Fluke Bath Fluids Data sheet

Bath Fluids

Finally, there’s a convenient source for small
quantities of bath fluids for any temperature range.
Why pay for more than you need?

Hart Scientific’s full line of bath fluids covering
temperature ranges from –100°C to 550°C.

Viscosity, volatility and other properties that change
with temperature affect the performance of fluids in
controlled baths and circulators. Hart 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, Hart Scientific has 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. Hart offers three standard bath models and custom-desig ned 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. Hart 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 Hart
bath.

PO Box 1073, 8 Leroy Road, Williston, VT 05495 USA • fax [phone] • ph 802-863-0085 • toll free 800-235-8367

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

Fluid
Halocarbon 0.8 Cold Bath Fluid –100°C to 70°C n/a 5019

HFE Cold Bath Fluid –75°C to 100°C n/a 5023
Dynalene HF/LO* –65°C to 58°C 60°C 5022
Ethylene Glycol (Mix 1:1 with water) –30°C to 90°C n/a 5020

Silicone Oil Type 200.05 –40°C to 130°C 133°C

Silicone Oil Type 200.10 –30°C to 160°C 163°C 5012
Silicone Oil Type 200.20 10°C to 230°C 232°C 5013
Silicone Oil Type 200.50 30°C to 278°C 280°C 5014
Silicone Oil Type 210H 175°C 5024
Silicone Oil Type 550 70°C to 228°C 230°C 5016
Silicone Oil Type 710 80°C to 300°C 302°C 5017
Mineral Oil 10°C to 175°C 177°C 5011
Bath Salt, 125 lb.‡

Potassium Nitrate 53%
Sodium Nitrite 40%
Sodium Nitrate 7%

§

Atmospheric pressure affects the usable ranges of some fluids. The temperatures quoted are at sea level.

§

Usable Range

180°C to 550°C n/a 5001

Flash

Point†

Model #

5010

†

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.)

*Electrical resistivity is greater than 20 MW-cm.

‡

125 lb. bath salt fills a 7.9-gallon tank.

PO Box 1073, 8 Leroy Road, Williston, VT 05495 USA • fax [phone] • ph 802-863-0085 • toll free 800-235-8367