Trans fill questions

[PriusDrIVER]

I am not sure this is the right place or not, since I'm not looking to do mixes at this point...but then, I wasn't sure if there was anyplace that was a better fit.

I am curious as to what the efficiency is of trans filling between cylinders. If you use a HP100 at 3500psi, how many 13cf fills could you get to 3000psi? How about 14cf fills to 2015? I wasn't sure where to find this info, or how to search for it.

What is required for trans fill? Just a whip that has DIN on each end, pressure guage and pressure release in the middle? Is using the source cylinder valve enough to control gas flow? Would you be able to use the same whip for argon and pre-blended nitrox?
Is the item that LP carries a decent price http://www.amazon.com/o/ASIN/B0000DYNY0/ref=s9_asin_image_1/102-7903226-8065731, how much would be saved by self assemble?

Thanks for any info, or if there is somewhere else I should look please point me in the right direction.

 

[Mark Vlahos]

An HP 100 that has a rated pressure of 3500 PSI will contain 100 cubic feet of air. That same cylinder at 3000 PSI will only contain 86 cubic feet of air. This means that if your destination cylinder was empty you would get ONE fill. 100 - 13 = 87. Pretty simple and straight forward math. If you were to only fill the same destination cylinder to 2015 PSI it would only have 9 cubic feet of gas in it so you could get ONE fill to 2015 PSI and your second fill, if you stopped when your HP 100 reached 3000 PSI would give you about 5 cubic feet of gas and you would need to stop the fill when the destination cylinder only had about 1100 PSI.

I hope this answers your question.

Mark Vlahos

 

[ppo2_diver]

I've got two transfill whips if you need one. One has a 4' hose, the other 6'. Both whips are serviced for O2.

 

[PriusDrIVER]

Mark, thanks. I was actually comparing a 13cf with working pressure of 3000psi and a 14cf with 2015psi working pressure. Figuring that the lower PSI is easier to achieve and would result in more fills from the source cylinder.

I wasn't sure if it was as simple as doing the obvious math. Let me make sure i get this right. Its easy with a 100cf cylinder, because each cf is 1% of volume...does this directly correspond to 1% of pressure also?

100cf - 14cf = 87cf remaining
3500psi - 14% = 3010psi

87cf - 14cf = 73cf remaining
3010 - 14% (of 3500) = 2520psi

73cf - 14cf = 59cf remaining
2520 - 14% (of 3500) = 2030psi

If that is correct, then I could get 3 14cf 2015psi fills from a single 100cf cylinder. I just think I am doing the math wrong, I know there is a margin of error that isn't included, such as the volume of gas lost in the whip to release pressure, etc. This also doesn't factor in that the 14cf cylinder wouldn't be starting at 0psi/0cf contents.

 

[Mark Vlahos]

I tried to post the following message right after my first, but my internet connection died, sorry...




I did not fully answer the question in my first post...

My first post example was that of the same 13 cubic foot cylinder

If you had a 14 cubic foot cylinder that was full at 2015 PSI you would be looking at only ONE fill since you need to stop when the HP 100 reaches 3000 PSI and 100 - 14 = 86, see the math in my first post.

The key to the answer is that you are starting with 100 cubic feet of gas, and you want to take away either 13 or 14 cubic feet of gas, and you are not willing to take the HP 100 below 3000 PSI so the HP 100 will have about 86 cubic feet of gas when the transfer is finished.

Don't let the pressures fool you, you are talking about cubic feet of gas, nothing more. You start with 100 cubic feet at 3500 PSI, and you end up with 86 cubic feet when that HP 100 gets down to 3000 PSI, you only have 14 cubic feet of gas to work with.

Mark Vlahos

 

[PriusDrIVER]

Ahh, stupid internet tubes on the fritz again. I think my original question was phrased poorly which is where the 3000psi is coming from. I was thinking it may be more cost effective to have fewer pony bottles and use some of the larger cylinders I already have. I currently have several 100cf 3500psi and a single 80cf 3500psi cylinder, I was thinking I could just use 1 of the 100cf cylinders to fill the pony between dives.

The pony options I was looking at was 13cf/3000psi working pressure and 14cf/2015psi working pressure. I see the advantage being in the 14cf at this time, due to the lower working pressure...it would allow me to get more fills out of a 100cf cylinder. Though a single fill out of a 100cf may not be bad, that would leave enough gas for me to dive with most of my buddies that use 80s and guarantee a full pony at the start of the dive.

Perhaps I am just thinking about this wrong entirely.

 

[JeffG]

Perhaps I am just thinking about this wrong entirely.

Why is your pony empty?

 

[PriusDrIVER]

I knew that would come up. Its complicated to type out and won't be my true "pony"/RBS.

 

[JeffG]

Its complicated to type out and won't be my true "pony"

Ok...LOL

 

[Mark Vlahos]

Ahh, stupid internet tubes on the fritz again. I think my original question was phrased poorly which is where the 3000psi is coming from. I was thinking it may be more cost effective to have fewer pony bottles and use some of the larger cylinders I already have. I currently have several 100cf 3500psi and a single 80cf 3500psi cylinder, I was thinking I could just use 1 of the 100cf cylinders to fill the pony between dives.

The pony options I was looking at was 13cf/3000psi working pressure and 14cf/2015psi working pressure. I see the advantage being in the 14cf at this time, due to the lower working pressure...it would allow me to get more fills out of a 100cf cylinder. Though a single fill out of a 100cf may not be bad, that would leave enough gas for me to dive with most of my buddies that use 80s and guarantee a full pony at the start of the dive.

Perhaps I am just thinking about this wrong entirely.

The lower working pressure destination cylinder will give you a few more options, but it is still the same basic size 13 or 14 cubic feet. If you get that pony you will need to be pretty careful when you trans fill it. Frankly you will need to be pretty careful when you fill either one.

You will rarely completely empty a pony so you are more likely to only need to top off the cylinder. In that case I would encourage you to think bigger. Look at a 30 or 40 cubic foot aluminum cylinder that will provide plenty of gas even if you let the pressure drop to only half of its intended fill pressure. That way you can go for a while between fills, and when you do, just have the shop that fills your back gas fill your pony. You will still need to keep and eye on the pony to make sure it has more than enough gas to get you out of whatever problem you might find yourself in.

Lots of options, good luck.

Mark Vlahos