Phenomenon:
1. The steam flow rate is abnormally less than the feed water flow.
2. In serious leakage, the main steam pressure drops sharply.
3. The negative pressure of boiler abnormal reduces or is inclined to positive pressure. In serious case, steam injects and smoke emits from the place of that is not tightly sealed.
4. The temperature of fume in the back of the superheater reduces or the temperature difference on both sides increases.
5. The temperature of superheated steam changes, if the steam leaks from the inlet side, the temperature of steam is high. If the steam leaks from the outlet side, the temperature of steam is low.
6. There is noise near the leak point.
7. When the high superheater and low superheater leak, the temperature of exhaust fume reduces.
Causes:
1. The chemical water is not strictly supervised, the structure of steam and water separator is poor or has defects, thus causing poor quality of steam, and scale occurs inside the superheater, and it has not been completely cleared during maintenance , thus causing the temperature of pipe wall to rise.
2. During ignition and pressurization process or running at ordinary times, if the operation is not proper, the steaming capacity of is not insufficient or the temperature of main steam is too high, thus causing overheating.
3. Because of the change in operating conditions and kinds of coal, the operation adjustment is not timely, the superheater tube wall is overheated.
4. The material of superheater does not conform to the standard, the manufacture, installation, and welding quality are poor, and ash-blowing is improperly operated.
5. The superheater is blocked by sundries.
6. It is abraded by flying ash and due to long running time, the tube creeps and bulges, and deforms.
Treatment:
1. Check the leakage situation, if it is serious, it must be immediately reported to the shift engineer in charge to shut down boiler in emergency in order to prevent the steam injecting from the damaged superheater from blowing and damaging the tunes of adjacent superheater and enlarge the accident.
2. If the leakage is slight, the evaporation capacity of boiler can be reduced, and the boiler can be operated within short time, but the gas leakage shall be regularly checked and the standby boiler shall be quickly started. If the failure situation intensifies, the boiler shall be stopped in emergency.
3. After the boiler is shut down, close the main steam valve and keep the induced draft fan continues to run in order to eliminate the flue gas and steam inside the boiler. If one boiler and one steam turbine are running, to close the main steam valve shall be approved by the shift-chief operator.
4 If the platen superheater leaks, after the boiler is shut down, the primary fan and the induced draft fan shall be kept running and the bed materials shall be discharged.
5. If the cyclone separator or outlet import flue superheater tube leak, then the returns fan shall be kept running and the ash materials shall be drained out from the separator.
Prevention for damage of superheater:
1. Strengthen the supervision on chemical water, improve the efficiency of separation of steam and water and improve the quality of saturated steam.
2. Control the qualified main steam temperature, timely adjust the combustion mode, and keep the fume temperature of left and right inlet of the superheater tend to be equal.
3. During overhaul and routine repairing, strengthen the measurement to the superheater tube, check the record, the maximum allowable pipe creep bulge value: for alloy steel: it is 2.5% of the pipe diameter; for the carbon steel, it is 3.5% of the pipe diameter.
4. If there is dirt inside the superheater tube, then the separator of steam and water inside the steam drum shall be checked to improve the quality of boiler water and feed water, improve the steam quality, The superheater shall be backwashed.
5. Adhere to the correct way of ignition and pressurizing regulation and combustion mode.
