The machine in dregs of a certain power plant in Shanxi Province lead to abnormal shutdown of unit analysis report

The machine in dregs of a certain power plant in Shanxi Province lead to abnormal stoppage analysis report 2019 - unit 06 - 29 a, event analysis unit number: 3 time: on December 12, 2018, 21:51 equipment brief: boiler no. 3 generating unit in one power plant in shanxi is made by the wuhan boiler co. , LTD. WGZ1053/17. 5 - Type 2 lean coal boiler. Model for the subcritical natural circulation drum boiler, medium speed mill positive pressure direct blowing pulverizing system, level of once-through shutter shade burner, four corners to decorate, tangential combustion mode. GBL - no. 3 boiler configuration 12× N type slag scraper fishing machine, scraper in dregs machine for a ship form of a cuboid. Slag by the big ash hopper fall to machine in dregs, and then by scraping board will slag slag crusher, slag crusher to break slag for 25 to 30 mm particles, slag by bucket elevator to warehouse outside eduction body. Prior condition: 06:30 on December 12, 2018, the 181 mw unit 3 load of a certain power plant in Shanxi Province, the main steam pressure 11 mpa, main steam temperature of 541 ℃, reheater pressure 2. 5 mpa, reheat steam temperature of 540 ℃, coal of 150 t, five sets of grinding operation, unit 3 with heating system, heating extraction flow of 155 t/h. Incident: 06:30 on December 12, 2018, the 181 mw unit 3 load of a certain power plant in Shanxi Province, the main steam pressure 11 mpa, coal of 150 t, five sets of grinding operation. Boiler no. 3 in dregs in the operation of the machine for chain rupture tripping, on-site inspection found that the west side of the nose of the chain rupture in dregs, maintenance staff to handle ticket to carry out repair work. 07:40 points, too many machine inner product residue in dregs, which appear in dregs machine hull overflow, load down to 110 mw, maintain the lower three grinding operation. At 10:30, start the circulation pump, electric network shut down the steam heat supply network circulating pump. 1 points, restore sports chain in dregs, the related machine in dregs. In dregs after the machine start found in dregs tail scraper with sloping phenomenon, maintenance staff to adjust when tight chain wheel height and firmness, adjusted many times cannot solve the problem of slope, and found that the west side of the chain operation is on the east side chain is slow, preliminary confirmation within guide wheel chain off. The plague, slag deposition increase more than cold ash hopper 4. 5 meters observation hole. 14:05 points, maintenance staff to open the nose department in dregs roller bearing cover, will begin idler pulley in whole dig out slag discharge, and fire water on in dregs of inclined section of the nose, the guide wheel outside of slag flushing and cooling work, plans to turn the head area at the bottom of the idler pulley product residue after clean internal guide wheel off the chain to repair. Points, and as a result of slag deposition more machine hydraulic ram cannot close in dregs, roller bearing cover are spot slag slag, high temperature spray water jet, the upper hull has a large area of high temperature slag deposition from time to time, workers can't close to the machine to carry out the repair work in dregs. In the case of unable to ensure the safety of operating personnel decisions after being immobilized to overhaul the machine in dregs. Notify the county government and a heating power co. , LTD for temporary repair heating system output reduction operation, and the county government and heating company understanding and support. Heating system with heat load by the startup boiler, heating system to maintain the lowest output, the night of a certain power plant in Shanxi Province tissue repair in the shortest possible time to recover the heating parameters. The choicest points, to start the boiler ignition. At 21:00, began to slide stop unit 3. 'To start the boiler with heating heat load, heat extraction flow of 20 t/h, did not cause significant impact to the heating system. 21:51, December 12, 2018 points, manually hits the brake unit 3, no. 3 generator and system solution, boiler fire-extinguishing. On December 13, 2018, 10:09 points, grid-connected power generation unit 3. Cause analysis: in dregs machine fault tripping in the operation of chain, the chain repair after start-up, found in dregs tail department is on the east side and west side chain chain scraper inclined slowly, the west side of judgment in dregs machine internal guide wheel within the chain off. Accident emergency repair for a long time and machine hull in dregs and cold chamber of a stove or furnace bottom ash hopper slag deposition is more, in dregs machine hydraulic ram cannot close. After open the roller bearing cover inside machine in dregs, roller bearing cover are spot slag slag, high temperature spray water jet, the upper hull has a large area of high temperature slag deposition from time to time, workers can't close to the machine to carry out the repair work in dregs. Manual brake, machine stop temporary repair. Exposed problems: 1, the captain in dregs cycle operation lead to equipment wear and tear, not regular inspection equipment wear, not comprehensive work on a regular basis. 2, accident repair time is long, maintenance personnel technical level is not high, accident forecast and emergency plan management does not reach the designated position. 3, burning coal deviates from the design value is bigger, intensifying ash slag system equipment wear and tear. 4, in dregs machine shut down after the failed to timely load down, failed to timely by reducing coal slag quantity control. Precautions: 1, improve the machine working on a regular basis in dregs, to chain, fittings, scraper, when tight round regular maintenance check, improve equipment reliability. 2, the use of unit maintenance opportunity to replace machine wear chain in dregs, spare parts reserve important parts. 3, perfect the emergency plan, strengthen emergency exercise, to strengthen the maintenance staff skills training, enhance the level of maintenance technology. 4, slag system failures, quit running, control the output of generating unit shall be at the lowest security load; When necessary, exit the coal mill run, in order to prevent the furnace ash accumulation is overmuch, until the slag system back to normal operation. 5, to strengthen the study of group similar non stop case, to avoid a recurrence. 6, to shut off the door of furnace bottom rigor of illness, studies the necessity of improvement. 7, in dregs machine failure occurs, should be out of work places to overhaul, maintenance work. Second, preventive measures to carry out the flow chart of table 3, abnormal downtime analysis attached figure 1: the scene picture attached figure 2: major accident process DCS parameter curve ( Source: the electric power production safety)