Pressure Drop

[fsa46]

What pressure drop can be expected on a "Great White" 97 CF tank after filling and the tank is hot.

I had my tank filled yesterday to 4800 psi ( in 12 minutes ) and it was hot. After it cooled down it read 4100 psi and stopped . When I woke up this morning, 12 hours later, it dropped another 100 psi to 4000 psi. Is this the norm ?

The place that filled it told me that when they fill firehouse tanks they leave them overnight to cool down and top them off in the morning and offered to do the same for me and I declined. Now I think I'll go back this morning and have them top it off and see what happens.

Adding another 800 psi to top it off shouldn't heat it up at all....correct ?

 

[Humdinger]

It will heat up some, but not nearly as much. If it is refilled to 4800 psi it should stabilize at around 4600 psi. The faster the fill the more friction and heat there is. I'd definitely take them up on the offer. Next time leave it there overnight.

 

[fsa46]

"Humdinger"It will heat up some, but not nearly as much. If it is refilled to 4800 psi it should stabilize at around 4600 psi. The faster the fill the more friction and heat there is. I'd definitely take them up on the offer. Next time leave it there overnight.
.
.
.
I had it topped off a little while ago and it's as cool as before he started. I'll keep and eye on it and if it stabilizes at 4600 psi I'll always leave the tank overnight to be topped off as suggested.

 

[Dirte]

Big change in pressure from hot to cold. Compressing gas will generate heat just as expanding gas cools. I fill my Great White slowly with a Shoebox compressor and it is still warm. After I let it cool I will come back and re-top it off.

 

[fsa46]

Well the tank is holding at 4500 so there isn't a problem. Being new to this I was concerned I had a leaking tank. I knew it would drop in pressure but not 800 psi.

I learned a good lesson and whenever I have it filled I'll leave it overnight and have them top it off in the morning. After all, what's the purpose of having a 4500 psi tank if you lose 18% before getting started. jmho

 

[FunGun]

Ask them to fill it slower, this will keep the PVT relationship from creating so much heat by the quick change in pressure. More importantly it will help your tank last longer. Slamming tanks during the filling process is very stressful on the tanks.

 

[fsa46]

"FunGun"Ask them to fill it slower, this will keep the PVT relationship from creating so much heat by the quick change in pressure. More importantly it will help your tank last longer. Slamming tanks during the filling process is very stressful on the tanks.
.
.
.
This is a huge commercial operation and although I did ask him to fill it slow, and I thought 12 minutes was considered slow, lol I should have taken him up on his offer to top it off in the morning.

Now that I have my " firehouse fitting" I'm going to see if the firehouse in town ( a mile away ) will fill for me and top off in the morning on future fills.