The issues which can arise when switching brand and/or type of hydraulic oil, is a question I get a lot. And the crux of this problem, is:
1. You can never completely drain ALL of the original oil out of the hydraulic system; and therefore:
2. There WILL be some mixing of the original and the new oil, so how do you make sure they are miscible (compatible)?
Oil additive makers and oil blenders face the very same issue when they want to run field trials to compare the performance of their latest creation with an existing ‘control’ fluid. And the way these guys approach this problem offers some insight for us regular hydraulic hacks.… continue reading »
As you’re hopefully well aware, an unrestricted case-drain line is essential on a piston-type hydraulic motor, whether it’s axial, radial or bent-axis design. But when it comes to gear designs: external, internal and gerotor, a case-drain line is generally considered optional. This is because these types of motors don’t have a large-volume case or sump like piston motors do. But they do have internal leakage which by design, usually accumulates in a small cavity just before the shaft seal.
In theory, by installing a high-pressure shaft seal and two check valves as shown in the inset picture, internal leakage is drained into the return line (something that’s not acceptable for a piston motor or pump).… continue reading »
Noise reduction in hydraulic systems often involves isolating the pump/prime-mover assembly using flexible mounts (isolators). In these cases, the use of hose is necessary to maintain the isolation between the pump/prime-mover and the rest of the system.
The flip-side to this though is, although long lengths of hose can reduce structure borne noise, hose is actually an efficient radiator in the frequency range where most of the energy is generated, typically around 600, 900 and 1200 Hertz.
In terms of vibration and noise conductivity, a long length of pipe or tube is the worst configuration. A long length of hose is better than pipe or tube, but still bad.… continue reading »