National Electrical Code

Analyzer Cable Tray Systems and the NEC

Dec. 2, 2014

Tubing bundles containing tubing sample lines and electrical wiring

All petrochemical plants have analyzer shelters or stations. These analyzers take samples of the gases and liquids in the process and test them for quality, purity, contaminants, temperature, etc. There are tubing bundles associated with the analyzers that run to sample points, which are sometimes located several hundred feet away from the analyzers. These sample tubing bundles are typically routed in cable tray. The tubing bundles are usually a composite assembly with tubing for the process sample along with electrical conductors for heat tracing and/or controls, as shown in the Photo.

Section 300.8 of the National Electrical Code (NEC) specifically states that cable tray containing electrical conductors shall not contain any pipe, tube, or equal for steam, water, gas, air, etc. or any service other than electrical. So placing these prefabricated bundles may appear to violate the requirements of the NEC. However, in the case of a prefab bundle, they are specifically made to be run as an assembly. The intent of 300.8 is that where bundles like this exist in a cable tray, you wouldn’t be allowed to run them in the same tray with any of the other wiring methods found in Table 392.10(A) without a barrier separating the bundles and the other wiring methods. In other words, either the analyzer tubing bundles need their own tray system, or a barrier must be installed between the tubing bundles and the other electrical wiring. Once you install a continuous barrier in a tray, it becomes a multiple tray even though, in essence, it is still only one cable tray.

The Photo (courtesy of Thermon) shows a custom tubing bundle with a heated core section used in a continuous emissions monitoring system.

About the Author

Eddie Guidry | Senior Fellow

Eddie Guidry is a senior fellow with Fluor Enterprises, Inc., Sugar Land, Texas. He is highly skilled in electrical and control systems for industrial construction, design, and engineering (both domestic and abroad). The majority of Eddie’s 38 years of experience includes upstream and downstream portions of petrochemical plants and refineries. He is also heavily experienced in water and wastewater treatment facilities. Eddie is very active in the development of U.S. national (ANSI) and international codes and standards, and has been a principal member of the National Fire Protection Association (NFPA) National Electrical Code (NEC) committee since 1999 and NFPA’s National Advisory Committee on Electrical Safety Research since 2008. Eddie, who has also developed and conducted many electrical courses and seminars over the years, currently holds the corporate Master Electrician license for Fluor Corporation in the State of Texas and is also an ICC/IAEI certified electrical inspector.