Tank to tank fill?

[rx7diver]

My question is that I don’t want to leave my tanks empty to long after an inspection and getting them filled right away isn’t always an option. My idea is to use what I believe to be called a whip and add air from a full tank to a empty tank. Has it does anyone currently do this?

Absolutely! Personally, I consider a tank equalizing whip to be an (almost-) essential part of your diving gear--right up there with your save-a-dive kit. It has many uses. For example, are you and your buddy diving similar tanks, and about to do a recreational repetitive dive? Then if you equalize your tank with your buddy's, dive planning for that repetitive dive is made so much simpler.

I purchased my very simple, inexpensive, equalizing whip many, many years ago (maybe 1994) from Northeast, iirc. If I were to purchase one now, I would choose to have DIN ends (instead of A-clamp ends), and I would add a pressure gauge (for maximum flexibility).

Gotta go. I took the day off. So, of course, I'm playing with scuba gear. I'm about to change out the K-valve on my steel 72 for a Y-valve (for winter diving). This means eventually using my equalizing whip for putting some air back into the 72 once the Y-valve is in place.

rx7diver

 

[AhoyFed]

Is there a mathematical formula for knowing how much gas you can transfill from tank to tank? Like if you had a 3442 steel 100 and wanted to top off a LP72 at 2450 to 2800. How would one go about that?

AhoyFed

 

[rob.mwpropane]

Is there a mathematical formula for knowing how much gas you can transfill from tank to tank? Like if you had a 3442 steel 100 and wanted to top off a LP72 at 2450 to 2800. How would one go about that?

AhoyFed

Why yes there is!;

Gas Planning

Scroll down the page you'll see it. If doing doubles always better to do one at a time with the isolator turned off.

 

[rx7diver]

Is there a mathematical formula for knowing how much gas you can transfill from tank to tank? Like if you had a 3442 steel 100 and wanted to top off a LP72 at 2450 to 2800. How would one go about that?

AhoyFed

Well, you don't need no stinkin' mathematical formula! Um, other than

1. Boye's Law (here, P1V1 = P2V2), which will give you the nominal interval volume of a given scuba cylinder; and

2. Simple proportions (here, for example, using a steel 72 that you want to top up from its current 500 psig: x / 1,975 psig = 71.2 ft^3 / 2,475 psig).

It really doesn't need to be any more "complicated" than this. (For example, you do NOT need to know about yielding a particular EANx or Tri-Mix mix simply to top off a cylinder with the same gas.)

rx7diver

 

[rob.mwpropane]

Well, you don't need no stinkin' mathematical formula! Um, other than

1. Boye's Law (here, P1V1 = P2V2), which will give you the nominal interval volume of a given scuba cylinder; and

2. Simple proportions (here, for example, using a steel 72 that you want to top up from its current 500 psig: x / 1,975 psig = 71.2 ft^3 / 2,475 psig).

It really doesn't need to be any more "complicated" than this. (For example, you do NOT need to know about yielding a particular EANx or Tri-Mix mix simply to top off a cylinder with the same gas.)

rx7diver

I know I am forever dumber for using the calculator... but it just works and I can think about other stuff. I get the math, I just don't want to work it out every time

 

[JahJahwarrior]

I think that's the first time I've seen my calculator shared by someone else Made my day Rob, thank you!

I really enjoy thinking through things, but math is not my strong suit and I don't care to do it every time. I think it's important to understand the principles so you can make sure your answers are in the ballpark, but one of the ways to keep people doing something is to make it easy. Same thing with checklists, they have to be easy or else people discard them.

Anytime someone has given me a calculation question, I have tried to take the time to build the calculator for it so I can answer it faster in the future.

The piranha fill whip is dirt cheap and my own old cheap one, made out of high pressure paint spraying hose, finally bit the dust. I give DGX as much business as I can but for something like this I'd go cheap. The only advantage of the gauge is if you want to stop filling before they equalize, or if you wanted to confirm the pressure of the receiving tank because you don't trust my calculator, or you don't want to wait to put on your regulator. If you have a tank checker and aren't worried about the small time it takes to swap, you can save the extra money for the gauge. But I do think a gauge would be nice.

 

[Coztick]

By using Couv's rig, you can have an spg on the bottle being filled.
A needle valve added to the line between regs would allow for precise control over the fill.
***CAUTION***
At this point you are the only control in place to avoid over pressuring the tank being filled from a source that exceeds the rating of the tank.
A needle valve will allow precision in the flow rate and the spg will give tank pressure. DO NOT leave unattended if the possibility of over pressure exists!

 

[rob.mwpropane]

I think that's the first time I've seen my calculator shared by someone else Made my day Rob, thank you!

I really enjoy thinking through things, but math is not my strong suit and I don't care to do it every time. I think it's important to understand the principles so you can make sure your answers are in the ballpark, but one of the ways to keep people doing something is to make it easy. Same thing with checklists, they have to be easy or else people discard them.

Anytime someone has given me a calculation question, I have tried to take the time to build the calculator for it so I can answer it faster in the future.

The piranha fill whip is dirt cheap and my own old cheap one, made out of high pressure paint spraying hose, finally bit the dust. I give DGX as much business as I can but for something like this I'd go cheap. The only advantage of the gauge is if you want to stop filling before they equalize, or if you wanted to confirm the pressure of the receiving tank because you don't trust my calculator, or you don't want to wait to put on your regulator. If you have a tank checker and aren't worried about the small time it takes to swap, you can save the extra money for the gauge. But I do think a gauge would be nice.

No Sir, thank YOU for the calculator I'm not the only one that uses it, as a matter of fact it was shared to me but a couple wreck divers out of NJ and PA that dive way more than me... They and I think it's awesome.

As far as the gauge goes, I like having a gauge. It's not really needed, but it's nice to know where things are. I bought my tank checker and whip both used on SB, I think total for shipping and everything was ~ $110. I use both. I always thought that just throwing a valve on the whip would be nice. Tank checker and whip in one, but JUST the valve was ~ $60, so when I saw a checker brand new for $45 or whatever it was I jumped on it.

 

[Bowers]

This method is cool, however the only place I can see it being viable is at the house or in the back of a vehicle. I like that my whip stays in my bag, easy to use. Bleeder built in...no issues on a boat, and I bought mine used for $70 shipped from a SB member. Rocking on a boat and removing spg's from 2 different regulators....I would for sure envy the guy standing next to me having a whip (I would most likely ask to borrow it!).

I like @couv thinking outside the box....definitely would work in a pinch. I guess it just depends on the end goal.

I have a spare hp hose with a fitting in it as described in the $2.50 method. This way I do not remove the spg. I just take out the second hp plug in each first stage and screw in my adapter. An allen wrench and maybe a crescent wrench (if orings are hard), and about 30 seconds is all you need to instal it.

 

[rx7diver]

Hmmm. What could be simpler/easier than what's pictured here? Backstory: I was draining down my HP 80's to take them in for their hydroes. Got distracted, and allowed them to drain empty. So, of course, I had to grab another cylinder (here, my OMS/Faber LP 66) in order to put back into each HP 80 a couple hundred psi. (Note: I had to use a 300 Br DIN adapter on the HP 80's because my equalizing whip has A-clamps on both ends.)

ETA: I actually keep my equalizing whip in my gear bag. So, the whip goes on the boat with the rest of my gear (if a boat is involved).

rx7diver