I can almost guarantee wet lycra will not go anywhere in the early stages of
a fire. Ever put a paper cup or plastic bag full of water in a fire?
Let's assume the first heads goes off without any delay. Let's even assume
the lycra below the fire is gone. These are reasonable assumptions given
the lightweight nature of lycra. Control mode sprinklers don't necessarily
attack the fire direct. Much of the success is based on pre-wetting things
that aren't burning yet. So as the fire spreads to areas under wet lycra
the overhead system is not pre-wetting this stuff. The sprinklers are
suddenly playing catch up and we know they don't do so good playing catch
up.
Also keep in mind the diameter of the hot gasses rising are only about 5.5'
at the lycra level. Your area for water getting to the floor may only be
5.5' in diameter or less if the lycra just shrinks away from the heat like
other plastics and doesn't release fully. This is another reason I don't
think individual fusible links are the solution. The lycra 1' beyond this
diameter will only be seeing ambient plus a little radiant, very little
given the orientation.
Here's a twist, this is also a good case where one should consider heads at
more than one level operating.
I have never had one of these so I speak theoretical.
Chris Cahill, P.E.
Fire Protection Engineer
Sentry Fire Protection, Inc.
763-658-4483
763-658-4921 fax
Email: chr...@sentryfiremn.com
Mail: P.O. Box 69
Waverly, MN 55390
Location: 4439 Hwy 12 SW
Waverly, MN 55390
-----Original Message-----
From: sprinklerforum-boun...@firesprinkler.org
[mailto:sprinklerforum-boun...@firesprinkler.org] On Behalf Of Allan Seidel
Sent: Thursday, April 16, 2009 10:17 AM
To: sprinklerforum@firesprinkler.org
Subject: Re: Is there test information that shows whether or not obstructing
lycrafabric ceiling elements are an issue?
What I have learned so far is that Lycra is strong polyurethane fiber
segments joined with stretchy (soft) polyester or polyether fiber segments.
The amounts of each varies with the blend. The polyurethane provides the
mechanical body to the fiber while the other stuff provides the elasticity.
The elasticity is constant in the range from 50F to 113F which is why it
works well for clothing. Beyond 113F up to about 356F (depending on the
blend) it contracts to 15% of what it was at 113F. Somewhere near 374F the
polyester/polyether parts turns plastic and melt. The fiber breaks at that
point. There is nothing to connect the polyurethane fibers to each other.
Incidentally, the solvent dimethyl acetamide is used to make the stuff and
some remains in the fiber after manufacture. It is the buyer's
responsibility (the mill I guess) to keep the product ventilated enough
while the residual solvent concentration is still at hazardous levels.
One might say the kites would tighten up as they are in the shrinkage
temperature range assuming that they are not being cooled by sprinkler spray
faster than what is heating them up and they would rip apart at that 374F
temperature range. Based on that assumption, would increasing the design
area by 30%, as in delayed water-to-fire situations and also increasing the
application rate to OH1 be a logical fire protection approach to this
situation to bring to the Fire Marshall?
Thanks again for your comments,
Allan Seidel
St. Louis, MO
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