Filling Small Buddy Bottles from a Compressor

[Ezana4CE]

I have a small portable carbon-fiber buddy bottle. It is approx 100 cubic inches in volume. I can and have filled it from my Alkin compressor. When filling from empty the bottle became very warm around 150 bar. At that point I shut everything off and let the bottle cool for about 90 minutes before finishing the fill. This is to be expected when filling from empty, but it gets warm when topping it off too. I thought I'd filled it to 305 bar on the last fill. When I went to top off a gun the buddy bottle pressure was around 250 bar. I'm trying to determine the best way to fill this small tank. Would filling a larger tank then topping off the buddy bottle form a larger tank be e better way to fill it? Advice would be appreciated.

 

[AlanMcD]

I have a 500 cc buddy bottle that I use for my target pistol, and I only fill that off of other bigger tanks, but yours is much bigger at about 1600cc. That said, I can see how that size would lead to a very fast fill from an Alkin . . .
I have a splitter that I use to fill two tanks at the same time - that would slow down the fill into your buddy bottle. I use this one and like it, unfortunately it shows out of stock right now . . .

TMAN PCP Tee Block air Splitter – Female Quick-connect to (2) Male Quick-connect Fittings

Use this to cascade more tanks, or to tether multiple air guns together through our Regman for all day shooting

airtanksplus.com

 

[Trucker3573]

That probably would work as you could fill it more slowly off the bigger bottle. I know alkins are designed to fill large bottles and it is probably just filling that 100 cu in bottle a bit too fast. Another thing to try would be to dip the 100 in tank in water when filling it from the alkin to cool it and help alleviate some of the heat. My local dive shop does this when filling.

 

[Ezana4CE]

I have a 500 cc buddy bottle that I use for my target pistol, and I only fill that off of other bigger tanks, but yours is much bigger at about 1600cc. That said, I can see how that size would lead to a very fast fill from an Alkin . . .
I have a splitter that I use to fill two tanks at the same time - that would slow down the fill into your buddy bottle. I use this one and like it, unfortunately it shows out of stock right now . . .

TMAN PCP Tee Block air Splitter – Female Quick-connect to (2) Male Quick-connect Fittings

Use this to cascade more tanks, or to tether multiple air guns together through our Regman for all day shooting

airtanksplus.com

@AlanMcD Thanks. I was considering purchasing one of those. I'm just not a fan of filling tanks from a compressor via a microbore hose. I'm trying to see if there is another way. If you fill using micro bore hoses do you ever notice the hoses getting warm? Do your SCBA tanks ever get warm filling with them?

That probably would work as you could fill it more slowly off the bigger bottle. I know alkins are designed to fill large bottles and it is probably just filling that 100 cu in bottle a bit too fast. Another thing to try would be to dip the 100 in tank in water when filling it from the alkin to cool it and help alleviate some of the heat. My local dive shop does this when filling.

@Trucker3573 I was thinking that it fills that little tank too fast. It filled it quick from empty even though I broke the fill into two sessions. I'll have to look at a few videos of how shops use water as a coolant when filling tanks.

 

[AlanMcD]

I fill with a Shoebox compressor, so heat is never an issue for me - but I get what you are thinking of and can understand the concern. Not sure what advice to give on that . . .

 

[Scotty1]

@AlanMcD Thanks. I was considering purchasing one of those. I'm just not a fan of filling tanks from a compressor via a microbore hose. I'm trying to see if there is another way. If you fill using micro bore hoses do you ever notice the hoses getting warm? Do your SCBA tanks ever get warm filling with them?


@Trucker3573 I was thinking that it fills that little tank too fast. It filled it quick from empty even though I broke the fill into two sessions. I'll have to look at a few videos of how shops use water as a coolant when filling tanks.

I fill from my Alkin using what I believe is a micro bore line (from Airtanks Plus), the line does not get warm, but my SCBA bottles do heat up as they are filled. I will sometimes fill all three, let them cool a bit, then top off again.

 

[Ezana4CE]

I fill from my Alkin using what I believe is a micro bore line (from Airtanks Plus), the line does not get warm, but my SCBA bottles do heat up as they are filled. I will sometimes fill all three, let them cool a bit, then top off again.

@Scotty1 Thanks for your input. I did too off from a larger bottle with a microbore hose between the. It equalized the pressure and stabilized somewhere in the middle.

What really concerns me is the pressure level while the bottle is warm and after it cools. Do you usually let yours cool and then top off? If so, what have you noticed to be a normal amount of pressure to lose in the cooling process?

 

[Scotty1]

@Scotty1 Thanks for your input. I did too off from a larger bottle with a microbore hose between the. It equalized the pressure and stabilized somewhere in the middle.

What really concerns me is the pressure level while the bottle is warm and after it cools. Do you usually let yours cool and then top off? If so, what have you noticed to be a normal amount of pressure to lose in the cooling process?

It kinda depends on my starting pressure. If I start at 3k and fill to 4500 on a 45 minute bottle, I’ll lose at least 30 bar to cooling and more on my 60 minute. What I’ll usually do I’d fill to 290, let them sit for an hour or more, then top off to 4500 psi. My bottles live in my unheated garage, so even more drop in winter.

 

[Ezana4CE]

It kinda depends on my starting pressure. If I start at 3k and fill to 4500 on a 45 minute bottle, I’ll lose at least 30 bar to cooling and more on my 60 minute. What I’ll usually do I’d fill to 290, let them sit for an hour or more, then top off to 4500 psi.

@Scotty1 Now I’m a bit confused. I am asking specifically about the heat associated and pressure loss invoked in cooling when filling a 90 cu in - 100 cu in CF buddy bottle from an Alkin W31 Mariner.

 

[Scotty1]

You also asked if the SCBA bottles heat up, hence my response. Sorry for wasting your time.

 

[Ezana4CE]

You also asked if the SCBA bottles heat up, hence my response. Sorry for wasting your time.

@Scotty1 Not a waste of time. I see where the confusion came in. It sounds like the larger tanks heat up the same whether filling with microbore hoses or the larger ones. I don’t use microbore hoses to fill from my compressor. I don’t think mine larger SCBA tanks start feeling warm until they get to around 2600 psi and I top off from there up to around 305 bar. From empty the buddy bottle got really warm around 1500 psi. On a top off from around the same it was a lot warmer than the larger tanks by the time it hit 300 bar. I’m just trying to see if this is normal. If it isn’t, I’d like to know what I can do differently.

 

[Ezana4CE]

Strangely enough I recently topped off my buddy bottle directly from my compressor starting around 220 bar to around 300 bar after filling a couple of larger tanks and experienced no noticeable heat on the buddy bottle. That was unexpected and I don’t know why I didn’t feel any heat. Perhaps because the compressor didn’t add much compressed air to the bottle. The room temp was 78-80F.