Winter is approaching – how can chemical companies survive it safely?

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Midsummer has passed, and winter is approaching. The cold temperatures, dry weather, strong winds, and frequent snowfalls in the north pose many difficulties for people’s daily lives, especially for outdoor activities. These conditions further complicate the safe production processes in chemical manufacturing enterprises. Before winter arrives, experienced drivers always replace their vehicles’ lubricants and windshield washer fluid with those suitable for low temperatures. So, as \"drivers\" in petrochemical companies, how should we cope with the challenges of winter and ensure that the large and complex petrochemical facilities can survive through the winter safely? Case 1: Failure to timely treat the equipment’s circulating water nearly destroyed important equipment. A unit was shut down for maintenance in December; the operators on duty, preoccupied with dealing with urgent process issues, forgot to drain the water from one of the compressor cylinders. Additionally, due to prolonged operation, some of the water channels in this equipment were blocked by sediment within the system, resulting in poor performance of the circulating water system. This led to severe freezing inside the compressor cylinder, and the expansion caused the cylinder to bulge. Lessons from accidents: For equipment in the circulating water system that operates for extended periods of time, it is necessary to regularly check whether the circulation system itself is functioning properly. After the equipment stops operating, the water inside it should be drained promptly to prevent damage due to freezing. Underground pipelines and their drainage systems should be buried below the permafrost layer. The main pipes for fire water, surface water, utility water, and cooling water shall be laid underground. Anti-freezing measures for the main water supply and return pipes on the ground: Circulating water bypass pipelines are installed between the inlet and outlet main pipes as well as between the ends of these main pipes. For branch pipes leading off from the main pipe, a shut-off valve should be installed at the high point of the horizontal section near the main pipe. The length between the cut-off valve and the main pipe should be as short as possible. For pipelines that require anti-freezing protection, steam tracing and insulation should be used. The heating medium should be low-pressure steam, with a drain installed at the lowest point. All pipelines should, as much as possible, be designed for self-drainage, and the steam in the heat tracing pipes should flow downward. Conduct a thorough inspection of the steam tracing for the instrument pipelines, and work together with the instrument technicians to check whether the tracing pipelines are unobstructed, in order to prevent instruments equipped with interlock functions from being damaged by freezing and causing the plant to stop operating. Accident Case 2: Shutdown caused by untimely inspection of instrument heating. A chemical processing plant operated stably throughout the winter, and comprehensive anti-freezing measures were taken for the equipment on site before winter arrived. However, since the instruments were under the responsibility of another department, no thorough inspection of their heating systems was carried out. One night as winter set in, a sudden strong wind and drop in temperature occurred. Due to a malfunction in the heat-traced steam trap at one of the pressure control points in the circulating water system, the pressure gauge was damaged by freezing; as a result, the pressure rose to the interlock level, causing the entire circulating water system to stop operating. Cause of the accident: The accident occurred due to insufficient and timely inspection of the instrument heating, particularly as comprehensive inspections were not carried out in a timely manner for instruments with interlock points. Strengthen management and establish records for anti-freezing and anti-condensation measures. Strengthen winter patrol inspections; focusing on the anti-freezing checks of pipelines, pumps, and instruments. While ensuring energy conservation and emission reduction, it is necessary to prevent water accumulation, freezing, ice formation, or frost in the plant area. After understanding the main challenges faced by chemical enterprises in ensuring safe production during winter, how should we respond? In terms of personnel and management: 1) Strengthen the inspection of the implementation of various tasks, urge operators at all levels to overcome weather-related difficulties in order to complete their work more effectively; standardize the use of protective clothing, and strictly control the use of any clothing or accessories other than work uniforms, with special attention to the use of scarves, insulated gloves, insulated masks, and ear protection ； Train employees to consciously discharge static electricity before entering flammable and explosive areas. 2) Arrange work reasonably; for example, when conducting supervision during winter operations, reduce the duration of individual supervision and rotate supervisors more frequently ； Employees are reminded to pay attention to traffic safety after snowfall and icing in winter, to be cautious of the risk of ice falling from heights, and to remove snow and ice from the equipment promptly. 3) Before carrying out the work, whether it is the risk identification by the personnel on duty or the training and JHA analysis provided to contractors prior to their work, the specific characteristics of safe production in winter must be fully taken into account; weather conditions and the various risks they pose need to be thoroughly identified and communicated ； During the execution of various tasks, it is necessary to enhance self-protection awareness based on the risks identified prior to starting the tasks, pay attention to one’s surroundings, carry out all tasks in a proper manner, and remind and supervise each other to ensure that risks in winter are under control. 4) Pay attention to and understand the difficulties of working in extremely cold weather during winter; for example, in the reward programs organized by various companies to identify potential hazards, it is necessary to take into account the difficulty of detecting such hazards in cold weather as well as the severity of their consequences, and increase the rewards accordingly to boost the enthusiasm of employees for their work. In terms of equipment, ensuring its safety through the winter is the foundation and key to safe production during this period. The main focus is on carrying out a series of measures to prevent freezing and condensation during winter, with an emphasis on starting these efforts in advance, implementing them thoroughly, and maintaining them throughout the whole season. Six key elements should be taken into consideration: breaking down the winter-related tasks and assigning responsibilities to specific individuals; it is necessary to assign the entire process of implementing a particular measure for safe winter production to specific roles. For example, in the case of a heat tracing system, one single role is responsible for the entire process – from testing, troubleshooting, operation in low-temperature conditions, making adjustments based on temperature and production levels after it starts operating, inspection and maintenance during use, to shutting it down after winter. This approach ensures both continuity in the work and its quality. Preparations before winter: Planning should start as early as possible, leaving enough time for contingencies. Preparation work must begin early, and when scheduling tasks, uncertainties must be taken into account. For example, testing a steam tracing line may take a few hours, but if leaks are detected during this process, fixing those leaks could take a day; and if it turns out that the tracing tubes need to be replaced while fixing the leaks, the replacement process could take 2 days. Similar situations often occur, so it is important to plan ahead and have a surplus. Preparations before winter: Preparation of auxiliary production systems such as electrical and instrumentation equipment; on one hand, it is necessary to prepare the professionals and equipment accordingly ； On the other hand, preparations are made to establish communication with production operators regarding special conditions in winter. In actual production, when instrument failures have a significant impact on production, time is of the essence, and resolving such issues is difficult, close cooperation between instrument specialists and production staff is necessary to speed up problem resolution; therefore, it is important to define the responsibilities of all parties involved in the emergency handling process for instrument problems. During winter: Adjustment and inspection of countermeasures. Throughout the winter, due to changes in weather conditions and production adjustments, it is necessary to keep making adjustments to various measures. A typical example is the steam tracing steam traps, which need to be adjusted promptly in response to changes in temperature ； On the other hand, it is necessary to ensure that various measures meet the relevant requirements and are functioning properly; therefore, checking these measures is essential. For example, the status of instruments can be determined by comparing the readings from DCS instruments with those on-site, and the amount of steam used for heat tracing can be checked based on the actual temperature at the site ； After adjustments and inspections, attention should be paid to the handover of tasks; a detailed handover system should be established. Within the contents of shift handovers at each position, winter-related countermeasures should be listed separately, with emphasis placed on the status checks and adjustments of these various measures. Strive to ensure proper inspection and adjustment, thorough inspection, accurate recording, and proper handover. During winter: Special handling plans should be developed to address issues arising from localized freezing incidents. These plans aim to control and resolve such problems promptly and prevent them from spreading. When formulating these plans and carrying out the actual handling, the characteristics of winter must be taken into account. For example, when dealing with the problem of valve freezing, cold water should be used first, followed by hot water, and then steam heating should be employed, in order to prevent excessive temperature rises that could damage the valves and lead to larger accidents and losses. During winter: Responding to extreme weather. Winter extreme weather conditions such as extremely low temperatures, heavy snowfall, and strong winds can have a serious impact on both daily life and economic activities; therefore, specific plans for dealing with such situations should be formulated before winter arrives. When formulating and implementing plans, attention should be paid to the impacts of extreme weather on aspects other than production. For example, after heavy snowfall, travel is severely disrupted, which may prevent replacement staff from arriving at the plant on time; in such cases, the possibility of current staff working overtime should be considered. Preventing freezing and condensation of pipes, equipment, and valves in winter installations: In the design of pipes, it is advisable to make use of the fluid circulation within the system to prevent freezing, thereby avoiding the need for heating systems. For example, in a cooling water system, when the equipment is shut down, a bypass near the heat exchanger can be used to enable the circulation of supply and return water. In the design of fluid flow pipelines, dead corners where freezing may occur should be avoided. For unavoidable dead zones, insulation and heat tracing should be used to prevent freezing. Try to avoid pipelines with no fluid flow or those that are used intermittently; if such pipelines are unavoidable, insulation and heat tracing should be considered in the design. By utilizing proper drainage for anti-freezing purposes, in utility pipelines such as those for water, condensate, and steam, liquid accumulation and freezing can occur during shutdowns; therefore, appropriate drainage, venting, and self-drainage measures should be considered to prevent freezing. During parking or deactivation, these pipelines should be completely drained. “Areas that require special attention to prevent freezing: ★ Fire pumps must always have their nozzles pointed downward, and any water remaining inside them should be drained to prevent freezing damage ； Inspect and improve the exposed parts above ground of fire monitors and fire sprinkler pipelines, as well as the outdoor fire water lines for various production units. ★In the tank area, it is necessary to check whether there is water remaining in the pipeline behind the fire spray valves of the storage tanks, and drain that water completely ； Crossings, dead ends, and dead zones in the pipelines for process water, demineralized water, circulating water, and easily solidifying media. ★Shut off the cooling water for machine pumps, eyewash station supplies, etc ； Pipelines for easily solidifying materials and water lines that are used intermittently. ★The glass in the doors and windows of the room, as well as the indoor fire-fighting equipment located near them ； Fire steam tapes must be readily available to ensure that small fires can be extinguished promptly. ★The vent valves of each storage tank must be properly maintained to prevent malfunctions due to the entrainment of materials in the gas phase, which could lead to accidents ； Anti-condensation for pressure gauges and pressure transfer pipes ； Ensure the air purification device is operating properly to prevent water from entering the instrument air supply ； Heat tracing, traps, etc. ★After rain, snow, and heavy fog, water and ice accumulation in work areas such as passageways, stairways, and floors, as well as in areas where people walk, must be cleared promptly. The overhead pipes used by people, as well as the ice icicles under the eaves, must be removed promptly. ★Frozen cast iron pipes and valves must not be heated rapidly; they should be thawed slowly using warm water or a small amount of steam, to prevent damage caused by sudden heating.