tlon very well as a hydraulic oil. In systems that
operate over 1000 psi or use a piston or sliding
vane pump, a fluid with an anti-wear additive is
usually required. Where the system operates in
an area of great temperature extremes, an oil
with a high viscosity index might be required to
provide desirable high and low temperature vis-
cosity characteristics.
operate over 1000 psi or use a piston or sliding
vane pump, a fluid with an anti-wear additive is
usually required. Where the system operates in
an area of great temperature extremes, an oil
with a high viscosity index might be required to
provide desirable high and low temperature vis-
cosity characteristics.
In some instances, although very rarely in a
hydroelectric plant, a fire resistant hydraulic fluid
may be required. These fluids are usually either
a water based or a synthetic fluid. In either case,
the system must be designed specifically for the
fluid it will use. Water based fluids have a very
Iow viscosity and the synthetic fluids many times
are not compatible with most seals.
hydroelectric plant, a fire resistant hydraulic fluid
may be required. These fluids are usually either
a water based or a synthetic fluid. In either case,
the system must be designed specifically for the
fluid it will use. Water based fluids have a very
Iow viscosity and the synthetic fluids many times
are not compatible with most seals.
7.3 Hydraulic Governor Systems
A hydraulic governor system is simply a hydrau-
lic system and in most cases can use the turbine
oil used in the unit bearings. In some cases,
such as low plant temperatures or extremely
long control lines, a lighter viscosity oil may be
required.
lic system and in most cases can use the turbine
oil used in the unit bearings. In some cases,
such as low plant temperatures or extremely
long control lines, a lighter viscosity oil may be
required.
7.4 Wicket Gate Bushings
Grease for the wicket gate bushings must be
adhesive, water resistant, able to withstand high
bearing pressures, and of a consistency that can
be pumped at the lowest temperature en-
countered. Usually a grease with extreme
pressure or antiwear capabilities is specified.
The grease's dropping point has little relevance
in this case.
adhesive, water resistant, able to withstand high
bearing pressures, and of a consistency that can
be pumped at the lowest temperature en-
countered. Usually a grease with extreme
pressure or antiwear capabilities is specified.
The grease's dropping point has little relevance
in this case.
There are a number of different greases that
have Shown to provide adequate lubrication in
wicket gate bushings. Most of these greases
have a lithium or calcium soap base, but it
should be noted that not all lithium or calcium
based greases are acceptable. The additives
contained in a grease enhance or impart many
of the grease's characteristics, so when select-
have Shown to provide adequate lubrication in
wicket gate bushings. Most of these greases
have a lithium or calcium soap base, but it
should be noted that not all lithium or calcium
based greases are acceptable. The additives
contained in a grease enhance or impart many
of the grease's characteristics, so when select-
ing a grease, all of its characteristics should be
considered. While a very adhesive grease may
be desirable, the adhesiveness may make it
very difficult to pump through a centralized
system. Conversely, a grease that is easily
pumped may not stay in the bushing. Some
compromise is usually required.
considered. While a very adhesive grease may
be desirable, the adhesiveness may make it
very difficult to pump through a centralized
system. Conversely, a grease that is easily
pumped may not stay in the bushing. Some
compromise is usually required.
7.5 Gears
Gears vary greatly in design and in their require-
ments for lubrication. When selecting a lubricant
for any gear application the type of gears, and
operating conditions, such as speed, load, and
temperature must be considered. Enclosed
gears, that is gears encased in an oil tight
housing usually will use a mineral oil with
various additives depending on the conditions.
Rust, oxidation, and foam inhibitors are
common, as are extreme pressure additives
where loads are severe.
ments for lubrication. When selecting a lubricant
for any gear application the type of gears, and
operating conditions, such as speed, load, and
temperature must be considered. Enclosed
gears, that is gears encased in an oil tight
housing usually will use a mineral oil with
various additives depending on the conditions.
Rust, oxidation, and foam inhibitors are
common, as are extreme pressure additives
where loads are severe.
Worm gears are a special case as the action
between the worm and its mating gear is sliding
rather than the rolling action found in most
gears. The sliding action allows fluid film lubri-
cation to take place. Another difference is the
fact that the mating gears, that is worm and the
bull gear, are usually made of dissimilar materi-
als which reduces the chance of galling and
reduces friction. Extreme pressure additives are
usually are not required for worm gears but
lubrication can be improved by oiliness addi-
tives.
between the worm and its mating gear is sliding
rather than the rolling action found in most
gears. The sliding action allows fluid film lubri-
cation to take place. Another difference is the
fact that the mating gears, that is worm and the
bull gear, are usually made of dissimilar materi-
als which reduces the chance of galling and
reduces friction. Extreme pressure additives are
usually are not required for worm gears but
lubrication can be improved by oiliness addi-
tives.
A highly adhesive lubricant is required for most
open gear applications. An open gear lubricant
must resist being thrown off by centrifugal force
or being scraped off by the action of the gear
teeth. Most open gear lubricants are heavy oils,
many times asphalt based, or soft greases. De-
pending on the service conditions, oxidation
inhibitors or extreme pressure additives may be
added. As these lubricants are very adhesive,
they also attract dust and dirt. These contami-
open gear applications. An open gear lubricant
must resist being thrown off by centrifugal force
or being scraped off by the action of the gear
teeth. Most open gear lubricants are heavy oils,
many times asphalt based, or soft greases. De-
pending on the service conditions, oxidation
inhibitors or extreme pressure additives may be
added. As these lubricants are very adhesive,
they also attract dust and dirt. These contami-
(FIST 2-4 11/90)
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