What are the fault types of 01classPLC? External device failure
External devices are various switches, sensors, actuators, loads, etc. that are directly related to the actual process of the PLC. The failure of these devices will directly affect the control functions of the PLC system. Therefore, to repair the PLC, it is first necessary to distinguish whether the external equipment is faulty or the PLC itself is faulty.
system error
1) System failure is a global failure that affects the operation of the PLC system.
2) PLC system faults can be divided into fixed faults and accidental faults.
3) After the fault occurs, it can be restarted to restore the system to normal, which is an accidental fault. If the reboot cannot be recovered, but the hardware or software needs to be replaced, the system can be restored to normal, and it is considered a fixed fault.
hardware malfunction
PLC hardware failure mainly refers to the failure caused by the damage of the template and circuit in the PLC system.
Software failure
PLC software failures include software errors, operational errors, and so on. PLC software faults can generally be viewed and checked by the PLC's own self-diagnostic test function or software.
What is the failure rate of the 02classPLC control system? 1) CPU and memory failure rate accounts for 5%.
2) I/O module failure rate accounts for 15%.
3) Sensor and switch failure rate accounts for 45%.
4) The actuator failure rate accounts for 30%.
5) The failure rate of other aspects such as wiring accounts for 5%.
What are the failure points of 03classPLC? 1) Relays, contactors.
2) Valves and gates.
3) Switches, extreme positions, safety protection, some components or equipment for on-site operation.
4) Sub-devices in the PLC system.
5) Sensors and meters.
6) Noise from power, ground, and signal lines.
What are the general methods of 04class maintenance PLC?
Table 1 General rules for some methods of repairing PLC
What is the order of 05class maintenance PLC? First move again
1) When repairing the PLC, do not immediately start directly, but first ask about the situation before and after the fault, the fault phenomenon
2) If you are repairing a rusty PLC, you should first understand how it works.
Clean and then repair
When servicing the PLC, you can turn on the machine and first clean the PLC.
First outside and inside
When servicing the PLC, first check the external phenomenon and cause. If the external is normal, then check the inside of the PLC.
First, no electricity judgment, power-on judgment
First, in the absence of power, first determine whether the fuse is damaged, whether it is not energized, you can determine the point of failure. If it is not possible to judge, power up and check the PLC.
What is the process of 06classPLC system maintenance and troubleshooting? Overall diagnosis
The general direction of the fault point can be found according to the overall inspection flow chart, and then the specific fault is gradually refined.
Power failure diagnosis
If the power light is off, check the power supply system and the power light itself.
Operational troubleshooting
If the power is normal and the running indicator is off, the system may terminate normal operation due to some abnormal cause.
Input and output troubleshooting
1) Input and output are channels through which the PLC communicates with external devices.
2) Whether the input and output work normally, in addition to the input/output unit, it is also related to the status of components such as connection wiring, terminals, and fuses.
What is the procedure for 07class to find general PLC faults?
When the PLC is being repaired, insert the programmer and turn the switch to the RUN position, then find the following steps:
1) If the PLC stops at a position, state (local) where some outputs are energized, and is generally in an intermediate state, it looks for a signal that causes the next operation to occur, and the programmer displays the ON/OFF state of the signal.
2) If the signal is input, the status displayed by the programmer is compared with the LED indication of the input module. If the results are inconsistent, the input module needs to be replaced. Before replacing the module, you need to check whether the I/O extension cable and related connections are normal.
3) Compare the status of the LED and the input device if the input status matches the LED indication of the input module. If the two are different, you need to measure the input module. If you find a problem, you will need to replace the I/O device, field wiring, power supply, and so on. Otherwise, the input module needs to be replaced.
4) If the signal is a coil, there is no output or the output is different from the state of the coil, then the programmer is required to check the drive logic of the output and check the program list.
5) If the signal is a timer and stops at a non-zero value less than 999.9, the CPU module needs to be replaced.
6) If the signal controls a counter, the logic that controls the reset needs to be checked first, and then the counter signal is checked. Then check and judge whether the relevant components are abnormal and need to be replaced.
08class how to repair PLC common faults?
Table 2 Methods for repairing common faults of PLC
How does 09class exclude PLC faults based on changes in the indicators on the panel?
Table 3 Methods and points for troubleshooting PLC based on changes in indicators on the panel
How do 10class repair some PLC faults?
Table 4 Methods and points for repairing some PLC faults
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