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Setting the Standard for Tray-Rated Fiber Optic Cable


By Del Williams F


or copper wiring installations, engineers often choose tray-rated cables to deliver sig- nals and power to industrial control systems,


heavy machinery, and other ancillary business equipment. As outlined in the National Fire Protection Association’s NFPA 70, these ca- bles must be third-party tested and certified to ensure that they can withstand the dan- gers of harsh industrial environments while exposed in cable trays. However, with no specific equivalent


for fiber optic cables, some fiber optic manu- facturers have begun offering “tray-rated” options despite the fact that there is little in the way of specific ratings, testing, or evalu- ation criteria. This has led to considerable confusion,


as engineers and installers are left to sift through competing claims and interpreta- tions of which products are equivalent to the standards. “We constantly get requests from engi-


neers, consultants and installers asking about ‘tray-rated’ fiber. But there’s no such thing.” says Jeff Miller, a registered commu- nications distribution designer (RCDD) at Optical Cable Corporation, a company that manufactures a broad range of fiber optic ca- bles for demanding industrial environments.


Tray-Rated Cable One of the most common methods of


Tray cables are often subjected to harsh indoor and outdoor environments.


supporting wire and cable, cable trays are often used in harsh industrial environments in manu- facturing plants, refineries, oil platforms, utilities,


600V. Other alternatives include power limited tray cable (PLTC), instrumentation tray Cable (ITC), and wind turbine tray cable (WTTC). For ex-


substations, and mining. The most common form of wire certified to


NFPA standards is tray cable (TC), a multi-con- ductor control, signal or power cable rated for


posed runs (ER) where cables extend six feet or more outside the tray, even higher standards of crush and impact resistance are required. The purpose of the tray rating is to define the mechanical and environmental performance specifications of cables that will be bundled together, often on top of each other, in open trays exposed to harsh indoor or outdoor en- vironments. One issue is the construction and jack-


eting of the cable, which can be damaged due to aggressive pulling or bending during installation, impact from falling debris, by heavy cabling, or damaged over time as a re- sult of degradation by weather or the infil- tration of oil or water.


“We constantly get requests


from engineers, consultants and installers asking about


‘tray-rated’ fiber. But there’s no such thing.”


Compared to cabling in enclosed con-


duit or raceways, a split or broken cable jacket can increase the risk of shock, short circuits, or electrical fire. As a result, the NFPA 70 sets standards for the safe instal- lation and use of this type of wiring. However, given that the codes are pri-


marily focused on fire safety and installation with electrical conductors, the code does not set forth


Continued on page 40


May, 2017


See at EWPTE, Booth 1211


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