7102
User’s Guide
16
Safety
Always consider the safety issues associated with any fluid. Where there are conditions of extreme hot
or cold, there can be danger to people and equipment. Fluids can be hazardous for other reasons.
Some fluids are considered toxic. Contact with eyes, skin, or inhalation of vapors can cause injury.
W Warning
To prevent personal injury, be aware that fluids at high temperatures can cause burns,
fire, and toxic fumes. Use caution and safety equipment. Use a proper fume hood if
hazardous or bothersome vapors are produced.
Some fluids are flammable and require special fire safety equipment and procedures. Always consider
the flash point of the fluid. The flash point is the temperature at which sufficient vapor is produced that,
when mixed with sufficient oxygen and an ignition source, ignites the vapor. This does not necessarily
mean that fire is sustained at the flash point. In a bath environment, the flash point can be either the
open-cup or closed-cup type. The closed-cup temperature is always the lower of the two. The closed
cup represents the contained vapors inside the tank. The open-cup temperature represents the vapors
that escape the tank. Oxygen and an ignition source are less available inside the tank.
Environmentally hazardous fluids require special disposal according to applicable federal or local laws
after use.
Cost
Cost of bath fluids varies greatly. Cost is an important consideration with bath fluids.
Commonly Used Fluids
A description of some of the more commonly used fluids and their characteristics are in the subsequent
sections.
Mineral Oil
Mineral oil or paraffin oil is often used at moderate temperatures above the range of water. Mineral oil
is inexpensive. At lower temperatures, mineral oil is quite viscous, and control can be poor. At higher
temperatures, vapor emission is significant. The vapors can be dangerous, and Fluke Calibration
highly recommends a fume hood. As with most oils, mineral oil expands as temperature increases so
do not fill the bath so full that it overflows when heated. The viscosity and thermal characteristics of
mineral oil are poorer than water so temperature stability will not be as good. Mineral oil has very low
electrical conductivity.
W Warning
To prevent personal injury, use caution with mineral oil. Mineral oil is flammable and
can cause serious injury if inhaled or ingested.
Silicone Oil (Dow Corning 200.05, 200.10, 200.20)
Some silicone oils offer a much wider operating temperature range than mineral oil. Like most oils,
silicone oils have temperature control characteristics which are somewhat poorer than water. The
viscosity changes significantly with temperature and thermal expansion occurs. These oils have very
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