Help Gas pressure? (Cylinder)

[NellyGoes]

So I bought a 50 cu ft nitrogen cylinder about 2.5 months ago. Pressure on regulator gauge read 1800 psi (as told by the associate).

Then I got a different regulator (a flowmeter-regulator bc the first one didn't have a flowmeter). I remember the pressure reading was a bit lower on the new device but I don't remember exactly by how much (ugh wish I had recorded it then!!). Anyway I ran a few purity and leak tests but nothing super lengthy (maybe total 10 mins max? At our recommended flow rate of ~20LPM/42CFH). Then I moved the tank to my room (same temp as other room).

I have a picture of reading it about ~1500 psi from 2 weeks ago. Now (after 2 weeks, unmoved) it's reading ~1420.

Is this a problem?? I've done bubble leak tests every time I made any connection change. No leaks. (But I know small internal leaks are possible.)

I've researched and calculated how much gas approx. might still be in it now (minus the tests and just from the pressure reading etc). It says it should still be enough but I'm just a bit paranoid now.
ChatGPT says it's "not normal" that a tank would lose so much pressure in that time…

Idk what to do now. Can't find external leaks. I cannot take it in anywhere bc I'm ctb'ing on Sunday. I'm just wondering if any "gas people" have any insights. Has your tank pressure gauge changed over time? Diff reading from diff device? Are you worried?! Is 50 cubic feet to start with still enough either way??

If anybody has any insights I'd be rly appreciative.

 

[VoidBlessed]

I would take it back to the shop where you got it filled. Unless you didn't tighten your regulator enough and/or left the regulator pressurized for a long time it sounds like a valve issue, which they should be able to address. If you got it filled recently, it might even be covered by the shop's warranty or gruarantee.

 

[NellyGoes]

I would take it back to the shop where you got it filled. Unless you didn't tighten your regulator enough and/or left the regulator pressurized for a long time it sounds like a valve issue, which they should be able to address. If you got it filled recently, it might even be covered by the shop's warranty or gruarantee.

I can't do that. I'm house-bound. Ctb'ing on Sunday.

left the regulator pressurized

Wait so yeah I think it's been "pressurized" this whole time. The regulator has a shit knob which doesn't have a clear "off". All you can do is turn it until the flow goes down (but there is no "click" or stop or anything). The valve has been tightly shut this entire time though.

 

[VoidBlessed]

I can't do that. I'm house-bound. Ctb'ing on Sunday.

Wait so yeah I think it's been "pressurized" this whole time. The regulator has a shit knob which doesn't have a clear "off". All you can do is turn it until the flow goes down (but there is no "click" or stop or anything). The valve has been tightly shut this entire time though.

If the valve leading from the tank to the regulator has been tightly shut then it must be a valve issue I think. The ideal gas law (PV = nRT) can calculate the volume of gas remaining. That's what I plan to do to check whether my tank has enough gas in it.