A welding tank has a gauge pressure of 2000psi at 40.0°F. What is the new gauge pressure if the temperature rises to 100°F?

Answer 1

At constant volume, P/T = constant.
To use this formula, P must be the absolute pressure and T must be absolute (Kelvin or Rankine).

To convert Fahrenheit temperature to Rankine, add 460. The ideal gas law says:
(2000 + 14.7)/(40 + 460)
= (P + 14.7)/(100 + 460)
where P is the final gauge pressure.
14.7 ps1 has been added to gauge pressures to convert to absolute pressure in psia

2014.7/500 = (P + 14.7)/560
P + 14.7 = 2256.4

P = 2241.8 psi is the final gauge pressure.