1、 Daily Maintenance: Basic Inspection and Operating Standards

1. Running status monitoring
   • Indicator light inspectionObserve the status of PLC panel indicator lights (power light, running light, fault light) daily. If the power light goes out, check the power supply circuit; Abnormal flashing of the running light may indicate program errors or hardware failures; Record and troubleshoot immediately when the fault light is on.
   • signal monitoringReal time monitoring of key data such as input/output signals, temperature, pressure, etc. through human-machine interface (HMI) or programming software (such as Siemens TIA Portal, Mitsubishi GX Works) to confirm consistency with on-site equipment actions. If no response or misoperation is found in the signal, the wiring or sensor should be checked.
2. Operational standardization
   • Start stop processStrictly follow the regulations to start and stop the PLC, avoiding direct power outages that may cause program or data loss.
   • Permission ManagementNon professionals are prohibited from modifying programs or parameters, and all adjustments must be authorized and backed up.

2、 Regular maintenance: systematic inspection and preventive measures

1. Hardware inspection
   • Clean dust removalWipe the PLC casing and heat dissipation holes with a dry soft cloth every month to remove dust (especially the ventilation openings) and prevent poor heat dissipation. Disassemble and clean the power rack, CPU motherboard, and input/output board every quarter or half a year, and clean the heat dissipation holes and air ducts.
   • Tightening of wiringCheck the power supply and I/O module wiring terminals for looseness every month (which is easily caused by vibration environment), and tighten them one by one with a screwdriver to avoid poor contact.
   • Module StatusConfirm whether each module (CPU, I/O, communication module) is normal through PLC diagnostic function or indicator lights. If the module temperature rises abnormally or the indicator light reports an error, it needs to be replaced in a timely manner.
   • Battery MonitoringCheck the voltage of the CPU backup battery (such as the Siemens S7-300 battery, which has a lifespan of about 3-5 years) to avoid program loss caused by battery failure.
2. Software and Data Maintenance
   • Program BackupBackup PLC programs and parameters to external storage devices (such as USB drives and servers) every month through programming software, and label the backup date and version.
   • Program diagnosisUse the online diagnostic function of programming software (such as Siemens' "diagnostic buffer") to view historical fault records, analyze program errors or communication interruptions, and optimize logic.
   • Software UpdateRegularly update PLC software versions as needed, fix vulnerabilities or improve performance, and ensure backup programs before updates.
3. environmental monitoring
   • Temperature and Humidity ControlRecord the ambient temperature and humidity (PLC working temperature 0-55 ℃, humidity 20% -85% without condensation), and adjust the air conditioning or dehumidification equipment if it exceeds the range.
   • Cleanliness managementAvoid metal dust and corrosive gases, and install air purification equipment if necessary.

3、 Fault handling: rapid location and recovery

1. Troubleshooting process
   • power supply inspectionIf the POWER indicator light is not on, check the power supply circuit and fuse.
   • System self-testStart the PLC and check if the "RUN" indicator light is normal and if there are any alarms.
   • I/O module testingCheck the power supply voltage and input/output port signals of the module, and confirm that the corresponding indicator lights are displaying normally.
2. emergency measures
   • data recoveryIf the program is lost due to battery failure, immediately restore it from backup.
   • Module replacementReplace faulty modules (such as CPU, I/O board), power off and take anti-static measures before replacement.

4、 Environmental management: ensuring long-term stable operation

1. Physical environment control
   • Installation locationAvoid placing the PLC near vibration sources, high-temperature equipment, or direct sunlight. It is recommended to install it in the control cabinet and reserve heat dissipation space.
   • Cleaning and maintenanceRegularly clean the dust inside the control cabinet (especially the cooling fan and ventilation openings) to prevent dust accumulation from causing short circuits.
   • Waterproof and insect proofTake waterproof measures to prevent water from splashing onto the equipment; Check if there are any small animals gnawing on the wiring or excreta contamination inside the cabinet.
2. Electromagnetic environment protection
   • grounding protectionThe grounding resistance of the control cabinet should be less than 4 Ω to avoid static electricity or induced electrical interference.
   • Line separationStrong current lines (such as power cables) and weak current lines (such as PLC signal lines) should be wired separately with a minimum distance of 30cm, and shielding layers or magnetic rings should be added if necessary.