Hi Mike,
Thanks for the comment. Yes I'm pumping gas, but the thing is that my volume is constant (pump internal volume), and my temperature is raising rapidly, so the only cause for the uncontrollable temperature is the pressure. However, I don't how I could control the pressure inside the scroll pump, and also I can't seem to find the cause of the increase of pressure other than the compression. The compression should be essential for the scroll pump, and the heating from many scroll pump I know off is controllable. The one I designed, the temperature just go berserk!!! Is there possible for a gas trapped inside the pump that caused the raise in pressure?