health and safety plan solid waste management unit assessment

HYDRAULIC FLUID 68-7
68.1 MAJOR USES AND COMPOSITION
68.1.1 Major Uses
Hydraulic fluids are used in all kinds of applications but
especially in machinery that moves or lifts objects. Aircraft,
automobiles, trucks, forklifts, compressors, garden tractors and many
others all use hydraulic fluids in their hydraulic components to
magnify a relatively small force to do useful work. Automobiles need
hydraulic fluids as transmission and brake fluids, while supersonic jet
and commercial aircraft uae them in landing gear and other equipment
(21).
68.1.2 Composition
Traditionally, most hydraulic fluida have been mineral base oils,
specifically those high in paraffins. Their advantages include
stability to oxidation and good resistance to foaming and wear.
Another major advantage of mineral base fluids over synthetics is their
lower cost (1823,1824).
The development of synthetic hydraulic fluids arose from the need
for fluids with a greater range of operating temperatures. Synthetic
hydraulic fluids such as the phosphate esters provide excellent fire
resistance, increasing the maximum operating temperature by perhaps
15O'C over mineral oils. In most aircraft, hydraulic lines pass close
to high temperature parts while high altitudes and speeds can produce
temperatures well below 0-C. Commonly, temperatures can range from
-53'C to 260'C (1824). It is this range of operating temperatures that
dictates the type of fluid and additives used. Under these conditions,
synthetic fluids of high autoignition temperatures and superior
temperature-viscosity characteristics are used especially if there is
the possibility of fluid leakage or spray on or near hot surfaces.
Table 68-1 provides a list of typical hydraulic fluids including
mineral base and synthetic base fluids.
Mineral base and synthetic base hydraulic fluids are fortified
with approximately O-20 volume percent additives (1825), which in most
cases are identical to those used in the crankcase oils (see Chapter
69, Table 69-2). The most common additives in hydraulic fluids are
used to modify physical/chemical characteristics: they include
viscosity improvers, inhibitors of ruat and corrosion, and inhibitors
of wear, foaming and oxidation. Generally, detergent use is minimal
(21,1823,1824). Tables 68-2 and 68-3 List reported hydraulic
oil/lubricating oil base stocks and their additives.
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