Coalgun- Puff backs & Explosions

Re: Coalgun- Puff backs & Explosions

PostBy: watkinsdr On: Thu Oct 11, 2012 10:54 am

Well... I started this thread eons ago; but, I had another ka-boom on Tuesday night 10/9/12... I offer the following to my fellow AHS drivers out there:

1. Watch your fire "height" very closely. It varies as a function of boiler load; and, load varies as a function of weather---so watch it carefully. I realize lifting the tombstone cover off the sight tube to inspect your fire is a pain in the arse; but, it sure beats writing four digit checks to the oil/propane company...

2. Further---The height of the fire is directly proportional to the Dwyer programmable controller Set Variable (SV) setting.

3. I made the mistake of just "leaving" the controller "SV" set at the "factory recommended" 130 degree set point---this was a mistake; because, for my current load, 130 allowed my S260's fire to get way too low…

4. With the low fire, coal gas volatiles accumulated (obviously) following the boiler's normal run cycle fan shutdown; and even with good draft---KABOOM!!!

5. I've since lowered the "SV" to 115; and, the fire is back up where I can see a nice red/orange glow through the sight tube.

6. Of course the usual coal burning requirements apply: clean exhaust pipe, good draft, coal hopper loaded correctly, etc.

7. I highly doubt coal quality/deep mined/strip mined/red ash/white ash has any bearing WRT this "booming" problem; although, I recently started burning Blaschak again. BTW: This batch of Blaschak looks really nice, clean, shiny, etc.

Comments are invited!

Happy Burning
watkinsdr
 
Stoker Coal Boiler: AHS S260 Boiler

Re: Coalgun- Puff backs & Explosions

PostBy: lsayre On: Thu Oct 11, 2012 12:40 pm

I've now ran my AHS S130 for 4 days shy of one full year, and I have yet to experience a single kaboom. I have on a few occasions (when I was standing in the boiler room) noticed a very low volume "pop" immediately following the fan/blower shutting down, but no pipe shaking or baro disruption has resulted from this. I have ran mine at all sorts of SV values for the ash grate ranging from 110 to 140 degrees, and I've seen no difference. I have fed it Blaschak, Stockton, and Harmony, and seen/heard no kaboom level poofs. I'm currently set at an SV of 130 degrees, though I just bumped this up from 120 degrees about a week ago. For nearly all of last winter (after I got tired of changing the SV settings up/down) I left it alone at 130 degrees. For all of the summer months I had it at 120 degrees.

The main reason why I changed my SV (early on, back when I was meessing with it) was in an attempt to see if it alleviated finding partially burnt coal in the ash, which changing it did not do. Consistent firing during colder weather does alleviate it however.

I was told by my coal supplier that Harmony coal has a bunch more volatiles in it than does Blaschak (and I have no means whereby to verify or refute this), so now that I'm burning straight Harmony I will see if that changes anything. I've been on straight Harmony since Spetember 29th, post my boiler clean-out and re-firing.
lsayre
 
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Anthracite Pea
Other Heating: Resistance Boiler (if I ever get it fixed)

Re: Coalgun- Puff backs & Explosions

PostBy: Bob On: Thu Oct 11, 2012 5:21 pm

watkinsdr wrote:Well... I started this thread eons ago; but, I had another ka-boom on Tuesday night 10/9/12... I offer the following to my fellow AHS drivers out there:

1. Watch your fire "height" very closely. It varies as a function of boiler load; and, load varies as a function of weather---so watch it carefully. I realize lifting the tombstone cover off the sight tube to inspect your fire is a pain in the arse; but, it sure beats writing four digit checks to the oil/propane company...

2. Further---The height of the fire is directly proportional to the Dwyer programmable controller Set Variable (SV) setting.

3. I made the mistake of just "leaving" the controller "SV" set at the "factory recommended" 130 degree set point---this was a mistake; because, for my current load, 130 allowed my S260's fire to get way too low…

4. With the low fire, coal gas volatiles accumulated (obviously) following the boiler's normal run cycle fan shutdown; and even with good draft---KABOOM!!!

5. I've since lowered the "SV" to 115; and, the fire is back up where I can see a nice red/orange glow through the sight tube.

6. Of course the usual coal burning requirements apply: clean exhaust pipe, good draft, coal hopper loaded correctly, etc.

7. I highly doubt coal quality/deep mined/strip mined/red ash/white ash has any bearing WRT this "booming" problem; although, I recently started burning Blaschak again. BTW: This batch of Blaschak looks really nice, clean, shiny, etc.

Comments are invited!

Happy Burning


My experience is fully consistent with yours. Since I stopped adhering to the recommended SV and began monitoring/controlling fireheight I no longer have puff backs.
Bob
 
Stoker Coal Boiler: AHS 130
Coal Size/Type: Pea/Anthracite

Re: Coalgun- Puff backs & Explosions

PostBy: lsayre On: Sat Oct 13, 2012 9:23 am

I read the 1952/53 published U.S. Bureau of Mines report 4936 on the Axeman Anderson Anthratube 130 boiler (posted on this forum by Yanche), and it states this regarding puff-backs:

The equipment was tested under regular house-service operating
conditions. To use Buckwheat in the Anthratube it was found necessary, owing
to its more compact fuel bed, to drill a 7/l6-inch-diameter hole in balance
plate W (fig. 4), so that more air could be provided over the fire. Without
this air, the CO in the products of combustion would frequently, during
start-up periods, build up to some 13 percent or enough to create an
explosive mixture. The mixture would ignite and cause a “bump” or small
explosion.


Here is an Internet link to the archived 4936 report:
http://digital.library.unt.edu/ark:/67531/metadc38592/m2/1/high_res_d/metadc38592.pdf
lsayre
 
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Anthracite Pea
Other Heating: Resistance Boiler (if I ever get it fixed)

Re: Coalgun- Puff backs & Explosions

PostBy: Bob On: Sat Oct 13, 2012 10:47 am

lsayre wrote:I read the 1952/53 published U.S. Bureau of Mines report 4936 on the Axeman Anderson Anthratube 130 boiler (posted on this forum by Yanche), and it states this regarding puff-backs:

The equipment was tested under regular house-service operating
conditions. To use Buckwheat in the Anthratube it was found necessary, owing
to its more compact fuel bed, to drill a 7/l6-inch-diameter hole in balance
plate W (fig. 4), so that more air could be provided over the fire. Without
this air, the CO in the products of combustion would frequently, during
start-up periods, build up to some 13 percent or enough to create an
explosive mixture. The mixture would ignite and cause a “bump” or small
explosion.


Here is an Internet link to the archived 4936 report:
http://digital.library.unt.edu/ark:/67531/metadc38592/m2/1/high_res_d/metadc38592.pdf


My personal experience is that I continued to experience puff backs with the hole in the balance plate fully open and the SV setting as specified in the AHS manual. It was only when I began to adjust SV to achieve a "higher" fire height that I stopped the puff backs.
Bob
 
Stoker Coal Boiler: AHS 130
Coal Size/Type: Pea/Anthracite

Re: Coalgun- Puff backs & Explosions

PostBy: Yanche On: Sat Oct 13, 2012 11:03 am

Forum member "steamup" post a link to a 1945 conference. See:

http://nepacrossroads.com/download/file.php?id=37035

There are many interesting sections. One in particular is on the "Antratube". This is a term coined by Penn State that describes burning anthracite in a narrow diameter pipe. The physics of how coal burns in such a tube is described with considerable suggestions for how it can be used to develop a heating appliance. Read and understand what the report says and you will have a better understanding of the "puffbacks". I would expect the severe "puffbacks" occur when the fire portion of the coal varies greatly from the suggestions in the "Antratube" design characteristics. All the suggestions forum members have made for ashing temperature controller set temperatures is really about adjusting the position of the burning coal in the "Antratube" column. I'd like to post a more complete explanation but I just don't have the time right now.
Yanche
 
Stoker Coal Boiler: Alternate Heating Systems S-130
Coal Size/Type: Anthracite Pea

Re: Coalgun- Puff backs & Explosions

PostBy: Bob On: Sat Oct 13, 2012 2:13 pm

The discussion of the Anthratube starts on page 58 of the bulletin.
Bob
 
Stoker Coal Boiler: AHS 130
Coal Size/Type: Pea/Anthracite

Re: Coalgun- Puff backs & Explosions

PostBy: dchartt On: Sun Oct 14, 2012 9:16 am

i also just wanted to include that mine stopped with dropping my ashing temp down to 110 with a 8 deg. diff. and therefore raising the fire in the pot...works for me
dchartt
 
Stoker Coal Boiler: AHS 130
Hand Fed Coal Stove: Glacier Bay

Re: Coalgun- Puff backs & Explosions

PostBy: Pa papa On: Sun Oct 14, 2012 9:28 am

Same here. Although the SV differential is 5 degrees.
Pa papa
 
Stoker Coal Boiler: AHS-130
Coal Size/Type: Pea; anthracite
Other Heating: oil fired boiler; LP insert

Re: Coalgun- Puff backs & Explosions

PostBy: Rob R. On: Mon Oct 15, 2012 6:13 am

Maybe it's just me, but there is seems to be a lot of variability in the settings required for boom-free operation of the S130 and S260.
Rob R.
 
Stoker Coal Boiler: EFM DF520
Hand Fed Coal Stove: Hitzer 50-93
Other Heating: Dad's 1953 EFM Highboy

Re: Coalgun- Puff backs & Explosions

PostBy: blrman07 On: Mon Oct 15, 2012 7:09 am

In reading the pages of this thread, the key seems to be the fire height, not the settings. As each install and operation characteristics are different the settings will change from machine to machine. Somebody's non-boom settings might not work for you. What appears to work is the flame height no matter what setting you have to use on your individual installation. Booms are not just for the coal guns. They can happen on any coal burning appliance when you do not have enough fire to burn all the gasses off. Take a hand fired cover the bed to the point where you have very little or no flame and see what happens!!

Could I recommend instead of concentrating on who has what settings, concentrate on estimating the fire height where no booms occur and then adjust your settings to carry that consistent fire height?

What was the estimated fire height on your equipment when the booms went away?
blrman07
 
Hand Fed Coal Boiler: Bucket a Day
Hand Fed Coal Stove: installing a VC 2310
Coal Size/Type: Pea/Nut/Wood in the VC and anything that will fit in the Bucket a Day. It's not fussy.

Re: Coalgun- Puff backs & Explosions

PostBy: Pacowy On: Mon Oct 15, 2012 8:03 am

blrman07 wrote:Booms are not just for the coal guns. They can happen on any coal burning appliance when you do not have enough fire to burn all the gasses off.


Do people really have this issue with flat/inclined or underfeed stokers? I've operated a bunch of those in an assortment of designs and sizes over a period of many years and never had anything resembling a boom.

Mike
Pacowy
 
Stoker Coal Boiler: H.B. Smith 350 Mills boiler/EFM 85R stoker
Coal Size/Type: Buckwheat/anthracite

Re: Coalgun- Puff backs & Explosions

PostBy: coalnewbie On: Mon Oct 15, 2012 8:39 am

All this revolves around whether or not puffbacks are a critical fault in the minds of the owner. Whistlenut laughs at it but others are really upset. Handfeds seem to have this potential but there are very few variables and the average user can learn. Nobody seems to have been seriously injured although being thrown across the basement raises my eyebrows. Is this fault is critical then we go for ISO 9002 validation and none of the posts validate where the failure points are. What am I getting in a snit for, San Offre would not validate either and we were treating an operating nuclear power plant in an offhand manor who cares about the odd explosion in the basement. I'm getting too fussy. As far as S260/130's are concerned, I need one but can't afford one so the choice is easy. Hey, have an idea get an AA boiler and put it on top of a foolproof fire system - I think I will patent the idea. Oh that's right LL make one now.
coalnewbie
 
Hot Air Coal Stoker Stove: LL AnthraKing 110K, Pocono110K,KStokr 90K, DVC
Hand Fed Coal Stove: Hitzer 50-93, Jotul 507
Baseburners & Antiques: Red Cross Invader 2
Coal Size/Type: Rice, Chestnut
Other Heating: Heating Oil CH, Toyotomi OM 22

Re: Coalgun- Puff backs & Explosions

PostBy: Rob R. On: Mon Oct 15, 2012 9:04 am

Maybe I haven't talked to enough AA owners, but my impression is that the Axeman Anderson units don't have nearly the amount of problems with puff-backs as the Coal Guns. The AA owners I've talked to seem to fall into two groups: The guys that have never even touched the anthrastat, and the guys that set it according to the manual's recommendation. Perhaps I just haven't talked to enough AA owners. :confused:

coalnewbie wrote:Hey, have an idea get an AA boiler and put it on top of a foolproof fire system - I think I will patent the idea. Oh that's right LL make one now.


Foolproof? My neighbor had a hopper fire in a LL stove this past weekend...turns out the rheostat for the power vent got bumped and the draft was too strong. Operator error. I'm not finding fault with LL, just arguing that there is no such thing as a foolproof solid fuel appliance.
Rob R.
 
Stoker Coal Boiler: EFM DF520
Hand Fed Coal Stove: Hitzer 50-93
Other Heating: Dad's 1953 EFM Highboy

Re: Coalgun- Puff backs & Explosions

PostBy: coalnewbie On: Mon Oct 15, 2012 9:33 am

Rob, your point (as usual) is a good one. The rheostats on the powervents are c rap, I know. If failure of that Chinese POS is critical (I have had one fail and keep a few spares) causes a critical chain of events then ISO 9002 applies to both units in operation. In fact it is a design fault and needs to be addressed. That is why it is a 9002 standard.
coalnewbie
 
Hot Air Coal Stoker Stove: LL AnthraKing 110K, Pocono110K,KStokr 90K, DVC
Hand Fed Coal Stove: Hitzer 50-93, Jotul 507
Baseburners & Antiques: Red Cross Invader 2
Coal Size/Type: Rice, Chestnut
Other Heating: Heating Oil CH, Toyotomi OM 22