I. General
427.1 Scope. The requirements of this article shall apply to electrically energized heating systems and the installation of these systems used with pipelines or vessels or both.
FPN: For further information, see ANSI/IEEE Std. 515-
2002, Standard for the Testing, Design, Installation and
Maintenance of Electrical Resistance Heat Tracing for In-
dustrial Applications; ANSI/IEEE Std. 844-2000, Recom-
mended Practice for Electrical Impedance, Induction,
and Skin Effect Heating of Pipelines and Vessels; and
ANSI/NECA 202-2001, Recommended Practice for Install-
ing and Maintaining Industrial Heat Tracing Systems.
427.2 Definitions.
Impedance Heating System. A system in which heat is generated in a pipeline or vessel wall by causing current to flow through the pipeline or vessel wall by direct connection to an ac voltage source from a dual-winding transformer.
Induction Heating System. A system in which heat is generated in a pipeline or vessel wall by inducing current and hysteresis effect in the pipeline or vessel wall from an external isolated ac field source.
Integrated Heating System. A complete system consisting of components such as pipelines, vessels, heating elements, heat transfer medium, thermal insulation, moisture barrier, nonheating leads, temperature controllers, safety signs, junction boxes, raceways, and fittings.
Pipeline. A length of pipe including pumps, valves, flanges, control devices, strainers, and/or similar equipment for conveying fluids.
Resistance Heating Element. A specific separate element to generate heat that is applied to the pipeline or vessel externally or internally.
FPN: Tubular heaters, strip heaters, heating cable, heating tape, heating blankets, and immersion heaters are examples of resistance heaters.
Skin-Effect Heating System. A system in which heat is generated on the inner surface of a ferromagnetic envelope attached to a pipeline or vessel, or both.
FPN: Typically, an electrically insulated conductor is routed through and connected to the envelope at the other end. The envelope and the electrically insulated conductor are connected to an ac voltage source from a dual-winding transformer.
Vessel. A container such as a barrel, drum, or tank for holding fluids or other material.
427.3 Application of Other Articles. Cord-connected pipe heating assemblies intended for specific use and identified as suitable for this use shall be installed according to Article 422.
427.4 Continuous Load. Fixed electric heating equipment for pipelines and vessels shall be considered continuous load.
II. Installation
427.10 General. Equipment for pipeline and vessel elec- tric heating shall be identified as being suitable for (1) the chemical, thermal, and physical environment and (2) installation in accordance with the manufacturer's drawings and instructions.
427.11 Use. Electric heating equipment shall be installed in such a manner as to be afforded protection from physical damage.
427.12 Thermal Protection. External surfaces of pipeline and vessel heating equipment that operate at temperatures exceeding 60°C (140°F) shall be physically guarded, isolated, or thermally insulated to protect against contact by personnel in the area.