Coalgun- Puff backs & Explosions

ValterBorges wrote:In combination with a fast actuator.
http://www.siemens.com/press/en/pressre ... 105015.htm

At 2 seconds that may seem fast, but it's not fast enough! The puff backs happen in way less than a second after the door drops open. The idea of the anti-boom device is to get the door open while the fan is still running and allow it to purge out the explosive gasses. I let the fan purge for ten seconds. I have not tried a countdown to see if 8 or 5 or 3,2,1 is enough. Ten seemed like a good number.

Freddy wrote:At 2 seconds that may seem fast, but it's not fast enough! The puff backs happen in way less than a second after the door drops open. The idea of the anti-boom device is to get the door open while the fan is still running and allow it to purge out the explosive gasses.

We are moving in the correct direction with this anti boom device Freddy has invented. But, the ash dump motor must be wired to run only when the fan runs. That holds true for the boilers that have the thermo ash controller not the timer models. It seems that if we find a device that operates as fast as Freddy's but without the noise, we will have a solution. Good job forum members.

No clue how i was managing to create puff backs while it was running either, I have lowered my ash temp to start ashing at 110 and stop at 118, and have spent quite a few hours in the barn while it has cycled several times and have had no explosions, now im not at all saying im not having explosions but I haven't caught it yet, Im burning Stockton buckwheat

Freddy wrote:

ValterBorges wrote:In combination with a fast actuator.
http://www.siemens.com/press/en/pressre ... 105015.htm

At 2 seconds that may seem fast, but it's not fast enough! The puff backs happen in way less than a second after the door drops open. The idea of the anti-boom device is to get the door open while the fan is still running and allow it to purge out the explosive gasses. I let the fan purge for ten seconds. I have not tried a countdown to see if 8 or 5 or 3,2,1 is enough. Ten seemed like a good number.

There has to be some simple switch out there that delays a signal by a few seconds

dchartt wrote:No clue how i was managing to create puff backs while it was running either, I have lowered my ash temp to start ashing at 110 and stop at 118, and have spent quite a few hours in the barn while it has cycled several times and have had no explosions, now im not at all saying im not having explosions but I haven't caught it yet, Im burning Stockton buckwheat

My experience with the hysterisis at 5 vs 10 seemed to produce less clinkers and less fine ash, it produced oatmeal looking ash.

Again raising the ashing to 130 caused decent puff back.

I would like to see if it happens with nut, when i get a chance ill pick some up.
I also have a good amount of fresh combustion air, maybe your barn does too and this makes it worse??

Since I'm not having any puff-backs, have I mentioned that by design my boilers internal water temp is set up to never drop below 145 degrees? This is accomplished by shutting down the circulator at 145 degrees, and not permitting it to start back up again until the water in the boiler recovers and reaches or exceeds 155 degrees.

Also, my ash grate motor only runs when the fan is on.

Just trying to think of what might be different between my set-up and that of others who are having the occasional puff-backs.

I just purchased a S260 and hope to start the install Tuesday after the holidays. I am very concerned about the puff back problems. I have two options of how I can run my flue pipe depending on how I position my boiler . If I move my hot water heater I can install the boiler against the wall sideways with a 6'' to 8'' adapter connected with the 8'' barometric damper straight into my SS 8" flue . This will be the same as my present boiler eliminating any horizontal runs in the system. The draw back is cleaning the flue at the end of the year. If draft is causing the puff back issue this will be worth all the effort . I asked AHS at pickup on the primary secondary pump running all the time in the system vs using an aquastat energizing the pump when the boiler reaches temp. recommending have the pump run all the time.

When I asked about the puff backs at AHS they claim it was a draft issue with to long of a horizontal run. Isayre what length of horizontal run do you have?


Mac

macdabs wrote:
When I asked about the puff backs at AHS they claim it was a draft issue with to long of a horizontal run. Isayre what length of horizontal run do you have?


Mac

My flue pipe rises vertically from the boiler for 16" and then it goes flat horizontal, but its entire length (from boiler to chimney) is a very short run of only 53 inches. My horizontal run is therefore 37".

This picture taken during my install shows my entire flue pipe assembly;

lsayre wrote:This picture taken during my install shows my entire flue pipe assembly;

Nice, That is kinda what I would need to do if I position my boiler the other way. I think when I move my old boiler out I just may position the new boiler both ways and see how things look best.

Mac

Merry Christmas fellow AHS/AA boiler explosion troubleshooters. Horizontal run length has zero effect on the problem. It's all about having proper draft, keeping/maintaining proper draft; and, allowing the boiler to operate as designed. I honestly believe you're turning a simple problem into a complicated one. I've had ZERO puff-backs; large or small, since performing the following:

1. Added fresh make-up air with 4" dust collection hose directed at the tombstone intake.

2. Significantly loosened the sight tube cover (per recommendation from AHS); such that, the sight tube cover DOESN"T form a tight seal when the boiler is running. Loosening the spring assembly holds the top of the sight tube cover out; such that, air is always being drawn over the top of the coal bed. Per AHS: "A tight seal over the sight tube isn't necessary. Keeping the sight tube cover loose has no effect on boiler performance."

3. Reduced ashing temp from 140 to 130 degrees; keeping, 10 degrees of hysteresis. I recommend finding an ashing temp which works for your boiler; and, stay with this setting---130 seems to be working great for me.

4. Installed a new Field Controls type M baro; and, resisted the primal temptation to touch/play with/caress/fondle the baro weights. Field Controls ships their dampers with the weights set and calibrated for drawing 0.06" of water---keep the baro that way.

5. Continuously monitor your draft with an accurate manometer. If you can't maintain at least 0.04" of draft with or without the boiler running you'll have problems.

6. Burn pea coal per AHS' recommendation; although, other coal sizes can probably be mixed in and might provide different results---YMMV.

MERRY CHRISTMAS TO ALL!!!

My flue rises 32 in, then 90 and 24 in horiz.

1. have fan in a can dropping air by the blower.
2. Will try this.
3.120/10 works for me.
4.5.6. dito

Hey Valter:

I highly recommend directing your "fan in a can" make up air directly at the tombstone intake. I highly suspect supplying fresh air directly at the tombstone intake; and, loosening the sight tube cover are the two most important changes I made to eliminate puff backs. The amount of air which flows directly into the tombstone on my boiler is pretty compelling. The third most important change was installing a new type M; and, let the baro do it's job.

Further---the main reason I know I'm not having puff-backs anymore is because I no longer find black soot deposits around the exhaust; and, at exhaust pipe joints. Now I just have a slight amount of "normal" fly ash/white dust on the boiler---which easily cleans up about once a week...

Merry Christmas

macdabs wrote:When I asked about the puff backs at AHS they claim it was a draft issue with to long of a horizontal run.

My horizontal pipe is only 33" and I still have booms so AHS claim that the booms are caused by a long horizontal pipe is crap I do have a 90 degree pipe at the top of the boiler and that helps prevent fly ash falling back into the boiler and clogging the cone. My friend with a AHS 130 has a vertical pipe above the boiler before his 90 and his cone is continually getting clogged. I have to vacuum out my horizontal pipe in he middle of the heating season as the fly ash fills the pipe by 50%.

The booms will not be eliminated by just having a good draft and a good source of air. Freddy's solenoid design along with wiring the ash dump motor to run only when the fan is running is our best chance to find a real solution. Unless you have a power vent to create a super draft, you will be succeptable to booms as the coal gasses will accumulate and ignite, BOOM. We are moving in the right direction and as soon as we can locate the proper solenoid we will have a solution.

I have had two explosions this week thus far so I'm lowering my ash dump temperature to 105 from 110. Both times the ash was being dumped when the fan stopped. My hope is that there will be more hot coal in the fire tube that will consume the coal gas produced during ash dump. Again, for those that haven't been following this thread, I have great draft, short horizontal stove pipe run, ample available air and good qaulity coal. I'll keep everyone posted.