[rbastiaan]

Dear experts,

we are building a pressure measuring instrument for use in high temperature processes. The process temperature is approximately 400-425 C. the fluid in the process is a heat transfer fluid. To measure is the pressure we use a fluid filled measuring system. Experience tells us that to withstand the temperature for longer period 2-5 years, the fluid in this closed system must be of a higher grade so approx 450-475C. The problem we are facing is that most fluids has a vapour pressure that is to high for this system, or is not in a liquid state are room temperature.

So in short I am looking for a fluid that is in a liquid phase at room temperature, can withstand 450-475C with low vapour pressure.

if anyone has an idea it would be great!

thanks in advance for your reactions.

Robert

[typhoon2028]

look into molten salt technologies.

KNO3/NaNO3 mixture.

Search hitec solar salt. 

My company uses molten salt technology.  We use a nitrate/nitrite blend.  Nitrate/nitrite blends have a lower melting point, but nitrite can break down.

Potassium nitrate and sodium nitrate should be thermally stable at your operating temperature.