[Weekly Topic] Talk about the topics that have happened around you this week (September 5th---12th)

1. It’s mainly technical discussions. 2. Technical theory. 3. Industry information. 4. Technical differences and advantages and disadvantages among companies in the same industry. 5. Compensation issues.

Reply to 1# zgj2405: Should this reply be hidden? During maintenance work at a factory next to ours, the workers entered the tank without having the necessary permits; there was nitrogen inside the tank, which led to their death from asphyxiation； The person behind, not understanding what was going on, immediately followed and hung up as well. Ah, during today’s meeting it was mentioned that accidents happen in the blink of an eye; all rules and regulations were written in blood.

This post was last edited by dongjiang1001 on 2011-9-22 at 17:56. Our boilers use steam-mechanical misting nozzles; they burn residue oil, heavy oil, and diesel. They are startup boilers, and the oil pressure is adjusted using the oil return rate.

As of September 8, the Class A maintenance work on Unit #4 has been in full swing for nearly half a month. Over these little over half a month, the mill operators worked at the site for more than ten hours each day, which allowed the various construction teams to complete the disassembly of the equipment ahead of schedule and to enter the critical phase of maintenance work; what awaits them is a challenging task. Whenever we enter the boiler room at ground level, what catches our eye first are those large, cylindrical coal mills arranged in a row. Perhaps such large-scale equipment may seem intimidating to others, but for the technicians in the coal grinder maintenance team of the grinding unit, it is like the second life of the workers, worthy of all their effort and sweat to protect. During this maintenance period, the coal grinding team is required to disassemble, clean, replace bearings, and reinstall the four massive coal mills, as well as the reducers, gear sets, and related auxiliary equipment. They said we are ready to fight a tough battle. The maintenance conditions at the coal grinder site are undoubtedly harsh: the first issue is dirt. Every employee was covered in dark coal dust mixed with grease, making it impossible to tell the original color of their work uniforms ； The second is fatigue. Coal mills are large-scale equipment, and maintaining such a large number of them at the same time requires a high level of physical effort ； The third is suffering. Construction workers are constantly exposed to dust inhalation and intense light inside the cylinders while at work. It was in such an environment that they worked hard without complaint, dedicating ten hours a day to their tasks. In their eyes, dirt, fatigue, and hardship mean nothing; the only thing on their mind is not to hold up the project timeline and not to bring shame to those who work in flour production. The maintenance of the coal grinder in #4 furnace is a top priority among the tasks involved in this major overhaul. For this purpose, shift leader Xiao Hansheng, technician Li Jing, along with several other skilled workers from the team, carried out extensive preparatory work over a period of two months to carry out the equipment maintenance. First, they analyzed and studied the problems that have arisen in furnace coal grinder #4 over the past few years due to its prolonged operation period, such as excessive vibration of the large and small gears, as well as separation between the cylinder and the end caps. They devised safe and effective solutions and planned to carry out a disassembly repair of the grinder during the major overhaul, in order to eliminate defects such as separation between the cylinder and the end caps, misalignment of the mating surfaces of the large gears, and any gaps, thereby addressing the vibration issues associated with these gears once and for all. The equipment in the grinding unit is spread out over a large area with few personnel available; it is not an easy task to carry out a thorough maintenance check on such a large amount of equipment on schedule, while ensuring both quality and efficiency. Once the start date was determined, the maintenance team rushed to the site immediately, making the race against time the main focus of the grinding team’s work. In the first few days of the overhaul, removing the bolts that connected the large gear to the end caps was the main task. Faced with those 20 massive positioning bolts, 20 connection bolts, and 96 retaining bolts, the maintenance workers took turns using sledgehammers to break them apart; if one person couldn’t manage to break a bolt, another would take over immediately. Some screws required two people to apply force together, and the sound of hammering echoed continuously at the work site. Finally, everyone managed to knock off these bolts that had been tightly fastened or even rusted in place, one hammer blow at a time, in the shortest possible time. The scene was filled with cheers and joy. Although the weather was already a bit cool, the strenuous physical work made everyone sweat profusely while hammering. During the disassembly process, coal dust kept falling down with a ‘puffing’ sound, landing in their eyes and mouths. The workers responsible for grinding the coal had no time to pay attention to such things; they were so focused on their work that it made them forget all difficulties. The disassembly work has just been completed, and no one at the site stopped working. The experienced worker Huang Baogang immediately sent the removed pinion gears to be heated in order to align them properly. Huang Kewei quickly started cleaning the bearing housings, while He Jie inspected the bearing balls… Everything was carried out in an orderly manner, as if the loud knocking sounds from earlier had never happened. New tasks have now taken the place of the temporary sense of satisfaction achieved earlier. After several days of intense efforts, the powder makers are steadily making progress toward achieving the overall goal of completing the major overhaul of the unit. We have reason to believe that as long as we maintain firm confidence, unite as one, and overcome difficulties, we will be able to wage a successful campaign to tackle the coal grinder issue.

This post was last edited by pzhmotor on 2011-9-11 15:05. Accident notice to all processes and teams: Between 1:05 and 7:45 on September 7, 2011, an accident occurred in the steam production process: the #2 boiler had to be shut down for emergency repairs due to the detachment of the secondary bed air cap, which caused coking inside the secondary bed and the air chamber; this incident had a certain impact on the users’ production operations. The accident timeline and cause analysis are as follows. I. Accident Course 1. At 14:00 on September 4th, the Ding shift noticed a blockage in the slag discharge pipe of Boiler No. 2; bed cleaning was carried out during a period of low load on the boiler. During bed cleaning, it was found that a wind cap had fallen off next to the left slag discharge pipe in the secondary bed of Boiler No. 2. Considering that the user’s position will require steam in 30 minutes, the material needs to be replenished again to resume operation. In response to this situation, the process team gave instructions to the four work teams: the auxiliary bed fan of Boiler No. 2 must not be stopped to prevent ash from entering the air chamber. 2. On the 9th and 7th, Shift C noticed burnt residues on the secondary bed; bed cleaning and removal of accumulated material were carried out at 18:00 in the afternoon. At shift handover, the difference between the temperature above and below the secondary bed was 300°C. When Shift A took over, they asked for the reason; Bing told them that Shift A suspected a faulty thermocouple. After taking over at 20:00, the shift leader instructed an electrician to deal with the issue, and after checking, the electrician confirmed that the thermocouple was fine. 20:25, a slag discharge pipe on the auxiliary bed became blocked. At 21:00, the secondary bed of Boiler No. 2 was cleaned, and two large coke lumps were found. After cleaning, the material was reloaded at 22:30. At 23:50, upon startup, it was found that the temperatures above and below boiling in the secondary bed were abnormal, with a difference of 100°C, indicating poor boiling conditions. After shutting down the furnace for inspection, it was found that there were numerous low-temperature coke lumps in the secondary bed; therefore, at 0:15, the process supervisor was informed that the distribution of air in the secondary bed was problematic due to the loss of one air cap, which prevented the secondary bed from being put into operation. The process supervisor consulted with the workshop manager and the plant control team, and approval was given to shut down Boiler No. 2; it was shut down at 1:05 a.m. Due to the high temperature inside the boiler’s secondary bed, the fan was turned on to cool things down by 4:30; thereafter, maintenance personnel entered the furnace to weld the air nozzles and open the air chambers. It was found that the air chamber was filled with a large amount of dust, which had blocked the entire chamber; personnel were organized to handle the situation, and everything was resolved by 6:50. At 7:00, Boiler No. 2 began to be ignited; by 7:45, the ignition was successful and steam supply was established. II. Cause Analysis 1. On September 2, during the pre-startup inspection for Furnace No. 2, a thorough and careful inspection was not carried out, and the potential hazards associated with the auxiliary bed air nozzles were not detected in time. Despite objective factors such as the tight schedule for starting up Furnace No. 2 one day earlier, the shortage of staff due to shutdowns for maintenance, and the fact that the personnel on duty were busy, there was a certain degree of recklessness in the organization of the preparations before the boiler was put into operation, which failed to prevent the main factors that could lead to accidents from emerging in the first place. It is the main cause of this accident. 2. On September 4, improper operation by Shift D led to coking in the secondary bed and the need to clean it, which resulted in one of the air caps on the secondary bed falling off; this was a contributing factor to the accident. In subsequent work, production can only be maintained passively at the cost of adapting to the equipment. The process failed to report potential hazards in a timely manner, resulting in passive management in the workshop. 3. On September 7, Shift C, despite being aware that one of the wind cap covers on the auxiliary bed had fallen off, carried out operations carelessly, which led to coking on the auxiliary bed and poor discharge of slag. After cleaning the bed, the accumulation of debris caused ash to enter the wind chamber and cause blockages, resulting in uneven air distribution. The fact that they still handed over shift duties despite knowing about these problems was another factor that contributed to the accident. 4. On September 7, Shift A failed to pay sufficient attention to the problems identified upon taking over the shift, and the actions taken to address them were not timely; as a result, a large amount of ash entered the air distribution chamber, causing uneven air distribution, which was the direct cause of the accident. 5. From the date when the wind cap fell off on September 4 to the accident that occurred on September 7, the failure to report this potential hazard to the workshop in a timely manner was due to managerial shortcomings. III. Lessons Learned and Rectification Measures The occurrence of this accident was a process of continuity and the escalation of hidden risks. The root cause lies in the lack of attention to details and carelessness in thinking. In the next step, it is necessary to focus on strengthening the following tasks: 1. Enhance the inspection of equipment readiness, and assign responsibilities to specific individuals in accordance with the detailed requirements for readiness. 2. Serious attention must be paid to existing potential hazards, which should be addressed promptly and thoroughly; there should be no reliance on luck or delay in dealing with them. 3. Any issues discovered should be reported promptly and resolved thoroughly. 4. Strictly enforce shift-handover procedures; do not take over the shift until issues are resolved. 5. Operations must be carried out carefully to reduce the frequency of failures. IV. Assessment Comments: A fee of 500 yuan is imposed for the steam production process assessment. All processes and teams are requested to carefully study this notice, draw lessons from this accident in light of their own circumstances, and prevent similar accidents from occurring. Workshop XX, September 9, 2011