Reprint--Analysis and treatment of common faults in thermal control

Source: Thermal Control Circle

Part I

1. Fluctuation of temperature measurement points

Accident phenomenon: The measurement point shows irregular fluctuations

Cause of the accident:

1) Loose wiring of local equipment.

2) The junction box wiring is loose.

Solution:

1) Look for loose spots.

2) Re-tighten.

3) Replace the screws immediately if they cannot be tightened.

Treatment effect: the reason for the loosening of the screw is that it is not tightened well during installation and commissioning, and because the anti-loosening washer is not used, the long-term vibration of the unit is large. Plans have been made to purchase anti-loosening washers and replace them gradually in an effort to minimize such accidents.

2. Temperature measurement point dead pixel

Accident phenomenon: The measurement point indicates the minimum or maximum, which becomes a dead pixel

Cause of the accident:

1) Loose wiring of local equipment.

2) The junction box wiring is loose.

3) Short circuit in the wiring of local equipment.

4) Short circuit in junction box wiring.

5) The temperature element is short-circuited and the element is damaged.

6) The temperature element is open and the element is damaged.

Solution:

1) Measure the resistance of the temperature element.

2) Check the in-place wiring.

3) Check the junction box wiring.

4) Replace the temperature element.

5) Tighten or replace the screws.

Treatment effect: For the components that are repeatedly damaged, the sampling location and special protective sleeve are replaced. After the loose part is tightened, it performs well.

3. Sootblower travel switch

Fault phenomenon: the sootblower does not work, and the limit is exceeded

Cause of failure:

1) The travel switch does not work: the switch does not operate due to the mechanical jam. The switch itself is damaged, causing it to not function. The mechanical limit is overrun, and the switch cannot be automatically reset, resulting in inaction.

2) The position of the travel switch is not set well: the position is set forward or backward, and the sootblower cannot be stopped after it travels in place, and it continues to walk, resulting in the dislocation of the soot blower, and the limit needs to be set again.

3) Line failure: the line is connected or loose, resulting in the switch not operating or malfunctioning.

Solution:

1) Check the switch: whether the switch is jammed, whether the action is flexible and accurate.

2) Position check: Manually run the sootblower to observe whether the stroke is in place and whether it is overrun. Re-set the switch position reasonably and correctly.

3) Circuit inspection: check whether the line connection is loose, tighten the terminals, replace the screws and other necessary accessories.

Treatment effect: the main problem of the soot blower is manifested in the travel switch, as long as the travel switch is carefully and carefully reset, the thermal part can ensure that it is in good operating conditions.

4. Coal mill outlet gate feedback failure

Fault phenomenon: the feedback of the exit gate door of the coal mill is not correct or the door cannot be operated

Cause of failure:

1) Switch feedback failure: Due to the harsh environment, the mechanical part of the switch is ashed, resulting in the switch jamming and inability to operate correctly. The switch body is dusted, causing the switch to fail to operate correctly. The switch itself is faulty, causing the switch to not operate or malfunction.

2) Because the feedback of the switch is not in place, the program can not be executed correctly, such as the signal that is closed in place when it is opened but does not come back, and the feedback is not correct, resulting in the door can not move.

Solution: Check and clean the switch: replace the switch with better quality. Check whether the switch action is good, whether the dust is in, and whether the action feedback is correct.

Treatment effect: The treatment effect is good. Strengthen the intensity and frequency of inspections, prevent such accidents before they occur, regularly clean up the dust accumulation of the travel switch, and take preventive measures. If there is a problem with the switch itself, replace the switch with better quality in time.

5. Coal mill sealing damper feedback failure

Fault phenomenon: the feedback of the sealing damper of the coal mill is not correct or the door cannot be operated

Cause of failure:

1) Switch feedback failure: Due to the harsh environment, the mechanical part of the switch is ashed, resulting in the switch jamming and inability to operate correctly. The switch body is dusted, causing the switch to fail to operate correctly. The switch itself is faulty, causing the switch to not operate or malfunction.

2) Because the feedback of the switch is not in place, the program can not be executed correctly, such as the signal that is closed in place when it is opened but does not come back, and the feedback is not correct, resulting in the door can not move.

Solution: Check and clean the switch: replace the switch with better quality. Check whether the switch action is good, whether the dust is in, and whether the action feedback is correct.

Treatment effect: The treatment effect is good. Strengthen the intensity and frequency of inspections, prevent such accidents before they occur, regularly clean up the dust accumulation of the travel switch, and take preventive measures. If there is a problem with the switch itself, replace the switch with better quality in time.

6. Ignition gun and oil gun failure

Fault phenomenon: the fault feedback of the ignition gun and oil gun is incorrect or unable to operate

Cause of failure:

1) Solenoid valve failure: due to the harsh environment, the solenoid valve is injected, resulting in inadequate action, solenoid valve gas string, air leakage, so that the ignition gun, oil gun action is not in place or does not act.

2) Switch feedback failure: due to the harsh environment, the mechanical part of the switch is ashed, resulting in the switch jamming and unable to operate correctly. The switch body is dusted, causing the switch to fail to operate correctly. The switch itself is faulty, causing the switch to not operate or malfunction.

3) Due to the feedback of the switch is not in place, the program can not be executed correctly, such as the signal that is closed in place when it is opened but does not come back, and the feedback is not correct, resulting in the door can not move.

Solution:

1) Check and clean the solenoid valve: manual trial operation, observe whether the solenoid valve is in action and whether the action is good. If there is a problem with the solenoid valve, disassemble the solenoid valve for cleaning, lubrication and reassembly. Replace the solenoid valve with a new one.

2) Check and clean the switch: replace the switch with better quality. Check whether the switch action is good, whether the dust is in, and whether the action feedback is correct.

Treatment effect: The treatment effect is good. Strengthen the intensity and frequency of inspections, so that such accidents can be prevented before they occur, regularly clean up the dust accumulation of solenoid valves and travel switches, and take preventive measures. If there is a problem with the solenoid valve and switch itself, replace the solenoid valve and switch with better quality in time.

7. Flue air system damper feedback

Fault phenomenon: the feedback of the damper baffle of the flue air system is incorrect or the baffle cannot be operated

Cause of failure:

1) Door Block: This reason accounts for the majority of such failures.

2) Switch feedback failure: due to the harsh environment, the mechanical part of the switch is ashed, resulting in the switch jamming and unable to operate correctly. The switch body is dusted, causing the switch to fail to operate correctly. The switch itself is faulty, causing the switch to not operate or malfunction.

3) Due to the feedback of the switch is not in place, the program can not be executed correctly, such as the signal that is closed in place when it is opened but does not come back, and the feedback is not correct, resulting in the door can not move.

Solution:

1) Notify the maintenance staff to deal with it.

2) Check and clean the switch: check whether the switch action is good, whether the dust is in, and whether the action feedback is correct.

Treatment effect: strengthen the intensity and frequency of inspections, prevent such accidents before they occur, regularly clean up the dust accumulation of the travel switch, and take preventive measures. If there is a problem with the switch itself, replace the switch with better quality in time.

8. The pressure transmitter indication is inaccurate

Fault Symptom: The pressure indication is high or low

Cause of failure:

1) Transmitter zero drift.

2) Transmitter leakage.

Solution:

1) Close the secondary door.

2) Use a communicator to check the zero point of the transmitter.

3) Adjust the transmitter zero point.

4) Check for leaks.

Treatment effect: The zero drift of the transmitter is a normal phenomenon, and the effect is better after the processing is completed. Rarely, it is an external problem of the transmitter, such as leakage, and the effect is good after treatment.

9. Local pressure gauge

Fault phenomenon: the pressure gauge indication is inaccurate and damaged

Cause of failure:

1) Quality problems: Some local meter manufacturers are not good, and the quality of the meter is poor, resulting in damage.

2) Improper selection: improper selection of the measurement range of the in-situ meter, small range selection, and the fluctuation of the instrument is easy to cause damage. The vibration resistance type should be selected at the outlet of the pump body, but the ordinary pressure gauge should be used, which will cause damage

3) Installation problems: where there are large fluctuations, no damper is installed, resulting in damage to the instrument.

Solution:

1) Reset the check.

2) Check and repair.

3) Replace the table with a new one.

4) Add dampers.

Treatment effect: The treatment effect is good, and there is basically no repetitive failure. Limited to the influence of equipment operating conditions and the constraints of spare parts, it cannot be completely eradicated

10. Hydrogen station pressure reducing valve

Fault phenomenon: the pressure reducing valve is leaking or the pneumatic door is not working well

Cause of failure:

1) Gas corrosion: The environment where the hydrogen station is located contains a large amount of corrosive gas, which corrodes the sealing ring of the pressure reducing valve greatly, and the sealing ring is damaged due to long-term corrosion, resulting in the leakage of the pressure reducing valve. When the leakage is serious, the pneumatic door does not operate well.

2) Pressure reducing valve quality problems.

Solution:

1) Disassemble the pressure reducing valve.

2) Replace gaskets and seals.

3) Fastening and reloading.

4) Replace the pressure reducing valve.

Treatment effect: It is recommended to replace all pressure reducing valves with high corrosion resistance.

Part II

1. In the production temperature measurement of industrial thermocouples, if it is found that the thermoelectric potential of the thermocouple is smaller than the actual value, it may be caused by the following reasons:

1. Short circuit.

2. The compensation wire is short-circuited due to burning insulation.

3. Short circuit between the binding posts in the thermocouple junction box.

4. The compensation wire is reversed from the thermoelectric dipole

5. The compensation wire does not match the thermocouple.

6. The temperature of the cold end of the thermocouple is too high.

7. The insertion depth is not enough and the installation position is wrong.

The right way to deal with it:

1. After inspection, if it is caused by moisture, it can be dried; If it is due to poor insulation of the porcelain tube, it should be replaced.

2. Re-insulate the short-circuit or replace it with a new compensation wire.

3. Open the junction box and brush the wiring board clean.

4. Reconnect correctly.

5. Replace with the same type of compensation wire.

6. The connecting wire of the thermocouple is replaced with a compensation wire to move the cold end away from the high temperature area.

7. Change the installation position and insertion depth.

2. In the production temperature measurement of industrial thermocouples, if it is found that the thermoelectric potential of the thermocouple is larger than the actual value, it may be caused by the following reasons:

1. The insertion depth is not enough or the installation position is incorrect.

2. The compensation wire does not match the thermocouple model.

3. Deterioration of the thermoelectrode.

4. The temperature of the thermocouple reference end is high.

5. There is an interference signal entering.

The right way to deal with it:

1. Change the installation position or insertion depth of the [Industrial Electrical Appliance Network-CNELC].

2. Replace the compensation wire of the same model.

3. Replace the thermocouple.

4. Adjust the temperature of the reference end or make corrections.

5. Check the source of interference and eliminate it.

3. In the production temperature measurement of industrial thermocouples, if it is found that the potential error of the thermocouple is large, it may be caused by the following reasons:

1. Deterioration of the thermoelectrode.

2. The surface of the thermocouple protective sleeve is overscaled.

3. The installation position and installation method of the thermocouple are improper.

4. The thermocouple circuit is disconnected.

5. Short circuit of measurement line (thermocouple and compensation wire).

6. The binding post is loose.

The right way to deal with it:

1. Replace the thermocouple.

2. Clean the surface scale of the thermocouple protective sleeve.

3. Change the installation location and installation method.

4. Find the disconnection and reconnect it.

5. Replace the insulation of the short circuit again.

6. Tighten the binding post.

4. In the production temperature measurement of industrial thermocouples, if it is found that the indication of the measuring instrument is unstable, sometimes coming and falling, sometimes high and sometimes low, it may be caused by the following reasons:

1. Thermocouples have intermittent short circuits or intermittent grounding.

2. The contact of the thermoelectrode at the terminal post is poor.

3. The thermocouple is not firmly installed and swings.

4. The thermoelectrode has been broken or seems to be broken.

5. The compensation wire has grounding or intermittent short circuit.

The right way to deal with it:

1. Take the thermode of the thermocouple out of the protection tube, find out the fault point and eliminate it.

2. Reconnect it.

3. Install firmly.

4. Replace the electrode with a new one.

5. Find out the fault point and eliminate it.