Boiler shutdown
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I read in the documentation that when shutting down a boiler, first stop the fuel supply and the blower, and then reduce the exhaust airflow. Why don’t the exhaust fans and fuel stop at the same time? Why do the supply fans and fuel stop together? I don’t quite understand; please explain, extra points appreciated
If the induced draft is stopped first, a high positive pressure will occur inside the furnace, which has a significant impact on both equipment safety and human safety. Generally, when the exhaust fan stops, it will cause the supply fan to stop as well, triggering an MFT action
If there is no interconnection, the fuel supply and the exhaust fans should be stopped first; this allows the fuel remaining in the furnace to be gradually removed, after which the exhaust flow can be reduced step by step. This is done for safety reasons, to ensure that all the unburned fuel in the furnace is expelled.
After feeding is stopped, some combustion in the boiler will not be complete; it is necessary to continue supplying air and exhaust air. Only after the furnace cools down to a certain temperature should the supply of air and exhaust air be stopped
The induced draft finally stops, ensuring that the heat inside the furnace is carried out. When the air supply stops along with the fuel, no heat is supplied anymore
Prevent the accumulation of combustible gas resulting from fuel precipitation, to avoid causing harm. A piece that stops may not explode, but stopping it at different times can prevent explosion or at least reduce the likelihood of one occurring :)
First, you probably don’t have a boiler operator’s license. Second, you likely weren’t trained to work with boilers. Third, it’s best for you not to operate boilers at all; you still need to ask basic questions about this task. By the time you get an answer, the boiler might already have exploded. For your own safety and that of your colleagues, it’s recommended that you change careers
The boiler exhaust fan is definitely turned on first and off last. In particular, boilers that burn coal powder, oil, natural gas, etc., and are prone to forming scale*. If the draft stops along with the fuel, a mixture of fuel and air will remain inside the furnace. If this mixture is within the explosive range of the fuel, even a single spark can cause an explosion in the furnace. Therefore, whether it is starting up or shutting down the furnace, the flue gas must be used to clean the furnace chamber first before proceeding.
First, you probably don’t have a boiler operator’s license. Second, you likely weren’t trained to work with boilers. Third, it’s best for you not to operate boilers at all; you still need to ask basic questions about this task. By the time you get an answer, the boiler might already have exploded. For your own safety and that of your colleagues, it’s recommended that you change careers
Shutting down the boiler involves a gradual reduction of the flue gas temperature. This is achieved by first reducing the feed rate, and simultaneously decreasing the air supply to weaken combustion. The amount of exhaust air is adjusted according to changes in the negative pressure inside the furnace. Even after feeding is stopped, cooling continues at a certain rate of temperature drop; as the air supply decreases, the exhaust air volume also needs to be controlled until the boiler reaches its minimum required temperature.