Silicon Pressure Cell Fill Oil Volume Verification Methods
Confirm fill oil volume using pre- and post-injection micro-gravimetric mass checks combined with non-contact laser interferometric diaphragm dome profiling.
Fluorolube
Fill Fluid
Halogenated oil is used as a non-reactive pressure transfer medium in systems measuring oxygen or corrosive chemicals. Chlorofluorocarbon liquids sold under the trade name fluorolube act as the fill fluid in transmitters where hydrocarbon oils present an explosion hazard. These fluids possess high density and low compressibility.
They are prepared by polymerizing trifluorochloroethylene.
Material Compatibility
Chemical stability ensures that no reaction occurs in the presence of strong oxidizers. When sealing diaphragms isolate the sensing element, fluorolube prevents hazardous interactions even if a breach occurs. This chemical inertness makes the fluid suitable for chlorine and oxygen service.
Standard industrial transmitters must be cleaned for oxygen service before being filled with this substance.
Temperature Response
Thermal behaviour governs the change in viscosity and density across the operating range of the transmitter. In high-temperature applications, fluorolube exhibits a more pronounced change in viscosity compared to silicone oils, which affects the response time of the pressure transmitter. Metrologists must calibrate the sensor to account for this temperature dependency.
Because the density of the fluid is high, the head effect in vertical installations must be calculated and corrected during the zero-point adjustment.
Performance Limit
Low-temperature operations are constrained by the pour point of the fluid. Extremely cold environments can cause fluorolube to become highly viscous or solidify, which blocks the transmission of pressure to the sensor. This phase change occurs below minus fifteen degrees Celsius depending on the specific grade used.