Shutdown of the hottest petrochemical production u

Once the shutdown plan is determined, the shutdown time, shutdown procedure and various safety measures determined in the shutdown plan should be strictly followed. Shutdown operation and precautions are as follows: (1) pressure relief. The pressure relief of the system should be slow, from high pressure to low pressure. It should be noted that the pressure should not drop to zero, let alone create negative pressure. Generally, it is required to maintain a weak positive pressure in the system. Do not disassemble the equipment before pressure relief. (2) Cool down. The cooling shall be carried out at the specified cooling rate to ensure that the specified requirements are met. High temperature equipment cannot be cooled suddenly to avoid equipment damage. It is better to cut off the heat source and then forced ventilation or natural cooling. Generally, it is required that the medium temperature in the equipment and the room should have enough space to be less than 60 ℃. (3) Drain. Discharge the gas, liquid and solid materials stored in the production system (equipment and pipelines). If the materials cannot be completely discharged, they should be recorded in detail in the "safety maintenance handover book" and further safety measures should be taken. The discharge of residues must be carried out in strict accordance with the specified location and method. It is not allowed to vent or discharge into the sewer at will to avoid environmental pollution or accidents

2. The main steps of safety treatment after shutdown are: isolation, replacement, purging and cleaning, and the production department and maintenance department should strictly handle the handover procedures of safety maintenance before maintenance

(1) major accidents caused by toxic, flammable, explosive, corrosive, asphyxiating and high-temperature media entering the maintenance equipment due to unreliable isolation occur from time to time; Therefore, the maintenance equipment must be reliably isolated. Depending on the specific situation, the safest and most reliable isolation method is that this kind of printer is mainly applicable to the removal of pipelines or the extraction and insertion of blind plates in digital pressure testing machines. The removal of pipelines refers to the removal of removable parts such as pipelines connected with maintenance equipment, valves and expansion joints on pipelines. Then install a blind plate on the flange on the pipeline side. If there is no detachable part or the disassembly is very difficult, the valve should be closed tightly and a blind plate should be inserted at the flange connection of the pipeline connected to the maintenance equipment. This method is easy to operate, safe and reliable, and is widely used. The blind flange extraction and insertion is a dangerous operation, so the "blind flange extraction and insertion work permit" should be handled, and various safety measures should be implemented at the same time: ① the blind flange extraction and insertion operation diagram should be drawn, and the blind flange extraction and insertion operation should be carried out according to the diagram, and records and inspections should be made. The position where the blind plate is added shall have obvious signs to prevent missing insertion and extraction. When removing the flange bolts, loosen them gradually and slowly to prevent the residual pressure in the pipeline or the ejection of residual materials, so as to avoid accidents. The position of adding blind plate is generally at the rear of the incoming valve. The effect of microsphere drug loading on microsphere size and ζ Both sides of the blind plate should be shimmed and fastened with bolts of the size that can cover the lower jaw to ensure no leakage

② blind plates must meet safety requirements and be numbered. Make a suitable blind plate according to the actual situation on site: the size of the blind plate should conform to the diameter of the valve or pipeline; The thickness of blind plate shall be determined by calculation. In principle, the thickness of blind plate shall not be less than the thickness of pipe wall. The material of blind plate and gasket shall be selected according to the medium characteristics, temperature and pressure. The blind plate shall have large lugs and be painted with special colors for tag numbering and identification

③ safety measures on the site for extracting and inserting blind plates: confirm that the system materials are discharged completely, and the pressure and temperature fall to the specified requirements; Attention should be paid to fire and explosion prevention. Explosion proof tools and lamps should be used when pumping and inserting flammable and explosive media windows or pipe blinds in the fire ban area. Fire is strictly prohibited within the specified range, and special personnel should be assigned to patrol and monitor during operation; When pulling and inserting blind plates indoors, windows must be opened or ventilation equipment meeting safety requirements must be used for forced ventilation; When pumping and inserting the blind plate of the toxic medium pipeline, the operators should wear appropriate personal protective equipment as required to prevent poisoning; When extracting and inserting blind plates at heights, the safety requirements for high-altitude operations shall be met at the same time, and safety helmets and safety belts shall be worn; There should be rescue backup measures and gas prevention stations for operations with great risks, and medical personnel and ambulances should be on site; The operator should not spend too long in the continuous operation of extracting and inserting blind plates, and should take turns to rest