Electrical and Heat Trace Installation Review in a Classified Area at a Power Plant (2020)

In 2020 we reviewed new electrical and instrumentation work on an addition to a power generating facility, at the request of counsel. The work served heat trace on process piping in a classified area. The location and the parties are withheld.

Why the heat trace mattered

The process fluid in this system has to stay hot. If it cools in a pipe or a valve it can solidify and block the line, and the system stays out of service until the pipe is cleared by hand. Insulation and electric heat trace keep the temperature up. The area around the new heat exchanger and its piping is classified as Class I, Division 2 under the National Electrical Code^®, meaning flammable gas can be present if containment fails or equipment runs abnormally. In an area like that, the wiring itself must never become an ignition source.

Two passes

We first reviewed photographs and notes taken by others and issued a short letter with our initial observations. A couple of weeks later we examined the installation on site, without destructive testing, and documented it with notes and photographs. Our report followed the site visit and built on the letter.

What we found

Conduit fittings were missing gaskets and plugs, which lets moisture, dust and gas into the raceway. Where the heat trace has ground fault protection, water in the raceway means nuisance trips and, sooner or later, a heat trace system that does not work. Flexible conduit was used where no flexibility was needed, which NEC^® 501.10(B)(2) does not allow in this area, and some flexible runs to heat trace loads had no bonding jumper. Locknut bushings were being relied on for grounding where the code calls for a separate bond.

Support was poor throughout. Conduits and cables were held with wire ties, strapped or taped to railings, fixed to insulated piping or left loose for long runs. In places, metal clad cable ran more than ten feet unsupported, where the code limit is six. Cable tray dividers had been dropped loose into the tray or fixed down its middle, so they did not separate the cable classes as intended. One cabinet in the classified area was not marked for that location. Heat trace connection kits were mounted below the pipe, and the low points in the conduit had no drains, so condensation would collect where it does the most harm.

Our opinion

We concluded that the installation fell well below the standard of care for industrial hazardous area work and needed reconstruction before it was energized. The report drew on NEC 110.12 and NECA 1 for workmanship, NECA 202 for heat trace drainage and IEEE 515 for heat trace grounding. Reviews like this are part of our forensic electrical engineering practice. Fires and failures at plants and other industrial sites are covered on our page for industrial fire investigation services.