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Back to Basics with hydraulic troubleshooting

Pilot Crushtec’s technical Help Desk’s recommended basic checklist for hydraulic troubleshooting:

1.       Check hydraulic oil level and oil appearance -this should be clear with no particles.

2.       Check hydraulic return filters – ask the question: when last were these items 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, its best to start at one point i.e. start at the pump supply and work your way through the system. Use a schematic related to the machine to understand the system before attempting troubleshooting.

a.       Pump supply

b.      Valve bank and relief valve

c.       Driven motor and check valves5.       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 shows you that a pressure gauge can be mounted to this point. Always ensure the rated pressure in the system is understood so that the testing pressure gauge is not harmed. Start with a large pressure gauge if unsure (+- 600 bar).

Spring loaded check valve: This symbol indicates an inline spring return check valve that will only allow flow in one direction. Mostly used on conveyors to prevent roll back of the conveyor belt when stopped with material present.

Hydraulic filter: This symbol indicates a hydraulic filter and is usually located on the hydraulic tank.

Fixed displacment pump with one direction of flow : This is usually the symbol for a gear pump driven by an engine or an electric motor.A pump is used to supply hydraulic oil to drive a motor or raise cylinder.

Fixed displacement Reversible motor with case drain: Hydraulic motors are used to drive items such as screen box shafts or conveyor belt drums. The case drain is a good indication of the internal wear, if the case drain is fed into a bucket it should not exceed more than 5 % of the motors rated displacement.

The symbols above are just a few of the important items but there are many more. Reading a schematic correctly involves understand the symbols and the components involved. Once a schematic can be read correctly troubleshooting will be a step by step process yielding positive results and understanding the reason for failure.