I disagree with your assumption that you only add the in-rack demand
when the arrangement without excessive clearance would otherwise call
for in-rack sprinklers. The supplemental in-racks are offsetting the
clearance operating simultaneously with the ceiling sprinkler.
Having said that 12.1.3.4 is SLIENT on this issue. Call that an
OOPS. I will pursue it at the ROC stage.
As for Class IV exceeding Group A plastic, it happens. The Class IV
criteria is judgement driven with minimal testing behind it so a
strong dose of conservatism was warranted. Group A plastics have had
a ton of tests and when the same storage arrangement for Group A has a
lower demand than Class IV, you can apply the Group A criteria (see
16.1.2.2)
Roland
On Feb 17, 2011, at 7:13 AM, Bill Brooks wrote:
Me too until the 2010 language. Now it appears a single row of in-
racks can
be used to make up for the excess ceiling clearance requirements for
Chapters 16 and 17. With this set of in-racks in place the racks
can be
calculated at the actual storage height rather than the theoretical
Ceiling
- 20 Chapter 16 (or Ceiling - 10 Chapter 17) height required by
13-2007.
The way I read this is the "ceiling clearance in-rack" flow does not
have to
be added to ceiling flow if the commodity class and "assumed
acceptable
clearance" would not otherwise require in-racks. When the actual
storage
height would necessitate the in-racks, then the in-racks could serve
double
duty as the required in-racks as well as the "ceiling clearance in-
racks".
In this case the in-rack flow is added.
All this being stated, my concern is whether this approach is OK for
the
Chapter 17 plastics.
Bill Brooks
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