Helium Question

[Bardo]

Originally Posted by Garf

cheers mark, you are spot on, my mistake

Thanks for the info everyone.

With a single bottle of helium? Simple answer - forget it. What you want is more than one bottle - three being the optimal number - so you can 'cascade' the gas. Makes the whole set up far more efficient...

[G man]

i think the easyest way is to find the ammount of He in a J in Litres.
50x200 = 10,000

and the amount of Litres in a 45 bar fill of twin 12's 12 x 2 x 45 = 1080l

then assuming the twinset is empty after each use you would get

1) 10,000 - 1080 = 8920 (8920 / 50 = 178 bar left in J)
2) 8920 - 1080 = 7830 (7830 / 50 = 156.6 bar in J)
3) 7830 - 1080 = 6760 (135 bar left in J)
4) 6760 - 1080 = 5680 (113.6 bar left in j)
5) 5680 - 1080 = 4600 (92bar left in J)
6) 4600 - 1080 = 3520(70 bar left in J)
7) 3520 - 1080 = 2240(44.8 bar left in J)

pressure after 7 fills would be equal on J and the twinset so 7 fills given that the twinset is empty before each fill.

G.

[Mark Chase]

Originally Posted by Richie

Mark, why would this be a problem / waste of time?
Cheers
Richard

I am told Helium has a habit of screwing up pumps due to over heating. I know for a fact (because its happened to me) it can blow past the seals on the cheep boosters (like my mini booster) I can pump he to 140bar max then it blows past the seals. Same pump same seals i can pump 02 to 250 bar no problem.

The "waste of time" bit if for gas driven booster pumps. Once the supply gas gets down to below 50bar its takes so much gas to boost the 50 bar up to anything usable its not worth it. The first stage driving the mini booster turns into a block of ice the pump gets hot and I have got through 11ltrs of drive gas just trying to fill a 3ltr cylinder

Seeing as i can get Helium fills in the J which are charged by the ltr not by the fill, there is no pint trying to scavenge the last 50 bar. Frankly i get a refill at around 70bar.

ATB

Mark Chase

[Mark Chase]

Originally Posted by Garf

cheers mark, you are spot on, my mistake

Thanks for the info everyone.

A bit more to think about.

You can get premix from Kevin the Gas at 300bar in the 50ltr Js Running a cascade of three for this and using a booster pump is a good plan as you can top off part used tanks with ease and cut out the dive shop altogether.

Allow £1000 for the mini booster and hoses gauges etc.

Then get all three of your buddies to chip in for a cascade of three Trimix and a cascade of three 02 and a 10bar drive pump.

£2000 should cover it


I looked at the numbers for home fills on OC and I couldent justifie it. On CCR it makes sense. 1 J of 1845 would last me well over a years diving. Ill use about 150ltrs of gas on a dive so id get about 100fills out of a 300bar J.

ATB

Mark Chase

[milldog]

I have 3 J's of helium in the garage and they are all 250bar

[Richie]

Originally Posted by Mark Chase

I am told Helium has a habit of screwing up pumps due to over heating. I know for a fact (because its happened to me) it can blow past the seals on the cheep boosters (like my mini booster) I can pump he to 140bar max then it blows past the seals. Same pump same seals i can pump 02 to 250 bar no problem.

The "waste of time" bit if for gas driven booster pumps. Once the supply gas gets down to below 50bar its takes so much gas to boost the 50 bar up to anything usable its not worth it. The first stage driving the mini booster turns into a block of ice the pump gets hot and I have got through 11ltrs of drive gas just trying to fill a 3ltr cylinder

Seeing as i can get Helium fills in the J which are charged by the ltr not by the fill, there is no pint trying to scavenge the last 50 bar. Frankly i get a refill at around 70bar.

ATB

Mark Chase

Thanks Mark.