Sorry, I misread the original post - thought it said foam cups. Solid
plastic cups are, in fact, the standard commodity used for unexpanded
plastic protection development.
Be that as it may, foam coolers, plates, trays, and cups are expanded
plastic. The standard commodity used for developing expanded plastic
protection guidelines is polystyrene trays. I've witnessed commodity
classification testing that established that polystyrene foam coolers
and polystyrene insulation are expanded plastic. I've been to many
craft stores and have seen the variety of foams there. What I have
seen are expanded plastic in terms of required protection. I am unaware
of any polystyrene foam in common use that isn't an expanded plastic.
All polystyrene foams start out as a mixture of solid polystyrene and a
blowing agent. Through either extrusion or casting, foams of varying
densities are produced. They are all significantly less dense than
unexpanded polystyrene, which means they have increased surface are for
a given mass. Increased surface area means increased air access, which
means faster combustion, which means higher heat release rate than an
unexpanded plastic.
Joe
[EMAIL PROTECTED] wrote:
There are different kinds of extruding processes for styrene based
foams. Expanded foams inject air (or other gases) into the process so
that the end product has more dimension but not more mass. Christmas
tree balls used to use this type of process, that way they could be
large but not heavy.
Other foams are compressed to various degrees to increase mass and
strength but not cubic dimension. Often these are used for impact
protection or similar types of applications where density is the
objective, or as we are discussing for foam cups or plates, coolers,
insulation, etc.
When expanded foams are melted the final mass will be less dimensionally
than the original product.
If you go to a craft store and look at the different types of foams it
becomes rather obvious.
Craig L. Prahl, CET
Fire Protection Group
Mechanical Department
CH2MHILL
Lockwood Greene
1500 International Drive
PO Box 491, Spartanburg, SC 29304-0491
Direct - 864.599.4102
Fax - 864.599.8439
[EMAIL PROTECTED]
http://www.ch2m.com
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Joe
Hankins
Sent: Thursday, May 08, 2008 2:13 PM
To: [email protected]
Subject: Re: Exposed unexpanded plastic
How are foam cups not an expanded plastic?
Joe
[EMAIL PROTECTED] wrote:
By definition I could consider this unstable as you described no
actual container, just the cups encapsulated in plastic holding up the
next pallet. When heated, they are going to change shape and could
potentially collapse the stack.
Honestly don't see a way to get around not changing the sprinklers.
Control mode (for unstable) would put you at .51/2500, but can the
piping network deal with that increase without excessive pressure
drops and velocities?
ESFR might be a nightmare in an existing pipe network plus the water
and pressure issues.
Your 15/50 was for expanded plastics, foam cups would not be expanded.
Craig L. Prahl, CET
Fire Protection Group
Mechanical Department
CH2MHILL
Lockwood Greene
1500 International Drive
PO Box 491, Spartanburg, SC 29304-0491 Direct - 864.599.4102 Fax -
864.599.8439 [EMAIL PROTECTED] http://www.ch2m.com
Fletcher, Ron wrote:
We have an existing building with Viking large drop heads at
.45/2000.
Storage is being changed to 18 ft high Group A unexpanded plastic. 40
oz cups nested inside each other, shrink wrapped on four sides,
cardboard over the top on pallets on the floor, 32 ft. roof, no
racks.
We want to add a pump without changing the sprinklers but I can't
find
any criteria that suits the 32 ft. roof with LD heads. The closest we
can come to finding appropriate criteria is 15 heads at 50 psi but
it's for a 30 ft.
roof. The existing pipe size won't support 1.1/2500 and we are not
sure if we could classify the storage array as unstable to get to
.6/2500.
Is there a way to determine pile stability without a burn test or is
test data out there that I haven't found? Ideas appreciated.
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