Silicone 704 for Vacuum Applications – fill fluid
specifications
Temperature Limits:
Below Atm pressure: See Figure 1-2 for Vapor Pressure Curve
At or above Atm pressure: 0 to 315 °C (32 to 600 °F)
Viscosity at 25 °C (77 °F): 39 cs
Specific Gravity @ 25 °C (77 °F): 1.07
Coefficient of Thermal Expansion: 0.00095 cc/cc/C (0.00053 cc/cc/F)
Chemical Name: Tetramethyltetraphenyltrisiloxane
CAS Number: 3982-82-9
1.5.1 Description/applications
Silicone 704 for Vacuum Applications is specifically designed for applications below 14.7 psia
(1bar-a) that have higher operating temperatures than Silicone 200 for Vacuum Applications
can support. This specialty silicone fluid has a much higher molecular weight than Silicone 200,
which increases its operating temperature and lowers its vapor pressure. Its primary limitation is
its higher viscosity, so heat tracing of capillaries or use of the Rosemount Thermal Ranger
Expander is suggested for many outdoor applications. The 0.03-in. (0.7 mm) ID capillary is not
allowed for Silicone 704 for Vacuum Applications because of its higher viscosity. Refer to the
vapor pressure curve below for acceptable operating pressure and temperature limits.
