PSI Temperature Variations
When I arrived at the range the other day it was about 30F so I checked and my AF tank psi and found it was down a good bit so I pumped it up before shooting.
Before leaving the range I checked my ending PSI with my Hill Pump and it was about 2,750 psi.
Today at home with the AF tank at room temperature about 74 F the Hill pump shows PSI about 2,950. If I had pumped it up to 3,000 when finished at the range the other day, it would probably be at 3,200 now.
So, would it be OK (safe) to pump it up to 3,200? The weather report shows high temps of below 30 F for the next 4 days so it won’t get above 74 F here in the house.
Has anybody noted psi changes in excess of 200?
All Replies
Savagesam,
I haven’t given the reg a good test as even though I read the instructions, I still dropped a couple spacers off the pin/plunger whatever it is. Not knowing they have different shapes I just stuck them back on. Then, I thought I knew better and didn’t replace the tank o-ring with the new one supplied because mine was thicker. Thicker is better sometimes, isn’t it? Well not in this case. Over night my old o-ring became semi liquid and began to ooze out. So, when MM provides a new o-ring and says replace the old one, he knows what he is talking about. Then with some leaking and some initial testing and eventually replacing the o-ring and more testing and a little reading about some other regs being modified, I realized the spacers I dropped and stuck back in place just may not be in the correct orientation. Anything new can and will confuse me for a while. Of course, hearing that a reg needs a little break in didn’t help me realize that I may have created a problem. My initial strings weren’t bad except for an occasional variation of maybe 7 fps. I wanted to use the JSB Monster .22s at 25.4 gr. Others reported poor performance with them but I still think it was a matter of over powering them. I just tried the JSB 18.1 .22s and they really impress me as the best over Kodiaks and Baracudas.
So, the setup is Condor .22 x24″ stock hammer and tank with polished Valve Pin/Top Hat.
Still mixing in experimenting with o-ring behind the Top Hat and think that has the greatest potential for improved performance of anything I have tried so far.
I got my best ever 50 yard group with the 18.1 gr JSBs the other day at 0.490″ while experimenting with the o-ring and a wide range of Top Hat Power Wheel Settings.
When I get my new E-TaC I’ll finish tuning and publish strings and groups with the o-ring. Actually, Powderburner has already done it all for us. It’s hard to understand why others haven’t got on the band wagon. Even though you need to move the Top Hat out some, the o-ring reduces air useage a lot and as far as I can tell comes close to regulated consistency. I think the resistance is the insistence on trying for maximum velocity without regard for tighter groups at 1-200 less fps.
Lurker, no not saying that at all. As Pab said, these things have a wide safety margin built in. I didn’t know you had a reg. either. How do you like the 2500Psi output? What are the specifics of your setup? Barrel length? Pellet weight? Fps? Thanks.
Thanks for all the comments 😯
Savage,
Hey, I like airgun preaching.
BUT,,,I’m having trouble seeing how it’s any different filling the tank all warmed to room temperature to 3,200 psi or filling it at 30 degrees F to 3,000 psi? When I leave the house with the 3,200 psi tank it cools by the time I get set up at the range and would be about 3,000, just right for use with my 2,500 Regulator.
Are you saying ‘don’t let it warm up in the house so it never sees above 3,000 psi.’
Actually my last 20 shot string was from cold, 30 degree tank at 3,000 psi down to 2,750 psi cold. When I started to prepare for my next trip I found the tank, warmed, is at 2,950. Wanting to do the pumping in comfort, I need to go up to 3,200. So, it seems to me that I’ve only pumped it up 250 psi. The drop in temperature outdoors will take the psi back down to 3,000 where I want to start my shooting at. Then I’ll shoot out just about 250 psi for 20 shots and refill to 3,000 cold. Still it’s only a spread of 450 psi from low cold to warm high of 3,200.
All that said, I haven’t got the Reg set up right and will be sending it to MM to correct MY Screw- Up. But not until I have a new E-TaC to use in the meantime. Somethings just can’t be done without once you’ve seen the light. That goes for my WokButt too. Like they say, no going back.
Lurker, when they hydro test (80 Cu.Ft./3000Psi scuba) tanks, they test it @ 1.5 X 3000Psi=4500Psi. Having said that, I wouldn’t do what you are doing. IIRC, it’s hardest on the metal (causes the metal to become brittle) when you go from one extreme to the other, i.e. 3200Psi to 1500Psi. IF, I say again, IF, your gun works best at a FULL 3K (which I think more than half don’t)fill to 3K and then top off again at 2500. What me and my friend do is leave our tanks at the scuba shop for several hours, they charge to 3K, then top off once more before we leave. Then when we’re outside (in the summer) and our tanks are @ 3K we leave them in the shade (if any) when they drop we let the sun do its thing. In the winter, put your tank in the garage where it’s COLD then fill to 3K. I know you’re probably about the guns tank Vs. a scuba tank, but the principal is the same. I hope this comes across as trying to be helpful and not preachy.
will still be 0 degrees.
Wind chill only ‘cools’ things that produce heat above the ambient temp.
Want to know cold 0 degrees with a 70 mile an hour wind.
IMO, Our worst weather in Lima, Ohio is at 30 F with 60%+ humidity and a breeze. It cuts right through the cloths and stings the skin. Snow causes it to feel a lot warmer than humid cold.
They changed how they calculate the wind chill in 2001 and it became much less relevant. They need to do a sober study with the humidity factor given more consideration.
If you filled that 80 cuft tank at 0 F I wonder how much it would increase when brought up to room temperature?
Pab,
Thanks, I just pumped it up to 3,200 and feel safe with it.
just plug into the formula
3459psig at room temp.
Walter….
Dog,
IMO, Our worst weather in Lima, Ohio is at 30 F with 60%+ humidity and a breeze. It cuts right through the cloths and stings the skin. Snow causes it to feel a lot warmer than humid cold.
They changed how they calculate the wind chill in 2001 and it became much less relevant. They need to do a sober study with the humidity factor given more consideration.
If you filled that 80 cuft tank at 0 F I wonder how much it would increase when brought up to room temperature?
Pab,
Thanks, I just pumped it up to 3,200 and feel safe with it.
I had an aluminum 80 cubic foot tank filled to 3000 psi, I wanted to see the change if I left it outside overnight when the temputure got down to 0°, when I checked it in the morning the pressure read 2300 psi, a 700 psi loss.
A tank also weights less empty than when full.
dog
let’s see…..
P2 =( P1 * T2)/T1
P2 = (3014.5 * 460)/530
P2 = 2616.35 – 14.5 = 2601.85 psig
Your tank filled at 3,000psig and 70 Far will be 2600psi at 0 Far.
Air tanks have a pretty huge safety margin in them. If it says safe working pressure of 3000 psi, you know it will be perfectly safe at 3200, even 3500.
Living in Minnesota it gets cold.
I had an aluminum 80 cubic foot tank filled to 3000 psi, I wanted to see the change if I left it outside overnight when the temputure got down to 0°, when I checked it in the morning the pressure read 2300 psi, a 700 psi loss.
A tank also weights less empty than when full.
dog
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Here in L.A., it’s backwards. Before I bought my compressor, I would take my black aluminum 80 from the 70F garage and place it out in the 90-100F sunshine. It would go up from the low 2000’s up to 2800-2900psi.
Thanks for the equation, Walter. 😀