How to prepare a list of abnormal operating conditions?

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I. What are abnormal operating conditions? 1. The Ministry of Emergency Management explained that on April 25, 2024, the General Office of the Ministry issued a notice regarding the publication of the \"Guidelines for Safe Handling of Abnormal Conditions during the Production Process in Chemical Enterprises (Trial Version)\\" (Notice No. 17 from the Ministry of Emergency Management). Abnormal conditions are defined as situations such as the start-up and shutdown of equipment during the production phase in chemical enterprises, unplanned inspections and maintenance, abnormal operating parameters, abnormal operations or equipment failures, as well as other situations that pose a risk of accidental release of energy. 2. Foreign industry regulations, namely the foreign document “Guidelines for Managing Abnormal Situations,” define abnormal operating conditions as follows. In the process industry, abnormal operating conditions occur when conditions deviate from the normal state or operating range, to the extent that the basic process control system is unable to return to a normal state. If abnormal operating conditions are not corrected in their early stages, they may develop into serious accidents, such as: (1) failures of control valves, resulting in the tank level exceeding the safe operating range ； (2) Fault in the level sensor, causing the tank level to exceed the safe operating range ； (3) An incorrect dosage of a certain component caused the temperature in the batch reactor to exceed the safe operating range ； (4) The safety valve activates and gets stuck, causing the pressure to start dropping ； (5) Omission or delay of critical steps, resulting in errors during operation ； (6) Instrument air leakage, causing the valve to close. Typical intervention measures involve the operator taking action, including adjusting the setpoints of the control loops to restore the system to normal operation, performing a controlled shutdown, or even initiating an emergency stop. If abnormal operating conditions cannot be addressed promptly, it may lead to further deterioration of the conditions, which could eventually result in serious accidents. 3. In China, it is generally understood that during the operation of a production facility, deviations from the standard operating procedures and corporate management regulations that are not desired occur; such situations require human intervention, and failure to address them promptly can lead to accidents. The main scenarios include the following: 1. Problems with utility systems, including power fluctuations, interruptions in circulating water supply, or issues with instrument air ； 2. Moving equipment that affects production, including equipment trips and online fault maintenance, etc ； 3. Deviations from process parameters that pose high risks (excessive temperature, overpressure, explosive polymerization), including the analytical parameters of the materials ； 4. Increased resistance due to clogged filters, scale buildup in pipelines, etc., which can even lead to blockages, requiring on-site handling ； 5. Handling of valve failures (including instrument control valves), poor operation, or failure to reach the proper position ； 6. When dealing with leaks in devices or pipelines, as well as during pressure-related operations such as plugging leaks under pressure or making openings under pressure ； 7. Detection of toxic flammable gases, process interlock actions, safety valve activation, electrical protection, etc ； 8. Temporary parking for maintenance, as well as abnormal operations necessary due to abnormal production conditions ； 9. When issues such as internal failures of tower internals, internal leakage in the heat exchanger tube bundles, or uneven packing flow need to be addressed ； 10. Recovery after stirring failure in two-phase reactions (e.g., nitration reactions) ； 11. Handling of issues such as material cross-contamination, temperature rise, and overpressure caused by operational errors ； 12. When the operation of production equipment is affected under extreme high or low temperatures. II. Typical accident cases Case 1: On May 3, 2024, an explosion occurred in a pentafluoroiodoethane synthesis reactor at a technology company in Zigong, Sichuan Province, resulting in 3 deaths. Lessons to be learned from handling abnormal operating conditions: After feeding materials into the reactor, issues such as internal leakage in the seal and poor reaction performance were detected. During maintenance and restart attempts, illegal methods such as using steam for heating and adding an excessive amount of catalyst (antimony trifluoride powder) were employed to restore normal reaction conditions, which resulted in an explosion of the reactor. Case 2: On December 23, 2003, a severe oil spill occurred in Kai County, Chongqing, forcing the emergency evacuation of over 60,000 people affected by the disaster. This resulted in 243 deaths due to hydrogen sulfide poisoning and 2,142 people being hospitalized as a result of it. Lessons to be learned from handling abnormal operating conditions: Ignition was not initiated in the early stages of emergency response to effectively prevent the spread of natural gas containing high concentrations of hydrogen sulfide. Moreover, the emergency decision-maker and commander at the accident site failed to seize the opportunity to organize flaring and ignition. Case 3: A leak occurred in a vinyl chloride gas tank at a chemical plant in Hebei, and an explosion ensued when it came into contact with an open flame, resulting in 23 deaths and 22 injuries. Lessons to be learned from handling abnormal operating conditions: After detecting that the gas tank was stuck, the operators still increased the compressor reflux using conventional methods, which increased the amount of gas entering the tank. The rapid adjustment led to vinyl chloride breaking through the ring-shaped water seal and leaking outside the plant, where it ignited and caused an explosion. Case 4: On March 12, 2018, an explosion occurred in tank V501, the feed tank for the 600,000 tons per year diesel hydrogenation unit at a petrochemical company in Jiujiang, resulting in 2 deaths and 1 person suffering minor burns. The direct economic loss amounted to approximately 3.38 million yuan. Lessons to be learned from handling abnormal operating conditions: The operator mishandled fluctuations in the lubricating oil system of the cycle hydrogen compressor, which led to the shutdown of the compressor. After jumping out of the vehicle, the team leader failed to close the outlet valve of the feed pump as required by the emergency response plan; moreover, the emergency response plan did not specify any measures for dealing with overpressure in the buffer tank. Case 5: On September 7, 2023, a high-pressure gas leak occurred in the gasification workshop of Yiding Ecological Agriculture Development Co., Ltd. in Hangjin Banner, Ordos City, resulting in 10 deaths and 3 injuries. Lessons to be learned from handling abnormal operating conditions: During operation, while trying to resolve the issue of poor flow of crude syngas to the shift reaction unit, an incorrect assessment of pipeline pressure led to forced removal of the valve cover, resulting in the release of high-pressure crude syngas. This caused a large gathering of people at the site, leading to severe casualties. Case 6: On March 30, 2022, an accident occurred in Furnace No. 3 of Unit 2 of a chemical processing plant in Maoming, Guangdong Province. The accident did not result in any casualties, but it caused direct economic losses of approximately 623,900 yuan. Lessons to be learned from handling abnormal operating conditions: Operators failed to strictly comply with safety management regulations; emergency response procedures were not followed properly when abnormalities occurred in the equipment’s operating conditions and parameters, resulting in inadequate emergency handling. Case 7: On April 15, 2004, an explosion of liquid chlorine occurred at the chlorohydrogen plant of a chemical factory in Chongqing. During the efforts to deal with the accident, 9 people lost their lives while on duty, and 3 were injured. Lessons to be learned from handling abnormal operating conditions: During on-site handling, relying on past operational experience, the accident chlorine treatment unit was activated on its own to pump out liquid chlorine from the storage tanks and vaporizers. During the suction process, NCl3 at the water seal of the accident chlorine treatment unit comes into contact with air and experiences vibration. Case 8: On May 1, 2023, an explosion and fire broke out at the hydrogen peroxide production unit No. 1 of a chemical manufacturing company in Liaocheng, Shandong Province, resulting in 10 deaths, 1 injury, and direct economic losses of 54.45 million yuan. Lessons to be learned from handling abnormal conditions: When attempting to draw off a small amount of the working solution floating on the surface of 70% hydrogen peroxide in the finished product tank and transfer it to the working solution preparation vessel, a large volume of 70% hydrogen peroxide was drawn in instead ； Impurities in the working solution preparation tank cause exothermic decomposition of high-concentration hydrogen peroxide, which ultimately leads to violent decomposition and explosion of the high-concentration hydrogen peroxide, resulting in the catastrophic destruction of the working solution preparation tank. Case 9: On August 15, 2023, an explosion occurred at a new energy materials company in Zhejiang, resulting in 3 deaths and 1 injury. After lithium perchlorate, a solid raw material, clogged the salt-adding pneumatic valve, the on-duty operator used dangerous methods such as chiseling, scraping, and digging to clear the blockage, which caused the lithium perchlorate saturated with organic solvents to explode. III. How to prepare a list of abnormal operating conditions? Abnormal operating conditions can be divided into three major categories: index deviation, abnormal operations, and potential accidental release of energy. 1. List of abnormal operating conditions related to index deviations; this list can be drawn from HAZOP reports. For each flowchart related to the production layout, and for the process parameters of each unit’s pipelines or equipment, there are 7 guiding terms available for any deviation from those parameters: NONE, MORE, LESS, AS WELL AS, PART OF, REVERSE, and OTHER THAN. By pairing each process parameter with these keywords one by one, certain deviations are generated; by evaluating the risks based on these deviations, an abnormal operating condition is identified. 2. Abnormal operations: A list of abnormal operating conditions can be developed by drawing on the achievements of the dual prevention mechanism, utilizing Job Hazard Analysis (JHA) sheets. By breaking down the operation into several steps and assessing the risks for each step, an abnormal operating condition is obtained. 3. The potential for accidental release of energy refers mainly to abnormal operating conditions that occur in situations such as leaks, blockages in the processing system, or the opening of equipment. The above are three tools or methods of expression; they can be used in combination without having to be strictly separated. It is also possible to draw on reaction risk assessment reports (for fine chemical enterprises), accident cases of similar facilities, and suspected incidents (attempted incidents), and use brainstorming to identify abnormal operating conditions. Operation procedures, similar risks, and similar types of equipment under certain abnormal operating conditions can be combined into the same type of abnormal condition. When analyzing abnormal operating conditions, it is recommended that the production department take the lead and have representatives from various departments participate, especially experienced front-line operators. This ensures that the identification of abnormal conditions is thorough and comprehensive, covering all potential risks associated with such conditions in the facility. Here are some types of abnormal operating conditions listed for reference. 1. Problems with utility services, including power fluctuations, interruptions in circulating water, and instrument air supply ； 2. Moving equipment that affects production, including equipment trips and online fault maintenance, etc ； 3. Deviations from process parameters that pose high risks (excessive temperature, overpressure, explosive polymerization), including the analytical parameters of the materials ； 4. Increased resistance due to clogged filters, scale buildup in pipelines, etc., which can even lead to blockages, requiring on-site handling ； 5. Handling of valve failures (including instrument control valves), poor operation, or failure to reach the proper position ； 6. When dealing with leaks in devices or pipelines, as well as during pressure-related operations such as plugging leaks under pressure or making openings under pressure ； 7. Detection of toxic flammable gases, process interlock actions, safety valve activation, electrical protection, etc ； 8. Temporary parking for maintenance, as well as abnormal operations necessary due to abnormal production conditions ； 9. When issues such as internal failures of tower internals, internal leakage in the heat exchanger tube bundles, or uneven packing flow need to be addressed ； 10. Recovery after stirring failure in two-phase reactions (e.g., nitration reactions) ； 11. Handling of issues such as material cross-contamination, temperature rise, and overpressure caused by operational errors ； 12. When the operation of production equipment is affected under extreme high or low temperatures.