Electrostatic Precipitator

'"We are observing abnormal sound ..." Please clarify this "sound". This is like taking a car to the mechanic and saying it doesn't sound right. As Mr. Vader points out, this could be a fire, or could be a mechanical break, or other problem.

"... as well as heavy smoke from stack." Again, please clarify. Is this truly "smoke", as from a fire, or just a heavy concentration of ash particles? If truly smoke, then, again, Mr. Vader could be correct that you have an arcing problem between your plates or wires and you are igniting dust inside. The mini-dust explosions could be what you are hearing, or results of a small fire. However, if your "smoke" is really ash, then your ESP is no longer functioning properly and you need to evaluate the problem more deeply. As mentioned, if this is wet ESP, make sure your water supply is adequate and plates are properly cleaned, and not caked with wet ash. Make sure your hoppers are cleaned out.

As a precaution, check exhaust flue gas for CO before opening the ESP for inspection as a smoldering fire could exist that would erupt into full fire with exposure to oxygen when access doors are opened.