What are the reasons why the current of the induced draft fan in a coal-fired heat transfer oil furnace cannot increase?
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One of our plants is equipped with a 2T vertical coal-fired heat transfer oil furnace. Recently, the current drawn by the exhaust fan was too low; initially, it was thought that the issue was caused by a blockage in the flue. As a last resort, the furnace had to be shut down for maintenance. Upon inspection, it was found that there was only a lot of dust, but the flue inside the furnace was not blocked. After cleaning the dust, the furnace was restarted, but the current drawn by the exhaust fan still remained abnormal. By opening the dust removal door at the bottom of the heat exchanger, the current drawn by the exhaust fan increased, but after a week, the current dropped again. The insufficient exhaust flow led to a slight positive pressure inside the furnace. What could be the cause of this phenomenon? I hope experts can provide guidance as soon as possible. Thank you!
There are two reasons: one is that the boiler needs to have its ash cleaned, usually once every 2 months; the second is that you should check the impeller of the induced draft fan, as there might be a thick layer of dust on it
Yesterday, the impeller of the exhaust fan, as well as the inlet dampers, were inspected; there wasn’t much dust, as they had been cleaned just a week earlier. At first, the current level was good, but after one or two days, the current related to the exhaust fan gradually decreased.
When the heat transfer oil furnace is in operation, the slag removal port at the bottom of the furnace is opened.
This post was last edited by jianbo-h on 2016-11-5 at 10:39. It has no effect when activated; currently, only a slight positive pressure combustion can be maintained
Find an entrance that allows air to enter the exhaust fan without passing through the furnace, and ensure that there are absolutely no unexpected obstacles from this air inlet to the exhaust fan’s inlet (you can try opening a larger manhole in the smoke duct at the exhaust fan inlet). If the current drawn by the exhaust fan increases, it indicates that there is definitely a blockage somewhere in the furnace or the smoke ducts; search carefully for it.
I encountered a similar situation during testing; from the very beginning there was positive pressure. The blower’s dampers were not opened even to one-third of their maximum position, which resulted in positive pressure, and the current drawn by the exhaust fan could not increase. There was no indication showing the degree to which the exhaust fan’s dampers were open. It took a long time to figure out the problem – it turned out that the dampers of the exhaust fan hadn’t been opened at all. How silly! Since the fans weren’t from reputable manufacturers, they didn’t have indicators for the degree of opening of their dampers, and everyone assumed that the dampers were fully open. Could the issue the original poster encountered be due to the vibration dampers gradually closing? It’s just my humble opinion, but it’s worth having them checked thoroughly.
Has the damper been checked? Is it not a false indication? The current doesn’t increase, so the load can’t be driven; it seems to be either due to the baffle or the motor.
OP, I’d like to get in touch with you. Is there a way to message you privately?