Why Air is One of the ‘Big 4’ Contaminants of Hydraulic Oil

cavitation erosion on valve plateAir is both a normal ingredient, and a contaminant, of hydraulic oil. It’s a normal ingredient because hydraulic fluid typically contains between 6 and 12 percent by volume of dissolved air. There’s no avoiding this. And provided this dissolved air stays dissolved, it poses no problem to the hydraulic system or the fluid itself.

But if this dissolved air comes … Read more

When It’s OK Not To Load Test a Hydraulic Pump Rebuild

Rexroth A2VSL1000 hydraulic pumpDuring a recent conversation with a client, the issue of testing hydraulic pump rebuilds came up. As I explain in Insider Secrets to Hydraulics, it is essential that all hydraulic components are properly tested after rebuild. Ensuring a repaired component will perform the way it should when it’s installed on the machine BEFORE it leaves the repair shop, instills … Read more

What to Do With a Hydraulic Cylinder Rod With ‘Soft’ Hard Chrome

cyl-rod-scratchesI was recently consulted about a situation where the glass-reinforced nylon, rod guide-bush in a hydraulic cylinder was scratching the hard chrome plated rod. So in effect, the guide-bush was harder than the hard chrome plating. And this should NOT be the case. In other words, the hard chrome plating on the rod was soft. Or more correctly, not hard … Read more