Sharing common cold and freeze prevention measures used in power plants

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As temperatures continue to drop, to ensure that the equipment can survive the winter safely, power plants should actively improve their maintenance systems, increase the frequency of inspections of the equipment, establish clear responsibilities for personnel at all levels, and make cold and freeze prevention efforts more systematic, thorough, and standardized. Proactive measures for cold and freeze prevention should be taken in advance to guarantee the safe operation of the equipment throughout the winter. I. Anti-freezing methods: Common anti-freezing and anti-condensation methods used in power plants include evacuation, insulation, heat tracing, and circulation. In winter, to prevent freezing and condensation, one or more of these methods should be employed, taking into account the operating conditions of the equipment and pipelines, as well as the problems that have occurred during previous anti-freezing efforts and the relevant experience gained. 1. Emptying: Methods for emptying systems to prevent freezing and condensation can be roughly divided into three categories: the first is the emptying of equipment and pipelines that are operated intermittently on the ground or not used for extended periods of time. The emptying process can be carried out following these steps: (1) Close the relevant valves; if necessary, install blind flanges to prevent leaks inside the valves ； (2) Open the high-point vent valve and the low-point drain valve to empty the material inside the equipment ； (3) Purge and displace residual materials with nitrogen ； (4) Keep the normally open low-point drain valve open and inspect it regularly. Second, empty the facilities and pipelines in the underground valve chamber. It mainly refers to unheated fire-fighting equipment (such as water cannons and fire hydrants); the root valve is closed from within the valve chamber, the water above the valve is drained through a drain valve, which remains open, with the fire cannon nozzle pointed downward. Third are temporarily used equipment, pipelines, or hoses. After use, empty the medium in the tube promptly and purge it with nitrogen ； If possible, it can be placed in a insulated building. 2. Thermal insulation: From the perspective of preventing freezing, thermal insulation in power plants mainly involves the following three aspects: First, insulating materials are used to insulate equipment, pipelines, and their accessories. Before winter arrives, it is necessary to take into account the problems that have occurred in previous years, to carefully examine this aspect of work and make improvements. Special attention should be paid to the insulation of equipment and pipeline ends, dead ends, as well as on-site pressure gauges that rely solely on the temperature of the material for freeze protection, to ensure that proper insulation is in place. Second, ensure the sealing and insulation of indoor spaces such as factory buildings. Check to ensure that the doors, windows, and door curtains in the factory building are in good condition, and activate the heating system inside the building promptly. Third is the sealing and insulation of underground valve chambers. For valve chambers, plastic sheeting should be used to ensure airtight sealing in advance, and insulation measures should be taken if necessary. 3. Heat tracing: For preventing freezing in winter, common heat tracing media include hot water tracing, steam tracing, and electric tracing. Hot water tracing is suitable for situations where the operating temperature is not high or where high-temperature tracing media cannot be used. Steam tracing is generally used for tracing applications where the operating temperature of the medium inside the pipe is below 150°C. Electric heating is suitable not only for various situations involving steam heating but also for pipelines carrying thermosensitive media; it enables effective temperature control to prevent the pipes from overheating. It is appropriate for heating pipelines or equipment that are dispersed or located far from the supply point, as well as equipment with irregular shapes. The selection of the heat tracing medium should take into account factors such as the properties of the material, required specifications, construction difficulties, and operating costs. Construction must be carried out in accordance with relevant standards, so as to achieve frost and condensation prevention while avoiding the emergence of new problems. 4. Circulation: The method of using circulation for anti-freezing and anti-condensation is mainly applied to equipment and pipelines that operate intermittently or are not in use for long periods of time, where the aforementioned methods (emptying, insulation, heat tracing) have not been used for anti-freezing purposes, or where such methods are insufficient to meet the anti-freezing requirements. This method is roughly divided into four approaches: the first is to circulate the material exiting the operating equipment back to the inlet of the standby equipment. This method is commonly used to prevent freezing and condensation in standby mechanical equipment, such as through a bypass line adjacent to the check valve at the pump outlet, or by making an opening in the valve disc of the check valve. The second method is to connect via a bypass pipe from the equipment inlet line to the equipment outlet line. This method is commonly used to prevent freezing of the inlet and outlet pipelines of heat exchangers that are not in use. Smaller-diameter pipelines are connected in front of the inlet valve and behind the outlet valve of the heat exchanger, thereby maintaining circulation of the fluid in the inlet and outlet pipelines. Third, perform a small number of cycles in normal operation mode. Generally, it is advisable to close the outlet valves of the standby equipment as much as possible to reduce the flow rate of the medium, thereby meeting the anti-freezing requirements. Fourth, a small amount of medium is discharged continuously or intermittently. This method is primarily used for situations where it is not possible to install anti-freezing measures at the ends of circular pipelines, such as hose stations, drain pipelines and valves of storage tanks, drain valves at the lowest points of steam pipelines, and eyewash stations. II. Equipment Protection Against Cold and Freezing (I) Measures for Protecting Turbine Equipment from Cold and Freezing (1) Close all doors and windows in the turbine room and ensure proper insulation. (2) Promptly eliminate leaks of water, oil, and air (vapor) in the machine room, and promptly remove accumulated water and oil on the floor. (3) 3–4 rooftop fans should be operated for each unit to maintain air circulation indoors and prevent the accumulation of flammable gases. (4) The shut-down units should drain all the water from the condensers, deaerators, heaters, unused coolers, various unused water pumps, as well as from the steam and water pipelines. (5) The standby turbine should have its rotor rotated regularly to ensure flexibility, and the cooling water must remain flowing. (6) Check that outdoor oil and water pipelines have proper insulation. (7) For pipes in which water cannot be completely drained, their air release valves should be slightly opened to maintain fluid flow. (8) All thermal control transmitters and dashboard heating devices shall be reliably activated. (9) For generator sets used as short-term backups, the internal cooling water pumps should remain in operation (electrical heating devices should be activated if necessary). (10) In motors equipped with electric heating devices, the electric heater shall be activated after the motor stops operating. (11) The electric heating devices of the lubricating oil system, seal oil system, and EH oil system should be activated before the oil pumps start up, in order to appropriately raise the oil temperature, reduce the motor starting current, and protect the motor. (II) Anti-cold and anti-freezing measures for boilers: (1) For boilers that are not in use, dry anti-corrosion methods such as the \"hydrazine method\" or the \"ammonia filling method\", or other chemical treatment methods, should be employed for their maintenance. The \"heating and pressurization method\" should not be used in winter; it is necessary to maintain a boiler pressure of at least 0.2 Mpa. (2) All doors and windows in the factory buildings, auxiliary rooms, etc., should be closed properly. The temperature in the control rooms and duty rooms should remain at least 15°C; otherwise, air conditioning or heating systems should be turned on. (3) All parts of the boiler itself and various thermal instruments that require steam heating should be activated, and the drain valves should be opened appropriately. (4) The cooling water for each turbine, the water seals in various areas, and the nozzles in the ash and slag channels should all be turned on to maintain a continuous flow of water. Pumps that are not in use, as well as fire hoses, should have their water drained or the fire hydrants should be left slightly open to ensure a certain level of leakage. (5) All system pipes must not have any exposed parts; proper insulation should be applied before winter arrives. (III) Cold and freeze prevention measures for electrical systems: (1) Operators should intensify their routine inspections, ensure that the doors and windows of the factory building and distribution rooms are properly closed, and regularly measure the temperature inside the factory building. (2) After shutting down in winter, the room temperature should be maintained above 5°C. When the room temperature is below 5°C, measures can be taken to maintain the stator cooling water temperature above 5°C, using water circulation to prevent freezing. (3) Electrical personnel are responsible for closing the doors of the cooling fans and oil pump distribution boxes of the main transformer, high-voltage plant transformer, and standby high-voltage transformer. They also conduct regular inspections of the temperature controllers in various switch distribution boxes and electrical control cabinets to ensure that the switching heating systems can be activated reliably. Check that the insulation covers for the distribution box are fully installed and the markings are clear. (4) When the temperature drops, it is necessary to carefully check the oil level in each oil-immersed transformer. If any abnormality is detected, it should be reported promptly, and maintenance personnel should be contacted to handle the issue. (5) Carefully carry out regular insulation testing of motors, and record the insulation data accurately. For motors with unqualified insulation values, report to the shift supervisor promptly and arrange for maintenance to address the issue. (6) Strictly implement the regular equipment switching system, identify problems in a timely manner, and take action to address them. For standby equipment, conduct regular trial runs; after the trials are complete, clean it thoroughly and drain any remaining water. (7) On days with heavy snow, it is necessary to check the melting of the snow in order to determine whether there is overheating at joints and other areas, as well as to check for ice formations on insulators that could cause arcing. (8) When the temperature is low, the water temperature and oil temperature of the diesel generator should be checked regularly; if the temperatures are too low, heating should be activated. (9) When the temperature drops sharply, check that the electric heating devices in the electrical control box and the hydraulic control box are operating properly. (IV) Cold and freeze protection measures for the chemistry department: (1) Close all doors and windows in the water treatment workshop, the advanced treatment and regeneration area, as well as the areas where acids and bases are stored, as much as possible, to ensure proper insulation. (2) Put into operation the steam mixing heating device in the high-level alkali tank for make-up water, and conduct regular inspections to prevent steam leakage. (3) The standby turbines should have their rotors rotated regularly to ensure flexibility, and all inlet and outlet valves for the cooling water of these turbines should remain open to maintain unobstructed water flow.