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?
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Bearing in mind Kuwait City is on the edge of a rather warm desert, I’m guessing it was air temp at the runway. The airport would shut down a few times during the summer each year, and it was VERY hot for those months. Cars left out in the sun were untouchable until the sun had been down for a good few hours type hot.
F**k that!!!
Don’t know actually Sam’
Bearing in mind Kuwait City is on the edge of a rather warm desert, I’m guessing it was air temp at the runway. The airport would shut down a few times during the summer each year, and it was VERY hot for those months. Cars left out in the sun were untouchable until the sun had been down for a good few hours type hot.
Pab, do you mean the runway surface or the air temp?
When I lived in Kuwait, they shut down Kuwait City Airport when the runways hit 140 😯 The special high temp resistant tarmac would get too soft.
No thank you, ill keep them inside 😛
DAMN!!!!!!!!!!!!!…..Does it really get to 120 ??? That’s hot as the Mojave desert.
5psi change per degree f is an excellent estimate when the pressure is about 2625 psi.
No thank you, ill keep them inside 😛
For 2800psi at 140F you would fill inside at 2500psi.
imagine filling it here at room temps & taking out where the temp here goes easy to 120F, ofcourse if you leave it outside for some time than you might hit 150F easy.
No thank you, ill keep them inside 😛
And a rule of thumb (correct me Walt) is about 5psi per 1F change in temperature based on a 75F start pressure. Or put another way… from 75F to Texas summer is +200psi and from 75F to a Texas winter is -200psi.
Don’t ask me how I found this thread… I found Walt’s equation helpful… here’s a consolidated version for the Excel inclined… psi2=((psi1+14.5)*(temp2+460)/(temp1+460))-14.5
Thanks Walter,
I feel so much better. I went deeper in my Convertbot App and found they had Rankine temperatures un-checked. Now even I can work the formula.
Thanks,
Edmund
Perhaps if I admit how stupid I feel right now maybe I won’t look so stupid…Duh…
I take
T1 = Initial Temperature
P1 = Initial tank PSI at T1 Initial temperature
T2 = Secondary tank temperature
P2 = Unknown PSI to be solved
So, what are 460 and 530?
Are they conversions from the Fahrenheit temperatures?
Dang, I haven’t worked with formulas for a long time. I’d rather be doing Vedic multiplication of 2 seven digit numbers in my head and getting an exact answer that my computer can’t.
You got it fine….
0 Far = 460 Rankin absolute temperature
pressure is in absolute so you must add 14.5psi atmospheric, do the math
then subtract 14.5 to get to gauge pressure (psig)
Walter….
Walter,
Perhaps if I admit how stupid I feel right now maybe I won’t look so stupid…Duh…
I take
T1 = Initial Temperature
P1 = Initial tank PSI at T1 Initial temperature
T2 = Secondary tank temperature
P2 = Unknown PSI to be solved
So, what are 460 and 530?
Are they conversions from the Fahrenheit temperatures?
Dang, I haven’t worked with formulas for a long time. I’d rather be doing Vedic multiplication of 2 seven digit numbers in my head and getting an exact answer that my computer can’t.
LUKKER,
You don’t need to tell me about wind chill, your right it cut right thru like you don’t have any pants on 😯
I have not done a 0° F fill, don’t think I will because I have had a burst disk blow, it was in the basement it scared the shit out of my girlfriend :lol:, I think it was from repeated filling a 3000 psi tank to 3200 – 3400 psi.
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Pab, do you mean the runway surface or the air temp?
A black object left in the sun can get close to 200F in California (surface temperatures)…
Typical NASCAR track is 160F with the sun out but not directly on the track. But a jumbo jet is very different than a racecar… I would imagine a hot day in those parts of the world would produce 140F+ runway surface temps often. 😯