NORSOK and hazardous areas: heat tracing on offshore installations

Three layers of requirements

• NORSOK standards: the Norwegian petroleum industry standards used on the Norwegian continental shelf. NORSOK E-001 Electrical systems covers the design of electrical installations, including electrical heat tracing, and the documentation the operator expects.
• IEC 60079 series: the international standards for equipment in explosive atmospheres. For trace heating the relevant part is IEC/IEEE 60079-30-1 (general and testing requirements) with 60079-30-2 for application, installation and maintenance.
• ATEX and IECEx certification: the certificates that show a product complies. Every component in the circuit needs one: cable, junction box, thermostat, controller and cable gland.

What NORSOK expects of a heat tracing installation

The practical requirements the operators and EPC contractors bring to us are consistent across projects:

• Self-regulating heating cables sized per circuit from a documented heat loss calculation
• Stainless steel AISI 316L junction boxes with high ingress protection, mounted on the pipe or on the wall next to it
• Temperature control per circuit, with a separate limiter where the cable T-class depends on it, and alarm to the control room
• Tagging of every box and circuit, caution labels on the cladding, and as-built documentation with certificates
• Materials and components rated for the site ambient temperature, typically −20 °C to −40 °C on the northern fields

Ex zone 1 and zone 2 in practice

Zone 1 is where an explosive gas atmosphere is likely in normal operation, zone 2 where it is not likely and short-lived if it occurs. Heat tracing in both zones uses Ex e (increased safety) equipment: the Tranberg TEF 1058 junction boxes are certified II 2 G Ex eb IIC T5 Gb, which covers zone 1 and zone 2 for gas group IIC. The heating cable itself is certified to IEC 60079-30-1 with its own temperature class, and the thermostat or controller is certified as a complete Ex unit.

The Tranberg heat tracing system for hazardous areas

• TEF 1058 heat trace junction boxes, pipe mounted and wall mounted, built to NORSOK requirements and found on most oil installations in the North Sea
• TEF 1058 end seal terminations with indicator lamp, marshalling boxes and switch boxes on the same platform
• Raychem BTV, QTVR, XTVR, HTV and VPL heating cables with ATEX and IECEx certificates
• TEF 1058 capillary and electronic PT100 thermostats, and ThermoConnect TTC controllers with Raychem Elexant 5010i, certified for zone 1
• E204/622 Ex e cable glands, TEF 9179 connection kits and the accessories for cladding, flanges and mechanical protection

Documentation we deliver

For every part number: datasheet, ATEX and IECEx certificates, EU and UK declarations of conformity, user manual and 3D model, all on the product page. For a project: the circuit list with cable type and output, the box and thermostat list with tags, and the certificates collected for the handover documentation.

Standard numbers and editions change; the applicable NORSOK and IEC editions are the ones referenced in the project specification.