Calibration Bath
General Operation
21
About the Chart
Figure 3 illustrates some of the important qualities of the fluids shown.
Temperature Range: The temperature scale is in degrees Celsius. The shaded bands indicate
the general range of application of the fluid. Qualities that include pour point, freeze point,
important viscosity points, flash point, boiling point, and others may be shown.
Freezing Point: The freezing point of a fluid limits stirring. As the freezing point approaches,
high viscosity can also limit performance.
Pour Point: This represents a handling limit for the fluid.
Viscosity: Points shown are at 50 centistokes and 10 centistokes viscosity. When viscosity is
>50 centistokes, stirring is poor and the fluid is unsatisfactory for bath applications. Optimum
stirring generally occurs at
≤10 centistokes.
Fume Point: Fume point is the point at which you must use a fume hood or ventilation system to
prevent health hazards posed by fume vapors. In the graph, it is assumed that the bath access
hole is covered at this point. This is subject to you company policy. Fluke Calibration
recommends the use of a ventilation system as soon as the fluid produces vapors. Keep the
access hole covered to reduce evaporation.
Flash Point: The point at which ignition may occur. The point shown can be either the open or
closed cup flash point. Refer to the flash point discussion in Safety.
Boiling Point: At or near the boiling point of the fluid, temperature stability is difficult to maintain.
Fuming or evaporation is excessive. Large amounts of heater power may be required because of
the heat of vaporization.
Decomposition: The temperature can reach a point at which decomposition of the fluid begins.
To further increase the temperature can accelerate decomposition to the point of danger or
impracticality. Silicone oils can oxidize, which causes the fluid to thicken. Replace at the first sign
of viscosity increase.
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