frequency should be increased until it is determined that all of the old grease has been purged from
In wicket gate greasing systems and other underwater applications, a grease must be chosen that
is water resistant, somewhat adhesive, and has extreme pressure characteristics, as well as being
pumpable. A grease that is impervious to water and has excellent lubricating qualities is useless if
it doesn't get to the bearing. The consistency must be thin enough to be pumped through the
grease lines but thick enough to stay in the bearings once it is there. Some compromise in the
desired qualities is required to obtain a workable grease.
The main purpose of a hydraulic oil is to transmit power, but it must also
lubricate the components of the hydraulic system. In many systems, a lubricating oil such as
turbine oil can be used as the hydraulic fluid. If the system uses a gear pump, operates at
less than 1,000 pounds per square inch (psi), and has similar viscosity requirements, a
turbine oil can function very well as a hydraulic oil. In systems that operate over 1,000 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, such as gate operators, an oil with a
high viscosity index might be required to provide desirable high and low temperature viscosity
Testing and Filtering.
Cleanliness is extremely important. All seals should be installed and in good
condition. Dirt, water, or other contaminants not only can cause premature wear of the bearings and
hydraulic system components, but they also can cause the depletion of some of the oil's additives. Samples
of the oil from large bearings and hydraulic systems should be tested for viscosity, acidity, and water
content. The tests should be performed at least annually and more frequently if a problem is suspected or
previous tests have indicated an impending problem. In any testing program, it is important to keep
complete and accurate records of the tests. A significant change in any of the measured properties from
previous tests may indicate a problem, although the oil may still be acceptable for service.
The oil from large bearings should be periodically drained, filtered, and the oil reservoir thoroughly
cleaned. The most efficient method of determining when to filter is through the results of the oil tests.
Filtering more frequently than is necessary is a waste of time, while waiting too long to filter the oil will
shorten the oil's life and damage the equipment being lubricated.
The oil from small bearings should be periodically drained, and the reservoir or case cleaned and filled
with new oil. Care should be taken when filling a bearing oil reservoir so as to not under or over fill. In
many cases, over filling an oil reservoir can cause as much damage as underfilling.
Another possible source of contamination is the mixing of incompatible oils. Different types of oils or even
similar oils from different manufacturers should never be mixed. Additives in different oils may not be
compatible and, when mixed, may have an adverse reaction, reducing the effectiveness of the oil.