Stopping maintenance of hot water boilers and steam boilers

Stopping maintenance of hot water boilers and steam boilers
In the steam boiler hot water boiler gas boiler oil-fired boiler coal-fired boiler, energy-saving and environmentally friendly boiler operation, often need to stop the furnace due to accidents, faults, power outages and the end of the boiler operation, which involves stopping the operation of the furnace and paying attention to stop The maintenance work after the furnace, the following describes the boiler shutdown method and maintenance.
Steam boiler hot water boiler gas boiler oil boiler coal-fired boiler, energy-saving environmental protection boiler shutdown
Boiler shutdown can be divided into three situations: pressure ignition, normal shutdown and emergency shutdown. The first two are planned shutdowns, which should be interrupted slowly and the load reduced until the load on the hot water boiler drops to zero. The latter is an accident in the operation of the boiler, which interrupts the combustion and causes the boiler load to drop sharply to zero.
Pressure ignition (hot standby) shutdown
When the external load is reduced, the boiler can be suspended by one or several boilers by means of pressure ignition. Thus, when the load increases, the boiler that stops running can resume normal operation at a speed of zui, and the ignition can be eliminated. Work and shorten boost time.
Steam boiler operation method:
Before the boiler is pressed, the actual party reduces the boiler load, and then according to the length of the shutdown time, the coal seam is thickened (generally only 200 mm), and the grate speed is appropriately accelerated, when the thickened coal seam is from the old millimeter eagle iron ( When the slag stopper is about 1 mm, stop the grate rotation, stop the drum and the induced draft fan, and adjust the regulating plate block and the flue baffle for the small-section air supply, and rely on natural ventilation to maintain the weak combustion of the coal, and then discharge the sewage. Raise the boiler water level to the high allowable water level. If the fire burns off the coal sluice, the grate can be activated again to move the coal back a distance. When the boiler needs to resume operation, as long as the pilot and blower are activated, adjust the opening degree of the smoke, wind baffle and sectional wind chamber to adjust the baffle. When the combustion is normal, adjust the thickness of the coal seam and start the grate to resume operation.
Hot water boiler pressure control operation method
The hot water boiler usually adopts the intermittent operation mode. For the combustion method using the layered equipment, the wet coal can also be used to stop the fire on the upper part of the grate on the grate. The fire block should also be closed after the fire is extinguished. The plate and the ash door open the furnace door (if the fire does not re-ignite during the fire, the furnace door can also be closed). However, it should be noted that the operation of the circulating water pump should not be stopped immediately after the ignition is stopped. The circulating water of the network should be continuously circulated in the system for a period of time, and the operation of the circulating water pump can be stopped when the temperature of the outlet water of the boiler drops below 50oC. Because the furnace temperature is still very high at this time, if the pump is stopped, the system water circulation is interrupted immediately. For the forced circulation of the hot water boiler due to the stop of the water circulation, the pot water will vaporize and cause water hammer or high temperature heating surface to overheat and burn out.
Precautions when boiler is fired and shut down
During the pressure ignition, there is still steam pressure in the pot, so it is necessary to pay attention to monitoring and keep the boiler high allowable water level;
When the pressure fire is stopped for more than 6 hours, the main steam valve of the boiler should be closed after a period of pressure ignition, and the steam trap of the superheater outlet header is opened to cool the superheater. If the air pressure rises after closing the main steam valve, it can be depressurized by the method of water supply to the boiler and simultaneous discharge. When the boiler resumes operation, it needs to be boosted and protected.
During the shutdown of the fire, proper drainage should be carried out to remove the sediment in the furnace;
For boilers equipped with cast iron gas, after the boiler stops supplying water, the provincial gas flue baffle should be closed, the side furnace baffle should be opened or used in the circulation pipeline to stop the water temperature in the gas from exceeding the specified value.
Normal hot water boilers are scheduled to be shut down due to reduced load, end of heating period and maintenance, etc., called normal shutdown. Normal shutdown, generally in the following order: stop supplying fuel; stop blasting, then stop the air; stop the water supply, reduce the pressure, close the water supply valve; close the steam valve, open the steam trap; close the flue baffle.
Emergency shutdown
When an accident occurs in the operation of the boiler, if the furnace is not immediately shut down, there is a possibility of expanding the accident and the human body and equipment. Therefore, the boiler operation must be stopped immediately, which is an emergency shutdown.
Emergency shutdown operation method
Emergency shutdown of steam boiler
First stop the coal supply and supply air, the chain furnace should be hung on the curved baffle, the throwing machine furnace stops throwing coal, and weaken the induced wind, close the small flue baffle.
Depending on the nature of the accident, some should release coal from the furnace, and some should not let off coal. The method of releasing coal is: the grate should send the coal into the ash hopper at a high speed. After burning the coal ash hopper, the water can be used to smear or use sand, and the ash of the wet furnace is pressed on the coal to extinguish the fire, but under no circumstances should the water be cooled in the furnace to cool the boiler.
After the steam boiler is extinguished, the main steam valve should be closed to isolate the main steam pipe from the steam main pipe, and the induced draft fan is closed. To make the nature of the accident, if necessary, open the air valve, safety valve and superheater trap to quickly discharge steam and reduce pressure.
Open the provincial gas bypass flue, close the main road flue, and open the large flue baffle, ash door and furnace door to promote air dredging and increase the cooling rate.
In the case of emergency shutdown, there is no shortage of water and full water. Water supply and sewage can be used to accelerate cooling and reduce boiler pressure. When the water temperature drops below 70oC, the pot water can be drained.
If the boiler is urgently shut down due to lack of water in the boiler, it is strictly forbidden to supply water to the boiler, and it is not possible to open the air valve or lift the safety valve to adjust the exhaust gas to prevent the boiler from being suddenly exposed to temperature or pressure changes.
When it is determined that the boiler is full of water accidents, stop the water supply immediately, turn off the small ventilation and flue baffles, reduce the combustion, and open the drain valve to release the water, so that the water level is properly reduced; at the same time, open the main steam pipe, superheater, steam mother The traps on the tubes and sub-cylinders prevent large amounts of steam from passing water and water shocks in the pipes.
Emergency shutdown of hot water boiler
When the engine is shut down in an emergency, the fuel should be stopped immediately. If necessary, the coal is burned out of the furnace or the ash is used to extinguish the fire. If the circulating water pump is normal, the pump should not be stopped immediately. When the water temperature at the outlet of the boiler drops below 50oC, the operation of the circulating water pump can be stopped.
Stop maintenance
After the boiler is shut down, the humidity in the boiler is very high and the ventilation is poor. The metal surface of the boiler is in a damp state for a long time. Under the action of oxygen and carbon dioxide, the boiler metal is corroded and rusted. After the boiler is put into operation, the corrosion is caused. Strong electrochemical corrosion continues to occur in the high temperature pot water, resulting in deepening of the corrosion and enlargement of the area. The thinning of the metal wall of the boiler will inevitably reduce the strength of the pressure component of the boiler, which will threaten the safe operation of the boiler and shorten the service life of the boiler. Therefore, in order to ensure the safe and economic operation of the boiler, it is necessary to do the anti-corrosion maintenance work after the boiler is shut down. According to the length of the shutdown time, the boiler's anti-corrosion maintenance usually has three kinds of heat maintenance, wet maintenance and dry maintenance. Thermal maintenance is suitable for hot standby; wet maintenance is suitable for short-term (generally no more than one month) decommissioning; long-term shutdown for more than one month of shutdown is dry maintenance.
Thermal maintenance
Keep a certain pressure in the hot water boiler, about 0.05-0.1Mpa, so that the boiler water temperature is higher than 100oC and there is no nutrient condition, and the pressure inside the pot can prevent outside air from entering the drum. In order to maintain the temperature of the boiler water, the steam of other boilers can be used to heat the boiler water. When a single boiler has no steam source during maintenance, it can be maintained in the furnace. This method is generally used for hot standby boilers or boilers that have been shut down for less than one week.
Wet maintenance
The maintenance method is to use a certain concentration of alkaline solution to contact the metal on the inner surface of the boiler to form an alkali protective film on the metal surface to prevent corrosion of the metal. After the boiler is shut down, the pot water is drained, the scale and soot are clear, all the holes, hand holes, valves, etc. are closed, and they are completely isolated from other operating boilers. Then, the softened water is poured into the boiler to the low water level of the Zui, and the configured alkaline anticorrosive liquid is injected into the boiler by a special pump. The composition of the antiseptic solution is: sodium hydroxide, adding 5-6kg per ton of pot water. Or carbonated sodium is added 5-10kg per ton of pot water. When the corrosive liquid is completely injected, the feed water valve is opened to fill the boiler with softened water (including the superheater and the boiler economizer) until the pot water emerges from the air valve. At this time, the air valve and the water supply valve are closed, and then the special pump is turned on for water circulation, so that the concentration of the alkaline antiseptic liquid in the boiler is evenly mixed. During the maintenance period, external inspection should be carried out frequently, and the water alkalinity of the pot should be checked regularly. If the liquid level or alkalinity is found to decrease, the cause should be ascertained in time, and the lye should be added; the pump should be periodically pumped to make the water circulation, so that the alkali is everywhere. The liquid concentration is the same; in winter, the pot water should be prevented from freezing, and the open-air boiler cannot be maintained by wet method. When the wet maintenance boiler is resumed, the pot water should be completely discharged and the softened water should be re-applied.
Dry maintenance
Dry maintenance is to use the dryer to absorb moisture to keep the metal inside the boiler dry to prevent corrosion of the boiler. Usually, quicklime or anhydrous calcium chloride is used as a desiccant. After the boiler is shut down, the pot water is drained, the scale and soot are removed, the steam pipe is closed, the valves on the water supply pipe and the sewage pipe are completely isolated from the other operating boilers. Then open the hole to make the drum dry naturally. If the boiler room is wet, Zui will use a slight fire to dry the boiler body, as well as the furnace wall and the flue. The tray (or wooden box) containing the quicklime or anhydrous calcium chloride is then placed on the hob, as well as in the drum header and the flue, and if necessary, hoisted in the drum with a bag to absorb moisture. The amount of desiccant is determined according to the volume of the boiler: massive quicklime, 2-3 kg per cubic meter of boiler volume; if anhydrous calcium chloride is used, 1-2 kg is used. After the zui close all the valves of the boiler, such as holes, hand holes, smoke to the windshield and damper, to isolate the boiler from the outside, to prevent external moisture intrusion. During maintenance, check the desiccant every 1-2 months. If the lime is changed from block to powder, replace the new quicklime. Check the service at the beginning of the maintenance. The failed calcium chloride can be heated to 105-110oC for drying. Practice has proved that the effect of dry maintenance and anti-corrosion is satisfactory, and the cost is very low, and the operation is simple. Therefore, it is suitable for long-term shutdown maintenance of any type of boiler, especially the heating and hot water boiler which is deactivated in summer.
The above is the aspects of the shutdown and maintenance process of the hot water boiler. In addition, we must pay attention to the maintenance work of auxiliary equipment, accessories and furnace walls, and regularly carry out maintenance work in a planned manner to ensure boiler safety. An important part of reliable, economic operation.
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