Page 313 - The Tribology Handbook

Synthetic oils c3

The data are generaiisations, and no account has been taken of the availability and property variations ofdifferent viscosity
grades in each chemical type.
Table 3. continued
I
Chlorinaied Silicate Ester Polyphenyl Fluorocarbon Mineral Oil
Diphenyl or Didoxone Ether (for comparison) Remarks
Proper9
\
Maximum temperaturein 315 300 450 300 200 For esters this temperature will be
absence ofoxygen ("C) higher in the absence of metals
~ ~ ~~~~~~
Maximum temperature in 145 200 320 300 150 This limit is arbitrary. It will be
presence of oxygen ("C) higher if oxygen concentration is
low and life is short
Maximum temperaturedue 100 240 150 140 200 With external pressurisation or low
to decrease in viscosity ("C) loads this limit will be higher
Minimum temperaturedue - 10 - 60 0 - 50 0 to -50 This limit depends on the power
to increase in v iscosi ty ("C) available tc overcome the effect
of increased viscosity
Density (g/ml) 1.42 I .02 1.19 1.95 0.88
Viscosity index -200 tc 150 - - 60 - 25 0 to 140 A high viscosity index is desirable
+ 25
Flash point ("C) 180 170 275 None 150 to200 Above this temperature the vapour
of the fluid may be ignited by an
open flame
Spontaneoos ignition Very high Medium High Veryhigh Low Above this temperature the fluid
temperature may ignite without any flame
being present
Thermal conductivity 0.12 0.15 0.14 0.13 0.13 A high thermal conductivity and
W/m "C) high thermal capacity are desir-
Thermal capacity (J/kg"C) 1200 1700 1750 1350 2000 able for effective cooling
Bulk modulus Medium Low Medium Low Fairly high There are four different values of
hulkmodulusforeachfluid but the
relative qualities are consistent
Boundary lubrication Very good Fair Fair Very good Good This refers primarily to anti-wear
properties when some metal con-
tact is occurring
-~
Toxicity Irritant Slight Believed to Non-toxic Slight Specialist advice should always be
vapour he low unless taken on toxic hazards
when hot overheated
Suitable rubbers Viton Viton (None for Silicone Nitrile
nitrile, very high
fluoro- tempera-
silicone tures)
Effect on plastics Powerful Generally Polyimides Some Generally
solvent mild satisfactory softening slight
when hot
~~~
Resistance to attack Excellen! Poor Very good Excellent Excellent This refers to breakdown ofthe fluid
by water itselfand not the effect ofwater on
the system
Resistance to chemicak Very Generally Resistant Resistant but Very
resistant poor attacked resistant
by alkali
and amines
~~ ~
Effect on metals Some Non- Non- Non-cor- Non-
corrosion corrosive corrosive rosive, but corrosive
of copper unsafe with when pure
alloys aluminium
and mag-
nesium
~ ~~
Cost (relative to IO 8 100 300 I These are rough approximations,
mineral oil) and vary with quality and supply
position
C3.2