Pressure transmitters for vacuum applications

[Steve010]

I want to use pressure transmitters and differential pressure level transmitters with diaphragm seal on the bottom of a vacuum tower. The pressure is 1.5 psia and the temperature is 400 C. I saw ultratherm 805, and as per the curve provided in the catalog, at 1.5 psia the maximum temperature that the fill fluid can withstand without vaporizing at this pressure is 350 C. At 400 C the pressure should not be less than 10 psia. Should i rely on the heat dissipation that will happen in the distance of the piping nozzle+piping isolation valve ? will this distance bring the temperature to below 350 C ? should i calculate the temperature dissipation or is it common ? Also i cannot make the nozzle very long as the temperature should not go below 150 C as the residue will solidify at that temperature. Shall i use another type of measurement. I am open to suggestions.