Oiled
for success
Fluid
Power delves into the intricacies involved in choosing the right hydraulic
oil for protecting your machines
Hydraulic
power transmission naturally lands itself in a wide range of purposes
where multiplication of force is required, or where accurate and dependable
control gear must be provided. The immense forces that may be developed
by the application of hydraulic principles and precision and flexibility
of hydraulic control could in many cases be provided only with extreme
difficulty by any other means. There is an almost endless variety of
hydraulic gear, but the hydraulic media employed necessarily have many
features in common. The prime requirements of a hydraulic medium are
that they should be relatively incompressible and sufficiently fluid
to permit the efficient transmission of power. These stipulations alone
are met by many liquids and in fact may have been employed more or less
satisfactorily in the past. Often service conditions in modern hydraulic
machinery are so precise that few liquids are able to match their complex
needs. Water for instance, suffers from a number of disadvantages –
not only does it have negligible lubricating properties but promotes
rusting too. Furthermore it is liable to freeze in cold weather and
boil at low temperatures. Therefore emulsions of soluble oil in water
are sometimes used in partially successful attempts to overcome the
above disadvantages, but even such emulsions in general, are quite unsuitable
for modern application. As hydraulic media, mineral oils are the most
satisfactory products available in sufficiently large quantities and
at a reasonably low cost. Where hydraulic medium with greater fire resistance
than mineral oil is required, various types of synthetic and water containing
fluids are available. In particular, fire resistant emulsion fluid is
a specially prepared water-in-oil type emulsion that is gaining popularity
in this field. Extremely fine clearances are usual in modern hydraulic
gear, and in order to avoid excessive wear, hydraulic mediums must have
lubricating ability of a high order. Furthermore, its design should
involve lubrication of associated mechanical gear by the hydraulic fluid.
Hydraulic oils must therefore perform dual functions – power transmission
and lubrication determining the viscosity, most suited for specific
applications. Rapid and efficient transmission of power can be attained
with oils of high viscosity than compared to those whose viscosity is
less. Since greater internal friction with the former may result in
a considerable loss of power and increase in operating temperature.
In addition, the knack of the oil to maintain fluid-film lubrication
of working surface is affected by its penetrating and spreading factor.
Oils of too high a viscosity may fail in this respect too. On the other
hand, the duties of...
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