Firestopping Plastic Pipes

Firestopping Plastic Pipes
Firestopping Plastic Pipes
The Right Products With
The Right Installation
Designs And Methods
Make Protection Of
Combustible Penetrants
Safe And Easy!
The use of plastic pipes in
construction is increasing with
each passing year. Most people
are aware of the economies of
using plastic pipes as well as some
of the benefits... Plastic pipes are
easier to install. They are
significantly lighter in weight and
they are durable in that they won’t
rust or corrode. The down side is
that these pipes are combustible
and can pose a fire hazard if not
properly firestopped!
A Properly Designed Smoke Seal Stops All The Smoke!
Smoke
Seal
Smoke Seals built into the collar may cut off
smoke from the room below, but will not stop the
smoke eminating from the burning pipe itself.
This design places the seal at the top of the opening, above the area of the pipe that is burning.
This not only prevents the passage of smoke
from the room below, but also from the decomposition of the pipe itself!
Understanding The Hazards: Plastic pipes when
exposed to fire will react differently according to the type
of material they are made from. Some will soften and
then char as the fire progresses. Others will soften and
melt. If not properly firestopped, these pipes may burn
out and leave a passage for fire into adjoining rooms and
cause a fire to quickly propagate.
How Intumescent Materials Work: It’s important to
understand how intumescent materials function when
designing a firestop system. Intumescent materials
contain ingredients that expand and increase in volume
as they are heated. This increase in volume is used to
exert pressure on surrounding surfaces to help fill voids
and exert pressure on materials that are softening.
The Special Hazards of DWV: Vented pipes are more
of a hazard then supply piping or electrical conduits. With
vented pipes, the fire is drawn into the pipes and then
blown through them by what is called the chimney effect.
The larger the pipe, the greater the airflow. Fire may spread
quickly if the pipe is not quickly constricted by an
appropriate firestopping device or system.
Designing Firestops for Plastic Pipes: Since intumescent materials expand when exposed to heat. It is
important to utilize a design that quickly introduces heat
into the system as well as an intumescent material capable
of expanding in sufficient volume under the conditions
present in the installation. Since heat is the key factor, it’s
important to understand that the construction that
surrounds the pipe is a vital consideration. Intumescent
materials embedded in thick concrete may not heat up
quickly enough to close off burning pipes due to the heat
sinking effect of the concrete.
Squeezing Off the Path for Fire: As we mentioned earlier,
constriction is the key to protecting plastic pipes. Many
products utilize intumescent materials to accomplish this
task. Intumescent materials expand when heated or burned
to many times their original volume. Some intumescent
materials claim to replace burning materials and fill the void
created by them. There simply isn’t enough time to replace
burning materials. The key is to squeeze the pipe shut before
the fire can burn up the pipe. With the right products and
the right installation designs and methods, the protection of
combustible penetrants can be made safe and easy.
Page 1 of 2
Some test labs use a principle developed in the days of
testing foam firestop products for nuclear plants. These
materials functioned by attrition during a fire and seals in
thicker walls and floors tended to perform better than the
same thickness seal in thinner walls or floors. Thus it
was assumed that firestops tested in thinner assemblies
could be used in thicker assemblies. Since intumescent
STI Technology Update • Firestopping Plastic Pipes
FOD-5048 12/99
materials require heat to work, systems that are tested
for thinner barriers may not be suitable for thicker
ones!
Shutting Off the Pipe is Not Enough! Testing has
also revealed that shutting off the pipe is not enough.
A second key is to reduce the amount of heat
transferred through the assembly. Some pipes may
reignite if the temperature rises too much on the
unexposed face.
Selecting the Appropriate System: Now that we
have acquainted you with some of the critical factors
affecting these installations, we’ll provide some help
in selecting an appropriate system.
Choose the Fastest System: Where possible
always choose the fastest system that is appropriate
for a given application. For example, testing has
shown that externally mounted devices or collars
react faster than systems that mount internally. This
is logical since heat can get to them more quickly.
Our experience shows that T Ratings are a pretty good
indicator of speed in a given application. Usually faster
reacting systems will produce higher T Ratings.
Use the Right Amount of Intumescent Material:
Always use the amount of intumescent material
shown in the system that you have selected. Too little
may mean a pipe that can’t be completely closed.
Too much may cause a similar problem. Remember...
speed is critical! Using more wraps may sound like a
good idea, but in reality it may mean more
intumescent material to heat up and this may slow
the reaction down too much. An indication of this
reaction may be found in some published systems.
Some systems for 4” PVC pipe have a 2 hour F and T
Rating using 3 wraps. These same systems have a 3
hour F Rating and a 0 T Rating when using 4 wraps.
This is clear evidence that increasing the mass for
this type of material slows its performance.
Appropriate Fasteners... Keeping it All Together!
The right materials and the right design may all be
for naught if everything doesn’t stay where it belongs.
This means using the right fastening methods. Surface
mounted collars should be secured to the wall or floor
using a non-melting, non-burning fastener that is
suited to the construction of the wall or floor. Since
burning or melting pipe may sag, some stress may
be applied to the fastener. Also aggressive expansion
of the intumescent material will apply some stress as
well. Thus, we do not favor the use of screws in
gypsum board. We recommend toggle bolts or
mushrooming steel anchors. In concrete, we
recommend wedge type anchors over pin and shot.
Page 2 of 2
Remember... all fasteners must hold in order to do
the job. When in doubt, put additional fasteners in.
We are often asked if a particular fastener may be
used. We’re not the fastener experts. That question
rightfully should be directed to the manufacturer of
the fastener. The questions to ask: Will every fastener
hold every time? Will the fastener induce stresses that
might crack the concrete? Will the fasteners, continue
to hold during a fire?
Collar Mounting Tabs: Did you ever see a stool with
two legs? It’s easy to see that two legs aren’t enough.
The same is true with collars. We mentioned the
stresses applied to the assembly. Good sense tells us
that even on the smallest collars, 3 mounting tabs
are the minimum required to be sure the device will
not rock, or be pushed ajar by the forces that are being
exerted on it.
Smoke Sealing: A few collars have appeared on the
market that claim to incorporate a smoke seal into
the device itself. The smoke in a fire will come from
two sources. Smoke will be produced in the room
that is afire, so there is the need to block the passage
of this smoke. Many mounting surfaces are not
uniform enough to count on such built-in seals. An
example of this is core drilled concrete.
The second source of smoke will be the burning of
the pipe itself. Built-in seals do not stop the passage
of smoke from the decomposition of the pipe within
the wall or floor cavity itself. For this reason, we
always recommend a caulked seal. The seal should
be applied on both sides of walls and floors. Minimally,
we recommend the top surface of floors, if both
surfaces cannot be reached.
STI SpecSeal® Products & Systems…Safer,
Easier, More Economical! The issues that we have
raised here are complicated and difficult to
understand. The important thing to remember is that
we have considered these issues as we have designed
these products and engineered our systems. Various
combinations of SpecSeal® products have been
tested and approved for PVC, CPVC, ABS, ABS Foam
Core, and FR Polypropylene pipes. Systems have been
designed and tested for vented (DWV) and unvented
(supply) applications in most common forms of
construction.
STI Technology Update • Firestopping Plastic Pipes
200 Evans Way, Somerville, NJ 08876
Specified
Technologies
Inc.
Phone: (800) 992-1180
Fax: (908) 526-9623
Facts-On-Demand: (888) 526-6800
www.stifirestop.com
FOD-5048 12/99
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