Electrical Resistivity; Fluid Lifetime; Safety - Fluke 7341 User Manual

Ending temperature, T
Starting temperature, T
Ending depth, D
D = 9.2/[0.00077 (300-25) + 1] = 7.59 inches
S
8.1.6

Electrical Resistivity

Electrical resistivity describes how well the fluid insulates against the flow of
electric current. In some applications, such as measuring the resistance of bare
temperature sensors, it may be important that little or no electrical leakage oc-
cur through the fluid.
In such conditions choose a fluid with very high electrical resistivity.
8.1.7

Fluid Lifetime

Many fluids degrade over time because of vaporization, water absorption, gel-
ling, or chemical break-down. Often the degradation becomes significant near
the upper temperature limit of the fluid, substantially reducing the fluid's
lifetime.
8.1.8

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 may
be considered toxic. Contact with eyes, skin, or inhalation of vapors may cause
injury. A proper fume hood or adequate ventilation system must be used if haz-
ardous or bothersome vapors are produced.
WARNING: Fluids at high temperatures may pose danger from BURNS,
FIRE, and TOXIC FUMES. Use appropriate caution and safety equip-
ment.
Fluids may be flammable and require special fire safety equipment and proce-
dures. 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 adequate oxygen present and an ignition source is applied the va-
por 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 open cup flash point is mea-
sured under the condition of vapors escaping the tank. The closed cup flash
point is measured with the vapors being contained within the tank. Since oxy-
gen and an ignition source is less available inside the tank the closed cup flash
point will be lower than the open cup flash point.
Environmentally hazardous fluids require special disposal according to applica-
ble federal or local laws after use.
= 300°C
E
= 25°C
S
= 9.2 inches
E
8 General Operation
Heat Transfer Fluid
29