Fault diagnosis of hydraulic equipment is a difficult problem. There are two diagnostic methods: simple diagnosis and precise diagnosis. For small and medium-sized enterprises, due to limited conditions, simple diagnosis methods are still the main method.

The simple diagnostic method is mainly for maintenance engineers to use simple diagnostic instruments and their own practical experience to diagnose the faults of hydraulic equipment, determine the location and cause of the fault, and provide corresponding troubleshooting methods. The simple diagnostic method includes the following points:

1.Observation：

Observe the actual operating conditions of hydraulic equipment, mainly including the following six aspects:

① Observe speed:

Check whether there are abnormal changes in the movement speed of the actuator.

② Observe pressure:

Observe the pressure of each pressure measuring point in the hydraulic system and pay attention to whether the pressure fluctuates.

③ Observe oil:

Observe whether the oil is clean, whether it is deteriorated, whether there is foam on the surface of the oil, whether the oil volume is within the specified range, whether the viscosity of the oil meets the requirements, etc.

④ Leakage:

Observe whether there is leakage or dripping in the hydraulic pipeline, valve plate joint, hydraulic cylinder end cover, hydraulic pump shaft end, etc.

⑤ Observe vibration:

Observe whether the moving parts such as the hydraulic cylinder piston rod or workbench are jumping due to vibration.

⑥ Observe the product:

Through the quality of the product operated or processed by the hydraulic equipment, judge the working state of the motion mechanism, the stability of the system working pressure and flow.

2.Auditory judgment:

judge whether the working state of hydraulic equipment is normal by hearing

① Listen to noise:

listen to whether the noise of pump and hydraulic system is too loud when working, and whether pressure components such as overflow valve and sequence valve have screaming sound.

② Listen to impact sound:

Listen to see if there is a loud impact sound when the workbench hydraulic cylinder is switched, whether the hydraulic cylinder piston hits the bottom of the cylinder, and whether the reversing valve hits the end cover when switching.

③ Listen to abnormal sound of cavitation and trapped oil:

Inspect the hydraulic system to determine if there is an air ingestion or severe oil leak problem. These conditions can negatively impact the performance and efficiency of the system and should be identified and resolved promptly.

④ Listen to knocking sound:

listen to whether there is knocking sound caused by damage when the hydraulic pump is running.

3. Touch: Determine the working status of moving parts by touching them:

①Touch the temperature rise:

If you feel a noticeable heat sensation within two seconds when touching the surface of hydraulic equipment, tanks or valves, this may be a sign that the cause of the elevated temperature of these equipment needs to be checked. This method is a quick and effective way to check if the hydraulic system is overheating, but please be careful to ensure safety when performing such inspections.

②Touch the vibration:

If you feel significant high-frequency vibrations when touching moving parts or pipes, this may be an indication that the source of the vibrations needs further investigation. High-frequency vibrations can be an early warning of certain mechanical problems, so prompt identification and treatment of any abnormal vibrations is critical. However, when conducting such inspections, always ensure your own safety and avoid direct contact with moving parts that may be dangerous.

③Touch the creeping:

When the workbench moves at a light load and low speed, touch it to see if there is creeping.

④Touch the tightness:

Tighten the stop iron, micro switch and fastening screws by hand to check their tightness.

4. Olfactory judgment:

Use the sense of smell to judge whether the oil is smelly and deteriorated, whether the rubber parts emit special odors due to overheating, etc.

① If the hydraulic oil smells a “coking” smell locally, it means that the hydraulic components such as the hydraulic pump are locally heated, causing the surrounding hydraulic oil to be scorched, and the heating location and cause can be judged based on this.

② Smell whether the hydraulic oil has a foul odor or a pungent spicy smell. If so, it means that the hydraulic oil has been seriously contaminated and cannot be used.

③ Smell whether there is any peculiar smell in the working environment to judge whether the insulation of electrical components is burned, etc.

5. Review:

Review the equipment technical files for relevant fault analysis and repair records, daily inspection and scheduled inspection cards, shift handover records, and maintenance records.

6. Inquiry:

Communicate with the equipment operator to understand the normal operation of the equipment. Mainly ask the following questions:

① Whether the hydraulic system works normally and whether the hydraulic pump has any abnormal phenomenon.

② When the hydraulic oil is replaced and whether the filter is clean.

③ Whether the seals or hydraulic parts have been replaced before the accident.

④ What abnormal phenomena occurred in the hydraulic system before the accident.

⑤ What faults have often occurred in the past and how they were eliminated, and which maintenance personnel are more clear about the causes and elimination methods of the faults.

⑥ Whether pressure adjustment or speed adjustment was performed before the accident, and what adjustments were made.

Simple diagnostic methods can quickly determine the fault conditions of hydraulic systems and are suitable for some common fault diagnosis. However, for some complex fault conditions, more sophisticated diagnostic techniques are required.