Calibration Bath Fluids

Key features

Bath fluids for ranges from -100°C to 550°C.
Provides bath salt for high temperature ranges.
Three standard bath models and custom units for use with bath salt.

Product overview: Calibration Bath Fluids

Viscosity, volatility and other properties that change with temperature affect the performance of fluids in controlled baths and circulators. Fluke Calibration has tested and used each of the fluids we sell. Over the ranges recommended in the following table, each fluid remains at a low enough viscosity to be adequately pumped or stirred. Whether your application is industrial or critical lab calibration work, Hart fluids give you top performance and stability.

For temperature ranges too high for oils, we have a bath salt with a viscosity in the molten state similar to the viscosity of water. For your convenience, it is shipped in a granular form, making it easy to fill your bath.

Between its melting point of 150°C and 550°C, this salt has the highest temperature stability and uniformity available in a bath fluid. It does not smoke like oils or give off dust like “sand" or fluidized alumina baths. Check with your bath manufacturer before using this salt to make sure your equipment is compatible. Fluke Calibration offers three standard bath models and custom-designed units for use with this salt.

Fluid specifications

It’s important to understand a few specifications before selecting a bath fluid. We’ve seen bath fluids advertised with a temperature range that spans from the freezing point to the flash point or beyond.

For example, type 710 silicone oil has a freezing point of –22°C, but freezing point has nothing to do with the point at which the oil becomes so thick it cannot be properly stirred. Type 710 oil should really only be used down to about 80°C. It’s a viscosity issue, not a freezing-point issue. Usable range is the question. Suitability for calibration work is the specification that counts.

The usable viscosity range is determined by your bath’s stirring or pumping design. Fluke Calibration baths can be operated using fluids with up to 50 centistokes viscosity. This gives you additional usable range in the lower temperature levels of the fluid.

Some baths advertised as calibration baths require fluids with 10 centistokes or less viscosity to operate properly. The usable ranges in our table on the previous page assume the use of a Fluke bath.

In addition to range and viscosity issues, there are a number of other issues to consider when choosing a bath fluid. The other considerations are:

Thermal characteristics
Lifetime
Change in characteristics due to temperature cycling
Absorption of water from the air
Vaporization—fumes and fume hood requirements
Expansion due to heat
Contamination—mixing oils or introducing contamination with unclean probes
Conductivity properties
Effects of using fluids outside of their range—fire, explosion, polymerization
Effects of altitude on boiling point

Specifications: Calibration Bath Fluids

Model	Description
5019	Halocarbon 0.8 Cold Bath Fluid Usable Range^§: –100°C to 70°C Flash Point^†: n/a
5023	HFE Cold Bath Fluid Usable Range^§: –75°C to 100°C Flash Point^†: n/a
5022	Dynalene HF/LO Usable Range^§: –65°C to 58°C Flash Point^†: 60°C
5020	Ethylene Glycol (Mix 1:1 with water) Usable Range^§: –30°C to 90°C Flash Point^†: n/a
5010	Silicone Oil Type 200.05 Usable Range^§: –40°C to 130°C Flash Point^†: 133°C
5012	Silicone Oil Type 200.10 Usable Range^§: –30°C to 209°C Flash Point^†: 211°C
5013	Silicone Oil Type 200.20 Usable Range^§: 10°C to 230°C Flash Point^†: 232°C
5014	Silicone Oil Type 200.50 Usable Range^§: 30°C to 278°C Flash Point^†: 280°C
5017	Silicone Oil Type 710 Usable Range^§: 80°C to 300°C Flash Point^†: 302°C
5011 - Mineral Oil	Mineral Oil Usable Range^§: 10°C to 175°C Flash Point^†: 177°C
5001 - Bath Salt	Bath Salt, 125 lb.^‡ Potassium Nitrate 53% Sodium Nitrite 40% Sodium Nitrate 7% Usable Range^§: 180°C to 550°C Flash Point^†: n/a ^‡ 125 lb. bath salt fills a 7.9-gallon tank.
^§ Atmospheric pressure affects the usable ranges of some fluids. The temperatures quoted are at sea level. ^† Flash point is the temperature at which a vapor (not the fluid) will ignite if exposed to an open flame. When the flame is removed, the vapor will stop burning. (Open cup method.)