1、 Daily inspection and basic maintenance

1. Visual inspection
   • Thermocouple wire inspectionRegularly inspect the metal casing of armored thermocouples for cracks, deformation, or corrosion, with particular attention to whether the welding points are secure. If the casing is found to be damaged, it should be replaced immediately to prevent short circuits or temperature measurement failures caused by exposed internal thermocouple wires.
   • Inspection of wiring terminalsCheck if the wiring terminals are loose, oxidized, or corroded. Loosening can lead to poor contact, oxidation can increase resistance, and affect temperature measurement accuracy. Use sandpaper to gently polish the oxide layer and re tighten the terminals.
   • Insulation layer inspectionCheck if the insulation layer (such as ceramic or fiberglass) is damaged or aged. Damage to the insulation layer may cause a short circuit between the thermocouple wire and the metal sleeve, and the insulation material needs to be replaced in a timely manner.
2. Environmental adaptability inspection
   • Temperature range verificationConfirm whether the working temperature of the thermocouple is within its rated range (such as -200 ℃~1200 ℃ for K-type thermocouples). Overtemperature use can accelerate the aging of thermocouple wires and even cause them to melt.
   • Protection against corrosive environmentsIf used in corrosive media such as acid or alkali, it is necessary to regularly check whether the casing is corroded. If necessary, choose corrosion-resistant casing materials (such as Inconel 600).
   • Mechanical vibration protectionWhen used in a vibrating environment, it is necessary to check whether the fixed bracket is loose to avoid thermocouple breakage due to vibration.

2、 Regular maintenance and calibration

1. Cleaning and maintenance
   • Dust cleaningClean the dust on the surface of the thermocouple with a soft bristled brush or compressed air to avoid dust affecting the temperature measurement accuracy.
   • Dirt removalIf the thermocouple comes into contact with a medium (such as liquid or gas), surface dirt should be regularly removed. Alcohol or specialized cleaning agents can be used for wiping, but corrosive cleaning agents should be avoided.
2. Calibration and Accuracy Verification
   • periodic calibrationCalibrate every 3 to 12 months based on usage frequency and environment. Calibration methods include comparative method (comparing with standard thermocouples) and fixed point method (calibrating at fixed temperature points such as freezing and boiling points).
   • Cold end compensation inspectionIf using a cold end compensator, it is necessary to regularly check if it is working properly. Cold end temperature fluctuations can cause temperature measurement errors, and it is necessary to ensure that the compensator is consistent with the actual ambient temperature.
3. Response time test
   • Dynamic response verificationIn scenarios of rapid temperature changes, it is necessary to test the response time of thermocouples. If the response slows down, it may be due to aging of the thermocouple wire or scaling of the sleeve, which needs to be replaced or cleaned in a timely manner.

3、 Fault handling and emergency measures

1. Abnormal temperature measurement handling
   • Large temperature fluctuationsCheck if the wiring is loose, if the compensating wires are compatible, and if the cold end temperature is stable. If the problem persists, it may be due to the aging of the thermocouple wire, which needs to be replaced.
   • Low temperature displayIt may be a short circuit in the thermocouple wire or fouling in the sleeve. Check the resistance with a multimeter, and replace it if there is a short circuit; If dirt accumulates, it needs to be cleaned.
   • No temperature displayCheck if the power supply, wiring terminals, and compensation wires are open circuited. If everything is normal, it may be that the thermocouple wire is blown and needs to be replaced.
2. Physical damage treatment
   • Bending or fracture of casingIf the casing is slightly bent, special tools can be used to correct it; If it breaks, it needs to be replaced immediately to avoid medium leakage and safety accidents.
   • Welding point detachmentIf the welding point becomes loose, it needs to be re welded. Temperature and time should be controlled during welding to avoid oxidation of thermocouple wires.

4、 Safety precautions

1. Power-off operationBefore maintenance, the power must be cut off to avoid the risk of electric shock.
2. Explosion proof environment adaptationWhen used in explosive environments, explosion-proof thermocouples should be selected and the junction box should be well sealed to prevent explosive gases from entering.
3. high-temperature protectionWhen operating in high temperature environments, it is necessary to wear heat-resistant gloves and protective face shields to avoid burns.
4. Media compatibilityEnsure that the thermocouple material is compatible with the contact medium. For example, copper based thermocouples should be avoided in sulfur-containing environments to prevent sulfide corrosion.

5、 Storage and Transportation Standards

1. storage environmentThermocouples should be stored in a dry and ventilated warehouse, away from direct sunlight and humid environments. The recommended storage temperature is -20 ℃~50 ℃, and the relative humidity is ≤ 80%.
2. Transportation ProtectionDuring transportation, it is necessary to use specialized packaging boxes to secure it and avoid severe vibrations or collisions. If not used for a long time, regular power on inspections are required to prevent components from getting damp.

6、 Record and traceability management

1. Maintenance RecordEstablish a maintenance register to record the time, content, replaced parts, and calibration results of each maintenance.
2. Lifetime trackingBased on the usage environment and frequency, establish a replacement cycle for thermocouples (usually 2-5 years). When it expires or irreversible damage occurs, it needs to be replaced in a timely manner.