feed problem with a keystoker kaa-2

hello everybody and happy new year. i have a keystoker kaa-2 boiler for the past three years and it has been running flawessly until 3 days ago. for the past 3 years the stoker has been set at 4 turns out from maximum stoke which kept the boiler at 160-180 with a stack temp of 350. well the other day i woke up to cold house an checked the boiler and it was running but the temp was only 100-120 with a stack temp barley 200 and running continously. i checked the flue and blower all seemed to be good. i raised the stoker to full stoke which made it better but still not enough heat. the only way i can get good heat is if i manually thow coal into the boiler and then it goes right up nicley. my friend has a keystoker 105 with the same stoker as my kaa-2 and i took some measurment of the stoker travel and compared them to mine. at full stoke on my unit i have a travel or 13/16-7/8 of an inch and his keystoker 105 has a fun inch travel at maximum stoke which gives me 1/8 less on my stoker. i looked inside the stoker and the only thing that i can see that could cause a problem is that the nylon wheel could be worn. has anybody else had this problem or can shed some light on my situation. i will be calling keystoker on monday to talk with them and to order some replacemnt parts.

chris

I don't have a kaa-2 but I would suggest you empty the hopper and see if something is stuck in the push plate.

that was the first thing i did. then cheked my t-connector then checked my blower and grates for any obstructions

Perhaps wet rice formed a bridge over the pusher? Any little gap down there will cause less coal to be pushed onto the stoker.

How much burning coal do you have on the grate? if you don't have a full grate of burning coal, then you have a restriction in the flow of the coal from the hopper, or a lot of wet fines clogging the pusher assembly.

An accumulation of fines under or around the pusher mechanism will cause it to bind, and a large piece of nut size coal or a hunk of wood at the bottom of the hopper resting in the feed opening will restrict the feed of coal..

See if you can manually move the pusher, and see if you feel any restriction to movement, if not, follow the above advice and empty the hopper, and inspect the area feeding the pusher.

Greg L

there is not a full grate of fire i have about 3 inches of coal then about 2 inches of fire and 3 inches of ash at full stoke i suspect a feed isue. i already emptied the hopper and there is nothing in the opening where the coal goes i even put a screw driver down there the see if anything was obstructing the coal feed and the was nothing in there. push plate seems to move free the only thing that gets me it travel distance between the two stoves. like a worn part, but could a 1/8 inch diffrece be so critical

I agree, that an 1/8" difference in travel seems to be insignificant. You mentioned worn parts.. and a nylon roller? The roller may be worn, and not providing the full stroke that it once did. But:

You said about 3" of coal, then 2" of fire, then 2" of ash. Is there normally so much coal that is not burning prior to the burning coal?? It could be that the first several inches of the grate has blocked air holes. From fines. You mentioned that you cleaned out under the grate,, did you poke through the holes in the grate with a wire or a small drill bit? If you got a slug of coal with a lot of fines, it could have plugged up the air holes in just a few hours of burning..

Can you get a straightened coal hanger wire through the holes in the non burning section? if not you may have to shut down the fire and clean all the holes and re-vacuum under the grate..

Greg L

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yes it always has had that much coal at the start about 3 inches.. the holes in the grate start right at the three inch mark and then go all the way to the end. i did clean all the holes out and all where clean. one thing i have noticed too which leads me to a feed problem is with 6 pins in the maintnance timer would have the hot coal right at the edge of the holed in the grates and now the coal ia about 1 inch back. here is a pic of full stoke running for about 3 hours non stop trying to keep up with the house. when i first installed the boiler i remember at full stoke it would be pushing hot coal off the fire bed and now it is not.

Make sure the nylon screws at the sides of the pusher block aren't worn or need adjustment. If there is too much side-to-side slop, you won't get full travel of the pusher.

You could also be having some binding issues that are slowing the motor rotation down. It should be at least 1 rpm on the cam rotation and shouldn't slow down or speed up much during the full rotation.

there is no play side to side and the push plate looks centered

chris

The cam can be measured for wear. It's best done with the hopper empty unless there is a way I haven't noticed to remove the stoker gear assembly.

The cam only seems to wear in one spot on mine. So I check it by measuring it's diameter then measuring in another spot 90 degrees from the first. It can be measured with a 12" dial caliper without pulling the stoker apart. The jaws on a 12" caliper are long enough to reach the cam.

If the cam is worn I had been thinking of drilling a new hole for the gearbox shaft since most wear is in one spot.

I just cleaned my KAA-2 last week. The walls were caked with ash.

Just thinking that with only 3 years of service if it were a cam failure because of material [nylon] I think we all would know that we have a design shortcoming mainly because we all would have had similar experiences. I do not recall ever hearing or reading about that. I have always wondered why nylon cam and sliders are used for this application.Very interested in what we can learn from this one since those wear zones can be replaced with more durable materialls without too much trouble should that ever be required.I am anxious to know what Keystoker thinks.There has been no talk about unburned coal in the ashes so that should eliminate blocked cupped surfaces on the squirrel cage combustion fan. Puzzled or as the Pennsylvania Dutch say Ferhoogled goot . Mike

just so you know i run my boiler 365 days a year so it does get alot of use. Machinist do you know the over diameter of a new wheel ? what i am seeing is either a worn wheel or a bent pushbar adjustment plate because like i said in a pevious post i am short 1/8 inch less of push bar movement over my buddy and over the lenth of the grates is about 12 inches i am short 1.5 inches of coal overall for a full stoker bed

chris

I made a sketch of the new cam I received after melting my old one into a pile of goo trying to run buckwheat.

It is 1.5" diameter with a 5/16" diameter shaft hole and the center of the shaft hole is offset 3/8" from the outside edge of the cam. There is a 1/8" thru hole on the side to pin it to the motor shaft. I didn't note the thickness of the cam.....

Please note that my cam is for a 90k stove. It might be different for the KAA-2 stoker.

Chris

Make sure your adjuster rod didn't come loose from the adjustment plate for feed, that has happened.