Transfer Technology ~ Fire
Resistant Fiberglass Pipe
By Sullivan D. Curran P. E., Executive Director Fiberglass Tank & Pipe Institute
Introduction and Scope
This paper discusses state-of-the-art fire resistance FRP piping designs and
potential applications for petroleum storage and handling facilities. There is
an opportunity to transfer technology because of new developments in the piping
materials used in marine chemical tankers, navy vessels and off-shore oil and
gas platforms. Composite materials such as Fiberglass Reinforced Thermosetting
Plastic ("FRP") pipe are being used in sea water fire ring-main and deluge
applications, sea water cooling, produced water handling, potable water and
waste drain lines. The real breakthrough is the emerging application of
nonmetallic FRP for both underground and aboveground fire main and water
spray piping applications. Of course the reader has to question if it is
appropriate to use fire protection piping that may burn up in the fire it was
intended to extinguish! However, there are new design developments to both
reduce flame spread in FRP piping for direct fire exposure applications and to
withstand direct fire exposure for over three hours.
There are problems with the traditional use of steel piping. Experience with
steel piping in marine fire main and water spray applications shows that
internal corrosion can plug the nozzle and sprinkler heads and render them
ineffective. For metallic piping systems, the solution is continuous maintenance
to reduce the effects of corrosion and internal scaling. Even so, it is
questionable how much of a metallic system is in effective operating condition
at any given moment.
Flame Spread, Fuel Contribution and Smoke Generation Indices
Material Flame Spread, Fuel Contribution and Smoke Generation requirements are
established in the fire and building codes. To meet these codes, burning tests
are conducted in accordance with ASTM E84-81a, "Standard Method of Test for
Surface Burning Characteristics of Building Materials" or other similar test
methods specified in ANSI No. 2.5, NFPA 255, UL 723 and UBC 42-1. Flame test
results are expressed in terms of Indices for Flame Spread, Fuel Contribution
and Smoke Developed during 10 minute exposure to flames. The results are
recorded as a ratio with glass-reinforced-cement board being 0 and red oak
flooring being 100. While building codes such as the Uniform Building Code,
generally call for a flame spread rate of less than 200, specific requirements
depend on the location of the material in the building, occupancy and other
criteria. As a result, model building codes and local jurisdictions will need to
be referenced to determine approved materials that may be used based on the
results of flame tests.
Indices for Standard FRP Piping
Fuel Contribution Index: Unprotected FRP pipe made with epoxy resin
systems will be consumed when exposed to fire, but is self extinguishing when
the flame is removed. Under continuous fire exposure and with water flowing
through the pipe, it tends to degrade to a given level and then maintains that
performance level.
The movement of fluid inside the pipe remains cool (i.e., FRP is a low conductor
of heat) and gives an extinguishing effect to the structural wall of the pipe.
As a result, the FRP Fuel Contribution Index is zero and there are certain
applications where unprotected FRP pipe may be used for fire main systems.
Flame Spread and Smoke Development Indices: The Flame Spread Index
differs for the various resins used in the manufacture of FRP pipe. In addition,
additives may be used to retard flame spread. For example, one epoxy resin pipe
Flame Spread Index is 40 and the Smoke Developed Index is 755. Flame retardant
additives can added to the resin and reduce the Flame Spread to less than 25,
which is optimum for building code applications. However, smoke generation is
another consideration which may limit the additized pipe application in occupied
building areas.
Coated FRP Pipe
Coatings have been developed which will reduce the rate at which fire exposure
will affect FRP pipe. One product is PPG Fire-Retardant Latex 42-7 Paint which
can be applied to the installed piping system. This is known as an
intumescent coating. Intumescent is defined in Webster’s as "swelling
and charring when exposed to flame."
Consistent with Webster’s definition for intumescent, the coating when
exposed to fire will blister and form a heat shield to reduce the rate at which
fire will affect the pipe. The following table shows that coating the same epoxy
resin pipe used in the foregoing example, will reduce the Flame Spread and Smoke
Developed Indexes significantly.
Indices
|
Test Specimen |
Flame Spread |
Fuel Contribution |
Smoke Developed |
| FRP Pipe |
40 |
0 |
755 |
| Coated FRP Pipe |
5 |
0 |
30 |
| Index Improvement |
35 |
0 |
725 |
There are potential applications
of coated FRP piping for use in distribution terminal and warehouse fire mains
and sprinkler systems. In addition, there may be an opportunity to apply this
technology to motor vehicle refueling facilities. The evolution of sumps located
under petroleum fueling dispensers has developed into an area of concern for
fire jurisdictions. The Uniform Fire Code and National Fire Protection
Association ("NFPA") codes reflect the old practice of filling pits "with a
noncombustible inert material" to suitably protect low melting point materials
and protect against the ignition of vapors. However, fire marshals recognize
that filling a dispenser sump defeats the ease-of-clean-up required for
pollution control purposes and are looking for an alternate means of protection.
If it is accepted that a clean sump with adequate ventilation is not a vapor
ignition source, then a solution to protect the FRP piping could be the
application of an intumescent coating.
Insulated FRP Pipe
Insulating material advancements make it practical to insulate the entire
surface of the pipe and fittings system. This is typically done with a thick
intumescent coating such as Pitt-CharÓ or equivalent.
This coating system has proven to be successful in enduring jet fire exposure,
in both wet and dry conditions, consistent with Norwegian Fire Research
Laboratory test requirements conducted by Southwest Research Institute.
Intumescent coatings are typically applied by spray coating, which is an
effective method to protect large surfaces, but not small diameter pipe.
Further, in a fire scenario, once intumescing occurs it must remain on the pipe
when impacted by water hose streams used to fight the fire. As a result, there
is a new development which incorporates the intumescent coating into the
filament winding process. This filament winding process provides an intumescent
coating that is of consistent thickness, void free, smoother texture and cannot
be removed inadvertently. The end result is a FRP pipe capable of maintaining
the serviceability of the piping in a fire for a minimum of three hours under
flow conditions. Currently intumescent piping is available in
diameters up to 40 inches, with an operating pressure rating of 150 psi at 200°
F.
Intumescent piping has gained acceptance in the marine industry because it
combines the corrosion resistance historically solved with stainless steel and
copper-nickel materials with the light weight important in marine construction.
While replacing alternative high cost materials, there may be an opportunity for
technology transfer to the petroleum industry in applications where life cycle
costs include the maintenance required to ensure that a fire main and sprinkler
system will perform when needed.
Future Developments
Phenolic pipe: The use of phenolic resin as the polymer matrix in FRP
pipe is being investigated as a fire resistant non-metallic pipe. The features
provided by phenolics include a low toxicity, Flame Spread and Smoke Developed
Indices. A recent technological break-through in this area will allow the use of
this previously difficult material for fire resistant piping.
References
- February, 1996, Ameron
Fiberglass Pipe Division, Development of Fire Resistant Fiberglass
Pipe", paper by Joie L. Folkers
- April, 1989, Smith
Fiberglass Products Inc. Technical Bulletin
- Spring, 1996, Composites
Institute article "FRP pipe finds its niche in specialty applications,"
Karen F. Lindsay
- April, 1993, Ameron
Fiberglass Pipe Division, Product literature
- April, 1996, HOBAS Pipe
Inc., Case Histories
- Southwest Research
Laboratory tests, ASTM E84-81a, "Standard Method of Test for Surface Burning
Characteristics of Building Materials"
- 1993 National Fire
Protection Association NFPA 30
- 1995 Uniform Fire Code
FRPipeFireRating96
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