Safety measures for hot work in the ammonia cooling storage tank area

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　　When enterprises carry out maintenance and technical upgrades on ammonia-based cooling tanks, they inevitably need to perform cutting, welding, and other hot-work operations. If awareness is lacking and appropriate safety measures are not in place, fires can easily occur. A fire in the ammonia-cooled storage tank area can be extremely hazardous. For the insulation of ammonia pipes, valves, and tanks, polyurethane foam is generally used. Although flame retardants are added during the foaming process, due to factors such as the amount of flame retardant used, the uniformity of its distribution, and the methods of application, the actual flame-retardant properties are not ideal; once a fire breaks out, it is very difficult to extinguish. At the same time, ammonia expands when heated, causing the pressure to rise sharply; when this pressure exceeds the system’s tolerance limit, an explosion occurs. When the concentration of ammonia released in the air exceeds 16%, it can also cause an explosion when exposed to an open flame. 　　Therefore, great emphasis must be placed on the safety of this construction work, adopting the philosophy that \"prevention is better than disaster relief\" to completely eliminate the occurrence of accidents. So, what specific measures should be implemented? 　　Safety preparations before construction 　　1. Inspect and remove all debris and flammable materials from the area where welding or burning will take place. Specifically, within a radius of 10 meters around the point where such operations will be carried out, there should be no flammable materials or any objects that could obstruct visibility. 　　2. Construction is not feasible when the ambient temperature is above 35°C and the wind force is above level 3. 　　3. All valve pipelines should be evacuated whenever possible; if this is not feasible, they should be properly isolated and carefully tested using phenol peptide test strips to ensure there are no leaks. 4. Remove the insulation from the pipelines at a distance of less than two meters from the welding area; wet the exposed parts of the remaining insulation by spraying water, and isolate them using damp flame-retardant materials. 5. At the site where welding work is carried out, water pipes must be positioned properly, and the distance for spraying water from these pipes should be more than ten meters (it’s better if the company has its own fire truck). Additionally, there should be at least three buckets filled with 30 kilograms of water each. 　　6. Completely isolate any areas that may cause the ammonia pipes to heat up, by sealing them with wet fire-resistant felt to prevent sparks from coming into direct contact with them. 7. Carefully inspect the relevant valves to confirm they are closed, then place warning signs and lock them in place. 　　Inspections before cutting and welding 　　1. When disconnecting the ammonia pipeline from the existing system, methods such as removing flanges, using a hand saw for cutting, or plasma cutting should be employed in order of priority, depending on the circumstances; methods like oxygen-acetylene flame cutting or electric welding should be avoided as much as possible. 2. Tungsten inert gas welding should be used whenever possible. The neutral wire must be connected directly to the welded part; it is absolutely not allowed to be connected to the ammonia pipeline at a distance. Additionally, the insulation of the neutral wire must be of good quality. 　　3. During welding, it is necessary to ensure that there are at least two people supervising the process, as the welder, with a welding helmet on, has a limited field of vision and is unable to detect fires in a timely manner. 4. If there are pressure gauges, sensors, and other devices at the construction site, they must be properly protected to prevent ammonia leaks resulting from collisions. 　　5. It is strictly prohibited to step on or collide with small-diameter ammonia pipes during construction. 6. Ensure a distance of at least ten meters between the oxygen cylinder, the acetylene tank, and the welding site; there must be absolutely no flammable materials in the vicinity of these three items. The first two cylinders should also be protected from direct exposure to sunlight. Ensure reliable insulation of the welding wire, and that there are no leaks of oxygen or acetylene. 　　Precautions during welding and finishing 1. During cutting and welding, attention should be paid to the direction of slag spread, and flammable materials should be avoided as much as possible. 2. The task that generates relatively large sparks during welding is the “material cutting process”; therefore, try to carry out the material cutting work in a relatively safe location. 　　3. Supervisors must never leave their posts; in the event of a fire hazard, relevant emergency measures must be taken promptly. 4. Cross-tasking is strictly prohibited during welding, and painting work is even more not allowed. 　　5. Even after the ammonia pipeline is evacuated, ammonia oil remains present, and combustion and explosion can still occur at the pipe opening during cutting; therefore, care must be taken to prevent fires by controlling the direction of the nozzle. For ammonia pipes that are essentially in a closed state, a pressure relief pipe must be led into water. 6. During construction, it must be carried out in accordance with the design to avoid deviations that could lead to accidents. 　　7. Try to avoid performing any hot work one hour before ending work; when personnel leave the site, the power supply should be turned off and the valves on containers and tanks should be closed. 　　8. After work, carefully inspect the site and ensure that there are no sources of fire before leaving the construction area. 　　The conditions at construction sites are constantly changing, so safety cannot be taken lightly at all. It is necessary to adopt various measures and implement targeted safeguards based on the actual situation.