Consensus on Overfilling Tanks?

[rjack321]

it is, but if it's actually 130F when you stop filling, then it should cool back down to 3000. I usually set the regulator at 3500 if they're coming up from low pressure and they almost always settle out a hair under 3000, and yes the regulator is calibrated and accurate to within 1%

If you have to overfill al80s by 750psi you are either starting with a crazy hot bank or going super fast

So 130*F (590 R) to 68F (528 R) would be 89% of the the pressure when hot. 528/590 = 0.89

@Jwoobs math of a ~10% drop is closer to my experience. My al80s are filled to 3300 and they cool down to 3000.

If I filled to 3750 they would cool to 3400-ish.

 

[Johnoly]

.... I've learned a ton and things that I didn't even think to ask that were made aware.....

You're going to have to start a new thread on what damage 3950psi fills do to 1st stage seats.
{disclaimer: I dive jacked up cave fills on LP108's every dive and the damage I do to my gear is just a cost factor I absorb as a harvester}

 

[BRT]

If you have to overfill al80s by 750psi you are either starting with a crazy hot bank or going super fast



@Jwoobs math of a ~10% drop is closer to my experience. My al80s are filled to 3300 and they cool down to 3000.

If I filled to 3750 they would cool to 3400-ish.

These numbers are what I see. But it takes me hours to fill 3 tanks.

 

[tbone1004]

If you have to overfill al80s by 750psi you are either starting with a crazy hot bank or going super fast

or both... big compressor, we fill one bank at a time while we are filling, and have to fill a bunch of bottles so they get filled fairly quickly. Again, important to note that it is MUCH slower than the cycling done at hydro and during failure testing required by the DoT, but much faster than you'd ideally fill them.

You're going to have to start a new thread on what damage 3950psi fills do to 1st stage seats.
{disclaimer: I dive jacked up cave fills on LP108's every dive and the damage I do to my gear is just a cost factor I absorb as a harvester}

Regs in Europe have to deal with 300bar/4350psi fills. It's obviously not ideal and it does more damage, but if you actually follow the manufacturer recommended service intervals, there is no way that they're going to be damaged prematurely. I may notice since I service based on failure not time, but I've never tracked it. I also rarely have anything filled much over 3600psi ish. They usually cool off to about that before I hook the regs up.

 

[rob.mwpropane]

You're going to have to start a new thread on what damage 3950psi fills do to 1st stage seats.
{disclaimer: I dive jacked up cave fills on LP108's every dive and the damage I do to my gear is just a cost factor I absorb as a harvester}

1st off, I don't own a compressor, so I make zero rules. I don't know that a tank needs to be filled to 5/4. Just because the code says 5/4 doesn't mean you have to, I would read that more as a absolute most you would add and not to exceed. My car can go 160ish....believe me, no intentions of ever taking it there. Having some type of literature or knowledge that states the tank can be filled to a higher pressure was what I was looking for, or at least the reasons why. I'm not looking to have my tank end up with more than what I'm supposed to get at room temperature....3442psi.

As per @MichaelMc

(d) “at 55 °C (131 °F) may not exceed 5/4 times the service pressure” except [plus rated]

I don't read that as take it to the red line.

 

[MichaelMc]

My P/T calcs showed that
- 3015 psia at 70F warmed to 131F becomes 3364 psia, that would cool to the 70F spec.
- While the 5/4 rule for 131F allows it to be a rather high 3750 psi.

The spec allows for more than is necessary to cool to the 70F pressure. But it still has to cool to the 70F preasure.

To cool to 3000 psig you fill to 3353 psig (at 131F) not the higher allowed 3735 psig.

All assuming you knew the temp inside. But we are not talking about filling AL to 3735 so they cool right.

 

[rob.mwpropane]

I'm not talking filling AL at all, my main tanks are 2 100cf steal 3442 psi tanks. My hope is that from here on out I can get whatever shop to fill to 3800 psi so it cools closer to what it should be and I have some knowledge as to why.

Edit: that's pretty on the money with the 10% that someone posted before

 

[rjack321]

I'm not talking filling AL at all, my main tanks are 2 100cf steal 3442 psi tanks. My hope is that from here on out I can get whatever shop to fill to 3800 psi so it cools closer to what it should be and I have some knowledge as to why.

Edit: that's pretty on the money with the 10% that someone posted before

The reality is that filling to 3800 hot is not overfilling. So stop using that language with them, its "scary" and not helping your cause.

Check them every time you pick them up and ask them to top them up to 3442 cold. If you ask them over and over again (every time) they will get annoyed and gradually fill them a little more each time until they are 3442 cold. See? no scary words in there. 3442 at 70F.

 

[rob.mwpropane]

The reality is that filling to 3800 hot is not overfilling. So stop using that language with them, its "scary" and not helping your cause.

Check them every time you pick them up and ask them to top them up to 3442 cold. If you ask them over and over again (every time) they will get annoyed and gradually fill them a little more each time until they are 3442 cold. See? no scary words in there. 3442 at 70F.

Point taken. That makes sense. Thank you.

I haven't used any language yet, I've never asked to have them filled at this place. The other day was my first trip there. Right now everywhere else is closed. I just needed some wisdom to be able to if and when I go next time. Again, thanks.

 

[rjack321]

So how far off they are before you complain too much. 3300 (cold) is 96cf so you aren't being shorted enough to complain about IMO. 3100 I would complain about and ask them to top off.

How they fill is going to dictate how much they cool off. For instance even if they are filling 20 cylinders at a time - so super slow - if its direct off the compressor that gas is going to be hot. Filling 50psi per minute from a giant bank in the cold basement is going to start off colder, heat up less, and cool down less.