In many turbine installations the
oil must serve not only the bearings but
also the reduction
gearing and perhaps the thrust
elements. Therefore, consideration of this type of lubricant is
necessary. The viscosity of the oil used in geared turbines is generally a
compromise since the bearings would require a lower viscosity than the gearing.
The base oil should be in the range of 300 to 500 SUS at 100 degree F. This oil
should be well refined so that
it will have
long life and so
that any naturally occurring
compounds which might
contribute to emulsions are
removed. All of these points to solvent refined oils.
Alkyl phenols, such as 2, 6-ditertbutyl – 4 –
methyl phenol, or “Ionol” in a
proportion of 0.1 to 1 per cent are
satisfactory oxidation inhibitors for most
turbine oil formulations.
Rust inhibitors should be of
a nature which will not
contribute to emulsions nor
be removed from the oil by water. Or this reason
“Lubrizol 850” or “Alox 1832” can be used. The former is effective in
concentrations o 0.05 to 0.10 per cent and the latter in amount up to 2.5 per
cent.
An antifoaming
agent, such as a dimethyl
silicon polymer, in a concentration of about 0.001 per cent, should be
present in turbine oils.
According to Landis et al. the
emulsive tendencies of antirust turbine oils can be reduced by the addition of small
amounts of aryl sulfonic acids or their salts. A typical composition consists of : a solvent refined
oil having a viscosity of 350 to 600 SUS at 100
degree F and containing
0.25 per cent by
weight of 2, 6 – ditertbutyl -4 – methylphenol; 0.1 per
cent of
phenyl alpha naphthylamine; 0.1 per cent of an antitrust agent obtained by
reacting oleic acid
with triethylenetetramine, in a
molar ratio of 1.3 to 1, to produce an
intermediate product which
is then reacted
with triisobutenyl succinic
acid anhydride in a molar ratio of 2.3 to 1; and 0.02 per cent
of sodium petroleum sulfonate. As a
substitute for the
last ingredient, 0.02 per
cent of either barium or zinc
petroleum sulfonate or
0.05 per cent of ammonium petroleum sulfonate, can be used.
The proportion of such demulsifies is critical and an excess defeats the
purpose.
