It is predicted that this winter will be extremely cold; have chemical companies taken adequate anti-freezing measures? Pay special attention to blind pipes! ! ! ! !

I. Anti-freezing methods. Common anti-freezing and anti-condensation methods in chemical plants include evacuation, insulation, heat tracing, and circulation. Winter anti-freezing and anti-condensation measures should be adopted using one or more methods, based on the operating conditions of the equipment and pipelines, as well as the problems and experiences encountered during previous anti-freezing efforts. Drain to prevent freezing. Anti-coagulation methods can be roughly divided into three categories: first, equipment that operates intermittently on the ground or is not used for extended periods of time. The pipeline emptying process can be carried out according to the following steps: (1) Close the relevant valves; if necessary, install blind flanges to prevent leaks from the valves ； (2) Open the high-point vent valve. The low-point exhaust valve empties the material from the equipment ； (3) Purge with nitrogen. Replace residual materials ； (4) Keep the normally open low-point drain valve open and inspect it regularly. Second, the facilities in the underground valve chamber: the pipes are drained, primarily those related to fire suppression systems that do not have heating elements (such as water cannons and fire hydrants). The gate valves in the valve chamber are closed, and the water above the valves is drained through the drain valves; these drain valves should remain open at all times. The fire cannon nozzles need to be directed downward. Third, for temporarily used equipment, pipes, or hoses, the medium inside them should be emptied promptly after use, and they should be cleaned with nitrogen ； If conditions permit, it can be placed in a insulation factory. From the perspective of frost prevention, insulation in chemical plants mainly involves the following three aspects: First, equipment, pipelines, and their accessories need to be insulated with insulating material. Before winter arrives, it is necessary to carefully examine and improve this work by taking into account past problems, paying special attention to the insulation of equipment without heat tracing that relies solely on the temperature of the material itself, as well as the ends of pipes, dead ends, and on-site pressure gauges, to ensure that proper insulation is in place. Second, ensure that indoor spaces such as factories are well-insulated, and check the doors and windows of the factory. Check whether the curtains are in good condition, and turn on the factory heating promptly. Third, seal and insulate the underground valve shaft. For valve chambers, seal them in advance with plastic sheeting, and take insulation measures if necessary. For winter anti-freezing, common heat tracing media include hot water tracing, steam tracing, and electric tracing. Hot water tracing is suitable for conditions where the operating temperature is low or high-temperature tracing media cannot be used. Steam tracing is generally used for tracing pipelines where the operating temperature of the medium is below 150°C. Electric heat tracing is suitable not only for various situations involving steam heating, but also for pipelines carrying thermosensitive media; it enables effective temperature control to prevent overheating of the pipelines. It is appropriate for pipelines or equipment that are dispersed or located far from the source of heat supply, as well as for equipment with irregular shapes. The selection of the heat tracing medium should take into account factors such as material properties, specification requirements, construction difficulty, and operating costs. And construct in accordance with the specifications, so as to achieve frost and condensation prevention and avoid new problems. The cyclic anti-freezing and anti-condensation method is mainly used for equipment and pipelines that operate intermittently or are not in use for extended periods. It is employed when other anti-freezing methods (emptying, insulation, heat tracing) are not used, or when such methods are insufficient to meet the anti-freezing requirements. This method can be roughly divided into four types: The first is to circulate the material exiting the operating equipment back to the inlet of the standby equipment, which is commonly used to prevent freezing and condensation in standby power equipment, such as through a bypass pipe beside the valve at the pump outlet or through an opening in the valve core. The second method involves connecting the equipment’s inlet pipeline to its outlet pipeline; this is often used to prevent freezing in the heat exchange inlet and outlet pipelines that are not in use. Pipes with a smaller diameter are connected before and after the inlet and outlet valves of the heat exchanger, thereby maintaining circulation of the fluid in these pipelines. Third, carry out a small number of cycles in normal operating mode; generally, it is advisable to close the outlet valves of the standby equipment to minimize fluid circulation and meet the anti-freezing requirements. Fourth, a small amount of medium is discharged continuously or intermittently. This method is primarily used for anti-freezing at the ends where it is not possible to establish circulating pipes, such as hose stations, tank drainage pipes and valves, as well as eye wash stations at the low points of steam pipes. II. Anti-freezing inspection. The anti-freezing inspection is an extremely important part of winter anti-freezing measures. Regular anti-freezing inspections allow for the timely detection and resolution of issues that arise during the anti-freezing process, effectively preventing further escalation of freezing blockages. The anti-freezing inspection primarily focuses on assessing the effectiveness of anti-freezing and antifreeze measures, identifying any gaps, and further improving these measures. The main inspection items and methods are as follows: 1. The steam tracing pipelines should be regularly inspected for the proper functioning of their traps; if any abnormalities are detected, investigations and corrective actions should be taken promptly. If it is not possible to directly check the hydrophobicity (for example, if it is concentrated at a hydrophobic waste collection station), a thermometer or the hand can be used to touch the valve body of the hydrophobic valve (an inspection hole should be provided when insulation is applied). For inspections, it is generally required that the temperature be above 30°C; normal heat levels are considered acceptable. However, the temperature sensed does not necessarily indicate that the hydrophobic treatment is functioning properly, especially in areas where hydrophobic materials are collected. 2. Use hot water for heating; check the water flow with a flow indicator, or use a thermometer to check the temperature of the electric heating tape at the designated inspection point to ensure it is within normal ranges ； When the heat-tracing hot water pipes are collected together, experience should be used to avoid thermal interference from the adjacent normal hot water pipes, which could affect inspection and judgment. 3. For electric heat tracing devices with temperature indicators, it is necessary not only to check the temperature readings regularly, but also to use a thermometer or touch the designated inspection points on the heat tracing cable, in order to prevent inaccurate temperature readings and ensure that the temperature of the heat tracing cable remains within the normal range. 4. Temperature sensors should be installed in enclosed workshops; the sealing of doors and windows as well as the heating temperature should be checked regularly, and the heating level inside should be adjusted according to the indoor temperature ； Check the insulation and sealing of the valve chamber, and monitor its internal temperature if necessary. 5. Regularly check whether there is any material flowing out or blockages due to freezing at the low points of the drainage equipment and pipes; this can also be determined by tapping the pipes with a wrench. If freezing blockage is detected, promptly check the source of the material and take appropriate action. 6. Regularly inspect the anti-freezing circulation circuits of equipment and pipelines. If there is a flow indicator or sight glass, check whether the indication is normal ； If there is no flow indicator or sight glass, it is difficult to determine the flow rate by temperature using a thermometer or by touching the device itself or the relevant anti-freezing wires; a listening rod can also be used to assess the flow of fluid through the equipment or pipes. For a small amount of external circulation antifreeze material, regularly check whether the discharge volume is normal. 7. Instrument heating: Regularly check the sealing condition of the instrument heating box as well as the temperature, and inspect the instrument heating using the appropriate heating method along with the methods mentioned above ； Furthermore, it is possible to compare instruments via on-site and remote transmission, and use the indicated values of normal instruments to determine whether an instrument has frozen. 8. Whether for long-term use or as a backup power unit, the equipment should be rotated regularly to detect any freezing or blockages in advance ； For equipment that cannot be rotated (such as canned pumps), in addition to checking the anti-freezing circulation, a spot check should be conducted during startup to measure the temperature of areas prone to freezing (such as the rear part of the canned pump), and only after it is normal should the equipment be started. 9. Drain valves at the ends of gas (vapor) pipelines, drain valves at the lowest points of U-turns, hose station valves, etc.: maintain an appropriate degree of opening or conduct regular drainage checks to prevent material from accumulating at those low points and causing pipe blockages due to freezing. 10. For instrument gas, in addition to regular drainage at the ends of the main pipelines and at the lowest points, it is also necessary to monitor its water content in order to prevent the water accumulated within the instruments from freezing, which could lead to failure in the instrument’s functioning. 11. Regularly check the outlets of the cleaning and consumption facilities to see if water is flowing from the low-point cleaning valves or if they have frozen; clear any blockages promptly if issues are found, and verify that the root valves are closed. 12. Regularly inspect the system’s exhaust outlets, such as the tank vent valves and flame arrestors, emergency exhaust outlets, air compressor exhaust outlets, and boiler safety valve exhaust outlets, to ensure that they remain unobstructed. 13. Regularly check whether the protective screens at the inlet of outdoor fans, filters, motor cooling fans, and other similar devices are frozen. If there is steam emission or snow around the equipment, it can easily get clogged. 14. Regularly check whether the liquid in the outdoor water seal tank or liquid seal tank has frozen; address any abnormalities promptly to ensure its proper functioning. 15. In case of a significant drop in temperature or at night, inspections should be intensified, and the heat supply, heating capacity in the factory building, and anti-freezing circulation volume should be adjusted according to the temperature; a one-time solution cannot suffice to prevent freezing and blockages. III. During the thawing process, frozen sealing treatment should also be carried out in light of specific circumstances. Generally, for small devices that freeze and get clogged, as well as short pipes, instruments, valves, etc., the frozen and clogged surfaces can be directly dissolved by steam purging. If insulation is in place, it should be removed in advance ； If the frozen equipment is large and the pipes are long, temporary heating (such as metal hoses) and insulation are usually employed to thaw it slowly. If the frozen equipment, pipes, instruments, and valves can be easily removed, they should be taken down as appropriate and placed in a high-temperature room to thaw, in order to avoid safety hazards such as the release of toxic and harmful gases and liquids or explosions during the process of thawing and clearing blockages. The following points should be taken into account during this process: First, check whether the frozen or blocked equipment, pipes, and valves are cracked or damaged, and whether the valves are open or closed. Second, isolate the relevant systems before proceeding with the treatment. Third, the operation should be carried out slowly, using low-temperature steam to dissolve the ice, in order to prevent sudden damage to the frozen equipment, pipes, and valves due to exposure to heat. Fourth, consider the impact of sudden drainage on the instruments and process conditions during thawing, and take preventive measures in advance. 4. Other matters: 1. Drawing on past experience with freezing issues, address these problems by preparing anti-freezing materials such as insulation materials, check valves, flexible hoses, temporary connectors, and anti-freezing gloves. Before winter arrives, preventive measures should be taken, various anti-freezing measures should be put into use and checked in advance, so as to have sufficient time to address any anti-freezing issues and avoid sudden cooling that could prevent these measures from being implemented. Adjusting the heating system in a timely manner not only meets the requirements of the antifreeze but also prevents waste caused by excessive heating, excessive process parameters, or inaccurate instrument instructions. Heated material pipelines should have an expansion direction to prevent the equipment or pipelines from being under pressure due to the thermal expansion of the material. If there is a pressure gauge, pay attention to monitoring its pressure 5. When the material pipeline is in operation and flowing, the heat tracing pipeline heats the material pipeline being traced. If the flow of material in the pipeline stops, it should be carefully inspected, and the heat tracing should be increased as appropriate6. The heating temperature of the eye washer should be appropriate, to prevent new damage caused by an excessively high heating temperature.7 If hot water or steam tracing needs to be temporarily stopped for maintenance purposes, be careful to prevent the tracing pipes and material pipelines from freezing and getting blocked.8 For equipment equipped with heating, if heat dissipation is required during operation, the insulation layer should be removed and the heating system should be reduced or turned off to prevent the equipment’s temperature from rising too high. When using electric heating, attention should be paid to the load on the heating strip to prevent overload trips or fires ； The power supply should be disconnected before carrying out maintenance on electric heat tracing, and anti-freezing measures for the heat tracing material should be considered during maintenance10. Issues such as steam tracing problems and abnormal drainage, including water hammer, insufficient or excessive drainage volume, and inadequate tracing heating, should be addressed promptly.11 The cyclic anti-freezing method is employed; under conditions that meet the anti-freezing requirements, the volume of circulation is minimized to avoid unnecessary waste caused by excessive circulation12. Similar to fire valve shafts, when underground valves are closed, tools for opening the shaft covers and valves should be available for prompt use in emergency situations13. Eliminate any instances of leaks, spills, or drips on site promptly to prevent ice formation on the ground and in the air; address such issues as soon as they occur.14 Conduct regular anti-freezing inspections to ensure their quality. At the same time, focused inspections are carried out based on different time periods, temperatures, and the difficulty of preventing freezing.