YD Scuba Diving Forums banner
1 - 16 of 16 Posts

·
A short fat well off crap cave diver. Likes wrecks
Joined
·
15,343 Posts
50ltr 300bar HE J about 10-11 fills, Id cost on 10.

With a booster?? thats not particularly rlevent as by the time the J gets down to 50 bar its not worth boosting. However asuming a limitles supply of cheep drive gas, then about two more fills.

Booster comes in for tops and possably 02. You dont want to run He through the booster if you can help it.

ATB

Mark Chase
 

·
His Holeyness
Joined
·
2,198 Posts
45bar * 2x12 = 1080 ltrs means a 23 bar drop in the J (X47) so

assume starting at 200bar
1/ 200 - 23 = 177
2/ 177 - 23 = 154
3/ 154 - 23 = 131
4 / 131 - 23 = 108
5/ 108 - 23 = 85
6/ 85 - 23 = 62

now you can't put 45 bar in the 12s 'cos there not enough pressure in the J.
 

·
Driving my truck with my high-heels on...
Joined
·
5,509 Posts
by my reckoning with a booster pump :-
you have a 50L "J" @ 200bar = 10000L of gas
twin 12 @ 45bar =24x 45 = 1080L of gas for each fill
therefore 10000 divided by 1080 = 9.25 fills .
I think thats right if not then I would be interested to know the correct workings ! :redface:
 

·
A short fat well off crap cave diver. Likes wrecks
Joined
·
15,343 Posts
Simple question, I hope. Need two answers...

How many fills of 45 bar-ish in a set of twin 12s could I get from a single J of helium without, and then with a booster. Forget cascading or anything else, just curious about a single cylinder.

Cheers

G


Do you meen 45 bar or do you meen a fill for 18/45? Coz I think thats about 105bar of He if you do. In which case its about 4 fills and a booster will get 5

ATB

Mark Chase
 

·
Nigel Hewitt
Joined
·
7,142 Posts
Booster comes in for tops and possably 02. You dont want to run He through the booster if you can help it.
Huh?
I boost everything so I always dive on full.

Even argon into the suit bottle.
 

·
Registered
Joined
·
20 Posts
I got 3 * 21/35 fills out a J and the last one was slighty weak when i did it last year. So you would only get 2 18/45 fills without cascading.

Ian
 

·
Registered
Joined
·
4,060 Posts
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...
 

·
Now a Silent Warrior
Joined
·
1,447 Posts
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.
 

·
A short fat well off crap cave diver. Likes wrecks
Joined
·
15,343 Posts
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
 
  • Like
Reactions: 1138

·
A short fat well off crap cave diver. Likes wrecks
Joined
·
15,343 Posts
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 :D


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
 

·
Utrinque Paratus
Joined
·
6,077 Posts
I have 3 J's of helium in the garage and they are all 250bar :)
 

·
Dunno really........ thinking about it
Joined
·
1,585 Posts
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.
 
1 - 16 of 16 Posts
Top