A brief discussion on safe hot work in chemical enterprises

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A brief discussion on safe hot work in chemical enterprises. Hot work generally refers to welding and cutting operations carried out in areas designated as no-fire zones within chemical enterprises, as well as temporary tasks that involve the use of blowtorches, electric drills, grinding wheels, and other tools that can generate flames, sparks, or hot surfaces in flammable and explosive environments. 　　In chemical production, the installation, maintenance, and technical upgrades of equipment often require hot work. In chemical plants, flammable and explosive substances are commonly present during such operations, and production usually continues alongside these tasks; any carelessness can easily lead to fires or explosions, causing significant economic losses for the company. It can be said that hot work in chemical enterprises is a special type of operation that is highly technical, requires high standards, is difficult to carry out, and involves significant risks. Therefore, ensuring proper safety procedures for hot work in chemical enterprises is a crucial matter for every such enterprise. Based on my many years of work experience, I would like to briefly outline the technical measures for safe hot work in chemical enterprises for everyone’s reference. 　　I. Disassembly operation. For tasks that require welding in no-fire zones, the equipment, pipes, and their accessories that can be removed should be taken off from the main structure and taken to a safe location where welding can be carried out; after the welding is completed, they should be reinstalled in their original positions. This is a safe method for performing hot work, but it should be noted that if the removed equipment, pipes, and their accessories contain flammable or explosive materials, dirt, or residues, they still need to be cleaned as required. 　　II. Isolation and covering. The equipment, pipes, and their accessories that are to be worked on, as well as the associated operating systems, must be effectively isolated. This can be achieved by installing blind flanges on the pipes, adding end caps, or removing a section of pipe, in order to prevent flammable and explosive materials and gases from reaching the area where work is being carried out. Be careful not to use simple methods such as closing valves or using water seals as a substitute for isolation. At the same time, it is also necessary to check whether flammable or explosive gases are generated in the surrounding areas where operations take place, especially in the upwind areas; if such gases are present, welding work should be prohibited or production halted. Before performing hot work, the openings of equipment such as tanks and vats should be covered to prevent electric sparks from entering ； Or enclose the welding area on all four sides with non-flammable materials to control spark splashing ； Proper coverage must be ensured; all areas where sparks could land need to be covered, including drainage ditches and manhole covers that are easily overlooked. 　　III. On-site cleanup. It is a basic requirement to clean the area before starting any welding work. Before starting any hot work, flammable and explosive materials located below and around the area where the work will be carried out must be moved to a safe location, and the site should be cleaned thoroughly. Everything that could be reached by electric sparks must be moved away, especially in high-altitude work, where electric sparks can be carried by the wind or strike objects, causing secondary splashing; it is difficult to determine the exact location where these sparks land. In such situations, the site must be taken care of with particular attention: flammable materials should be moved away if possible; those that cannot be moved should be covered tightly with non-flammable materials, and a dedicated person should be assigned to keep watch over them. The ground should be cleaned thoroughly, and any oily equipment or surfaces should be wiped down and washed. 　　IV. Cleaning and replacement. All production and storage equipment such as containers, devices, tanks, and pipes that have been used with chemical hazardous materials must be cleaned and purged before any hot work is carried out. The main methods of cleaning and displacement are as follows: A. Displacement with clean water. It can be used with water or media that are easily washed with water, and can be rinsed and replaced once or multiple times with clean water. 　　B. Vapor displacement. Materials and media that are difficult to clean with plain water can be washed with steam, such as those that solidify or clump upon condensation, as well as oily substances, residues, and dirt. 　　C. Air replacement. Use blowers, exhaust fans, or other air displacement equipment to displace combustible gases. 　　D. Inert gas displacement. If necessary, inert gases such as nitrogen or carbon dioxide can also be used for replacement. 　　V. Analysis and monitoring. Regardless of the method used for cleaning and replacement, it must be done thoroughly without any remaining residues; only after passing inspection and analysis can work begin. For accurate testing and analysis, the samples must be representative; when flammable gases are heavier than air, samples should be taken from the lower portion ； When the flammable gas is lighter than air, its upper part should be taken ； When the lower explosive limit concentration of the gas or vapor being tested is 10% or higher, its concentration should be less than 1% ； When the lower explosive limit concentration is greater than or equal to 4%, it should be less than 0.5% ； When the lower explosion limit concentration is less than 4%, it should be less than 0.2%. After cleaning and replacement, the process must not be halted for too long; generally, it should not exceed half an hour. If this time limit is exceeded, sampling and analysis should be carried out promptly, and if the standards are not met, replacement should be done again. 　　VI. Inspection and confirmation. After completing the relevant preparatory work, it is essential to conduct a thorough check and verification; this step is very important. The inspection and verification are generally carried out by the person in charge of the unit performing the hot work, the shift supervisor, the person in charge of the hot work project, the person who actually carries out the hot work, and the safety officer. While checking whether on-site cleaning, isolation, covering, and washing/flushing have been carried out as required, it is also necessary to verify: 1. Whether all covers and openings on the equipment used for hot work have been removed. Working with open flames is prohibited on sealed equipment, pipelines, and containers. 　　2. Whether the welding tools meet safety requirements. The tools used for welding must meet quality standards; welding torches and control valves should be airtight, and oxygen regulators must be sensitive and effective ； The welding machine should be equipped with a **power switch** ； The oxygen and acetylene hoses must be connected firmly, with no damage or leaks ； The secondary coil and casing of the welding machine must be properly grounded (connected to neutral) for protection. Welding tools must have good insulation, and it is prohibited to use damaged welding torches and cables as well as malfunctioning pressure regulators. 　　3. Have the appropriate emergency rescue measures been put in place? When working in oxygen-poor or toxic environments, it is necessary to have protective equipment such as gas masks, air respirators (oxygen respirators), safety belts (ropes), ladders, and other life-saving devices. When working in flammable and explosive environments, fire-fighting equipment such as fire extinguishers and hoses should be available. When working in highly corrosive environments such as those with acids and bases, an ample supply of clean water should be available. In addition, appropriate first-aid supplies should also be available for emergency use. 　　VII. Obtain a hot work permit. After verifying that all preparatory work is correct, a \"Hot Work Safety Permit\" is issued; for work inside tanks or boilers, a \"Safety Permit for Work Inside Equipment\" is also required, in order to clarify the responsibilities of the relevant personnel and implement appropriate preventive measures. 　　“The “Hot Work Safety Permit” is issued by the person in charge of hot work or the safety officer designated by the unit applying for to carry out hot work. The permit must specify the location where the hot work will be carried out, the object on which the work is to be performed, the method of carrying out the work, the person who will execute the work, the person in charge of the hot work, the start and end times of the work, the safety measures to be taken before starting the work, the level of risk associated with the hot work, and the person responsible for monitoring the work. For complex projects, additional details such as the person responsible for organizing the work, the person who conducts the hot work analysis, and the shift supervisor are also required. Then, approval is granted in accordance with the regulations based on the fire hazard level. The information on the hot work permit must be filled out accurately and properly; it is absolutely unacceptable to handle it perfunctorily as a mere formality, and it is strictly prohibited to carry out hot work without approval out of fear of inconvenience. For routine level-2 hot work tasks with low risk and simple procedures, the signature of the supervisor in the unit where the hot work is carried out is required, along with approval from the leader of the safety management department ； For Class 1 hot work tasks that involve certain risks and require higher technical standards, in addition to initial review by the supervisor of the unit where the hot work is carried out and reinspection by the leader of the safety department, approval from the plant manager or chief engineer is also required ； In the case of hot work involving special hazards, the safety management department shall organize the person in charge of the hot work unit, the person in charge of the hot work project, the person who carries out the hot work, the supervisor, the person responsible for hot work analysis, the safety officer, the plant manager, or the chief engineer, among other relevant personnel, to gather at the site of the hot work to review and approve it. Once the hot work permit is completed, the relevant personnel should sign it, each assuming their own responsibilities. 　　The hot work permit shall be issued in two copies, one to be given to the person carrying out the hot work and the other to be retained by the safety management department. A hot work permit may only be used within the scope specified for one hot work site; it shall not be transferred, altered, used in a different location, or have its scope of use expanded. The validity period of a hot work permit is generally 24 hours; it must be reissued if this period expires. 　　VIII. Designated person to monitor the fire. The unit where the hot work is carried out or the party conducting the hot work should assign a person with a strong sense of responsibility, experience in performing hot work, familiarity with the site conditions, and knowledge of fire safety measures to act as the fire watcher. This person is responsible for monitoring the area where the hot work is being done, extinguishing any sparks that may appear there at any time. If it is found that the hot work is not being carried out in accordance with the regulations, corrective action must be taken. If combustible gases or other safety hazards are detected, the person carrying out the hot work must be instructed to stop immediately, and relevant personnel should be contacted promptly to take appropriate action. The fire watcher must remain at their post; they are not allowed to leave their position or take on other duties. When performing welding work in areas with special hazards, the person in charge of monitoring the fire should be a safety officer. 　　IX. Each performs its own duties. Tasks such as on-site cleanup, isolation and covering, cleaning and replacement, as well as the relevant preventive measures to be taken before carrying out hot work, are the responsibility of the party conducting the hot work ； The safety performance of the welding tools, the condition of these tools, and compliance with regulations are the responsibility of the person carrying out the welding work ； It is the responsibility of the person in charge of the work involving open flames and the person in charge of the relevant project to check and confirm whether the preparations for such work are adequate and whether the appropriate preventive measures have been implemented ； The cleanup of the site after the hot work is completed is the responsibility of the person who carried out the hot work and the supervisor ； The safe operation during hot work is supervised by the safety officer ； The approver of the hot work permit is responsible for the safety of the entire hot work operation. 　　X. Other matters ①. Workers must properly wear personal protective equipment in accordance with the specified requirements. 　　②When working in narrow grooves or pots, welding cannot be carried out in multiple locations at the same time. 　　③When working at heights, welding or burning operations are not allowed to be carried out simultaneously on different levels ； Oxygen cylinders and acetylene cylinders must not be placed in areas where electric sparks may occur, nor directly below operating equipment, pipelines, or power lines, nor exposed to direct sunlight. 　　④There should be a safety distance of more than 5 meters between oxygen cylinders and acetylene cylinders; they must not be placed near heat sources, and should keep a distance of at least 10 meters from open flames. 　　XI. Post-event support. The cleanup of the site after welding work is often overlooked. After the hot work is completed, the person who carried out the work should turn off the power and gas supplies, remove the equipment used for the work, and together with the person overseeing the work or the safety officer, inspect and clean up the site to extinguish any remaining flames. Every area where electric sparks might occur must be thoroughly inspected, and only after confirming that there are no remaining embers can one leave. The welding operation should not continue for too long; breaks should be taken in between, and a site inspection should also be conducted before leaving – this must not be ignored. 　　In chemical production, there are many flammable and explosive substances, and the gas environments are complex. Specific operations must strictly comply with the \"Safety Regulations for Operations within Chemical Plant Sites\" issued by the Petroleum and Chemical Industry Bureau; careful handling is required based on actual conditions. It is absolutely forbidden to be careless, to act in violation of regulations, or to engage in risky operations. Only by strictly adhering to the safety procedures for hot work and taking thorough preventive measures can potential accidents be prevented, thereby ensuring the safe production and stable development of chemical enterprises.