×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Rain falling speed

Rain falling speed

Rain falling speed

(OP)
Does anyone out there know how fast I would have to run air out a vertical open ended duct in order to overcome an average rain fall (and not rain into the duct).  What are your sources or where should I look?  Thanks.

RE: Rain falling speed

If you're looking to keep water out, I would recommend a zero-loss stack. I don't have my ventilation handbook in front of me so I'll need some backup on this. On whatever the size of the exit stack, mount a piece of duct 1" bigger in diameter to the stack and extend it at least 4 diameters up. For example, a 6" stack leaves the process and exits the building. Mount a 7" x 28" long piece to the 6" piece (with angle, channel, etc). In theory, rain doesn't fall straight down so the rain that hits the inside of the 7" duct will run down the sides and out the annular area between the 6" and 7" piece. We have this design all over our plant with no complaints of water in the ductwork.

Or you can put a hat on it.

RE: Rain falling speed

Typically, a stack velocity greater than 20 fps will push water vertically up the inside of a stack.  You must have a contingency plan for times when the exhaust fan is not operating.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources