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!

*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.

Jobs

PRESSURE RELIEF VENTING IN CO2 SYSTEM

PRESSURE RELIEF VENTING IN CO2 SYSTEM

(OP)
Hi all,
I have designed a CO2 protection for a little electrical room (4m x 4 m x 4m). Now I would like to size the free venting area of the pressure relief venting. In order to do that I have followed the NFPA 12 requirements, using the formula:
X= 239*Q/radq(P)
Where Q= is the flow rate, in this case 22 kg/min
p = the allowable strenght of enclosure, i.e. 1,2 KPa
X =free venting area (mm^2)
Since the result is almost 0,005 m^2 I would like to ask if in this case the pressure relief venting could be avoided.

RE: PRESSURE RELIEF VENTING IN CO2 SYSTEM

Well you math demonstrates that it is needed [0.005m2 (7.75 in2)]. In order to say it isn't needed, you'd have to increase your "allowable wall strength", however 1.2 kPa (25 lbs/ft2) is rather high for commercial wall construction. I'd be more interested to know how you came up with 1.2 kPa and what the walls are constructed of. Brick walls can't handle a great deal of lateral loads. Steel on the other hand can. You need to take into consideration the "weakest link", which are doors frames, ducts and dampers.

Regards,
DM

"Real world Knowledge isn't dropped from a parachute in the sky but rather acquired in tiny increments from a variety of sources including panic and curiosity."

RE: PRESSURE RELIEF VENTING IN CO2 SYSTEM

(OP)
Hi DM2,
thank you very much for the answer. It is a concrete structure with masonry brick. I found this value of allowable strength in the NFPA 12 Table A.5.6.2.
Which is the limit value of m2 that can tell me if I need a pressure relief venting or not? Because obviously if you use this formula (X= 239*Q/radq(P)), you always obtain a number.
thanks

RE: PRESSURE RELIEF VENTING IN CO2 SYSTEM

Explain the function radq(P) as I am not familiar with it.

RE: PRESSURE RELIEF VENTING IN CO2 SYSTEM

Chicopee,
Good question. It should be the square root of P (wall strength in kPa). The equation can be found in NFPA 12, 2015 edition, section 5.6.2.2
The math does works however.

Regards,
DM

"Real world Knowledge isn't dropped from a parachute in the sky but rather acquired in tiny increments from a variety of sources including panic and curiosity."

RE: PRESSURE RELIEF VENTING IN CO2 SYSTEM

(OP)
Yes, radq is sqrt.

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


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close