Hydraulic Vane Pump Failure and How To Avoid It

vaneOne of our members wrote to me recently regarding the following problem:

“Recently, we bought a used hydraulic power unit (15HP electric motor directly coupled to a vane pump). A high-pitched, clicking noise is generated when the unit runs. We have checked the following:

–We thought it was a motor bearing, so we detached pump from motor, no noise heard.
–Pressure line was connected to tank line (to simulate low pressure < 100 psi), very little noise heard.
–As pressure is increased, noise gets louder and louder, very intolerable.
–Measured current draw of electric motor – no overload.

What do you think could be causing the excessive noise?”

Given that the symptoms described above are consistent with a restriction at the pump inlet, I inquired if there was a suction filter in the circuit.… continue reading »

A Principle That Must Be Understood When Troubleshooting Hydraulic Cylinder Drift

BentRodIn my free email series, on YouTube and in exhaustive detail in The Hydraulic Troubleshooting Handbook, I explain the concept of how a double-acting cylinder becomes a displacement cylinder if the piston seal leaks. And as part of the explanation of this concept I state: “…if the piston seal is completely removed from a double-acting cylinder, and its ports are blocked, it will hold its load indefinitely unless the rod seal leaks.” And this is precisely how a ram, which has NO piston seal, supports a load.

But for the physics involved to apply (and the above statement to be true) the load on the double-acting cylinder must be acting to retract the rod (positive load).… continue reading »

One More Hydraulic Part to Maintain

hydraulic schematic drawingA hydraulic machine has lots of moving parts to maintain. In fact, a hydraulic system is one of the most complex systems to maintain effectively. And here’s one more item to add to the list: the machine’s drawings. A machine’s hydraulic (and electrical) schematic diagrams don’t wear out, but they do tend to become inaccurate over time.

Even absent a major refit or redesign, it is not unusual for minor changes to be made to the hydraulic circuit over the course of the machine’s life. This could involve: change in make or model of components; additional filtration–or a reduction in filtration components, if, for example, a suction strainer is removed; re-routing of conductors–drain lines for example; installation of additional cooling capacity or the installation of pressure test points, oil sample points and other maintenance accessories.… continue reading »