Coalgun- Puff backs & Explosions

Re: Coalgun- Puff backs & Explosions

PostBy: franco b On: Tue Oct 29, 2013 4:28 pm

After 44 pages it's the customers fault. What's changed?
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Re: Coalgun- Puff backs & Explosions

PostBy: rychw On: Tue Oct 29, 2013 6:55 pm

I want to apologize to folks who have been looking for answers on the puff back issue and have not been seeing company rep participation in the forum.


The FIRST thing AHS needs to do is read the explosion thread from start to end before making recommendations concerning puff back solutions.
greenftechn wrote:Regarding puff backs, proper draft is the key. As long as we are maintaining the minimum .04 in, we will be removing volatiles from the top of the coal pot that are the source of the puff backs and explosions. A number of factors can interfere with attaining this minimum. The chimney may be cold, of insufficient height or in a poor location. Reduced duty cycles in the early and late parts of the heating season can lead to cold flues. If proper draft cannot be maintained, a draft inducer (power vent) should be installed. If the power vent is the main source of draft, apart from having natural draft, back up power must be in place.


We have tried all these solutions over and over again. The puff backs are caused by a design flaw with the function of the thermo ash dump system. I applaud the change in ownership and hope that we can finally have active AHS participation in solving the problem. My boiler was started 10 days ago and have had puff backs as usual. They are lessened by the changes I've made to the ash dump system (dump motor only runs when fan runs, slowed the speed of the dump motor with a rheostat) but a solution has eluded NEPA bloggers.
Last edited by Rob R. on Tue Oct 29, 2013 6:58 pm, edited 1 time in total.
Reason: Fixed quote reference.
rychw
 
Stoker Coal Boiler: AHS 130
Coal Size/Type: Pea
Stove/Furnace Make: AHS
Stove/Furnace Model: 130

Re: Coalgun- Puff backs & Explosions

PostBy: lsayre On: Tue Oct 29, 2013 7:18 pm

I'm convinced that Axeman Anderson understands this problem way better than AHS does, and that a majority of the problem involves the height (position or location) of the fire in the fire tube. When the fire goes too low in the tube you are prone to get puff backs, particularly with higher volatile anthracites. I don't believe for one moment that draft alone is at fault here. I believe the quantity of ash content in the coal has a lot to do with it, and that the coals with the least ash combined with the highest levels of volatiles are the hardest to control within the confines of the manual instructing us to never go below 120 degrees for the ashing set-point. Some very low ash and high volatility coals clearly require ashing initiation temperature settings below the absolute minimum setting permitted per the manual. The LC control does seem capable in my experience of dialing out the puff-backs, as I successfully rid myself of them through adjustments to the hysteresis and the ashing temperature. With Harmony coal (very low ash, and I'm told high volatiles) I had no problems once I stopped using oiled coal, and I lowered my hysteresis to 5 degrees, and my ashing temperature to 100 degrees. With Blaschak (relatively high ash) I never seem to get puff-backs, and for Blaschak I run 10 degrees of hysteresis and 125-130 degrees as the ashing temperature setpoint. I surmise that along with being higher in ash, Blaschak is also lower in volatiles.

That said, I believe that Darren Bricker at AHS has come to a clear understanding of this matter, and when contacted he is quite helpful in aiding users to dial in the proper settings to match their coal. He was of great help to me.

I believe Yanche has said this before, but perhaps the best solution would be for temperature sensors along the fire-tube in the vicinity of the fire itself dictating ashing initiation. Fire begins to go to high, and ashing begins (thus lowering the fire in the tube). Fire begins to go too low, and ashing is stopped, or ashing initiation is delayed (thus allowing for the fire to move higher in the tube).
lsayre
 
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Stockton Anthracite Pea
Other Heating: Resistance Boiler (13.5 KW)

Re: Coalgun- Puff backs & Explosions

PostBy: macdabs On: Wed Oct 30, 2013 6:03 am

greenftechn wrote:I want to apologize to folks who have been looking for answers on the puff back issue and have not been seeing company rep participation in the forum. First, regarding the ownership issue mentioned by the previous poster, I want to let you know that the company has come back to Jeff and Phyllis Gingerich, who stewarded the company during the best ten years of its existence, in my opinion.

Regarding puff backs, proper draft is the key. As long as we are maintaining the minimum .04 in, we will be removing volatiles from the top of the coal pot that are the source of the puff backs and explosions. A number of factors can interfere with attaining this minimum. The chimney may be cold, of insufficient height or in a poor location. Reduced duty cycles in the early and late parts of the heating season can lead to cold flues. If proper draft cannot be maintained, a draft inducer (power vent) should be installed. If the power vent is the main source of draft, apart from having natural draft, back up power must be in place.


I disagree on the draft as the cause. In my case all the major explosions occurred during the middle of heating season . My chimney is all double all insulated inside the heated building with only 6 ft above the roof in the cold. It is also 8" with a total length of 18 ft. The draft has no trouble maintain .06 on the warmest of days .
I burn over 12 ton of coal from November till spring so the boiler is not seating idle for any period of time. If it was a simple as adding a draft inducer you would be shipping every unit with one standard .
macdabs
 
Stoker Coal Boiler: AHS 260
Coal Size/Type: Pea
Other Heating: Pellet,oil
Stove/Furnace Make: AHS
Stove/Furnace Model: S260

Re: Coalgun- Puff backs & Explosions

PostBy: blrman07 On: Wed Oct 30, 2013 9:16 am

This really woke me up very quickly when I read the post saying the puff back ie explosions were the fault of the installation in an insufficient drafting chimney. I spent 27 years as an engineer for a boiler insurance company and during that time I got to where I can recognize when a company is trying to pass the buck to the consumer on a product that has something wrong. 45 pages of documentation on numerous installations that never had a puff back with their previous equipment and they get them on a regular basis AFTER they install a coal gun? And it's their fault or the fault of the chimney? Please......

Please don't insult the good people on this board who have worked and puzzled doing the companies R&D in the field. READ the entire post and then jump in with some real world experience. I suggest that you actually go to a location and view the unit in real life operation and have the people set up the parameters for a puff back so you can witness it first hand. The amount of engineering knowledge on this board is amazing and if you are trying to rebuild the companies rep after the deafening silence on this problem, blaming the operator or the chimney is not the way to go about it.

It comes right back to how much coal is loaded by the automatic systems. That has nothing to do with a lazy chimney.

Rev. Larry
blrman07
 
Hand Fed Coal Boiler: Bucket a Day
Hand Fed Coal Stove: Vigilant Casting 2310
Baseburners & Antiques: rebuilding a 1906 March Brownback Double Heater, using a UMCO 1920's Pot Belly stove in the church
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: franco b On: Wed Oct 30, 2013 12:15 pm

What it comes down to is the design violates basic combustion principles on shut down. The concern should not be how to exhaust volatiles but rather how to burn them in a timely manner. If one stage uses forced combustion air then provision must be made for the second stage which occurs when that blower shuts down. Throwing away good fuel up the chimney is a poor solution or worse having it explode.
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Re: Coalgun- Puff backs & Explosions

PostBy: EarthWindandFire On: Wed Oct 30, 2013 2:41 pm

I would hope that AHS brings in some outside engineers and consultants to evaluate, diagnose and engineer a solution to this problem. They need to re-write the manual based on the suggested design changes and make "kits" available in the field. The hardest thing for a company to do is FORGET what they "think" they know. They must admit defeat, capitulate, and start from scratch. Only by rising like the Phoenix from the ashes of its predecessor; can AHS resurrect the good will of its current and future customers.
EarthWindandFire
 
Hot Air Coal Stoker Furnace: Leisure Line Lil' Heater.
Hand Fed Coal Stove: Hitzer model 75. (sold)
Other Heating: Oil Furnace and Kerosene Heaters.

Re: Coalgun- Puff backs & Explosions

PostBy: lsayre On: Wed Oct 30, 2013 3:45 pm

This problem is shared with Axeman Anderson, and is not exclusively the domain of AHS. Under the skin they both uniquely burn coal in a narrow tube (instead of a fire box), and they both share similar overall designs. Both have a port cover that snaps shut when the fan comes on and springs back open when it shuts off. When the fan cuts off and the flapper (port cover) springs open, if the fire is too low in the tube there is the potential for a puff-back scenario. Makes little difference if it is AHS or AA.

I believe the essentials of this design go back to the mid to late 40's, and Penn State University was heavily involved in the design. The apparent goal was to design a boiler that would burn anthracite more efficiently than for any existing design known at at the time, with the objective of saving the anthracite industry from the post WWII invasion of NG, oil, and propane fueled boilers.
lsayre
 
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Stockton Anthracite Pea
Other Heating: Resistance Boiler (13.5 KW)

Re: Coalgun- Puff backs & Explosions

PostBy: Pa papa On: Thu Oct 31, 2013 7:36 am

lsayre wrote:This problem is shared with Axeman Anderson, and is not exclusively the domain of AHS. Under the skin they both uniquely burn coal in a narrow tube (instead of a fire box), and they both share similar overall designs. Both have a port cover that snaps shut when the fan comes on and springs back open when it shuts off. When the fan cuts off and the flapper (port cover) springs open, if the fire is too low in the tube there is the potential for a puff-back scenario. Makes little difference if it is AHS or AA.


Right on. rem. If you're not part of the solution, you're a part of the problem.
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: blrman07 On: Thu Oct 31, 2013 8:46 am

There is a reason that designs don't make it in the real world. Sometimes they just don't work right or they have controls that are too complicated for the application . The coal gun fire tube and control design may be too close to the 1940's failed attempt to get that technology on the market. That does not mean that it can't be done. It means that for the design to work, the manufacturer needs to R & D outside the realm of the existing product.

Stop defending the design and admit there is a problem related to ashing controlling the coal feed and actually look at it. Don't wait until there is a big enough explosion of unconsumed gasses where large amount of property and injury occur. Instead of making that work, has anyone tried separating the two functions and making them independent of each other?
blrman07
 
Hand Fed Coal Boiler: Bucket a Day
Hand Fed Coal Stove: Vigilant Casting 2310
Baseburners & Antiques: rebuilding a 1906 March Brownback Double Heater, using a UMCO 1920's Pot Belly stove in the church
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: McGiever On: Thu Oct 31, 2013 10:09 am

I can see where the chimney would factor in for increasing or lessening the chances of the puff back...but that would not be a solution or cure for this puff back problem. The cure or solution must come from more accurate control over the fire's position in the fire tube...period.
Yes, there is the fan and grating action that needs factored in as well...but bottom line...the fire's position has got to be right when the fan stops and fresh coal has just been piled on top of a fiery bed of hot coals.

CONTROL THE ASHING TO CONTROL THE FIRE'S HEIGHT/POSITION/THICKNESS

And sorry...there is no "Set it and forget it" Generally, it needs tweaked as the heating load changes throughout the heating season.

I am a AA owner, so I'll add this for comparison...
Axeman accomplishes control by allowing the operator to adjust two variables...
1.) Anthrastat...a simple, adjustable temperature sensitive bi-metallic switch located in the proximity of between the grate and the underside of the fire tube that will start and stop the grating action according to the set point chosen.

2.)Ashing Linkage Arm/Lever...adjustable linkage that controls speed at which ashing grate moves. Adjusted by the number of *clicks* allowed on ratchet pawl. (1 to 3 click setting range...42 total clicks equals 2" movement out and 2" travel back.

Note: No ashing can occur unless both the fan motor is running and the Anthrastat switch has closed.
Note: The volume of fresh coal added on top of the fire is equal to volume of ash displaced from bottom of the fire.
Note: AA's can and do have puff backs if not properly adjusted.
McGiever
 
Stoker Coal Boiler: AXEMAN-ANDERSON 130 "1959"
Hot Air Coal Stoker Stove: HARMAN MAGNUM
Hand Fed Coal Stove: RADIANT HOME AIR BLAST
Baseburners & Antiques: OUR GLENWOOD 111 BASEBURNER "1908"
Coal Size/Type: PEA / ANTHRACITE, NUT-STOVE / ANTHRACITE
Other Heating: Ground Source Heat Pump
Stove/Furnace Make: Hydro Heat /Mega Tek

Re: Coalgun- Puff backs & Explosions

PostBy: blrman07 On: Thu Oct 31, 2013 10:33 am

Thanks McGiever for the post which solidified what I have been saying all along. Through all the posts it has become very clear that the current coal gun application of directly tying the ashing to the feeding is contributing to the problem. Sure there are factors with draft and chimney just like on any coal burning appliance but this setup appears to be too advanced for any but the most savy of operators. If you separate the two functions as McGiever has outlined AA did but still kept automation in the appliance you can take control of the situation and minimize or eliminate the puffbacks.

When I was in the Navy I was on an experimental ship that had supercharged boilers that operated at 1200 psi with 1000 degree superheat. The boiler was round and had three burners with three stages per burner. We burned JP5 instead of the standard fuel oils at the time. The control system was the most advanced the Navy had and you had to go to special school to walk into the boiler room of one of the ships much less be top watch in charge. The console operator was the heart of the system as he had to be able to go to manual control at the first sign of trouble. Only problem was the system reacted so fast that manual control for anything other than attempting a controlled shutdown or steady speed operation was virtually impossible. Other than adjusting bias up or down on the settings the operator didn't do anything when we were in auto except watch gauges and the water level. The design, although it was great on paper, just wasn't sailor proof and the Navy stopped the program.

The key here IMHO is to separate the functions and allow a human to tweak the settings. However the human tweaking the settings has got to understand the relationship between coal loading, coal gassing, draft, over fire draft vrs underfire in all the ranges the unit can do. As McGiever pointed out these units are anything but set it and leave it. Until the severing of the automatic control of the those two functions is achieved, you will continue to see puffbacks as the system can't read all the nuances the unit will see during normal operation.

Rev. Larry
blrman07
 
Hand Fed Coal Boiler: Bucket a Day
Hand Fed Coal Stove: Vigilant Casting 2310
Baseburners & Antiques: rebuilding a 1906 March Brownback Double Heater, using a UMCO 1920's Pot Belly stove in the church
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: Bob On: Thu Oct 31, 2013 10:53 am

greenftechn wrote:I want to apologize to folks who have been looking for answers on the puff back issue and have not been seeing company rep participation in the forum. First, regarding the ownership issue mentioned by the previous poster, I want to let you know that the company has come back to Jeff and Phyllis Gingerich, who stewarded the company during the best ten years of its existence, in my opinion.

Regarding puff backs, proper draft is the key (emphasis added).


I disagree.

I have owned/operated an S130 for 7 years. Proper draft is necessary, but not sufficient, to avoid puff backs.

I have always had proper draft but only after I understood fire height and began to actively make adjustments to control it was my puff back problem resolved. Those adjustments included settings of the thermograte outside the range recommended to me by AHS. As I have posted earlier in this thread I think AHS needs to be much more explicit about the importance of fire height in its documentation and in its support. I also agree with lsayre's comments that AHS manual directions about minimum thermograte settings are a part of the problem for users.
Bob
 
Stoker Coal Boiler: AHS 130
Coal Size/Type: Pea/Anthracite

Re: Coalgun- Puff backs & Explosions

PostBy: lsayre On: Thu Oct 31, 2013 11:02 am

McGiever wrote:
Note: No ashing can occur unless both the fan motor is running and the Anthrastat switch has closed.
Note: The volume of fresh coal added on top of the fire is equal to volume of ash displaced from bottom of the fire.
Note: AA's can and do have puff backs if not properly adjusted.


For the AHS this becomes:

No ashing can occur unless both the fan motor is running and the temperature of the ash grate is 10 degrees below the setpoint for the LC.
The volume of fresh coal added on top of the fire is equal to volume of ash displaced from bottom of the fire.
AHS's can and do have puff backs if not properly adjusted.

The lower the setpoint on the LC (the temp selected for ashing initiation), the higher the fire resides within the tube.
And likewise the higher the setpoint on the LC, the lower the fire resides within the tube.
The proper settings for the LC in all cases being highly dependent upon the ash content of the coal.

Perhaps the problem is compounded for the AHS by the manual insisting that the LC setpoint be maintained at (from memory here) between 140 degrees and 120 degrees. This narrow range of temperature setpoint options may not be sufficient to cover all of the various coals available.

NOTE: Before AHS settled on the Love Control (LC), I believe they used a similar Fuji supplied temperature control, but that probably changes little here. And before that they used a timer to initiate ashing. The timer counted time only while the fan was running. After so many minutes of fan operation (cumulative over multiple fan on/off cycles) you got so many minutes of ashing, with the times being user selectable.
Last edited by lsayre on Thu Oct 31, 2013 8:37 pm, edited 1 time in total.
lsayre
 
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Stockton Anthracite Pea
Other Heating: Resistance Boiler (13.5 KW)

Re: Coalgun- Puff backs & Explosions

PostBy: greenftechn On: Thu Oct 31, 2013 2:09 pm

I have included the information from the troubleshooting guide in our manual in the attached image. Timing of ignitions is referenced, which helps in determining the specific cause in each case. All new Coal Guns come with controls necessary to maintain the fire in the correct position in the coal pot. As several folks have noted, this does influence the amount of volatiles that are present above the fire.

Image

Two additional points to be made: We are monitoring the forum, and will not ignore issues, and we will work with individual customers to solve any issues they may have.
greenftechn
 
Stoker Coal Boiler: Coal Gun S130
Hand Fed Coal Stove: Alaska Kodiak
Coal Size/Type: Nut
Other Heating: Wood Gun
Stove/Furnace Make: Alternate Heating Systems
Stove/Furnace Model: E100