Download this article in PDF format. The term “high pressure” is quite subjective when it comes to hydraulics. Among the strictest definitions is any system with operating pressure exceeding 10,000 psi. Perhaps a more general interpretation is 6,000 psi, which will be assumed for this discussion. In this article, high system pressure will be defined as 6,000 psi (410 bar), which is the pressure setting on some newer excavator functions.