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7.2.8
Safety
When choosing a fluid always consider the safety issues associated. Obviously,
where there are extreme temperatures there can be danger to personnel and
equipment. Fluids may also be hazardous for other reasons. Some fluids maybe
considered toxic. Contact with eyes, skin, or inhalation of vapors may cause
injury. A proper fume hood must be used if hazardous or bothersome vapors are
produced.
Fluids at high temperatures. May pose danger from BURNS,
FIRE, and TOXIC fumes. Use appropriate caution and safety
equipment.
Fluids may be flammable and require special fire safety equipment and
procedures. An important characteristic of the fluid to consider is the flash point.
The flash point is the temperature at which there is sufficient vapor given off so
that when there is sufficient oxygen present and an ignition source is applied the
vapor will ignite. This does not necessarily mean that fire will be sustained at the
flash point. The flash point may be either of the open cup or closed cup type.
Either condition may occur in a bath situation. The closed cup temperature is
always the lower of the two. The closed cup represents the contained vapors
inside the tank and the open cup represents the vapors escaping the tank.
Oxygen and an ignition source will be less available inside the tank.
Environmentally hazardous fluids require special disposal according to applicable
federal or local laws after use.
7.2.9
Cost
Cost of bath fluids may vary greatly, from cents per gallon for water to hundreds
of dollars per gallon for synthetic oils. Cost may be an important consideration
when choosing a fluid.
7.2.10 Commonly Used Fluids
Below is a description of some of the more commonly used fluids and their
characteristics
7.2.10.1
Water
Water is often used because of its very low cost, availability, and excellent
temperature control characteristics. Water has very low viscosity and good
thermal conductivity and heat capacity which makes it among the best fluids for
control stability at low temperatures. Temperature stability is much poorer at
higher temperatures because water condenses on the lid, cools and drips into
the bath. Water is safe and relatively inert. The electrical conductivity of water
may prevent its use in some applications. Water has a limited temperature range,
from a few degrees above 0 °C to a few degrees below 100 °C. At higher
temperatures evaporation becomes significant. Water used in the bath should be
distilled or softened to prevent mineral deposits. Consider using an algicide
chemical in the water to prevent contamination.
WARNING:
General Operation
7
7.2 Bath Fluid
7-3
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