Is there gas in the car?
Jeffrey Haynosch N.E. Hydraulic & Repair Sales Engineer, BSME
Recently, the team at The Hope Group helped a customer with a hydraulic unit that would not move.
The hydraulic unit in question is a very basic package. The unit uses a fixed displacement pump mounted inside the 5-gallon reservoir. This unit has a standard electric motor . Down a vertical shaft is the tank where the pump sits in the oil. The basic unit is 1.0 hp, 2.7 gpm with the safety relief at 1200 psi. It connects to a 2-station hydraulic manifold with 2 directional control valves, and flow controls. Each DCV lifts a pair of cylinders that raise a table.
However, this customer ran into a problem. The unit will not move its cylinders and the gauge reads zero. The first step is to check the rotation of the electric motor. No issues there, but still no pressure. Next, the customer checks the oil level sight gauge. This gauge is located on the side of the tank. The tank is full and when the customer removed the filler breather cap, oil could be seen at the bottom of the filler breather.
Now, we check for contaminant. The Parker design uses a cartridge relief in the hydraulic manifold. With the unit off and tagged out, the mechanic unthreaded the cartridge relief valve and pushed the dart on the cartridge inwards opposite the Allen pressure adjustment screw. The mechanic found no issues. The plunger moves freely and there was no sign of contaminant. Hoeever, the hpu will not lift the table when the directional valve solenoids are energized. The main symptom is sitll the pressure gauge reading zero.
Due to a fast-approaching deadline that could not be missed, we had to act quickly. Our local product specialist and an additional support person from Parker came to trouble shoot on-site. After going through the troubleshooting procedures, still no pressure.
Now it’s panic mode, it’s Friday and their customer is coming in Monday to witness test. As the New England Hydraulic Engineer at THG, I was asked to come to their facility right away. I am 1.5 hours away and the Friday afternoon traffic makes the drive 2 hours but fortunately they have their mechanic wait.
Potential issues to investigate:
– Coupling from motor to pump is a problem, electric motor is not turning the pump.
– Possible leak in the plumbing inside the tank “short in the hydraulic circuit”. Flow goes to the path of least resistance, hence pump is dumping inside the tank.
Both of the possible issues above require time and effort to pull the pump motor off the reservoir and inspect. Fortunately, the solution ended up being much simpler! After arriving at the facility and looking at the hydraulic unit with the mechanic, the problem was solved in 60 seconds
What is the problem? Liquid level sight gauge:
The oil level appeared good but there was no line on the sight gauge. The customer believed the unit was overfilled and the oil is really clean. After we removed the filler breather we could see oil at the bottom of the breather. Once we removed the whole filler breather assembly, we saw that the reservoir was actually empty!
In conclusion, always check oil level. You should see oil level line. If you don’t see the oil level line, it is overfilled or underfilled. Neither are good practice!
The puddle of oil at the bottom of the filler breather was left over from when the unit was last filled!
Remember a car won’t move without gas. No gas in the car! No oil in the reservoir!