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philjd26
23-04-2009, 04:23 PM
hi

anybody got info on allowence for presswure increase/decrease due to temperture change..ie pressure testing with ofn..

rgrds phil

nike123
23-04-2009, 04:25 PM
p/t chart will not help you, because you have superheated gas in pressure test.

1K change=~0,1bar change in gas pressure on normal ambient conditions (that is why it is used in airplane tires)
.....................

Bash1803
23-04-2009, 04:46 PM
Yeah actually, they gave us an equation at college to calculate the expected pressure loss for OFN with temperature change....

The method involves taking a pipe temperature when the OFN has been added and again when you come back to it..

I will try to dig my old book out of the van tonight and will let you know!

nike123
23-04-2009, 04:58 PM
For most practical purposes, nitrogen can be considered as an ideal gas. The ideal gas law states:

PV = nRT

with:
P- absolute pressure of the gas;
V- volume of the gas;
n- number of moles of gas (quantity of gas);
R- the ideal gas constant;
T- the thermodynamic (absolute) temperature of the gas.

Therefore if the temperature increases, to keep the system at equilibrium, the pressure and/or the volume must also increase. If the temperature decreases, the pressure and/or the volume must decrease.


http://www.getnitrogen.org/sub.php?view=nascar

Quality
23-04-2009, 05:07 PM
p/t chart will not help you, because you have superheated gas in pressure test.

1K change=~0,1bar change in gas pressure on normal ambient conditions (that is why it is used in airplane tires)
.....................

Good point that, we also used it in racing motor cycle tyres due the relativley small increase in pressure as the tyre temp increases ;)

nike123
23-04-2009, 05:26 PM
p2=(p1*(t2/t1))

Temperature must be in Kelvines (absolute), pressures in any unit you wish.

nike123
23-04-2009, 06:10 PM
p2=(p1*(t2/t1))

Temperature must be in Kelvines (absolute), pressures in any unit you wish.

I have made Exel table for calculation:
2826

Bash1803
23-04-2009, 07:02 PM
p2=(p1*(t2/t1))

Temperature must be in Kelvines (absolute), pressures in any unit you wish.

I have made Exel table for calculation:
2826

That's the one Nike!! Cheers for that, now I don't have to clean out the van !!!!