【Haichuan Safety and Environment Cup】--0007+Cooling tower overflow accident+Gongyu

Thread Content

This post was last edited by zhaolijun on 2015-8-8 21:17. Safety studies* – Record of study* time, location, safety officer, and topic of study. Account of the overflow incident in the cooling tower of the east half of the second circulation plant on 7·27. Purpose of the study*: To develop new approaches to safety management through the analysis of this accident, with a focus on prevention. Go beyond traditional management models, promote modern concepts of safety management, and vigorously implement proactive management aimed at achieving intrinsic safety. Safety Studies * Content: On the night of July 27, an overflow occurred in the cooling tower of the eastern half of the second circulation unit in the power plant, which led to an increase in the water volume at the wastewater treatment plant. I. Event timeline: At 16:47 on the 27th, the liquid level in the suction tank at the inlet of the pump in the east half of the secondary circulation plant dropped suddenly to 55%, which triggered a liquid level alarm from the DCS system controlling that area (the acceptable liquid level range is 55–75%). To prevent the water transfer pump from running dry and to ensure a stable water supply, the operators immediately took measures to supply fresh water directly to the inlet tank. They reported this to the plant engineer afterwards, who requested the following: 1. It is necessary to ensure a proper water supply to the refining plant; fresh water should be added until a safe water level is reached, so as to prevent the water transfer pump from running dry, while also avoiding discharge from the cooling tower ； 2. Adjust the outlet valve of the water pump to control the water output, thereby keeping the liquid level in the suction tank at a safe level. At 8:15 on the 28th, the on-duty operators received calls from both the power plant’s dispatch team and the head of the water supply department, who said that the wastewater treatment plant was generating a large volume of wastewater and requested that the amount of waste discharged be controlled. The Water Supply Department promptly organized efforts to identify the cause; after removing the debris that was blocking the return water inlet of Tower No. 3, overflow from Tower No. 3 ceased at 9:10. II. Cause analysis: 1. Upon inspection, it was found that the main reason for the overflow was the partial blockage of the cooling water return inlet grille by debris such as old plastic sheets, which prevented smooth return of cooling water. This led to an increase in the liquid level in the cooling tower, resulting in overflow. 2. The plant engineers and the operators on duty failed to promptly and accurately identify and resolve the cause of the sudden drop in liquid level. 3. When the water return volume was insufficient, the operator failed to properly control the amount of water added and the liquid level in the tank. III. Rectification measures: 1. Since the return water inlet grille at Liangshui Pit is currently made of fiberglass mesh, and this mesh is too small, it easily gets clogged at the return water inlet; the grille structure should be modified whenever possible. 2. Before the grid structure was modified, the grids were cleaned regularly on a weekly basis. Plant engineers and on-duty operators must check the return water condition of the cooling water system daily; any blockages or debris found must be removed immediately to maintain a safe liquid level in the pump suction tank. 3. Strengthen technical training for employees to improve their ability to identify and handle abnormal situations. In response to this incident, our department will conduct training for all staff on operational procedures as well as emergency response drills, so as to learn from this experience and prevent such incidents from occurring again. 4. Strengthen the connection between upstream and downstream production processes; in case of any problems during production, it is necessary to report them promptly to the power plant’s control room and the wastewater treatment plant. 5. Start by focusing on quality, systems, and implementation to comprehensively improve employee competence, ensuring that safe production remains under control through the reliability of personnel. IV. Penalty Recommendations 1. Luo*, the production director, who bears leadership responsibility, shall have 200 yuan deducted from his performance bonus ； 2. Equipment engineer Zhang **, who is directly responsible for management, has had 500 yuan deducted from his performance bonus ； 3. Shift leader Ding **, who is responsible for direct supervision, has had 500 yuan deducted from his performance bonus ； 4. On-duty operator Li*, who is directly responsible, will have 500 yuan deducted from his performance bonus. Insights from the cooling tower overflow incident* Through the study of this cooling tower overflow incident*, we realized that it led to an increase in the water volume at the wastewater treatment plant. The events unfolded as follows: in the system of the east half of the second circulation plant, the liquid level in the suction tank at the inlet of the water pump dropped suddenly to 55%, which triggered a DCS level alarm in the control room for that system (the acceptable range for the suction tank level is 55–75%). To prevent the water transfer pump from running dry and to ensure a stable water supply, the operators immediately took measures to supply fresh water directly to the inlet tank. They reported this to the plant engineer afterwards, who instructed that it was necessary first to ensure a proper water supply to the refining plant; fresh water should be added until a safe water level was reached, in order to prevent the water transfer pump from running dry, while also avoiding discharge from the cooling tower ； Adjust the outlet valve of the water pump to control the water output and maintain the liquid level in the suction tank at a safe level. The on-duty operator received calls from both the power plant dispatch center and the head of the water supply department, who said that the wastewater treatment plant was generating a large volume of wastewater and requested that the amount of waste discharged be controlled. The Water Supply Department promptly organized an investigation into the cause; once the debris blocking the return water inlet grille of Cooling Tower No. 3 was removed, the cooling tower stopped overflowing. We can analyze this incident as follows: 1. Upon inspection, the main cause of the overflow was the partial blockage of the cooling water return inlet grille by debris such as old plastic sheets, which prevented proper flow of the cooling water back to the tower. This led to an increase in the liquid level in the cooling tower and consequently to the overflow. This can reflect a lack of care and attention during routine inspections, which failed to detect and resolve grid blockages in a timely manner, resulting in overflow from the cooling tower. 2. The plant engineers and the operators on duty failed to promptly and accurately identify and resolve the cause of the sudden drop in liquid level. Following the overflow incident, the on-duty staff lacked the necessary professional competence to promptly assess and determine the cause of the accident. 3. When the water return volume was insufficient, the operator failed to properly control the amount of water added and the liquid level in the tank. The insufficient return water volume did not receive sufficient attention from the operators, and proper control was not implemented. III. Rectification measures: Since the return water inlet grille at Liangshuikou is currently made of fiberglass mesh, and this mesh is too small, it easily gets clogged at the return water inlet; therefore, the structure of the grille should be modified whenever possible. Before the modification of the grid structure, the grids were cleaned regularly on a weekly basis. Plant engineers and on-duty operators must check the return water condition of the cooling water system daily; any blockages or debris found must be removed immediately to maintain a safe liquid level in the pump suction tank. Strengthen staff technical training to improve their ability to identify and handle abnormal situations. In response to this incident, our department will conduct training for all staff on operational procedures as well as emergency response drills, so as to learn from this experience and prevent such incidents from occurring again. Strengthen the connection between upstream and downstream production processes; in case of any problems during production, it is necessary to report them promptly to the power plant’s control room and the wastewater treatment plant. Start by focusing on quality, systems, and implementation to comprehensively improve employee competence, ensuring that safe production remains under control through the reliability of personnel. This incident also reflects the incomplete implementation and failure to meet the requirements of the three understandings and six skills in practical operations. Handling this accident made me deeply understand the importance of the \"Three Understandings and Six Abilities\": understanding the principles, understanding the structure, and understanding the relevant plans and procedures; being able to read drawings, perform calculations, operate equipment, communicate effectively, carry out maintenance tasks, and troubleshoot problems. We must study these \"Three Understandings and Six Abilities\" in depth, not only to improve our technical skills but also to enhance our work experience and ability to identify and assess safety hazards. We need to truly grasp the essence of these concepts and use them as a guide for our work, striving to become modern \"iron men\" with excellent technical skills and high standards of competence. Comments from participants: