, in this case 500 psi.


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## akflightmedic (Sep 27, 2010)

And when all else fails...

I have an iPhone ap that calculates for me.


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## JPINFV (Sep 27, 2010)

Sassafras said:


> Some one needs to explain that to the peeps that did my orientation then.



You mean there might be more to running a cascade system past,


1. Connect portable
2. Open portable
3. Open tank 1
4. wait for hissing to stop, 
5. Close tank.
6. Repeat steps 3-5 for tanks 2, 3, and 4.
7. Close portable.
8. Disconnect portable
?


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## gary1969 (Sep 27, 2010)

*Said Hi to Dorathy for me ! Now O2*

I think that is way too much O2 for the situation, however I was not their so I will just leave it at that. Just remember O2 is not always needed and should be used with discression.

I have never heard of O2 getting too old, albeit we went through a lot of it everyday, maybe 3-4 main tanks a week. I would refer this question to your supplier. As for a formula how long a certain size tank will last at a given delevery rate ? Ya got me. Ask your supplier. I would like to know also.

Best of Luck


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## Sassafras (Sep 27, 2010)

Well, considering when he removed and refused the O2 he went hypoxic and started rapidly going down hill, I think I made the right decision and actually ended up giving him more being he dropped into the 60% for saturation and became VERY confused.  I am happy to report, he did not remain at 60% though and the confusion resolved.


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## MSDeltaFlt (Sep 27, 2010)

Well oxygen's kinda like milk and Brylcreem.  It does a body good and sometimes a little dab'll do ya.


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## gary1969 (Sep 27, 2010)

Great Observation Mike !


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## socalmedic (Sep 28, 2010)

MSDeltaFlt said:


> Y
> No you're not.  If a tank is bled dry, it will need to be static tested before it is refilled.  Most regulators have a red zone beginning around 500psi.  So basically you'll have a working psi of 500 less than you are showing.  So let's rework that above formula.



tanks only need to be tested every 5 years (3 years for composite cylinders). over testing can cause failure as they are tested to 7/5ths their working pressure (3000psi) which causes fatigue. you can bleed them down all the way and use everything that you paid for. the red zone on the gauge is like the red zone on your cars gas gauge, just to let you know you are getting low. and the term is hydrostatic test, the 5 year limit is for any pressurized cylinder that will be carried on a vehicle (DOT guideline), in a fixed location it is 6 years for aluminum/steal.


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## mycrofft (Sep 29, 2010)

*Linus, your post and some others here show me there's hope yet for EMTLIFE*

(Don't get cocky).

No, I'm not back.h34r:


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## bubbasheeko (Sep 29, 2010)

Definitely a great post!  Tanks always getting me confused :wacko:


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