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Giving a Jetstream base new life.

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by hobbyheater, Nov 21, 2011.

  1. hobbyheater

    hobbyheater Minister of Fire

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    A little frustrating as the pictures didn't load in order.

    top row, 3rd over. - Made a diagram of the wiring. Makes things just a little easier putting things back together.

    2nd row, 1st - Major cracks in the burn chamber and the tunnel is falling apart.

    2nd row, 2nd - New injection tube, new tunnel and refractory in the burn chamber. To this point, I have not removed the old stove cement seal as it helps hold the cracked refractory together until the new refractory has set and now supports the old liner. There are stainless steel needles mixed into the new refractory. I have made molds and I am now making my own tunnels and cleanout plugs.

    2nd row, 3rd - This is a new base and if you compare this picture and the previous one, you will see the difference in the thickness in the tunnel support area. Six years ago, the tunnel bridge between the burn chamber and tunnel areas had totally fallen apart, so at that time I made this area thicker, leaving the section low enough to clean and for the gases to go up the heat exchanger tubes. From the stand point of strength, it has been a success but the down side is that there is not as much area for the fly ash to settle out in this area which results in more frequent cleanings.

    top row, 2nd - This slot in the burning tube is very important. The original had burnt away, allowing combustion in the loading tube which creates more smoke than what could be burnt and a very inefficient burn. I attempted this repair six years ago and made lots of mistakes. First thing I did wrong, was to make a rigid mold inside the burn chamber. The refractory had to be mixed too wet so it could be poured. With the rigid mold, there was no way of getting the old refractory damp so that the new would adhere. I also didn't have any refractory needles and an insufficient curing. The new liner was placed in much the same way that you would make a sand castle. It took nineteen 2 hour burns with three pounds of kindling at a time to cure the new liner. How I learned this was by accident. After the five burns prescribed in the Jetstream manual, the new liner was still black with soot and I assumed this was because the fire was not hot enough to burn the soot. But I had already decided to do twelve burns and after burn number eight, the two lower inches of the new refractory had turned gray, and with each additional burn, more refractory started turning gray. The soot was clinging to the damp refractory that had not yet cured. So after nineteen burns, the whole thing was grey. I burned another three full loads with the loading door open. The boiler has now been in operation for six weeks and no cracks !

    bottom row - Moving the heat exchanger back to the base. I have permanently installed a barn door track over the boiler to make it easier to assemble and disassemble when necessary.

    top row, 1st - The heat exchanger is back on the base. I got preoccupied and did not get a picture of the one inch layer of stove cement making the seal. A good seal here is important to prevent gases from escaping and it also helps with good heat transfer from the base to the heat exchanger. The Jetstream and 1000 storage tank share the same water. I size my last burn loads so that all of wood is burnt when the top of the tank reaches 195 degrees and after the fire is out, I run the circulator another four hours. This raises the temperature at the bottom of the tank from 170 degrees to 180- 185 degrees with no fire so the heat transfer between the base and heat exchanger is very important.
    Even though the fire box inner dimensions are now smaller than original, it has not affected the boilers output, It is still netting 105,000 btus per hour to the storage tank.
    Allan

    Attached Files:

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  2. Vinced

    Vinced Member

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    Its great to actually see the insides of one of these. I heard and read alot about them but never seen one in person. What type and brand of refractory did you use to repair it. Is that pipe that goes through the heat exchanger and tunnel area the main air feed?
  3. hobbyheater

    hobbyheater Minister of Fire

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    Vince

    I used " Rutland Castable Refractory Cement" 2200 degree F.

    The tube is the main or only air supply to the burn chamber (60 cubic feet per minute). The first picture shows where the tube enters the base. When the blower is in place, the air path is split with a further ( 60 cubic feet per minute )of air being injected into the flue creating the draft inducer. When the loading door is open, the combustion air is cut off leaving only the draft inducer side of the blower working, so about 90% of the time you do not get smoke into the room.
    We learn by our mistakes. I have since learned that "AP Green/ Harbison-Walker" makes two products (Kast-o-Lite ) 2600 Degree F and (Versa Flow 60 Plus ) 3000 Degree F Castable Refractory. Had I know about them, I would have used the latter.

    http://www.budgetcastingsupply.com/Castable_Refractory_3000F.php This is a link to a product that I would have used.

    Allan
  4. tom in maine

    tom in maine Minister of Fire

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    These are great boilers and as you are finding out, pretty serviceable.

    Make sure you cure the refractory properly. Hopefully there were directions on the bag.
    First time I used some, I did not read the curing directions.
    As one who writes directions, I now understand why they are there!

    This is going to be fun to operate. I have had my hands on several over the years.
  5. hobbyheater

    hobbyheater Minister of Fire

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    Tom in Maine. You are very correct. Proper curing is everything with Castable refractory and reading the instructions on the bag as well.
    These boilers are very repairable. The Jetstream # 528 shown in the pictures; we have used for 27 years, and # 0175 (still new) sits on its shipping pallets waiting for a chance to go to work!

    What is your prototype gasifier? What does "DHW hx (home)" mean?

    Allan
  6. hobbyheater

    hobbyheater Minister of Fire

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    Four months of operation and the repair is standing up well with no cracks yet. Only downside is that with the smaller burn chamber area, I have had to reduce the amount of wood being burnt at one time to maintain an efficient burn.
    I have recently acquired a third unit, but am just going to use the box and install the spare refractory liner that I have into it. Could you tell me if the vermiculite that is used for insulation between the box and the liner is any different than the type that you would get from a garden shop?

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  7. tom in maine

    tom in maine Minister of Fire

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    Hi Alan,
    This should probably be a trade secret, but I use vermiculite that is used for packing material.
    I buy it from Uline. It is cheaper than plant vermiculite and stood up well in an early prototype that I built that needed it.
    Tom
  8. thecontrolguy

    thecontrolguy Member

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    OOoooh yah! Great Info. Why don't you live up North (mainland) so I can visit? I want one of these old gasser boilers in a bad way, but have settled for a big new shop (first) before the wife allows me to start experimenting with things that may burn down the old house faster than the other things I have done. (waste oil processing) I have the burn chamber and secondary chamber developed in the design sketch book (and many dreams) but the heat exchanger still eludes me. No one around here has a nice cast-iron 3-pass used (oil) fired boiler for sale. Dang! Maybe I need to design and weld one up and hope the insurance company doesn't ask about the pesky ASME badging. Prefer gas-tube with turbulators, exactly as you have. I seem to have arrived at the same limitations and usefulness of the design you're using as have many other engineers. Now, the patience and waiting game comes and need to focus on other things. Isn't anyone else limited from the boiler stage by budget and other immediate commitments? I know, poor me ....

    I still feel a vertical section of the flue-gas breaching needs to be through a quasi-expansion and return tempering tank that returns the (pre) heated water to the primary heat exchanger. Like a small hot-water tank on the flue stack, immediately after the heat exchanger. Thanks for the pics. Any more will be appreciated. Cheers, and hang on as I see more liquid sunshine is coming your way up the island.
  9. hobbyheater

    hobbyheater Minister of Fire

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    [quote author="thecontrolguy" date="1328007045"] Thanks for the pics. Any more will be appreciated. [/quote

    The draft inducer is very simple; just a small port sending half the blower's air up the chimney. In the initial start of the fire, the unburnt embers are less likely to be blown out of the top of the stack as the flare in the flue pipe just past the draft inducer port slows these embers down and they settle out in the clean-out of the chimney. The blower air splits - half goes up to the inducer, the other half goes down into the fire box. About four inches below the split, there is a steel ball bearing on a seat. When the loading tube door is opened, a lever connected to the loading door allows the ball bearing to fall on the seat, cutting off the combustion air. The Jetstream, because of its forced draft and many gaskets, is bad for blowing a very fine pumice like dust into the room. The original blower was mounted in a metal box on the back end of the heat exchanger and was exposed to this fine dust. This dust really kills the vacuum motor blowers. The solution for me was that I remote mounted the blower motor into the outside air duct in the room and plumbed the blower air to the boiler. This created some things that I still do not understand. The same blower in this configuration delivers more air than needed. The refractory was getting so hot, it was turning white. It normally glows a nice pumpkin coloured orangey red. So I installed a gate valve to dump the unwanted air. Another thing that I do not understand, is that the colder the outside temperature gets, the hotter the stack temperature gets?
    I burned some sandy wood and these little melted gobs showed up in the ash. Any idea what temperature it takes to make this happen? Would not normally ask a question like this but I have gathered from some of your threads that you may operate a boiler in a pulp mill.

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  10. thecontrolguy

    thecontrolguy Member

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    Allan; I think glass (silicon base) melts in the 2100 degF range. This is very incandescent yellowish-white. The oxidizer in the power plant where I work(ed) is operated by programming and human operators to less than 2200 degF as more than that starts to cause severe slagging (melting into lumps) of the fly ash and bonding onto the refractory. Which, in turn, causes damage to the refractory, accelerated erosion, and is a real *&itch; to clean out. I am not certain about why your re-piping of the combustion air path causes hotter burns except for a few hypotheses: One, the path of the piping may have reduced static losses of the air flowing in the pipes so you get more air flow into the boiler and a better draft-inducer flow. No way to prove this now unless you took air static pressure measurements at various points in the old piping and compared that to the new piping. Second, what is the temperature of the air as it goes into the boiler? I imagine that the piping is transferring some heat to the combustion air from the ambient air temperatures in your boiler room. Certainly cooler air is more dense and thus has more oxy's but there is a quickly decreasing benefit from this as very cold air will inhibit primary and secondary burn rates and possibly threaten your refractory if it should be overly cooled.

    I am no longer working at that heating plant (as of 29 Jan) and am starting a new job (tomorrow, actually) as an Electrician and Automation Specialist with the city of Prince George. Lots more $$$$ and the chance to get my ranch and the previously mentioned projects moving forward this summer. Woo hoo. In between haying, training the new logging horse (Gus) and other commitments! Aahh, the life.
  11. hobbyheater

    hobbyheater Minister of Fire

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  12. mikeyny

    mikeyny Feeling the Heat

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    colder air is much more dense than warm air, introducing much more oxygen, creating higher temps. Most internal combustion engines run better with cooler intake air. cooler air is more dense containing more o2 resulting in more horse power, especially in conjunction with a turbo charger. Your fan is the turbo, in order to fine tune your burn rate you would have to meter your air intake according air temp using some sensors. Lambda?? Just my 2 somewhat uneducated cents.
  13. hobbyheater

    hobbyheater Minister of Fire

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    Hobbyheater You have years of experience with this boiler, so I am going to keep picking your brain as long as you let me. Please comment on my observations, It appears that it is using a high pressure centrifugal blower and that a portion of the air is being piped in to the vent connector threw a venturi that should create a negative pressure to induce draft. Where does it pull the inlet air from? Does it dump any air into the secondary burn chamber? Could you better explain why there is little smoke when door is open

    bigburner

    The original blower was attached to the back end of the heat exchanger and drew its air from within the boiler room.

    There is no secondary air, just primary preheated air to the burn chamber.

    Pictured below is the refractory base; the round section is the burn chamber, the rectangular section is below the fire tubes in the heat exchanger. Two things happen in this chamber. Most of the fly ash settles out, but more importantly any unburnt gases have to pass through the refractory tunnel (nozzle) seen below the pipe that carries the blower air to the fire box There are two openings on either side of the tunnel at the back end of this chamber.
    Two pictures are of a small lever on the pipe carrying the combustion air to the fire box. When the "L" shaped lever is straight up and down. a 1" steel ball sits on a seat forcing all the blower's air through the draft inducer port - 99.2 CFM at 84" H2O. When the "L" shaped lever is pulled away from the pipe, the steel ball is lifted off its seat with the air being split between combustion and draft inducer.
    When the loading door is opened, the draft inducer draws combustion air through the loading door pulling the smoke with it. If I'm careful not to block the entrance to the tunnel with a block of firewood, I get no smoke into the room.
    Pictured is the 1" steel ball bearing that works as the valve.

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  14. hobbyheater

    hobbyheater Minister of Fire

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    Thank you for your input , I think its a good conclusion :exclaim:
  15. maple1

    maple1 Minister of Fire

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    Kind of weird how I'm just learning about these units now on here, all the while living only a half hour from the Kerr factory and my parents having another model Kerr in their place for years. Seems like they were a bit ahead of their time - seems a real shame they didn't make a go of it. I think the furnace builders around here could use a LARGE shot of new technology in what they're doing - and it was right under their noses to start with.
  16. hobbyheater

    hobbyheater Minister of Fire

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    The part that really makes the Jetstream successful in clean burning and efficent heat exchange, is its large refractory base component but it was also its downfall. The importance of adequate heat storage was not stressed by its sales personnel. Because of its tunnel design, it can be in full gasificication mode within 10 minutes of lighting the fire. I have always given mine a 1/2 hour before going into gasification mode to allow for a more gradual warm up of the base. After 2 hours of continuous burn, the refractory is yellow orange in color. Later in the burn, it can even be yellow white. At these temperatures, if the fire was to cycle, it is really hard on the refractory and likely lead to many early failures of the refractory component. In my opinion, the instructions in owner's manual for the initial curing fire were inadequate.


    Below is a link that will give you a idea of what the different colors of refractory can mean in temperatures .

    http://www.ceramicartdaily.net/PMI/KilnFiringChart.pdf
  17. Vinced

    Vinced Member

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    Very interesting stuff. I thought the Jetstream was the same has Richard Hill's stick-wood fired furnace. It seems like it is very similar, but the stick-wood furnace has primary air and secondary air. Also the tunnel is longer in the stick-wood furnace. The tunnel in the Jetstream looks like its only 4" long where the stick-wood it 12" long. Is that 1" steel ball a factory item or is that something you added?
  18. hobbyheater

    hobbyheater Minister of Fire

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    The tunnel is a total of 15" long and the steel ball is original equipment. It sit on a seat between the cotter key and the trigger slot in the air tube feeding the combustion chamber. I have always thought the Jetstream to be Richard Hills design. Would like to learn about the stick wood furnace.

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  19. Vinced

    Vinced Member

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    By your pictures the tunnel looked shorter. What size is the heat exchanger. If you Google "Stick-wood fired furance" it will bring up the documents that Richard Hill did for the US Department of Energy in 1979. It is a report of the design of this furnace and how it was built and how it performed. Sorry I don't have the website handy. Yes this is where the Jetstream came from.
  20. hobbyheater

    hobbyheater Minister of Fire

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    The heat-exchanger holds 50 gallons.
    Two pictures of the heat exchanger .
    Picture from the manual of how the trigger (lever) opens and closes the steel ball by lifting it of its seat.

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  21. Vinced

    Vinced Member

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    Dumb me!, I didn't see that the tunnel extends into the chamber that the heat exchanger sits on and has 2 outlets on the sides. Must have been too late last night. LOL
  22. Vinced

    Vinced Member

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    Those tubes look small. They must be around 2 1/2" in diameter. Does the heat exchanger go around the wood loading chamber too. I notice in the stick-wood info that it say the wood loading chamber needs a water jacket. All in all it is very much the same has the stick-wood, but with a few different twists.
  23. hobbyheater

    hobbyheater Minister of Fire

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    The tubes are 1 9/16" inside diameter. The heat exchanger surrounds the loading chamber. The area of the heat exchanger contacting the refractory base (sq in) is about half that of the total area of the fire tubes so there is a lot of heat transfered from base to heat exchanger; much like a kettle sitting on top of a hot stove. The circulator can be run up to four hours after the fire is out. Not big numbers but the water leaving the heat exchanger is 10 F hotter than the water entering.
  24. Vinced

    Vinced Member

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    Makes sense to me having the heat exchanger/ loading chamber surrounded by water and setting on top of the refractory base. It still seems strange that the only air into it is in the bottom of the loading chamber and that it enters the opposite direction of the the tunnel. The stick-wood furnace has primary air coming out of a 1" pipe with 10-1/4" holes in it and pointed at the tunnel. It also has a heated secondary air tube about where yours is. Maybe Jetstream found this has a better way to bring in the air?
  25. hobbyheater

    hobbyheater Minister of Fire

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    Two pictures of the base.The tube where it enters the burn chamber it has a slot in the end , but the slot is recessed about 3/8" on the right side creating a swirling turbulence in the burn chamber attacking the wood from all sides .

    The masking tape is just to give a idea what the slot should look like , when installed properly the main slot is horizontal.

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