Open or Closed System

Determine whether your bath is an open or closed system. Open systems baths are open to the atmosphere and in the presence of air. If you intend to heat the fluid in an open system, the fluid should have high resistance to oxidation, low vapor pressure and high flash points. In open system baths, viscosities below 5cSt should not be used above ambient temperature because they have low flash points, and will evaporate, requiring frequent replenishment.

Closed systems are systems in which air has been excluded…closed to the atmosphere. Due to the absence of air, most fluids will exhibit higher operating temperature ranges in closed systems.

Temperature Stability vs. Flash Point and Pour Point

Although some companies recommend fluids based upon their pour point and flash point, a fluid’s operating service temperature range should be your first consideration. Operating service temperature range is not synonymous with pour point and flash point. For low temp baths, it is not recommended to take the fluid to its pour point. Crystallization can occur before the pour point. When the fluid hits its pour point, it will no longer flow. For high temperature baths, we do not recommend heating a fluid to its flash point, especially in an open system. Heating a fluid to its flash point will lead to breakdown and eventual gelling of the fluid. Operating service temperatures ranges will always be below the flash point and above the pour point.

Viscosity at temperature (Viscosity-to-temperature coefficient)

Silicone fluids exhibit significantly lower changes in viscosity when compared to petroleum-based fluids. A fluids’ viscosity behavior is measure by its V.T.C. (viscosity-to-temperature coefficient). The lower the V.T.C., the lower the viscosity changes. This is critical in low temperature baths, especially if the fluid must circulate or be pumped. Many pumps cannot pump higher viscosity fluids.

Compatibility with Bath Instrumentation and Materials

When choosing a fluid, make sure that the fluid is compatible with the instrumentation and equipment. This includes compatibility with o-rings, gaskets, valves and seals. Silicone fluids are compatible with virtually all plastic and rubber materials, including buna-n, viton, nitrile and EPDM. However, silicone fluids are not recommended for applications with silicone o-rings due to the possibility of swelling the o-rings.

Safety First

For any fluid being heated in an open system, use all necessary precautions. A fume hood is recommended, especially for baths being operated over 150°C. (open system). Make sure that the flash point is well above the operating temperature range and that the fluid has a service temperature range that will meet the temperature at which the bath will be operated.

Low Temperature Silicone Bath Fluids (-60°C to 220°C)

Pure Silicone Fluid 1.5cSt Low Temperature Bath Fluid (-65°C to 25°C closed system only)
Pure Silicone Fluid 3cSt Low Temperature Bath Fluid (-60°C to 20°C open system) (-60°C to 90°C closed system)
Pure Silicone Fluid 5cSt Low Temperature Bath Fluid (-50°C to 65°C open system) (-50C to 120°C closed system)
Pure Silicone Fluid 10cSt Low Temperature Bath Fluid (-50°C to 100°C open system) (-50C to 150°C closed system)
Pure Silicone Fluid 20cSt Low Temperature Bath Fluid (-50°C to 120°C open system) (-50°C to 220°C closed system)

Medium Temperature Silicone Bath Fluids (-50°C to 230°C)

Pure Silicone Fluid 20cSt Medium Temperature Bath Fluid (-50°C to 120°C open system) (-50°C to 220°C closed system)
Pure Silicone Fluid 50cSt Medium Temperature Bath Fluid (-40C to 170°C open system) (-40 to 230°C closed system)
Pure Silicone Fluid 100cSt Medium Temperature Bath Fluid (-40C to 170°C open system) (-40 to 230°C closed system)

High Temperature Silicone Bath Fluids (170°C to 300°C)

DPDM-400 High Temperature Bath Fluid (25C to 250°C open system) (25°C to 300°C closed system)
PM-125 High Temperature Bath Fluid (25°C to 230°C open system) (25°C to 300°C closed system)
HT-110 High Temperature Bath Fluid (-40°C to 220°C open system) (-40°C to 220°C closed system)