Results 1 to 9 of 9
  1. #1
    Join Date
    Nov 2019
    Posts
    3
    Post Likes

    Industrial Exhaust application

    New to the site, appreciate any input

    I work as a systems integrator, and have an industrial/utility application where I have to 100% assure that a small 200 cfm exhaust fan is running and moving air 24/7, upon it's failure to exhaust air I have to generate an alarm that will be passed along to the DCS, so the appropriate action can be taken.

    I have several rooms and each have physical characteristics that are somewhat different for each. Overall I feel that the most reliable technique for all is likely monitoring the differential pressure across the fan. The fan at this point is very simple, and consists of a inside grill or vent, a 8" fan, an outside louver, and rain cap and there is no duct work. Of course with this setup the DP is very small and would be difficult to reliable monitor (i would think) although I seen some Dywer devices with a 1/2" water column range


    Example 1

    Room dimensions 14.5' long x 10.4' wide x 10.5' Tall (914 cf)
    The room has one door that can be opened at any time and closes automatically behind the person. The room is basically very tight, and has no other opening in the room other than the exhaust fan opening that has a 180 cfm fan running 24/7

    We preformed a test, by boring a 1/4 hole thru the wall beside the exhaust fan, and installed a 1/4 tubing to the outside, and connected a Fluke 922 and recorded the following DP readings.

    Door closed 0.097 "WC
    Door open = 0.019 "WC

    So the alarm set point would need to occur at something less than 0.01 "WC

    I feel that I need to increase the DP by adding additional duct for restriction, if I add duct I would have to increase the fan size so I still maintain the 180 CFM or close to it. I have searched looking for information on-line but have not came across any thing discussing type application from this angle. I have the funding to do whatever is required within reason, and would be interested of everyone input.

    Please Advise

  2. #2
    Join Date
    Nov 2019
    Posts
    1
    Post Likes

    Cool

    Quote Originally Posted by Wattman View Post
    New to the site, appreciate any input

    I work as a systems integrator, and have an industrial/utility application where I have to 100% assure that a small 200 cfm exhaust fan is running and moving air 24/7, upon it's failure to exhaust air I have to generate an alarm that will be passed along to the DCS, so the appropriate action can be taken.

    I have several rooms and each have physical characteristics that are somewhat different for each. Overall I feel that the most reliable technique for all is likely monitoring the differential pressure across the fan. The fan at this point is very simple, and consists of a inside grill or vent, a 8" fan, an outside louver, and rain cap and there is no duct work. Of course with this setup the DP is very small and would be difficult to reliable monitor (i would think) although I seen some Dywer devices with a 1/2" water column range


    Example 1

    Room dimensions 14.5' long x 10.4' wide x 10.5' Tall (914 cf)
    The room has one door that can be opened at any time and closes automatically behind the person. The room is basically very tight, and has no other opening in the room other than the exhaust fan opening that has a 180 cfm fan running 24/7

    We preformed a test, by boring a 1/4 hole thru the wall beside the exhaust fan, and installed a 1/4 tubing to the outside, and connected a Fluke 922 and recorded the following DP readings.

    Door closed 0.097 "WC
    Door open = 0.019 "WC

    So the alarm set point would need to occur at something less than 0.01 "WC

    I feel that I need to increase the DP by adding additional duct for restriction, if I add duct I would have to increase the fan size so I still maintain the 180 CFM or close to it. I have searched looking for information on-line but have not came across any thing discussing type application from this angle. I have the funding to do whatever is required within reason, and would be interested of everyone input.

    Please Advise
    There is a bit to unpack here, but if you are only running a single fan that will be expected to maintain a constant volume (CV) of air,
    you could install some Airflow measurement, but that sounds like overkill for your situation. You could sense velocity pressure either upstream, or downstream of the fan with atmospheric pressure as your reference. There are very small transducers available that would get into the range that you need. a .1" WC transducer should be sufficient for the purpose. Just take a scaled output from the device into your programmable controller and determine what your minimum velocity pressure will be to prove flow. You could also set this arrangement up to give High/Low flow alarms. Just be aware that a pitot is extremely susceptible to fouling, so periodic maintenance will be needed. There are some other technologies that are available for giving you an actual flow measurement at considerably more cost. Once the pitot plugs (and it will) you would get a low flow alarm if it were set up as i described. If you want to actually to measure flow rather than just prove movement, then I would suggest something like a Vortex-Shedding sensor to be a maintenance free as possible.
    Hope that helps.

  3. #3
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    8,356
    Post Likes
    Do you want to monitor static pressure or just that the motor is operating? You should be able to buy a load monitor with a set of dry contacts on it to send and alarm if the motor goes over/under load parameters
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    I know enough to know, I don't know enough
    Liberalism-Ideas so good they mandate them

  4. #4
    Join Date
    Sep 2002
    Posts
    27,168
    Post Likes
    I agree with this.

    How about something easy and not requiring any maintenance?

    https://tinyurl.com/yx4f75f7

    If the range is two low just loop the power wire through 2-3-4 times.

    PHM
    --------


    Quote Originally Posted by 2sac View Post
    Do you want to monitor static pressure or just that the motor is operating? You should be able to buy a load monitor with a set of dry contacts on it to send and alarm if the motor goes over/under load parameters
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  5. #5
    Join Date
    Feb 2016
    Location
    Louisburg Kansas
    Posts
    3,869
    Post Likes
    The object appears to be maintaining the room differential pressure. If so do it like the hospital isolation rooms do it. The only reason you are concerned about the fan is the result of it's performance.
    No man can be both ignorant and free.
    Thomas Jefferson

  6. #6
    Join Date
    Nov 2019
    Posts
    3
    Post Likes
    Thread Starter
    Yes, we feel we need to monitor the actual static pressure to be sure that the air is truly moving. The duct design will require the duct to be flat against the flat ceiling with intake slots cut as near the ceiling as possible, to allow the intake air to be evacuate from against the ceiling. There are batteries in the room that produce hydrogen gas (H2) while charging, this gas will collect first against the ceiling and quickly be expelled.

  7. #7
    Join Date
    Feb 2016
    Location
    Louisburg Kansas
    Posts
    3,869
    Post Likes
    If you are charging flooded lead acid batteries you need to do a lot more than monitor one fan. Start with the authority that has jurisdiction which should be the fire marshal and proceed from there. One thing I will tell you is you need two fans, one running and a standby. The fans should be explosion proof both the fan wheel and motor. Explosions although unlikely can be devastating. Don't gamble with this.
    We can't cover all the codes here so you need to dig into them.
    No man can be both ignorant and free.
    Thomas Jefferson

  8. #8
    Join Date
    Nov 2019
    Posts
    3
    Post Likes
    Thread Starter
    Just so the Thread does not get pushed off topic, I would like to say I appreciate your advise WAYNE3298 we are well aware of the complications of the application, and of the specifications required. I was not looking on this site for advise on the laws, standards and regulation IEEE requirements. Simply looking for some input on static & field related data.

  9. #9
    Join Date
    Feb 2016
    Location
    Louisburg Kansas
    Posts
    3,869
    Post Likes
    Please understand we don't know the extent of your knowledge. Not knowing your qualifications my advice was simply make sure you know what you are doing. We don't know the extent of what you are asking for unless you make it clear.
    No man can be both ignorant and free.
    Thomas Jefferson

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •