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Thread: ventilation system based on Vince Henley's article in Torchworked Marbles

  1. #1
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    Default ventilation system based on Vince Henley's article in Torchworked Marbles

    Hi there,

    This is my first post. I am looking for someone who has a ventilation system like the one that Vince Henley described in Torchworked Marbles by Drew Fitts - or maybe Vince Henley himself might be available to answer a question???

    My question specifically: i have heard of many vent systems that use fans 600 cfm fans. And many people on other forums suggest that range hoods are not sufficient for a lampworking ventilation system. So, just trying to work out the contradiction, as Henley's article was the first one I read and which I planned on using as the starting point for my system.

    Can someone explain why this system is OK with a much smaller fan?

    Thanks, lisa

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    Hi Lisa,

    Welcome!

    Thank you for your post and question. I emailed Vince Henley directly to let him know about your post. Please let me know if I can help in any other way.

    We appreciate having you with us on the ISGB Forum and we look forward to 'talking' with you more.

    Best Regards,
    Kendra

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    Thank you, Kendra. It would be great if I got some input from Vince directly.

    Two other things that I wanted to mention are: 1) I am using a small torch like a minor or a cricket or betta (haven't decided yet), and 2) my 7 inch round duct will have 2 or 3 bends.

    I, too, look forward to becoming more involved with other lampworkers.

    thanks, lisa


    Quote Originally Posted by KendraBruno View Post
    Hi Lisa,

    Welcome!

    Thank you for your post and question. I emailed Vince Henley directly to let him know about your post. Please let me know if I can help in any other way.

    We appreciate having you with us on the ISGB Forum and we look forward to 'talking' with you more.

    Best Regards,
    Kendra

  4. #4
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    Lisa,

    Sorry for the delay in response but I've basically been unavailable and not on my computer much of late.

    I don't know where you are getting your other recommendations but there is nothing wrong with using blowers that have more capacity, up to a point. In the system described in Drew Fitts' book the main difference is that that system has been instrumented and measured for capture, face velocity, temperature and noise. Very few other systems have been actually measured for performance with their corresponding torches as that one has so I think there are some "estimates" and "calculations" being used to describe their performance as opposed to actual measurements.

    All the systems that I've designed or experimented with have been instrumented and measured as well as calculated and I've learned to take the calculations with a healthy grain of salt. They can be very misleading as airflow rarely does what we think it does once we actually get some instrument probes in there to measure it.

    The system described in Drew Fitts' book is perfectly satisfactory for torches in size up to but not including the GTT Phantom class of torch. Phantoms and larger torches are a bit too much for that ventilation system but anything smaller will be fine. Minor burners, Lynx, Mini-CC, Bobcat and such torches will be well within the performance characteristics for that particular hood arrangement. The baffles are critical for capture and must not be ignored. The system as measured had two 45-degree bends in the exhaust duct which was about twelve feet long so you should be fine with three such bends. I would try to avoid 90 degree bends as much as possible.

    Systems that have larger hood capture areas will need to have more CFM in their blowers to maintain face velocity and perhaps that is where the 600 cfm number comes from. If you wish to construct a hood that has an area of say six square feet then you will want a 600 CFM blower, but if your hood as a smaller capture area and you can direct all the torch gas plume into that area then you can use less. As you can see from the measurements in the original article the face velocity of that hood is more than adequate for capture of the torch plume.

    Let me know if you have any additional questions.

    Vince

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    And now I apologize for the delay.

    Thank you for the additional information. I think you are right that sometimes when people are trying to estimate the size fan they need, it feels "safer" to overshoot.

    I am going to proceed with the design in Fritts' book. It seems reasonable to me and I appreciate the effort you've made to share the particulars. My HVAC guy was just here and it seemed like everything made sense to him. The exact NuTone hood is not available but they have several at 220 cfm and also one at 300 cfm. In the ducting, there will probably be one 90 degree turn and one 45 degree. He is calculating the make up air to account for 300 cfm.

    If you hear anything that sounds amiss, I would appreciate a brief mention. In any case, thanks for your help.

    lisa

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    Lisa,

    good luck with your project. Remember what I said in my previous post about the baffles. All the parts in this system make a contribution toward its effectiveness with reasonable cost. My objective in describing this system was to ensure that bead makers could put together an effective ventilation system with minimum cost and have some assurance that it would actually work and contribute toward their safety. I've seen and measured a few systems that made a lot of fan noise but which did not actually capture and exhaust the fumes from torch work. It sounds as if your approach in employing a professional HVAC person will ensure that your system does work correctly. After the system is installed, have your HVAC person make a few measurements to provide confidence that it is working as intended.

    Vince

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    So... For the rest of us who do not have instrumentation and don't have access to technicians who can do the testing, is 100cfm per square foot opening of a "fume cabinet" and 125 cfm per square foot of a "canopy hood" opening and calculating the static pressure of duct run and including loss for bends still a good way to go for selecting a particular fan/blower, and hopefully have functional safe ventilation...

    Also would a canopy hood similar to this one be safe if the advertised cfm value can be believed... And also removal of "grease filters" for better efficiency....

    http://www.euro-kitchen.com/search.a...ox=true&sman=1

    Dale

  8. #8
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    The numbers you quote are good starting numbers for any installation. The problem is in actually achieving those numbers and that is where measurement comes in. Canopy hoods without baffles may not be effective depending on where the torch plume is captured. The torch plume gas velocity may be high enough to simply "blow by" the capture area and continue into the room environment. Torch plume velocity can easily exceed 200 fpm at a distance of 36 inches from the torch face for a small torch.

    I have no opinion on the referenced hood. A measurement would be required to evaluate any specific hood and I would not recommend anything for which there was not a traceable and repeatable measurement.

    Vince

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