Stewart, Yes, I can imagine. Hi-ex foam generators are very sensitive. They need to be fed at the exact operating pressure (premix-side), not too much and not little. In addition, the same amount of air that is blown-in with the foam has to be able to escape from the room. The vents must prefarably be on the same side of the building as the foam generators, because under windy conditions the difference in outdoor air pressure on different sides of the building (upto 10 or 15 mbar) is enough to decrease the expansion ratio of the foam.
The hall in the Youtube movie has 20 large foam generators on the roof and 14 even larger smoke vents also on the roof to let the superfluous air escape smoothly. With the vents closed, the pressure in the hall builds up so much that you can't hold the doors when you open them. This causes a serious back pressure that will affect the foam production of the generators. Frans Stoop TOS architecture & fire protection Netherlands <[email protected]> Tel. +31-24-324 0112 At 22:57 23-11-2009 +0000, you wrote: >Frans > >Hi ex foam can sometimes not work to suppress >fires in complex structures due to back >pressures. I had a failure in a basement and >tunnel system some years ago. There have also >been problems with foam systems in cable tunnels >in power stations. I think the only areas where >foam is fully trusted is for aircraft hangers >and for internal bund protection where >containment of foam without back pressure is guaranteed. > >Stewart > >On 23 Nov 2009, at 22:45, Frans Stoop wrote: > > > OK, I see. I have to elaborate a little on this. > > > > The discussion was caused by the case of a client > > who has a warehouse full of pallets with paint stored in racks. > > The paint contains combustible liquids. > > The client wanted to be able to move his racks > > freely around in the warehouse and doesnot want in-rack sprinklers. > > He might want to change the layout of the racks from one day to the other. > > That's why he choose total flooding hi-ex foam and payed the higher price. > > > > In that given situation the question came up what > > he should do with his stacks of idle pallets. > > Can he safely store high stacks of idle pallets in that same warehouse? > > Must he limit the idle pallets in the hall to > > small stacks only and store the bulk of idle pallets elsewhere? > > > > Btw, you might want to see this: > > http://www.youtube.com/watch?v=PK46hFMpetI > > > > (Not all the warehouses like this have hi-ex > > foam; the adjacent warehouses are sprinklered.) > > > > Frans Stoop > > TOS architecture & fire protection > > Netherlands <[email protected]> > > Tel. +31-24-324 0112 > > > > At 11:57 23-11-2009 -0600, you wrote: > >> Is there a reason that you would prefer to use > >> hi-ex foam instead of sprinklers only? > >> > >> Matt Grisé PE*, LEED AP > >> Sales Engineer > >> Alliance Fire Protection > >> *Licensed in KS & MO > >> > >> 913.888.0647 ph > >> 913.888.0618 f > >> 913.927.0222 cell > >> www. AFPsprink.com > >> > >> > >> -----Original Message----- > >> From: [email protected] > >> [mailto:[email protected]] On Behalf Of Frans Stoop > >> Sent: Monday, November 23, 2009 11:50 AM > >> To: [email protected] > >> Subject: Storage of idle wooden pallets and hi-ex foam > >> > >> Dear colleagues, > >> > >> The 2 questions below caused some discussion > in my professional environment: > >> > >> For Palletized, Solid Piled, Bin Boxes, or Shelf > >> Storage NFPA 13 - 2007 paragraph 14.6 and 15.5, both tell us: > >> > >> "High Expansion Foam - Reduction to Ceiling Density. > >> A reduction in ceiling density to one-half that > >> required for Class I through Class IV > >> commodities, idle pallets, or plastics shall be > >> permitted without revising the design area, but > >> the density shall be no less than 0.15 gpm/ft2 (6.1 mm/min)." > >> > >> For Rack Storage of Class I Through Class IV > >> Commodities Stored Over 25 ft (7.6 m) in > Height paragraph 16.3.5.1 tells us: > >> > >> "Where high-expansion foam systems are used for > >> storage over 25 ft (7.6 m) high up to and > >> including 35 ft (10.7 m) high, they shall be used > >> in combination with ceiling sprinklers. The > >> maximum submergence time for the high-expansion > >> foam shall be 5 minutes for Class I, Class II, or > >> Class III commodities and 4 minutes for Class IV commodities." > >> > >> Paragraph 12.12.2.2 tells us how to protect idle > >> plastic pallets by the combination of hi-ex foam and sprinklers. > >> > >> Nothing in section 12.12.1 about idle wooden pallets and hi-ex foam. > >> Questions: > >> - Can high stacks or rack storage of idle wooden > >> pallets be protected by the combination of hi-ex foam and sprinklers? > >> - Can of idle wooden pallets be protected by > hi-ex foam without sprinklers? > >> > >> My opinion is that hi-ex foam only (without > >> sprinklers) will not extinguish a fire in high > >> stacks or rack storage of idle wooden pallets, > >> because wooden pallets contain a lot of air by > >> themselves and the foam will not penetrate inside > >> the stacks. The foam will only envelop the > >> complete stacks but will not prevent the air > >> (oxygen) inside the stacks from reaching the wood. > >> Foam, however, may hinder the fire from jumping > >> from one stack or rack to another, when > sprinklers do their extinguishing job. > >> > >> Please share your opinion. > >> > >> > >> Frans Stoop > >> TOS architecture & fire protection > >> Netherlands <[email protected]> > >> Tel. +31-24-324 0112 _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field)
