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Low capacity, battery driven, explosion proof blower

  1. Oct 29, 2013 #1
    Hello I am in a bit of an engineering bind. I need to evacuate a small room of a flammable, explosive gas that is at a nominal pressure of 3 mbar by pushing it from room to another room (both at equal pressure). The environment is Class 1 Div 1. The rooms have valved piping that enable me to attach a device to the exterior.

    The main difficulty with this project is that the device has to be portable. So anything electrically driven from an external power source is out of the question because plugging it in could create a spark (also any blowers I have seen are far too large of a capacity). I have examined some pneumatically driven pumps that may work, but they are not designed for gases and most of them, even plastic ones, have some steel parts that could in the worst case scenario spark. Also these pumps are designed for liquid use so a gas may not work.

    So now I am stuck. I have considered hand pumps, but again most of these have components that could spark and are designed for liquids. What would be ideal would be a small, battery ran, explosion proof Class 1 Div 1 certified blower. If anybody has any suggestions I would greatly appreciate it.
     
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  3. Oct 29, 2013 #2

    berkeman

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    Welcome to the PF.

    I did a google search on 12v explosion proof fan, and got some promising hits. Maybe try that search to see if any of the links get you what you want.
     
  4. Oct 29, 2013 #3

    Bandit127

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    I also did a quick search using "ATEX blower" as keywords and came up with a portable venturi blower that works on compressed air or saturated steam.
     
  5. Oct 29, 2013 #4

    UltrafastPED

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    Last edited by a moderator: May 6, 2017
  6. Oct 30, 2013 #5
    Thank you all for your replies. However I am beginning to think the only solution to this problem is a small manually operated pump simply because the size of the room to be purged is so small (less than 90 cubic foot). However it would have to be made entirely out of a non sparking material, so aluminum or plastic. Is anybody aware of such a product, or of a resource who would be willing to design one?
     
  7. Oct 30, 2013 #6

    UltrafastPED

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  8. Oct 30, 2013 #7
  9. Oct 30, 2013 #8

    UltrafastPED

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  10. Oct 30, 2013 #9
    Budget, I am unsure. Obviously this PVC pump would be preferable to a custom made pump of a groundable, non sparking material. The OSHA report frightens me, especially when there is concern regarding friction. They give advice on grounding, but whether or not I could do this properly without training is a concern. I think perhaps it is time to reevaluate the validity of this project, unless I can get a pump made of a non sparking material for a reasonable price.
     
  11. Oct 31, 2013 #10

    rollingstein

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    Can you describe your application more. Lot of things seem weird:

    (a) A 90 cuft room. That's hardly 5 feet sided cube. Can you even call it a "room"

    (b) 3 mbar is that the gauge pressure? When you say you want to evacuate it what's the target end point pressure? That's a crucial detail.
     
  12. Oct 31, 2013 #11
    It is a service box on top of a digester, it is very small. 3 mbar is the gage pressure, the original request was to bring the room down to atmosphere, and then open a valve to allow air entry and place a CH4 monitor inside the room to measure methane content and continue to pump out the gas (the entire pumping operation will direct the gas back into the headspace of the digester) in the room until it is safe. The device would have to be portable. This was an idea given to myself by a superior, and I am trying to determine how to do it, but it is very frustrating because nothing seems to be completely safe due to a host of reasons. A summary of the options I have examined and their reasons for being unsafe or impractical:
    - a small blower : every blower I have seen would be much too large to perform this action, and would cause too much of a vacuum inside the service box, on top of this all blowers need an external power source and if it is portable it would have to be plugged in, creating a potential spark source
    - a pneumatic diaphragm pump: none of these are designed to move gases, and although they may work, using a device not designed to move gases on an explosive gas seems foolish. Also, although it is possible to get a pump in conductive nylon so it is groundable, there are still steel clips and structural components in the pump that could spark if the device were to malfunction, which also concerns me
    -a hand operated PVC pump: although the material is non sparking, static electricity buildup is concerning to me
    -a venturi blower: would pull in too much air into the digester

    I think this may be a project not worth the risk. If anybody else can think of any other options, let me know. Short of a very expensive custom made hand pump constructed out of a groundable, spark proof material such as aluminum or copper, I cannot think of a perfectly safe or practical option.
     
  13. Oct 31, 2013 #12
    Umm -- Pretty sure fire companies use this type of device.... OH -- THanks Google.... Intrinsicly Safe.

    Ref: http://www.firerescue1.com/fire-pro...1356972-Ventilation-fans-6-types-to-consider/

    Ref: http://store.gomed-tech.com/ramfan-intrinsically-safe-16-electric-smoke-ejector-p1796.aspx [Broken]

    I can not think of any case where seeking professional input or support on anything explosive is not the proper course of action. I like DIY myself - but this would not be a case for it.

    Also -- look into laboratory hoods and ventilators - they will probably use the same Intrinsically Safe language for working with solvents.
     
    Last edited by a moderator: May 6, 2017
  14. Oct 31, 2013 #13
    I agree completely. I think a blower as you have recommended would be the best course of action if the process just involved purging the room. It is pulling a vacuum to quickly with one of these blowers during depressurizing that concerns me. Right now I am putting this hold until I have a chance for further consultation. Thanks everyone for their help!
     
  15. Oct 31, 2013 #14

    rollingstein

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    Somehow your approach sounds wrong. 3 mbar is a very tiny excess over atmospheric anyways.

    Can you provide details as to what exactly is the composition? Isn't just plain venting to atm. an option? Even if you want to vent to the digestor headspace why not have a one way, non return breather valve on the room? That way no vacuum will result. Air drawn in will continually replace the gas. If you don't like air push in N2.

    What's the pressure / vacuum rating of the box. Why not inert & purge in cycles? No pump will be needed.

    Another way to avoid a blower: Create a vacuum in a secondary chamber & use that to draw in the vapors. Pump is never on during vapor exposure.
     
  16. Oct 31, 2013 #15
    I agree, approximately 1 cubic foot of gas needs to be displaced to bring down to atmosphere. This project was not conceived by myself, and these are flaws I have already thought of. I need to discuss within my group. I have a feeling not too much consideration was made when conceiving this idea. Thanks for reply.
     
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