My EFM has become a dust machine

Here's my situation:

I'm running an older EFM 520 (round door), auger to barrel setup, rice coal.

Recently, I have been getting very fine coal dust (think black baby powder) everywhere around and inside my furnace. I am also getting about a shovel full of fines when I open the grate every night - normally I would get less than a handful. The gearbox has started hammering slightly (like every 50th time it would ratchet) when running - you don't really notice it until you're laying in bed and it sounds like someone in the basement hit a snare drum. I also seem to be going through more coal than normal.

I have emptied the hopper and cranked the coal out, then took out the pin and cranked it backwards for good measure. I was thinking that I had a rock or something caught in the feed, but got nothing.

The auger outside of the furnace does not look worn and isn't bent or bound up in the pipes. I didn't look inside because I'm assuming that would involve major surgery.

In the past, I added a 5' extension to my auger and moved the barrel back because I was getting sulfur/CO coming out of the barrel. This setup has worked fine for me for the past 2-3 years, but I am beginning to think that it may be putting too much strain on the gearbox.

This also started about the time I switched breakers. I got this last load in South Tamaqua - straight from the chute, and it looks beautiful - shiny, black, no slag, not as dusty as the stuff I was using. Is it maybe too brittle?

I've been banging my head off this for two weeks now and I'm at a loss. Any ideas?

Bob, my first suspect is that you have a gap between your auger pipes. This will cause coal grinding, and fines can come out of the coupler. It is also possible your extensions pipe is pitted inside and doing tbr same thing.

Rob R. wrote: ↑

Sat. Jan. 09, 2021 12:59 am

Bob, my first suspect is that you have a gap between your auger pipes. This will cause coal grinding, and fines can come out of the coupler. It is also possible your extensions pipe is pitted inside and doing tbr same thing.

Yes ^ , and to much exposed auger beats up the coal, and creates fines.

Rob & Dave,

Thanks for the suggestions. By the gap between the pipes, do you mean the gap between the flytes of the auger and the inside wall of the pipe, or the gap where the augers couple together? I am thinking that if I narrowed the gap between the auger and the pipe, it would cause the pipe to twist.

I had the idea of bumping up to buck from rice, since the bigger coal would be less likely to get caught in the auger space. Anyone ever try that?

My neighbor had the same problem with co and sulfur smell. It turned out the his auger was worn out. He replaced it and the problem went away. I am not sure if he replaced the tube as well or not.

Buck will intensify the two issues. I burn buck, but its harder on your stoker. And will give trouble at the pipe union if the two do not mate well.

RESOLUTION

Following up on this, for the sake of anyone that has similar problems in the future...

My first step was to go to Mark's in Shenandoah, PA. They have everything you will ever need for a coal furnace and the experience to back it up. (No, I don't work there and, no, they are not paying me.) They told me:

-There is a newer design for the pipe that surrounds the auger. It has about 6" or so cut off the top half of the end that fits into the hopper. They told me that will allow the coal to compact better in the auger, and will reduce the ability of gas to travel from the furnace into the hopper. Cost about $80 (going off memory) for one. Installed it and removed the extension about a month ago - no gas now, except if I let the hopper go below half full. Win.

-My pot worm was shot. You actually have to pull it out of the furnace to check it. The first two flytes on the spiral off the drive were razor sharp and worn down a good deal. A new worm cost like $180 (again, going off memory). Replaced the pot worm and the dust/grinding did not stop, but decreased by about half.

My last suspicion was that there was something weird about the coal that I was using. As I mentioned in the initial post, I got coal from a new source when the grinding started. The new coal was the prettiest, most perfect looking coal that I have even seen - dark black, shiny like glass, and spotlessly clean. For my newest load of coal, I went back to my old supplier (Lehigh in Tamaqua). Yes, this load had some slag and wasn't as shiny. The wheelbarrow-worth per ton of snow and ice that they gave me with it kind of annoyed me and cost me a few bucks on the scale, but it melted in the coal bin. The sticks, clumps of dirt, and large pieces of coal that got around the screen at the breaker or was scraped off the ground had to be picked out by hand. BUT... it didn't grind. It's been a couple weeks now burning this coal and the black dust stopped.

Here's what I learned:
-If you're getting gas in your hopper, get the new pipe.
-Your auger is not immortal. Keep an eye on it, especially the part in the furnace closest to the fire.
-Pretty coal is not necessarily the best coal.

I blame 60% of the dust issue on the coal and the other 40% on the auger.

Oh, I forgot to add that I bumped my air setting from 4 to 4-1/2. That gave me a bigger fire, and the house seems warmer now. Not sure if that's a placebo effect, (sort of like how it seems that your car runs better after waxing it) or not, but my coal consumption is way down -even with the recent cold snap- and I'm back to getting about a handful of fines each night when I open the lever from what was like a shovel full.