Cavitation is the term used to describe the formation of gas cavities within a liquid. In a hydraulic system, this is normally taken to mean formation of vapor bubbles within the oil. But it can also mean dissolved air coming out of solution in the oil.

Cavitation erosion occurs when gas cavities in the oil collapse (implode) under pressure, in proximity to a metal surface. But in a hydraulic system, the formation of gas cavities is usually (but not always) associated with the presence of a vacuum (negative gauge pressure). And the presence of vacuum-induced, mechanical forces can be far more damaging, and catastrophically so, to hydraulic components, than pressure-induced bubble implosion.… continue reading »

A Hydraulics Pro Club member from South Africa sent me this story about a hydraulic system overhaul that turned into a troubleshooting nightmare:

“My company was contracted to overhaul the hydraulic system in a beverage pasteurizing unit. The system was extremely simple but the pasteurizer, after 20 years of trouble free service, was going to be critical in the launch of a new alcoholic beverage in South Africa. Cider at the time was virtually unheard of here and the whole lead up to the launch involved millions being spent in TV and print advertising. Promotions and launch parties were arranged throughout the country for the launch date – it was going to be a big thing.… continue reading »

One of our members wrote me about the following problem:

“We are facing the following problem with our European made moulding machines. If we fill the hydraulic tank with brand new oil, within less than 24 hours oil colour turns dark brown and gives burnt smell. But if we test the oil it shows fit for further usage. Initially we were using Shell Tellus 46 and recently we changed to Mobil DTE 10 Excel-46, which is a near to synthetic grade. But the result is the same with both oils. When we emptied the hydraulic tank we found thick, dark brown sludge in the bottom of the tank.… continue reading »