November/December 2021 | Vol. 26 No.6

by Nestor Chigne, Product Engineer, Atkore Inc. and Jim Stanley Technical Consultant, JMS Service

For more than a century, phenolic resin products have been mainly used in the production of circuit boards but are better known for producing molded products such as billiard balls, laboratory countertops, coatings, and adhesives.

Phenolic resins are versatile polymers. They are a synthetic thermosetting resin invented by Dr. Leo Baekeland in 1907 and the first plastic sold commercially.

Phenolic resins are divided into two types, novolacs and resoles. Both have high-temperature stability up to 572°F – 662°F, high water stability, and chemical stability.

PHENOLIC PRODUCTS IN THE ELECTRICAL INDUSTRY

For the electrical industry, flame-resistant electrical conduit can be manufactured from phenolic resins. Electrical manufacturers have been able to modify phenolic resins in the manufacturing of phenolic fiberglass conduit. NEMA Members have offered phenolic conduit for many years, primarily for tunnel installations. Phenolic conduit protects electrical wires that provide lighting in the event of an emergency. Phenolic electrical conduit is available in various trade sizes and wall thicknesses.

NFPA 502 Standard for Road Tunnels, Bridges, and Other Limited Access Highways (National Fire Protection Association) is the governing Standard for automotive tunnels. It provides fire protection and life safety requirements for limited access highways, road tunnels, bridges, elevated highways, depressed highways, and roadways beneath air-right structures. For transit tunnels, NFPA 130 Standard for Fixed Guideway Transit and Passenger Rail Systems is the Standard that dictates similar safety requirements.

In addition to the requirements imposed by the National Electrical Code® (NEC) Article 355, “Reinforced Thermosetting Resin Conduit: Type RTRC,” organizations such as UL, NEMA, and CSA have also defined the applicable Standards for the safety requirements and performance of RTRC products. Such NEMA Standards include the following:

• NEMA PRP 3, Expansion Epoxy-Based Fittings for RTRC Rigid Nonmetallic Conduit,
• NEMA TC 14.AG, Aboveground Reinforced Thermosetting Resin Conduit and Fittings,
• NEMA TC 14.BG, Belowground Reinforced Thermosetting Resin Conduit and Fittings,
• NEMA TC 14.XW, Extra Heavy Wall Aboveground Reinforced Thermosetting Resin Conduit and Fittings

PROPERTIES OF PHENOLIC CONDUIT FOR TRANSIT AND ROADWAY TUNNELS

Phenolic conduit is fire-resistant and can be exposed to temperatures of up to 1,850°F for two hours. This property allows it to meet the elevated temperature requirements for exposed conduits according to NFPA and UL 2196.

Other attributes that contribute to NFPA Standards and U.S. Occupational Safety and Health Administration (OSHA) compliance are a low coefficient of thermal expansion, low-smoke characteristics, and no toxicity since halogen is not released when burning.

PHENOLIC CONDUIT PROJECT BENEFITS

Phenolic conduit is a reliable conduit product for tunnels and other projects and offers the following benefits:

• Fire resistant — can withstand exposure to temperatures up to 1,850°F for two hours.
• Conforms to NFPA requirements
• Does not emit toxic halogens when burning
• Low coefficient of thermal expansion
• Wide resistance to industrial chemicals
• Streamlined installation due to light weight
• Corrosion resistance
• Fire-rated flexible conduit is able to retain its shape after impact or compression

Low coefficient of friction

• Will not melt or weld the wire to the inside of the conduit under fault conditions

Phenolic conduit offers durability, strength, and safety in roadways, trains, transit tunnels, and other critically demanding installations.

The entire BI-TC Technical Committee contributed to this report. ei