Discussion on fire safety measures in chemical equ

2022-10-22
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Talking about the fire safety measures in the maintenance of chemical equipment

under the action of high temperature, chemical or electrochemical corrosion, chemical equipment or pipelines, coupled with defects in materials, structures and manufacturing, often have cracks, perforations and other defects, so the maintenance is naturally inseparable from cutting, accelerating the promotion of welding on key projects of functional materials and other hot work. However, many media involved in chemical production are flammable and explosive, and open flames are strictly prohibited in the workshop during production. Therefore, the hot work in the maintenance of chemical equipment must be very careful, and the policy of "safety first, prevention cost lower" should be observed, the hot work management system should be strictly observed, and necessary safety technical measures should be taken. Here are some views on this issue. 1、 Strict approval of hot work permit and strict implementation of the system of application, review and approval of hot work permit for hot work in fire forbidden areas are effective measures to ensure safe hot work in chemical enterprises. The contents of the hot work permit shall include: hot work position, hot work method, hot work time, hazard analysis, safety technical measures, specific scheme, project leader, operator, supervisor, etc

the approval of hot work permit should be responsible at all levels and checked by everyone. The project leader, equipment management personnel, fire department and equipment management department should review and assume their respective responsibilities. Leaders at the plant level and equipment management departments should focus on checking and supervising the implementation of the hot work permit system and content, so that no hot work is allowed without a hot work permit or incomplete procedures, and no hot work is allowed after the hot work period, content or location is changed. 2、 Although the isolation chemical equipment and pipelines are controlled by valves, if the valves leak or are not closed tightly, misoperation, etc., flammable and explosive media enter the hot work equipment or the air to form an explosive mixture, which will burn or explode in case of open fire. Therefore, when hot work is required for local maintenance, it must be safely isolated from the production system

the pipes, valves, etc. connected with the hot work equipment should be removed, and then blind plates should be installed on the flanges. If they cannot be removed, blind plates should be inserted between the hot work equipment and the pipe flanges of the connected production system for isolation. Check carefully before drawing and blocking blind plates, but check whether there is residual liquid and pressure in the equipment and pipeline due to the low reliability of the anti rotation level switch, and prevent the formation of negative pressure to inhale air and explosion. An account shall be established for the blind plate pumping and plugging work. The blind plates shall be numbered according to the process sequence, and the registration and verification work shall be done well. Missing plugging will lead to accidents in maintenance operations, and missing pumping will lead to accidents during commissioning or production

in addition, safety isolation from surrounding equipment and inflammables should be considered; When hot work is carried out in the equipment, the deeper containers shall be isolated in layers to prevent sparks caused by the falling of tools or objects; All hot work equipment or pipelines that can be removed and relocated should be removed to a fixed hot work area or other safe places for hot work, so as to minimize hot work in the fire ban area. 3、 Replacement in order to ensure the safety of hot work during maintenance, hot work equipment must be replaced. The replacement method is generally to fill the equipment or pipeline with steam, nitrogen and inert gas to discharge the flammable medium; Or press out the flammable medium with water injection and exhaust method

if the replaced medium has retention property, or its density is similar to that of the replaced medium, attention should be paid to the incompleteness of replacement or the possibility of mixing the two media. Therefore, whether the replacement is complete cannot be determined by the amount of replacement medium or the length of time, but by the results of laboratory analysis. 4、 Purge the equipment and pipelines with oil dirt, residue and sediment. After replacement, steam shall be used for purging. Steam shall be used intensively for purging; When purging the tower, kettle, heat exchanger and other equipment, the lowest part shall be selected for discharge, and attention shall be paid to prevent dead corners and unclean purging; Pay attention to purging sewers, Yin wells and trenches; Water repellent substances and equipment and pipelines with residual nitrogen trichloride cannot be purged with steam. 5、 Clean and remove the sediments that cannot be removed by replacement and purging, and take cleaning measures. According to the nature of the scale, acidic, alkaline solutions or solvents are used for cleaning, but the selected cleaning agent cannot form a dangerous mixture with the sediment, and it is suitable to be non combustible and low toxic. To improve the cleaning effect, steam can be introduced to boil the solution. After cleaning, clean water should be injected for secondary cleaning

sediments that are ineffective by the above methods should be removed manually. Those who need to enter the equipment for operation shall comply with the safety regulations for operation in the tank; When removing combustibles, wooden, copper, aluminum and other non sparking shovels, brushes, hooks and other tools should be used; Personal protection should be done to eradicate residual acid and toxic sediments, and the scraped sediments should be cleaned in time and properly treated

in addition, it should be noted that thermal insulation materials may absorb flammable media and become a source of danger. Thermal insulation materials should be removed before hot work. 6、 To remove combustibles, all combustibles within 10m around the hot work site, such as gasoline, flammable solvents, oil cotton yarn and empty barrels containing flammable substances that have not been cleaned, should be moved to a safe place. Acetylene and oxygen cylinders shall be free of leakage, and the distance between them shall not be less than 7m, and shall be more than 10m away from the open fire. The electric welding machine should be placed at the designated place, and the grounding wire should be connected to the equipment to be welded. The grounding point should be close to the place where 30million boxes can be saved in one day of welding. Remote grounding circuit is not allowed. For the equipment that cannot be moved around, such as flammable gas pipes, containers, etc., spray wet with water or cover with asbestos boards, wet gunny bags, etc. to isolate sparks. For hot work at heights, use a fire plate, install an iron cover, or use a asbestos fence to catch molten slag, and pay attention to the direction of sparks splashing, so as to prevent sparks from falling into the dangerous area. In case of strong wind above level 5, outdoor high-altitude hot work should be stopped. 7、 Sometimes, the fire-fighting chemical equipment is overhauled and produced at the same time. The site environment is complex, and combustion and explosion accidents may occur with a little negligence. Therefore, a certain amount of fixed or semi fixed fire-fighting facilities such as water, steam and inert gas should be set up at the hot work site, and suitable portable fire extinguishers should be equipped. Fire engines and firefighters should come to the scene to prepare for fire fighting when hot work is carried out in dangerous and important sections. 8、 Experienced personnel must be assigned to supervise the hot work site. The supervisor must be familiar with the situation of the hot work site and be able to find abnormal phenomena in time

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