CPVC in fire safety
Steel /
Iron pipes have been the preferred material for fire water distribution
ever since fixed fire sprinkler piping systems were introduced and adopted in
the late 19th century. After all, steel is strong, durable, and stands up well
to intense heat.
Sprinkler
systems offer fire detection and extinguishing functions in a single
system. Sprinklers only extinguish areas which need to be extinguished.
Sprinklers outside the source of the fire therefore remain closed. The
extinguishing water released reduces smoke and dangerous substances.
CPVC's
flash ignition temperature is significantly higher compared to other
thermoplastics, at 900°F (482°C). This high ignition threshold means CPVC
is less likely to catch fire, offering an added layer of safety in
environments where exposure to high temperatures might occur.
Fire
resistance in materials is not just about preventing ignition; it encompasses
several critical aspects that determine how a material behaves in a fire
scenario. CPVC (Chlorinated Polyvinyl Chloride) fire-resistant properties are
assessed through various parameters, like ignition resistance, burning
resistance, limiting oxygen index, flame spread resistance, smoke generation
resistance, including thermal conductivity of CPVC.
NFPA 13
2022: Table 7.3.1.1 : Pipe or Tube Materials and Dimensions
Before we begin, let’s quickly review
NFPA requirements:
·
The
2019 edition of NFPA 13: Standard for the Installation of
Sprinkler Systems (3.1.1) permits listed metallic and
nonmetallic materials for sprinkler pipe and tubing that meet or exceed various
American Society for Testing and Materials (ASTM) standards.
·
It’s
key that all pipes in fire sprinkler installations have been tested by a
third-party safety organization for use in sprinkler systems and are “listed”
as such. Metal pipes are listed to UL 852 and thermoplastic
pipes are listed to UL 1821. Listed pipes are easily identified by
the listing agency’s logo.
·
Some
pipes could fail to meet ASTM standards but NFPA 13 permits their use as long
as they are otherwise listed and installers mind any
limitations in the listing (3.2.1.1 and 7.3.3.1).
NFPA 13 requires manufacturers to include listing limitations in their
installation instructions (7.3.2.1.2). Bottom line: sprinkler
installers should carefully review a manufacturer’s instructions to account for
this.
To choose
a pipe material, you must determine which hazard level defines your
property. UL (formerly Underwriter Laboratories) only lists pipes for hazard
levels at which they can be counted upon to perform reliably.
Most
offices, for instance, are “light hazard” and can use any of these pipes, but
businesses that regularly stock more combustible materials have higher hazard
levels and thus cannot install CPVC pipes in their sprinkler systems.
The chart
below, also published in part one of our piping materials series, sums up
important differences between the most popular options:
Source:
National Institute of Standards and Technology
CPVC
inherent immunity to corrosion has had a huge impact on the fire protection
industry, creating sprinkler systems that typically remain in service for at
least 50 years. CPVC fire sprinkler pipes have a slick, relatively impermeable
surface that keeps bacterial contamination at bay and prevents deposits from
accumulating and clogging pipes. CPVC pipes also naturally resist degradation
from chemicals classified as acid, alkali, or inorganic material. All of these
characteristics enable water to flow through CPVC pipes with little friction,
earning them a C-factor of 150—a number that is equal to copper pipes’
smoothness.
CPVC's
ability to resist burning is measured by its Limiting Oxygen Index (LOI), which
at 60%, is exceptionally high. This means CPVC needs a much higher oxygen
concentration to sustain combustion than is available in the Earth's
atmosphere. Consequently, CPVC will self-extinguish once the flame source is
removed, unlike materials like polyethylene (PE) and polypropylene (PP), which
may continue to burn.
Extensive
testing and approval from UL helped dispel initial fears that CPVC pipes
would melt during a fire. In reality, CPVC must be forced to burn by putting
the pipe in direct contact with fire, and it stops smoldering as soon as the
flame is removed. Instead, a charring layer forms on the outside of the pipe,
creating a thermal barrier that protects the inside and enables water to flow
unheeded onto a fire.
CPVC fire
sprinkler pipe also costs less than metal pipe, it’s easier to handle due its
light weight, and installation is faster and safer—joints are chemically welded
together by hand without flame or heavy equipment. Easier installation
generally leads to labor-cost savings.
Flame Spread Resistance
The
resistance of CPVC to flame spread is crucial in minimising damage during a
fire. Certified under UL 94 for its flammability characteristics, CPVC achieves
the highest vertical burn rating (V0), indicating its excellent capacity to
prevent the spread of flames, thereby aiding in the control of fire within a
building.
Smoke Generation Resistance
As per
Euroclass (European Reaction to Fire Classification System) CPVC overall rating
to combustion is B, S1, d0.
Basis
above, the Concept of flammability is Ignition time, fire propagation and
energy contribution of the product. This is represented by a measurement of
heat released from the product and its potential contribution to propagation of
a fire.
CPVC falls
in B which denotes it’s an Inert material
In Smoke
release category CPVC is rated under S1, which denotes limited smoke release.
In fire
propagation through burning droplets CPVC falls under d0
CPVC Piping in High-Risk Environments
For
industries such as semiconductor manufacturing or other facilities requiring
cleanrooms, where the risk of fire remains a substantial concern, CPVC’s fire
resistance property makes it a great pick. Its compliance with FM Approval 4910
for low combustibility and minimal contaminant release underscores its
suitability for high-value environments where fire and smoke damage could lead
to a substantial loss.
CPVC pipe
is only listed for light-hazard occupancies since it does start to soften at
temperatures slightly higher than 200°F. The upper service temperature limit of
currently listed CPVC sprinkler pipe is 150°F (65.5°C) at 175 psi (12.1 bar).
CPVC pipe
can be safely used in single- and multi-family housing, as well as commercial
occupancies where fires develop slower with lower heat, such as offices,
schools, fire stations, hotels, hospitals, libraries without large stockrooms,
prisons, museums, and nursing homes. It can also be deployed in rooms rated
“ordinary hazard” that are smaller than 400 square feet and within an otherwise
light-hazard setting, such as kitchens in an institutional facility.
CPVC fire
sprinkler pipe is not listed for use in exposed outdoor settings, as prolonged
exposure to sunlight can impact its strength. It is also not recommended for
commercial dry systems since it can become brittle at cold temperatures,
creating a serious safety hazard if the energy of the pressurized gas is
released suddenly due to a pipe rupture. But Tyco does carry a UL-listed,
CPVC-based dry pipe system for residential occupancies that aren’t always
climate-controlled, like vacation homes.
It’s also
important to note that not all CPVC pipes and components are listed for the
same exact use in fire sprinkler systems. It’s essential for contractors to
confirm via the manufacturer that a product they want to install is not only
listed for fire sprinklers but also for the specific application they intend.
TFI,
FlameGuard, and FireLock CPVC pipe brands are all listed for sprinklers with a
respectable ASTM 05 rating, but BlazeMaster CPVC has a different manufacturing
process that gives it the higher ASTM 06 rating. This means it has 25 percent
greater estimated long-term strength, or hydrostatic design pressure, and is
slightly less likely to burst at higher temperatures.
Since CPVC
is a limited combustible piping material, it must be carefully installed to
prevent the pipe from failing during a fire. Protecting the pipe with a layer
of gypsum wallboard or plywood is a viable option. Lay-in ceiling tiles clipped
in place can be used as well. Don’t store CPVC outside, especially if it will
be exposed to sunlight for a long time.
The
relative fragility of CPVC pipe compared to metal is also a concern, with
damage possible if materials are dropped, banged, or stepped on during
installation. Mechanical stress caused by hanging methods or bending the pipe
beyond the manufacturer’s recommended limitations can cause stress failures
over time. NFPA 13 (A.7.3.2) also cautions installers to avoid
construction materials that can degrade the performance of CPVC pipe, including
materials used in the fabrication of sprinkler systems; additives to water
supplies, cable, and wiring; and certain insecticides and fungicides.
But when
proper precautions are taken, CPVC can be a safe, reliable, lower-cost
alternative to metallic pipes for light-hazard occupancies—an option that
limits costly corrosion issues.
C-PVC Pipe Standards
|
Organization
|
No.
|
Title
|
|
EN
|
1566
|
Plastics piping systems for soil and waste discharge (low and high
temperature) within the building structure – Chlorinated polyvinyl chloride)
(PVC-C)
|
|
Part 1: Specifications for
pipes, fittings and the system
|
|
Part 2: Guidance for the
assessment of conformity (CEN/TS)
|
|
EN ISO
|
15877
|
Plastics piping systems for hot and cold water installations –
Chlorinated polyvinyl chloride) (PVC-C)
|
|
1: General
|
|
2: Pipes
|
|
3: Fittings
|
|
4: Fitness for purpose of the
system
|
|
5: Guidance for the assessment
of conformity (CEN ISO/TS)
|
|
ISO
|
7675
|
Plastics piping systems for soil and waste discharge (low and high
temperature) inside buildings – Chlorinated polyvinyl chloride) (PVC-C)
|
|
IS
|
15225
|
Chlorinated Polyvinyl Chloride (CPVC) compounds used for pipes and
fittings – Specification
|
|
IS
|
15778
|
Chlorinated Polyvinyl Chloride (CPVC) pipes for potable hot and cold
water distribution supplies
|
|
DIN
|
8079
|
Chlorinated polyvinyl chloride (PVC-C) pipes – Dimensions
|
|
DIN
|
8080
|
Chlorinated polyvinyl chloride (PVC-C) pipes – General quality
requirements and testing
|
|
ASTM
|
D1784
|
Standard Specification for Rigid PolyVinyl Chloride) (PVC) Compounds
and Chlorinated Poly(Vinyl Chloride) (CPVC) Compounds
|
|
ASTM
|
D2846
|
Standard Specification for Chlorinated PolyVinyl Chloride) (CPVC)
Plastic Hot- and Cold-Water Distribution Systems
|
|
ASTM
|
F1970
|
Standard Specification for Special Engineered Fittings, Appurtenances
or Valves for use in PolyVinyl Chloride (PVC) or Chlorinated PolyVinyl
Chloride (CPVC) Systems.
|
|
ASTM
|
F402
|
Standard Practice for Safe Handling of Solvent Cements, Primers, and
Cleaners Used of Joining Thermoplastic Pipe and Fittings
|
|
ASTM
|
F437
|
Standard Specification for Threaded Chlorinated Poly(Vinyl Chloride)
CPVC Plastic Pipe Fittings, Schedule 80
|
|
ASTM
|
F438
|
Standard Specification for Socket-Type Chlorinated Poly(Vinyl
Chloride) (CPVC) Plastic Pipe Fittings, Schedule 40
|
|
ASTM
|
F439
|
Standard Specification for Chlorinated Poly(Vinyl Chloride) (CPVC)
Plastic Pipe, Fittings, Schedule 80.
|
|
ASTM
|
F441
|
Standard Specification for Chlorinated Poly(Vinyl Chloride) (CPVC)
Plastic Pipe, Schedules 40 and 80.
|
|
ASTM
|
F442
|
Standard Specification for Chlorinated Poly(Vinyl Chloride) (CPVC)
Plastic Pipe,(SDR-PR).
|
CPVC is a good material for fire sprinkler systems because
it's fire resistant, easy to install, and has other benefits:
CPVC has a high flash ignition temperature of 900°F (482°C),
which is higher than other thermoplastics. It's also a low flame spread
material. When exposed to fire, CPVC forms a thermal barrier that
restricts heat conduction. It needs three times more oxygen than the
Earth's atmosphere to burn, so it doesn't easily spread flames.
CPVC pipes and fittings are lightweight and can be connected
to conventional piping systems with basic hand tools and solvent cement.
CPVC is highly resistant to corrosion and won't rust or
corrode over time.
CPVC is generally less expensive than other materials used
for fire sprinkler systems, such as copper or steel.
CPVC pipes and fittings are durable and can withstand high
pressures and flow rates.
CPVC pipes and fittings are approved for installation in
non-industrial occupancies, such as hospitals, hotels, schools, and residences.
REF:
NFPA 13:
sprinkler system design approaches, system installation, and component options
to prevent fire deaths and property loss.
ASTM: Annual Book of ASTM Standards
