The “eight musts” for working inside containers and equipment”

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What are containers and equipment? What is referred to here are containers and equipment; in chemical production, various towers, vessels, boxes, cabinets, kettles, tanks, basins, furnaces, pipes, wells, ditches, ponds, hoppers, silos, as well as larger mechanical devices that may enter such spaces, along with other poorly ventilated confined areas, are all collectively referred to as container equipment. Dangers of working inside containers: 1. There is a risk of harmful and toxic substances leaking from connected containers or pipelines, thereby causing mutual harm; moreover, harmful and toxic elements from outside the container can enter it, making it difficult for those working inside to predict or avoid such threats. 2. Poor ventilation within the container prevents harmful substances such as toxins from spreading easily. Moreover, during operation, harmful and toxic residues may gradually be released, increasing the amount of toxic or flammable materials while simultaneously reducing oxygen levels, thereby raising the risk. 3. Poor lighting can lead to accidental operations. 4. The space inside the container is limited, increasing the risk of mechanical injuries and object strike accidents. 5. When performing maintenance in tall containers, the large height difference between components increases the risk of falls ； The combustible components inside the device (such as grids, scaffolding, packaging materials, etc.) are highly flammable and can cause fires, with rapid burning rates. 6. It is difficult to carry out rescue in case of an accident inside the container. 7. The temperature inside the container is high, the operator’s body temperature is high, the workload is heavy, respiration and blood circulation accelerate, resulting in an increased intake of toxins. It has been determined that the amount of air a human breathes is related to the level of physical activity; the amount of air required when at rest is eight times greater than that required when running. High temperatures accelerate the evaporation of residues inside the container, increasing the amount of toxins that reach the human body and making it easier for people to get poisoned. 8. High humidity inside the container. The residual liquid already present in the container, along with sweat from the operators, increases the humidity inside the container; an increase in humidity corresponds to an increased risk. The reason is: it increases the solubility of the toxin in the human body, thereby increasing its absorption. Some chemicals, such as cyanide, produce highly toxic hydrogen cyanide gas when exposed to moisture ； Some substances with low toxicity can become more toxic when exposed to moisture. Higher humidity reduces human resistance, increasing the risk of electric shock. Because in a dry environment, the human body’s resistance can reach 1000–1500 ohms, while in a humid environment it can drop to 600–800 ohms. Therefore, the voltage of portable lights should generally not exceed 36 volts; in humid environments as well as inside metal containers such as towers and tanks, it should not exceed 12 volts. The “eight musts” for working inside containers and equipment: Given the numerous dangers associated with working inside containers, which greatly increase the likelihood of accidents, it is essential to follow the “eight musts” when entering such containers or equipment to carry out work: First, it is necessary to apply for permits and obtain approval ； II. Safety isolation must be implemented ； III. The power supply must be cut off, and safety lighting must be used ； IV. Replacement and ventilation are necessary ； V. Safety analysis must be conducted within the specified time frame ； VI. Mandatory use of prescribed protective equipment ； VII. Someone must be outside the device to provide supervision and stay at their post ； 8. There must be backup measures for emergency rescue. ━ ━ ━ ━ ━ I. It is necessary to apply for a permit and obtain approval. A chemical production plant is a production system composed of various equipment and pipelines. During the production and operation of the system, equipment, pipelines, and other components are subject to continuous changes, such as chemical corrosion, erosion by media, stress corrosion and fatigue under alternating loads, wear, deposition, scaling, adhesion of materials to surfaces, loosening of internal components, and peeling off of linings, etc. Changes in some of the aforementioned items will lead to a deterioration of the control parameters, affecting safe operation and resulting in a decline in production; to a certain extent, it becomes necessary to shut down the system in order to carry out cleaning, maintenance, or modifications. Due to the dangers associated with working inside equipment and pipelines in chemical production, it is necessary to strengthen the control and management of operations carried out inside containers and equipment. Such work must be conducted in an organized and supervised manner, with a permit system in place; random entry into containers and equipment is not allowed in order to prevent accidents. When entry is necessary, an application must be submitted by the project leader, who will then review and approve it. Its purpose is to coordinate working hours, review supplementary safety measures, and clarify the responsibilities of personnel at all levels and categories. Leadership approval and signature are essentially a form of confirmation system that ensures proper management, prevents accidents, and stops actions from being taken without proper authorization or carelessly. Leadership approval should avoid formalism, and responsibilities must be clearly defined. In daily work involving entry into containers and equipment, there are countless cases in which accidents occur as a result of operators lacking knowledge of safety procedures or being careless, or failing to go through the necessary application, licensing, and approval processes before proceeding with their tasks... Applying for licenses and going through the relevant approval procedures helps to improve safety measures, clarify responsibilities among personnel, and ensure that these measures are actually implemented. Handling approvals and certifications carefully is the first and very important step in strengthening safety measures for working inside containers and equipment. It helps to avoid chaos resulting from reckless operations and reduces the risk of accidents; even in cases of emergency repairs, approval procedures are necessary. In emergency accident rescue situations, the on-duty safety officer must consider implementing appropriate safety measures for entering the container. II. Safety isolation is necessary. Safety isolation is a critical measure for working inside containers and equipment. It has two meanings: one is to define the scope covered by this task. Working inside containers or equipment is considered, from a management perspective, as a separate project, which is organized and carried out by a project manager; the contents and scope of such a project must be defined clearly. Isolate the equipment and pipelines outside the scope of this task to create a closed construction system. At the same time, the responsibility area was also defined. Second, it effectively prevents toxic and harmful substances from devices and pipelines outside the system from interfering with or causing damage to this system. Therefore, safety isolation must be taken seriously, and the methods must be reliable. First, check every device and pipeline outside the system one by one to ensure nothing is overlooked, and isolate them all from the system, not even the smallest pipelines. Secondly, isolation is achieved by installing blind flanges in accordance with specifications or removing the first-level (section) of piping before sealing it. It is absolutely not advisable to use closing valves and adding water seals as isolation methods, as many accidents have proven that they are unreliable. To ensure the safety and reliability of isolation, a plan can be developed first, a blind flange diagram drawn up to determine the locations and responsible personnel. The project leader shall oversee the process in accordance with the established sequence and schedule, and no one is allowed to give instructions or carry out operations without authorization. Note: Before adding a blind flange or removing a section of pipe, the pressure must be released and all material drained first. The plug mesh plate should be handled in accordance with safety technical regulations; if it contains highly toxic substances, they must first be replaced before the flanged pipes can be removed. III. The power supply must be disconnected, and safety lighting must be used. Before cleaning or maintaining any powered equipment, the power source must first be turned off. Entering containers or equipment results in a confined working space; if there are moving parts, working among these internal components without turning off the power supply can easily lead to personal injury accidents. There are many lessons to be learned in this regard, such as being ground to death inside the ball mill after entering it ； Got strangled inside the mixer and binder. The cause of such accidents is that some managers and operators lack a clear understanding of what it means to cut off the power supply, or they are reluctant to go through the hassle; some consider pressing the shutdown button to be equivalent to cutting off the power. As a result, in case of mistakes or improper operations, the machinery starts running again and injures the maintenance staff. Cutting off the power source means turning off the power switch and locking it with a sign, or removing the fuse protection and having it kept by the maintenance personnel. By taking the above measures, even in the event of an error, the machine will not start, thereby achieving intrinsic safety. There are also components driven by material flows (such as gases, liquids, etc.), for which not only must the valves be closed, but blind plates (including on the pipes) must also be installed to prevent accidental operations. Since the container is a closed space, even if access hatches are opened, the lighting inside the container is not sufficient to meet the requirements of the work; therefore, lighting equipment is generally required when working inside the container. When using lighting fixtures inside a container, it is inevitable that the fixtures may collide with objects inside the container and get damaged; moreover, it is also inevitable that friction and compression may occur when pulling the power cord, thereby damaging its insulation layer. Therefore, when working inside a container, the risk of electric shock from using lighting fixtures is much higher than when outside the container. To prevent electric shock accidents, safety-rated lighting must be used for working inside containers. When wires are inserted into a container, measures must be taken from the opening of the container to ensure no friction occurs and that they do not come into contact with sharp objects or materials, thereby preventing damage. The safe voltage for lighting fixtures inside metal containers is 12 volts. In cases where the container contains flammable materials, explosion-proof fixtures should be used; if necessary, the fixtures can be placed outside the container and used to illuminate its interior. It is dangerous to use other types of lighting in situations where safety lights are required, just for convenience. IV. Replacement and ventilation are necessary. When people need to enter containers or equipment to work, replacement is essential, both to prevent fires and explosions as well as to avoid poisoning; entry is only permitted after sampling and analysis show satisfactory results. Since chemical production involves many flammable, explosive, toxic, and highly corrosive materials, as well as complex gas environments, working inside equipment and containers without using displacement ventilation can easily lead to fires, explosions, poisoning, and personal injury accidents. To ensure the safety of personnel entering containers and equipment, ventilation must be carried out prior to entry, and exhaust ventilation should be provided after entry. Replacement involves using a safe medium to substitute the flammable or toxic and harmful substances inside a container, thereby ensuring that the container and equipment meet safety requirements. How to replace it? The medium used for displacement depends on the properties of the substance to be displaced, and no adverse reactions should occur when the two are mixed. If the container contains flammable gases, it must first be filled with non-flammable substances such as water, steam, nitrogen, carbon dioxide, or flue gas. Only after these conditions meet safety requirements can the container be filled with air before entry is permitted. If there are residues in the container that are difficult to remove by conventional methods, an appropriate cleaning solution should be used, or steam, hot water, or purging should be applied to decompose them. To ensure thorough displacement without any dead corners, a displacement plan should be prepared before the process begins, and a flow diagram of the displacement procedure should be drawn. It is important to note that due to process requirements, certain equipment designs may create dead corners; in such cases, gas displacement should be used for the final displacement step, as in the case of bubble columns and shell-and-tube heat exchangers. Under the operating pressure of the equipment and within the safe oxygen content range, the stepwise pressurization displacement method can be used. The outlet selected for displacement must not only ensure thorough displacement but also avoid creating an unsafe working environment around the outlet. The selection of replacement media and methods must ensure safety and reliability as well as economic Rationality; neither aspect should be neglected. Working inside containers and equipment involves poor air circulation, limited space, and crowded conditions. To prevent accidents, proper ventilation is necessary when working inside the device; mechanical ventilation can be used if required. But remember not to use oxygen or oxygen-enriched gases for displacement and ventilation, as this can easily lead to accidents. Replacement and ventilation are important measures to ensure safe operations inside containers and equipment. It is essential to attach great importance to this in terms of mindset and to implement it properly in operations; under no circumstances should there be any violations of regulations or reckless actions. Image 5: Safety analysis must be conducted in accordance with the specified time requirements. (1) Standards for analysis: 1. The analysis of the concentration of flammable gases in the air shall comply with the provisions set out in Article 106 of the \"Safety Management System for Chemical Enterprises\", as well as the requirements regarding gas analysis specified in the \"Six Prohibitions\" for hot work. 2. The oxygen level is 19–22%. 3. The content of toxic substances shall comply with the provisions of Article 32 of TJ36—39, \"Hygienic Standards for the Design of Chemical Enterprises\". When multiple poisons are present in a container, attention must be paid to their synergistic effects. When carbon monoxide is present together with hydrogen sulfide or carbon monoxide together with nitrogen oxides, an additive and a multiplicative effect occurs. The standard for the combined sampling analysis of multiple toxins is given by the following relationship: C1/M1 + C2/M2 + …… Cn/Mn ≤ 1. Here, C1, C2, …… Cn represent the actual concentrations of each substance (in mg/m3), while M1, M2, …… Mn represent the maximum allowable concentrations for each substance (in mg/m3). For example, the maximum allowable concentration of carbon monoxide is 30 mg/m3 ； The maximum allowable concentration of hydrogen sulfide is 10 mg/m3. And in actual measurements inside the container, the carbon monoxide level was 20 mg/m3 ； Hydrogen sulfide 6mg/m3. Calculating 20/30 + 6/10 gives 0.67 + 0.6 = 1.27. This shows that although CO and H2S are each within acceptable limits, their combined effect after mixing exceeds the allowed threshold. The safety conditions for working inside the container are not met. When taking samples for analysis, pay attention to representativeness to reflect the highest concentration of toxic substances inside the container. The sampler and project supervisor must go to the site in person to take samples from the most representative locations, based on the specific conditions inside the equipment and the properties of the medium. When sampling inside a container, samples should generally be taken from the upper, middle, and lower sections. For gases that are lighter than air, the sampling location should be at the upper and top parts of the container ； For gases that are heavier than air, the sampling point should be at the lower part or bottom of the container. (II) Timing and requirements for analysis: 1. After the container has been cleaned and purged, sampling and analysis must be carried out immediately. Only once the safety requirements are met can work be done inside the container; such work should be completed within 30 minutes. If this time limit is exceeded, sampling and analysis must be repeated. 2. Even after the container has been cleaned, replaced, and found to meet the requirements through analysis, during operation, toxic substances may continue to be released from deposits inside the container and adherences on its walls due to temperature changes and activities such as removing rust, which could render what were originally satisfactory conditions unsatisfactory. Therefore, during the operation, inspections should be carried out at least every 30 minutes, with a maximum interval of 2 hours; if the limits are exceeded, the operation must be stopped immediately and personnel evacuated promptly. At this point, it is necessary to actively identify the causes and eliminate potential hazards; only after further analysis confirms that everything is satisfactory can work be resumed inside the container. 3. Where conditions permit, reliable and calibrated gas detectors, explosion detectors, and alarm devices can be used to monitor the working environment inside the containers at any time, allowing for prompt action in the event of any changes. Analysis is a step that must be carried out before entering a container; it is an important means of verifying whether the conditions for safe operation exist inside the container. Working inside a container without conducting analysis, or without analyzing it as required or within the specified time frame, is highly arbitrary and dangerous; it has proven to be an unsound approach. Relying on unscientific methods such as simply sniffing is unreliable and should be abolished. VI. It is necessary to wear the required protective equipment. Protective equipment represents the final line of defense that must be employed when safety measures related to processes, equipment, and the working environment are in place, yet it still cannot guarantee 100% protection for workers from harm. As a precaution, appropriate protective equipment or tools must be worn for all general labor tasks. It is particularly important to wear protective equipment in containers and equipment where the working space is limited, the conditions are complex, there are many risk factors, and things change frequently. This is because objects inside the container can cause accidents such as impact injuries, mechanical injuries, falls from heights, chemical burns, and poisoning. At the same time, there are also issues such as dead corners, deposits, and adherences that make it impossible to eliminate them 100%, as well as human negligence and unforeseeable factors. Therefore, workers entering the container must wear the specified protective equipment to prevent accidents. How to wear protective equipment? Based on the working conditions inside the container and the potential hazards, protective equipment such as safety helmets, gloves, masks (gas masks, air (oxygen) respirators), eye protection, protective work clothing, safety belts, and explosion-proof tools should be selected to safeguard the physical safety of workers. In actual work, there are many cases of accidents occurring due to the failure to wear protective equipment as required. It is evident that wearing protective equipment is an essential safety measure for workers. VII. Someone must be stationed outside the equipment for supervision and to remain at their post. Working inside containers or equipment involves many risk factors, complex and changing conditions, a high likelihood of accidents, difficulties in entering and exiting the equipment, poor communication between the inside and outside, difficulty in detecting accidents once they occur, and challenges in providing rescue. Assign a dedicated person to monitor the operations inside the device from outside, so as to promptly detect unsafe conditions and provide rapid assistance. Appointing a supervisor is an important organizational measure to prevent accidents during operations in containers and equipment and to carry out emergency rescue. Guardians are required to have extensive practical experience and a strong physical condition, and must earnestly fulfill the following responsibilities: 1. Before starting work, guardians shall carry out the following inspections. Is there a permit for entering containers and equipment for work, which has been applied for and approved? Check whether the safety measures specified on the certificate are complete and properly implemented. Check whether the personnel entering the container are sick or have a weak constitution, and prevent those under supervision from entering the container to work while sick. Find out whether the personnel entering the container are clear about their tasks and have a clear division of responsibilities, especially the project leader and the contacts inside and outside the container. Check whether the protective equipment used in the inspection area is complete and meets the requirements, and whether safety facilities such as scaffolds, ladders, platform railings, and inspection instruments are up to standard. 2. After conducting an inspection, the guardian shall submit suggestions for improvement regarding hazardous operations for which safety measures have not been implemented or are inadequate. If no improvement is seen despite such requests, the person should be denied participation in guardianship duties, and the matter should be reported to the department head. 3. The guardian and the person under guardianship should agree on contact methods and signals. Otherwise, entry into the container for work is not permitted. 4. The guardian has the right to supervise the ward’s compliance with safety measure requirements. If any illegal operations are detected, they must be ordered to stop working immediately. 5. Guardians must be aware that it is strictly prohibited to use electrical equipment such as cranes and winches as tools for lifting workers. Because when a power outage occurs, the workers are unable to evacuate from the container. 6. The guardian must pay attention to their own safety, and the environment at the guardianship location must meet safety requirements. At the same time, preparations for handling accidents should be made; one must not participate in construction work, engage in any activities that could interfere with supervision, and under no circumstances leave the supervision post. 7. When working inside the container for an extended period, both the workers and supervisors should work in shifts, with strict handover procedures in place. Entering containers or equipment to work, without a supervisor present or with a supervisor who fails to remain at their post, has claimed many workers’ lives. During the course of carrying out their duties, some supervisors encounter urgent matters or are called away to handle other tasks, which results in delayed rescue efforts for those inside the device, or accidental operations that cause injuries. The absence of a guardian, the guardian’s failure to fulfill their duties, or the guardian’s departure to attend to other matters can all lead to workplace accidents inside the equipment, delay rescue efforts, increase the severity of the accidents, and render it impossible to prevent accidents that could have been avoided or to recover losses that could have been saved. VIII. Backup measures for rescue must be in place. Having ready backup measures for rescue represents the material and organizational preparations needed to carry out emergency rescue in the event of an accident while working inside containers or equipment. Now, when workers inside a container are in danger, supervisors and those around them will actively participate in the rescue efforts. However, due to the lack of proper backup measures for such rescues, actions are taken recklessly, resulting in chaos at the accident site. Rescue workers may enter the container in violation of safety rules, which can actually lead to tragic outcomes such as one person being poisoned and multiple others dying. Accidents often escalate because the supervisors are at a loss when faced with certain situations. Whenever anyone takes on the task of external monitoring, they must clearly anticipate potential dangers and determine the appropriate rescue methods as well as the necessary supplies. First of all, one must have a set of protective equipment that allows entry into the container for rescue purposes, such as gas masks or masks with long air supply tubes, as well as oxygen respirators. Secondly, determine how to rescue the people inside the container in case of danger – by going up into the container or coming down from it? If rescue is to be carried out from above the container, a safety belt should be worn regardless of whether there is danger or not; the rope should be held by a supervisor, and a metal ladder should be available from the working surface up to the container opening ； If assistance is provided using such devices, the methods vary, and thus the preparation work differs as well. Furthermore, the rescue methods for poisoning and fires are clearly different, as are the preparations needed. In the event of danger, the methods for guardians to report and the rescue measures must be predetermined in advance; this is the organizational preparation for carrying out rescue efforts. Emergency backup measures for working inside containers and equipment are often overlooked, and there have been too many lessons learned from this… Therefore, supervisors and project managers must pay close attention to this; while assigning someone to oversee the work, they should also implement appropriate rescue methods and measures to ensure that in the event of an accident, help can be provided promptly and losses can be minimized.