Explosion Vent on Pre-Engineered Building Walls

[nilaypathak]

I am working on Process PreEngineerd Metal building. I came across explosion vent requirements from Code compliance reports and ELM(Engineer loss Management) reports.

There are certain level of measure to void event of explosion. By this argument we submitted variance to safety officer.

He replied that provide assurance in you argument that there will not changes of explosion by this measures. Virtually it is not possible to state in the latter.

I would like to have input/help/suggestion on below items:

1)Looking for reference material which would provide me more detail to plug in explosion vent variance application to safety officer.

2) In case of disapproval variance, provide me agencies name would help me to decide upon locations and size of the vents on the building walls



Thanks you in advance.

 

[MiketheEngineer]

There are mfgs who make "bow-out" vents just for this purpose. Google them and I am sure you can find some help....

 

[JedClampett]

What's the lowest limit for these explosion relief vents? Because of the nature of PEMB walls, they're likely to fail before the explosion vent. Most of them are in the range of .5 psig or 70 psf.
See

http://www.fike.com/products/explosionvents.html

 

[nilaypathak]

Thank you for your reply.

2PSI set lowest limit for EV. I do not have any experience with EV.

We do have all kind of penetrations on all Walls. I have seen by googled that it cover full length of one side wall- typically. In my case I can not achieve intent of explosion vent if all walls have penetrations, Can I?.

 

[msquared48]

DO NOT place the vent through the sidewall "X" bracing.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[JedClampett]

nilaypathak, if your Explosion Vent is set for 2 psi (288 psf), I can guarantee that the vent will be there long after the walls fail.

 

[nilaypathak]

Thank you all,

I did confirm by ELM. It is confirmed that vent intent to set for 2PSI.

I just learn about fastener could be alternative to blow out vent. Any pro-cons known to other who can share.


Thank you in advance.


Cheers,

 

[hokie66]

As Jed implied, no metal cladding is going to withstand 2 PSI outward pressure, so the vents would be superfluous.

 

[hawkaz]

Agreed with the posts above- do the math, 2 psi = 288 psf. There aren't many conventional buildings designed for this load, let alone a PEMB.

 

[MiketheEngineer]

Hold your "vent" on with about 4 drops of Elmer's Glue and it may work??

 

[Sawbux]

I have had some experience in explosion vents. Is the explosion happening in the open room or with an enclosed space like a duct or vessel of some type?

If it is within an enclosed piece of process equipment, then you can design the equipment and vent piping to withstand the pressure and pass the vent through the wall. There are "rupture diaphragms" that can be placed to enclose the process until the pressure increases to the point the diaphragm will relieve it - hopefully below the pressure rating of the equipment. The open end of the vent can be weatherized by placing a "sock" over it. In a particle board plant we recovered a sock from about a mile away after a explosion!

If you are venting an open building space, a common rule of thumb is to provide 1 ft^2 of vent for 80 ft^3 of volume. This gets very out of hand with any substantial sized room - the vent area exceeds the available wall area! In a particle board plant it required removing about 1/2 the wall and roof area and covering with PVC panels and pull-through fasteners designed for 25 psf release.

Alot also depends on the rate of pressure rise. In a "detonation" - quick pressure rise, there is almost nothing you can do. The pressure will rise before any possible releif mechanism can respond. If it is a "defragration" you may have some hope of relieving it.

With a PEMB, the siding will act as the presure relief device. The siding will blow off at a low level of pressure.

 

[nilaypathak]

Thank you for informative reply.
This issue for in an open building not enclosed equipments. How do you come up with rule of thumb for area of panel? I have asked ELM (Engineer loss Management) to provide internal pressure and size of panels. In reply, I got nothing.
I talked to pull through fastener; they also provided me some internal pressure information for fastener generally designed.
Still looking for information how and who provide the information: internal blast pressure, area of explosion panel and location.

NP

 

[Sawbux]

I believe the criteria is laid out in the following NFPA Standard. I do not have a copy, as I have not been involved in this type of design in over 30 years. I appears that you can do a read only download if you register, otherwise it is $43 to buy it. Hope this helps!

NFPA 68 Standard on Explosion Protection by Deflagration Venting 2007 Edition