2. Hydraulic fluid
• Petroleum-based or mineral-based fluids are the most widely used fluids
today. The properties of a mineral-based fluid depend on the additives used,
the quality of the original crude oil and the refining process. Additives in a
mineral-based fluid offer a range of specific performance characteristics.
• Water-based fluids are used for fire-resistance due to their high-water
content. Water-based fluids can provide suitable lubrication characteristics but
need to be monitored closely to avoid problems. Water-based fluids used in
applications where fire resistance is needed.
Elevated temperatures cause the water in the fluids to evaporate, which
causes the viscosity to rise. Occasionally, distilled water will have to be added
to the system to correct the balance of the fluid. Whenever these fluids are
used, several system components must be checked for compatibility, including
pumps, filters, plumbing, fittings and seal materials.
Water-based fluids can be more expensive than conventional petroleum-
based fluids and have other disadvantages (for example, lower wear
resistance) that must be weighed against the advantage of fire-resistance.
3. Hydraulic fluid
• Synthetic fluids are man-made lubricants and many offer excellent lubrication
characteristics in high-pressure and high- temperature systems. Some of
the advantages of synthetic fluids may include fire-resistance (phosphate
esters), lower friction and thermal stability.
The disadvantage to these types of fluids is that they are usually more
expensive than conventional fluids, they may be slightly toxic and require
special disposal, and they are often not compatible with standard seal
materials.
4. Hydraulic fluid
Tasks for hydraulic fluids
• pressure transfer,
• lubrication of the moving parts of devices,
• cooling, i.e. diversion of the heat produced by energy
conversion (pressure losses),
• cushioning of oscillations caused by pressure jerks,
• corrosion protection,
• scuff removal,
• signal transmission.
