CPVC in fire safety

 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: 

• Fire resistance

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. 

• Easy to install

CPVC pipes and fittings are lightweight and can be connected to conventional piping systems with basic hand tools and solvent cement. 

• Corrosion Resistance

CPVC is highly resistant to corrosion and won't rust or corrode over time. 

• Cost-effective

CPVC is generally less expensive than other materials used for fire sprinkler systems, such as copper or steel. 

• Durability

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