The tool will be downhole with pressures up to 20,000 psi external. It is hard to explain without showing entire tool but hydrostatic pressure will move another piston that will fill void and keep pressure equalized across tool.
However, if fluid expands too much it can burst the tube. Bulk Modulus for another hydraulic oil showed pressure increase of 29,000 psi heating from 70 to 300F. Even a small increase in reservoir pressure will allow the pistons to come out and stick the tool in the tubing (wellbore id).
I just need to compensate so if heated up to 300F, the pressure will not increase over hydrostatic. Or to simply it, to make sure the reservoir pressure won't increase as fluid expand while heating in an autoclave so the pistons do not move (probably around 10-15 psi).If I take too much out, the tool will not work properly.
- CJ