One of our members wrote me with the following question:
“We are trying to give one of our customers a short definition of what constitutes a hydraulic oil leak. Is there a standard or a general definition of what constitutes a hydraulic leak?”
It’s not rocket science. In the case of a hydraulic system, any hydraulic fluid that appears on external surfaces can and should be classified as a leak. With one important exception, which I’ll get to in a minute.
By way of external arbitration, in their maintenance manuals the U.S. Army defines three classes of leaks:
–Class I: … continue reading »
A highly qualified, intensive care doctor is struck down with appendicitis. So he undergoes keyhole surgery at the hospital where he works. He is now a patient in his own hospital. In the recovery room, post surgery, he is awake but starts to feel light headed. A nurse takes his blood pressure and it’s way down. This triggers an emergency response.
The medical emergency team arrives at the patient’s bedside. Being a doctor himself, the patient argues with them. He can’t believe he’s having a heart attack, because he doesn’t have any chest pain. But the attending emergency doctor shows … continue reading »
While absolutely essential on a piston-type hydraulic motor, an external case drain line is usually optional on gear motor designs–external, internal and gerotor/geroller. 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 behind the shaft seal.
By installing a high-pressure shaft seal and two check valves as shown in the schematic diagram inset above, internal leakage is drained via the return line–something that’s not acceptable for a piston motor or pump!
So the presence of a high pressure … continue reading »