Back to Basics with Hydraulic Troubleshooting

Pilot Crushtec’s Technical Help Desk recommends the following basic checklist for hydraulic troubleshooting:

1. Check the hydraulic oil level and oil appearance – the oil should be clear with no visible particles.
2. Check hydraulic return filters. Ask the question: when were these items last replaced? Hydraulic return filters should be changed every 250 engine hours.
3. Hydraulic oil samples should be taken after every service to ensure the oil contains no foreign particles and is fit for use.
4. When troubleshooting a problem, it is best to start at one point (for example, the pump supply) and work your way through the system.
   Use a schematic related to the machine to understand the system before attempting troubleshooting:
   • Pump supply
   • Valve bank and relief valve
   • Driven motor and check valves
5. An effective fault-finding kit is recommended on site, containing a tachometer for speed checks and a pressure gauge to measure working pressure.

Gauge test point:

This symbol indicates that a pressure gauge can be mounted at this point. Always ensure the rated system pressure is known so that the test pressure gauge is not damaged. If unsure, start with a high-range pressure gauge (±600 bar).

Spring-loaded check valve:

This symbol indicates an inline spring-return check valve that allows flow in only one direction. It is commonly used on conveyors to prevent rollback of the conveyor belt when stopped with material present.

Hydraulic filter:

This symbol indicates a hydraulic filter, which is usually located on the hydraulic tank.

Fixed displacement pump with one direction of flow:

This symbol usually represents a gear pump driven by an engine or an electric motor. A pump supplies hydraulic oil to drive a motor or raise a cylinder.

Fixed displacement reversible motor with case drain:

Hydraulic motors are used to drive components such as screen box shafts or conveyor belt drums. The case drain is a good indication of internal wear.
If the case drain is fed into a container, it should not exceed more than 5% of the motor’s rated displacement.

The symbols above represent only a few of the important components used in hydraulic systems. Correctly reading a schematic requires understanding both the symbols and the components involved.
Once a schematic can be read correctly, troubleshooting becomes a step-by-step process that yields accurate results and a clear understanding of the cause of failure.