Pressure Temperature Chart - UN Tubes

The pressure temperature chart below can be used to find maximum allowable working pressure (MAWP) of compressed gases at different temperatures. The MAWP values stamped on UN Tubes is at 59 degrees F. As temperature changes, the MAWP value needs to be corrected which can be found from the chart below. The technical details and an example calculation is provided below the chart and also at the end of the document. The chart can be viewed in full screen or downloaded using the tools below.

Technical details:

Gay-Lussac's Law or Combined Gas Law when volume is constant:
P1/T1 = P2/T2

Temperature Conversions
C = (F - 32) x 5/9
K = C + 273.15
where C, F and K are temperatures in Centigrade, Fahrenheit and Kelvin respectively.

For UN tubes, pressure is known at 59° F. Pressure at any desired temperature can be calculated using Gay-Lussac's Law.

P1 = 3161 psi
T1 = 59 ° F = 288.15 ° K
T2 = 110 ° F = 316.483 ° K
P2 = ?
P2 = (P1 x T2) / T1 = (3161 x 316.48) / 288.15 = 3472 psi

For calculating volume and weight of gases at certain temperature and pressure, please go to the Gas Calculator under Technical section of this site.

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