I kept hearing this crack in my whop while working. always when my dc was on (clearview). I kept wondering what it was. had a customer see a flash from my dc. then the next time I saw it a nice big spark close to the top of the cyclone. I have had thsi setup for over 3 years and don't remember that happening. though about a month ago I changed the flex hose going to the can with a high grade rubber/plastic one from mcmaster. most fo my system is grounded. I have metal pipe and I have to ground the dc running to my cnc router. so that flex hose is grounded to the main duct and the wire then goes to a sprinkler pipe. the humidity was 45% so it was not super low. I guess the rubber hose somehow was causing it. I have a paper can so that would not do any grounding. so I ran a wire from the metal pipe to the cyclone and rubber hose to a sewer pipe and it stopped.
I used 6" hose from grizzly the clear stuff. I wore holes in it. time for some durable hose.