If liquid is not compressible, why do we need special hydraulic fluid? Why not just use water?
In: Engineering
A couple of things.
Water can cause corrosion – oil doesn’t.
Water can’t be used in environments where temperatures fall below 0C or go over 100C, oil based fluids can do both.
There is also something called lubricity – how well a liquid lubricates machinery. Water has a low lubricity which means it can cause additional wear and tear on machinery compared to oil based fluids.
But you can use water – especially if you need a lot of fluid. In fact, there were once hydraulic networks in several cities that used water. London’s used river water, pressurised it and delivered it across large parts of the city through cast iron pipes. It allowed companies to have powered machinery long before electric motors and an electrical grid became reliable. It was used to drive lifts, cranes, industrial presses, open dock gates and bridges – there were thousands of users. It operated until the 1970s.
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