Deflagration vent

[IFRs]

I need to design / fabricate or preferably purchase some deflagrationa vents. I downloaded NFPA 68 and am absorbing it. Please are there any suppliers or typical designs out there?

 

[pkhunt]

If it's for dust explosion, recommended reading is Lunn, G., "Dust Explosion Prevention and Protection - Part 1 - Venting", 2nd ed., Institution of Chemical Engineers, UK.

 

[smaug6]

FM HAS APPROVED RELIEF WASHERS. USING IBC CODE REQUIREMENTS 1FT2 VENT AREA FOR EVERY 50 FT3 INTERNAL BUILDING VOLUME. RELEASE FORCE OF 20 PSF APPLY APPROPRIATE NUMBER OF WASHERS. APPROVED WASHERS ARE FROM CAMCAR THEY START AT 70 LB PER WASHER. MAKE SURE TO FOLLOW CLEARANCE GUIDELINES FOR SIDE OF BUILDING VENTS ARE ON. MINIMIZE DISTANCES BY TETHERING THE PANEL TO THE BUILDING. REFERENCE IBC, IFC.

 

[IFRs]

Dear smaug6,
Please tell me what IBC and IFC are and who FM is.

Thanks

 

[smaug6]

DEAR IFRs, FM-Factory Mutual, IBC-International Building Code,IFC-International Fire Code. BTW remember you need to design your structure for 100 psf internal pressure. We are a detached flammable and combustable liquids storage building manufacturer and have experience with this application. You have the major requirements in the first post.

 

[IFRs]

smaug6 -
Thanks for the info. Perhaps a little clarification is in order. I am designing fixed and floating covers for an API oil/water separator. It is an outdoor concrete basin in which oily water is held. The fixed covers rest 2 feet or so above the liquid level. The largest is about 10 feet by 70 feet. You used an internal volume to size the vents, NFPA uses ineternal surface area. Comment?

 

[smaug6]

I am using guideline from FM approval standard 6049 for the design of flammable and combustable liquids storage buildings to size vent area. Which NFPA doc are you referring to NFPA 68? BTW, did you understand the venting concept I was referring to in the first post. Using your dimensions and FM guidelines you need 28 ft2 of vent area per item. However, FM recommends against vents opening upwards due to possible snow surcharge affecting release force. But you are venting reinforced concrete enclosures not buildings so this might be okay. I looked up the IFC requirement for area and it says 'The aggregate clear area of vents and venting devices shall be governed by the pressure resistance of the construction assemblies... You probably would be able to reduce the area and perhaps use hatch covers for venting? I guess all this depends on strength of the enclosure.

 

[frankw4875]

In answer to your original question... try Fike Metal Products as a possible supplier... they may be able to help you design/size your installation.

By the way... regarding the issue of sizing based upon volume versus sizing based upon internal surface area... the NFPA 68 guidance distinguishes between weak enclosures and strong enclosures. Vent sizing methodologies are based upon internal surface area for weak enclosures, and internal volume for strong enclosures.

The type of flammable or combustible material makes a big difference in the required vent area also.

NFPA 68 takes some experience to apply properly... find a reputable vendor.

 

[pierrepaul]

Did you manage to design your installation. I'd be interested to know which choices you made.

BF
SPK Eng

http://www.spk.fr/index 2.htm

 

[IFRs]

The customer decided that deflagration vents were overkill. The area of the vents required by NFPA calculated out to be too large for all practical purposes. They chose instead to include provisions for future Nitrogen blanketing.

 

[JoeTank]

IFR,
I have encountered similar results using NFPA for deflagration venting. Sometimes the vent size exceeds the diameter of the tank!!!

Steve Braune
Tank Industry Consultants

http://www.tankindustry.com