eli5: If water is non-compressible, then why not use it in hydraulic machines instead of hydraulic oil?

Question

eli5: If water is non-compressible, then why not use it in hydraulic machines instead of hydraulic oil?

In: 1817

Answer 1

Water has a few major issues as a working fluid:

1: it’s corrosive to metals and will dissolve seals and sealants.

2: it gets weird below 0C.

3: it gets weird above 100C.

We’ve engineered various hydraulic fluids to avoid these problems. You wouldn’t want to have your hydraulic cylinders all blow apart the first time you get a light frost overnight.