Starting Procedures for Hydraulic Pumps

It's necessary to have precautions when starting an hydraulic unit, (no matter if it's new or repaired), since a failure can occur at any time very quickly. The most important practice to be carried out is the cleaning of the hydraulic system. Foreign bodies that contaminate hydraulic fluid can cause certain problems. This is why it is recommended that lines that are disconnected to dismantle a unit remain covered during the process. It is also very convenient to clean and blow the pipes and the tank. If you have fluted arrows on the units, use grease before coupling them.

Installations of pumps in general.

Offer the pump the best suction conditions. If possible, as follows:

  • Mounting the pump to a level lower than that of the oil, either inside or outside the tank; Do not restrict the pump inlet at any point, ie, that the pipe is large enough so that the fluid velocity in the suction line does not exceed 1 to 1.4 meters per second.
  • Check that both the pump and the hydraulic motor are filled with oil inside the housing.
  • Take care when mounting the unit, that the support easily enters the base or mounting flange, it must never enter forced.
  • Hold and tighten the unit with its screws, always observing a good alignment. Then proceed to dock the unit.
  • In case the unit is not directly coupled, that is, using pulleys, gears, etc., check that the coupling does not exceed the limits specified by the manufacturer of the hydraulic equipment, in terms of axial, radial loads, etc.
  • Check that the suction filter is clean, and that it is of the required capacity, the same for the tank breather filter.
  • Check the cleaning carried out, and install a 25 micron filter, enough to keep the hydraulic oil clean.
  • Check that suction and return are tight enough to prevent air from entering the system.
  • Check that the oil level is correct.
  • Check that the direction of rotation is correct, check the adjustment of the relief valve.

  • Sometimes, when lowering the pressure of the system, it is very easy to increase it, turning the screw, or the adjustment nut of the relief valve, after the pump is repaired, or replaced with a new one, that pressure can be excessive , so it is recommended to start the operation with a low level, and increment it little by little until you reach the desired point, always use in these cases a manometer, in case the equipment does not have it, and always take readings from the pressure at the outlet of the pump, the highest in these cases.

    In the case of using round pumps, also called palette, certain special conditions must be met.

    Palette pumps are built to be started under load, the instructions of these pumps indicate the procedure in that way.

    The other types of pumps, the square ones, or of high performance, are built to start without load, in this way they can expel the air contained inside them. The pumps must be filled with oil before starting, to ensure a good purge.

    You should never start a square pump, or high performance pump, under the following conditions.

  • Against a closed-center directional control valve.
  • Against a charged accumulator.
  • Against a closed circuit with hydraulic motor.

  • The procedures to be followed for starting pumps of this type are the following:

  • Open the connection of the high pressure pipe a little to purge the air.
  • Energize a solenoid, or change the position of the lever of the directional control valve and adjust the relief valve when starting the pump against pressure.
  • Start and stop the pump immediately several times to allow air purge. Let it work when you already have enough oil.
  • Tighten the connection that was loosened once it is verified that the oil runs off without bubbles.

  • Once the pump has started, it can receive its normal working load.

    The procedure to start piston pumps, or variable displacement, is very similar, and its conditions are explained below:

  • Start a variable displacement pump with 50% or more of its maximum displacement.
  • Check pump start without load, either with an open center valve, or without load in the transmission.
  • Never operate more than 5" mercury vacuum, or with a pressure inside the housing greater than 5 psi.
  • Check that the casing is filled with oil and that the drain tube comes out of the top of the pump, extending below the oil level, to prevent the casing from discharging.
  • Check that the pump is working correctly during the first minute of operation. Otherwise, check the oil level in the tank.
  • Bleed the pump discharge line and slowly operate the cylinders in the system, (if any), from one side to the other, then re-purge the line. Repeat this operation as many times as necessary. In case the air persists inside the lines, check the suction lines to detect possible leaks.
  • If possible, operate the low speed pump during the purge time and check for possible line leaks. If you have an electric motor attached directly to the pump, start it and stop it several times.

  • Never remove the adjusting screw of the pressure compensator of the pump while it is in operation.

    Finally, we have to remember the procedures for starting hydrostatic or hydraulic transmissions.

  • When starting an internal combustion engine, either gasoline or diesel, allow it to operate at low speed for some time, to allow the transmission oil to reach the optimum operating temperature.
  • With the internal combustion engine working enough so that the engine can start without getting to stand again, (stall), operate the control lever again and move the vehicle slowly about 30 meters. The movement in this form forces the oil to return hot to the pump after having passed through the hydraulic motor, which is cold.
  • Avoid putting the equipment into operation before it reaches a temperature of at least 38 degrees Celsius, this simple step will not take more than 5 or 10 minutes, but it will guarantee to avoid equipment problems.