Overview: fault diagnosis that changes the system structure

1. determine the status of the component by replacing components in the system

After a preliminary diagnosis of the equipment's malfunction symptoms on the spot, it is suspected that the cause of the fault is above a certain component, and that it can be disassembled and loaded with a normal component. For example, for the solenoid valve, if it is in the direction of noise, it may be the electromagnet itself, may also be caused by other causes of the valve solenoid work is not normal. At this time, a good electromagnet can be used to change the electromagnet on the fault electromagnetic valve, and then observe the commutation noise, thereby judging whether the electromagnet is damaged or not.

2. determine the state by eliminating certain aspects of the control loop

This method is to cancel some aspects of the hydraulic circuit, and then observe whether the symptoms of the fault change. For example, the hydraulic pump abnormal noise, may be suspected of excessive oil absorption resistance, causing cavitation. In order to confirm this hypothesis, you can remove the pump oil filter, reduce oil absorption resistance, and then observe whether the pump sends abnormal noise.

The hydraulic system often has a more complex control circuit, the circuit has the question, inevitably causes the hydraulic system to work abnormally. In the analysis of the fault, we can try to cancel part of the link in the control circuit, and then observe whether the symptoms have changed.

For example, the hydraulic cylinder of hydraulic equipment in the movement appeared in the process of vibration, suspected to be caused by connecting the control circuit is not strong, so in the control circuit respectively through wires each related components from the circuit short circuit (Figure 8-13), find out the cause of the malfunction in hydraulic cylinder stop limit switch for spring fatigue, not often closed angle contact disconnect the circuit under pressure after the reliable reset to the closed state, and the signal is intermittent, caused by hydraulic cylinder vibration.

3. determine the state of the system by changing the connection of the circuit in the system

May include several circuits in the same or similar hydraulic system, if one loop does not work properly, the normal work of the loop detection is not working properly, namely the use of the normal work of the circuit, circuit experiment platform.

     A cement kiln hydraulic equipment as shown in Figure 8-14, A cylinder hydraulic system can run normally, cylinder B not action, because the hydraulic cylinder load in the kiln, the load do not know, it is more difficult to judge the condition of loop cylinder B. At this time, the upper cylinder A loop to cylinder B oil hose, and the cylinder top B loop hose receiving cylinder of A oil port, which can easily judge the relevant parts of cylinder B loop status: if this is still A B cylinder cylinder movement, cannot move, the cylinder or load B have a problem; in turn, if the cylinder A cannot move, can exercise the B cylinder, cylinder B loop control valve has a problem.