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  1. #1
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    Jun 2013
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    Cracked Heat Exchanger in Bakery Oven

    I have a customer with a rack-type Hobart bakery oven. It has a flame gun that shoots into a burner chamber then into multiple pipes which form the heat exchanger in the unit. I have visually located a 3" long, very fine crack in one of the multiple pipes after the burner chamber. The oven works but I am sure the crack will only get bigger. The customer wants me to arrange to have the crack welded. Does anybody think this is inadvisable? I'm sure they're going to use it anyway, but wouldn't it be better to at least try to isolate the damage? They do not want to pay for a new heat exchanger or replace the oven.

  2. #2
    Join Date
    Nov 2009
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    sudbury on, can
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    What is ther model number of the oven? depending on where you are located it may or may not be legal to weld it, I have seen it done, depends on the overall condition of the heat exchanger as well, if there is signs it is rusting at the seams etc. probably not worth it.

  3. #3
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    Thread Starter
    This is a Hobart HO210G2 oven located in central Washington State. No rust, it is an otherwise good looking oven, and other than the crack, a good looking heat exchanger.

  4. #4
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    Nov 2009
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    sudbury on, can
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    They can get expensive, I have seen replacements anywhere from 7 to 10 thousand dollars. If its allowed to do so in your state, nothing to lose by closing it up with a weld.

  5. #5
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    Sep 2011
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    Maryland
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    Before you condemn the heat exchanger you should use a combustion analyzer to measure the CO in the baking chamber. Do this by slipping the probe under the door gasket with the burner firing. Ideally you should have zero CO but a little is not harmful, say under 50ppm. Some heat exchangers will not release any CO with a crack but others will. It depends on the design.
    I'm not sure on the exact procedure for the HO210 but I could find out. Welding is ok if you can get to it but what about where you can't see? Don't back yourself in a corner, when it needs to be replaced it should be.

    OSHA requires every oven over a certain BTU to be inspected once a year by a factory authorized services to ensure the entegrity of the heat exchanger. A lot of small places don't do it until they blow the door off of the oven. I have seen two nasty explosions due to failed heat exchangers.

  6. #6
    Join Date
    Jul 2017
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    Heat exchangers in general…
    We have purchased 2 used Revent 624’s both have HE cracks. the ovens were built in 2001-02 and originally sold to costco. evidence that the HE have been replaced not by factory replacements.

    I revert back to my high school metal shop where heating and cooling of metal changes the properties of the metal. If I recall properly, heating and cooling of metal over time can make the metal brittle therefore increasing fatigue of the metal which in-turn causes the metal to crack. I believe the heat exchangers are worn out due to high use am I wrong in this belief?

  7. #7
    Join Date
    Oct 2016
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    Clearwater, Florida
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    Okay, I am going to step in on this one.

    I weld at work, a lot. Lots of different things, different metals, alloys, finishes and so on.

    The HE is most likely 304 S.S could be 308 or 316, might be a number 4 alloy, but I doubt it.

    DEFINETLEY able to be welded, get someone who is good at TIG welding, no MIG, no Stick. Get a TIG welder on the job and he will patch that thing up and make it look fantastic.

    I have had to weld studs onto the flange part of heat exchanger in an oven before, that was restricted welding, not out in the open and if you know what you are doing, its not a problem. I even had to make my own TIG cup to fit it in there. Anyways,

    ITs definetley possible, normally you drill an 1/8" or so hole at the end of each part of the crack which supposedly makes it stop cracking in the future, and then have him weld it up, it can even be refinished with a pipe sander if you want it to look spanking new.

  8. #8
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    Jun 2013
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    Something else to consider: Several years ago, a combi manufacturer sent me out to drill several/many holes in their (forced air) gas heat exchanger tubes at specific locations on each tube, inside the cooking chamber. I think I did 8 or 10 units at a military base.

    This was for the purpose of letting condensed water drain out of the tubes, instead of flashing to steam at some point, doing bad things and making bad noises.

    So, a small crack, or many holes in the heat exchanger seems to be Not-A-Big-Thing. At least to this one manufacturer.

  9. #9
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    Oct 2016
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    Quote Originally Posted by BadBozo2315 View Post
    Something else to consider: Several years ago, a combi manufacturer sent me out to drill several/many holes in their (forced air) gas heat exchanger tubes at specific locations on each tube, inside the cooking chamber. I think I did 8 or 10 units at a military base.

    This was for the purpose of letting condensed water drain out of the tubes, instead of flashing to steam at some point, doing bad things and making bad noises.

    So, a small crack, or many holes in the heat exchanger seems to be Not-A-Big-Thing. At least to this one manufacturer.
    Considering your letting exhaust fumes into your cooking chamber, I would say its "Very-big-thing" no matter what any manufacturer told you.

    I called Cleveland asking them some questions, the guy thought I was saying I had holes in the HE and told me to shut the oven down this very second and not let anyone use it. Maybe its different depending on manufacturer but logically speaking, allowing exhaust fumes into the same chamber you cook food, is not healthy and probably trashes the flavor of the food.

  10. #10
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    Jun 2013
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    Now that I think of it, don't some convection ovens (Vulcan snorkel?) recirc the exhuast gasses in the cooking chamber?

    And for that matter, range ovens have open burners in the bottom and exhuast gasses flow up along the open sides, then exit at the rear interior of the cooking chamber. All food thus gets exposed to exhuast gasses...

  11. #11
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    Oct 2016
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    Not too sure about that, I just know that I wouldn't think cooking food in exhaust fumes is a good idea.

    Otherwise, why bother with the heat exchanger and welding it completely 100%?

  12. #12
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    And lastly, I don't know if you have seen the big old rotating deck ovens, Fish, and others, they typically bake bread in. They have a what, 10 foot long burner in the middle bottom of the baking chamber that the shelves are in.

    So, I suspect it isn't exhuast gas getting in the food. Heck, think of your basic backyard charcol grill. One restaurant we service uses a wood-only steak chargrill.

    I suspect the added water from a condensing flame might be the issue. Lord knows there's enough water to be driven off in dough/bread baking.

    An interesting question though...

  13. #13
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    Quote Originally Posted by BadBozo2315 View Post
    And lastly, I don't know if you have seen the big old rotating deck ovens, Fish, and others, they typically bake bread in. They have a what, 10 foot long burner in the middle bottom of the baking chamber that the shelves are in.

    So, I suspect it isn't exhuast gas getting in the food. Heck, think of your basic backyard charcol grill. One restaurant we service uses a wood-only steak chargrill.

    I suspect the added water from a condensing flame might be the issue. Lord knows there's enough water to be driven off in dough/bread baking.

    An interesting question though...
    Good point, I guess it may be okay, but could also depend on the application, having the spritzer system like Cleveland, the HE is crucial to that working which allows you to steam without a boiler but I guess it wouldn't matter too much otherwise.

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