Winter is a high-load and high-risk period for the operation of steam boilers. Low temperatures can easily cause problems such as pipeline freezing and cracking, equipment start-up and shutdown failures, and decreased combustion efficiency. The core precautions revolve around five key areas: anti-freezing and anti-condensation, combustion stability, water quality control, equipment inspection, and emergency support. At the same time, both operation norms and safety protection should be taken into account. The specific key points are as follows:
Core anti-freezing and anti-condensation measures to prevent pipeline/equipment from cracking due to freezing (top priority in winter)
Operating equipment: Ensure that all pipelines such as boiler feed water, return water, steam pipelines, blowdown pipes, and sampling pipes are in good condition for heat tracing/insulation. Install insulation covers on exposed valves and flanges. The steam trap in the steam pipeline must be functioning properly to promptly discharge condensate water and prevent water hammer and freezing blockage inside the pipe.
Short-term shutdown: Completely drain the water from the drum, water tank and pipelines, and open the drain valve to maintain ventilation and dryness.
Long-term standby: Adopt dry maintenance (place desiccant and seal), or wet maintenance (add antifreeze to ensure that the freezing point of the boiler water is lower than the local minimum temperature).
Boiler room environment: The indoor temperature must not be lower than 5℃. Heating and hot air curtains should be installed, and cotton door curtains should be installed at the entrance. If the boiler room is not heated, electric tracing should be installed on key equipment (water pumps, water tanks, pipelines), and the heating lines of the electric tracing should be inspected by dedicated personnel to prevent short circuits.
Water replenishment system: Ensure proper insulation for the softened water tank and water replenishment pump pipelines. Regularly rotate and test run the water replenishment pump to prevent the pump body from cracking due to freezing. Ensure that the water level in the make-up water tank is sufficient to prevent sudden changes in the water temperature inside the furnace due to insufficient make-up water.
Optimize combustion adjustment to ensure efficient and stable operation
Fuel compatibility: In winter, the boiler load increases. Ensure that the quality of fuel (coal, natural gas, diesel, etc.) meets the standards. Install anti-freezing measures on the natural gas pipeline to prevent the pressure regulating valve from freezing and blocking. For oil-fired boilers, ensure proper insulation of the oil tank and heating of the oil filter to prevent diesel from solidifying.
Adjustment of the air-coal/air-fuel ratio: In winter, when the ambient temperature is low and the density of cold air is high, appropriately increase the supply air volume or adjust the exhaust air to ensure complete fuel combustion and reduce ash accumulation and coking. The outlet temperature of the furnace is controlled within the rated range to prevent the flue gas temperature from being too high and the thermal efficiency from decreasing due to incomplete combustion.
Furnace/flue ash cleaning: In winter, the load is high, and the furnace, convection tube bundle, and flue are prone to ash accumulation and coking. Increase the frequency of ash cleaning (such as regular operation of the soot blower and manual ash cleaning) to ensure heat exchange efficiency and prevent over-temperature inside the furnace due to ash accumulation.
Strengthen water quality control to prevent scaling and corrosion inside the furnace
In winter, the water temperature of boilers is high and the load fluctuates greatly. The water quality is prone to fluctuations, and the risks of scaling and corrosion increase. It is necessary to strictly follow the “Water Quality for Industrial Boilers” (GB/T 1576) standard:
Water supply treatment: The water softening equipment operates normally for 24 hours to ensure that the hardness of the water supply is ≤0.03mmol/L. Regularly test the quality of softened water, regenerate the resin in time, and prevent the hardness of the feed water from exceeding the standard due to the failure of the resin.
Boiler water monitoring: Increase the sampling and testing frequency of indicators such as pH value, alkalinity, and chloride ions in the boiler water (at least once per shift), ensuring that the pH value of the boiler water is between 10 and 12. Timely blowdown (combining continuous and regular blowdown) should be carried out to prevent scaling and caustic embrittlement inside the furnace.
Drainage operation: The drainage pipe should be well insulated. When draining, slightly open the valve first to preheat the pipeline, and then gradually open it wider. It is strictly forbidden to drain quickly and in large flow to prevent the pipeline from cracking due to excessive temperature difference. After discharging the sewage, close the valve in time and check for any leakage to prevent water from freezing and blocking.
Intensify equipment inspection efforts to ensure “early detection and early handling
Establish a special inspection system for winter, increase the inspection frequency by 50% compared to usual, focus on inspecting the following areas, and keep good inspection records
Main body and pipelines: Check for deformation or leakage in the drum and header. Check for freezing blockage, leakage or water hammer in the steam pipeline, steam trap and blowdown valve. Check if the insulation layer and heat tracing are damaged or fallen off.
Auxiliary equipment: The bearing temperature, vibration and lubricating oil level of the induced draft fan, forced draft fan and water pump. The lubricating oil should be replaced with a winter-specific low-temperature model to prevent the lubricating oil from solidifying and causing equipment jamming. Check if the couplings and belts are loose and take good wind and snow protection measures.
Safety accessories: pressure gauges, water level gauges, thermometers, safety valves, water level alarms, over-temperature and over-pressure alarms, etc. must all be calibrated and qualified and put into normal use. The water level gauge should be flushed regularly to prevent false water levels caused by freezing and blockage. The safety valve should be manually tested regularly to ensure its sensitive operation.
Electrical system: In the boiler room, the distribution cabinets, motors and circuits should be protected from moisture and snow to prevent short circuits and leakage caused by condensation. The grounding and zero connection protection are in good condition, and the explosion-proof grade of electrical equipment in the explosion-proof area (gas boiler) meets the standards.
Standardize operation procedures and eliminate human operational errors
Furnace start-up operation: Before starting the furnace in winter, the pipelines and equipment must be preheated. Open the steam trap and vent valve, and gradually increase the furnace temperature and pressure. It is strictly prohibited to start the furnace quickly to avoid thermal stress cracking of the furnace body and pipelines due to excessive temperature difference. During the furnace start-up process, closely monitor the changes in water level and pressure to prevent water shortage and overpressure.
Shutdown operation: After shutdown, cool down and reduce pressure step by step, thoroughly drain the accumulated water, and carry out anti-freezing maintenance. It is strictly prohibited to directly release water after an emergency shutdown of the furnace to prevent the furnace body from cracking due to sudden cooling.
Shift handover: Clearly define the content of the shift handover, with a focus on the operational status of the equipment, the implementation of anti-freezing measures, water quality testing data, and fault handling records, ensuring “clear handover and well-defined responsibilities”.
Improve emergency support to deal with sudden situations (such as power outages, gas supply cuts, and freezing and cracking)
Emergency material reserves: The boiler room should be equipped with antifreeze, insulation cotton, electric tracing, de-icing agents, as well as leak-stopping glue, valves, gaskets and other vulnerable parts. At the same time, prepare emergency lighting, flashlights, fire extinguishers, fire hydrants and other safety equipment to ensure they are in good condition and available for use.
Emergency response plan drill: Develop emergency response plans for common winter faults such as power outages, gas supply cuts, pipeline freezing and cracking, and water shortage or overpressure inside the furnace. Organize operators to conduct drills, clarify the fault handling procedures, and prevent panicked operations.
Backup power supply/equipment: Key equipment (make-up water pump, induced draft fan, circulating pump) is equipped with backup power supply (generator) or backup pump body. Gas boilers are equipped with gas leakage alarm devices and interlock shut-off valves to prevent explosions caused by leakage.
Sudden freezing and blockage handling: If the pipeline is frozen and blocked, it is strictly forbidden to directly bake it with an open flame. Instead, hot water should be used to slowly defrost it, or electric tracing should be used to gradually increase the temperature to prevent the pipeline from cracking due to local overheating.
Other Safety Precautions
The boiler room should take measures to prevent wind and snow. Snow should be cleared from the roof and the entrance in a timely manner to prevent the roof from collapsing and the entrance from being blocked by accumulated snow.
Operators should take good personal protective measures, wear anti-slip shoes and cold-proof clothing to prevent slipping and frostbite.
The expansion joints of the boiler body and pipelines are operating normally to ensure the compensation space for thermal expansion and contraction, preventing damage to the expansion joints due to low-temperature contraction.
For the operation and management of steam boilers in winter, “anti-freezing” is the bottom line, “stable combustion and water quality control” is the core, and “inspection + emergency response” is the guarantee. All measures must be assigned to individuals and responsibilities to positions, and any mentality of taking chances must be eliminated. At the same time, based on the model of the boiler (vertical/horizontal, biomass/oil and gas) and its rated parameters, a targeted winter operation plan is formulated to ensure the safe, efficient and stable operation of the boiler.