Complete Technical Guide to Norwegian Offshore Oil & Gas Cable Standard — BFOU, RFOU, TFOU Power Cables, Instrumentation Cables, MUD Resistant, Fire Resistant, Halogen Free
Anhui Feichun Special Cable Co., Ltd.
安徽飞纯特种电缆有限公司
What is NEK 606 Cable?
Complete Technical Guide to Norwegian Offshore Oil & Gas Cable Standard — BFOU, RFOU, TFOU Power Cables, Instrumentation Cables, MUD Resistant, Fire Resistant, Halogen Free
1. Introduction to NEK 606 Standard
NEK TS 606 is the Norwegian offshore industry technical specification (TS) covering a range of power, instrumentation and earth cables that are halogen free and/or MUD resistant, protecting them against the type of hydrocarbon-laden drilling liquid used in drilling operations which can have an adverse effect on cable sheathing materials. Originally published in 1993 by the Norwegian Electrotechnical Committee (NEK) as a successor to the ‘Recommended Practice for Specification of Cables’ of the Norwegian Oil Industry Association, NEK 606 has evolved to become an internationally accepted standard for offshore cable applications.
The NEK 606 cable standard technical specification has been widely adopted in Europe and internationally with BFOU (fire resistant) and RFOU (flame retardant) cables, and UX Earth cables in common use. NEK 606 cables are designed to withstand the harsh and hazardous operating conditions of the global oil and gas industry, with stringent requirements for conductor, insulation, screen, braid armour, bedding and cable jacket compounds.
| Full Title | Cables for Offshore Installations — Halogen Free and Mud Resistant |
| Issuing Body | Norwegian Electrotechnical Committee (NEK) |
| First Edition | 1993 |
| Current Edition | NEK TS 606:2022 |
| Scope | LV/MV/HV power, control, instrumentation, telecom, optical fibre cables |
| Voltage Range | 150/250V (instrumentation) to 18/30kV (HV power) |
| Key Features | Halogen free, MUD resistant, fire resistant, flame retardant |
| Related Standards | IEC 60092-350/353/354/376, BS 6883, IEEE 1580 Type P |
NEK 606 MUD resistant cables have many similarities with cables covered under IEEE 1580 Type P (American) and British Standard BS 6883, with distinct requirements in relation to the insulation, screening, braiding, bedding and sheathing compound. The standard requires SHF2 (thermosetting halogen-free) rated sheathing for MUD resistance as specified in IEC 60092-360.
Source: Eland Cables – NEK 606 Standard Cable
EspañolIntroducción al Estándar NEK 606
NEK TS 606 es la especificación técnica de la industria offshore noruega que cubre una gama de cables de potencia, instrumentación y tierra que son libres de halógenos y/o resistentes al LODO (MUD), protegiéndolos contra el líquido de perforación cargado de hidrocarburos utilizado en operaciones de perforación. Publicado originalmente en 1993 por el Comité Electrotécnico Noruego (NEK), NEK 606 se ha convertido en un estándar aceptado internacionalmente para aplicaciones de cables offshore. Los cables BFOU (resistentes al fuego) y RFOU (retardantes de llama), así como los cables de tierra UX, son de uso común. Los cables NEK 606 están diseñados para resistir las condiciones operativas adversas y peligrosas de la industria global del petróleo y gas.
繁體中文NEK 606 標準簡介
NEK TS 606是挪威離岸工業技術規範（TS），涵蓋一系列無鹵素和/或耐泥漿（MUD resistant）的電力、儀表和接地電纜，保護它們免受鑽井作業中使用的含碳氫化合物鑽井液的不利影響。NEK 606最初於1993年由挪威電工委員會（NEK）發布，作為挪威石油工業協會”電纜規格推薦實踐”的繼承者，現已發展成為國際公認的離岸電纜標準。BFOU（耐火）和RFOU（阻燃）電纜以及UX接地電纜是常用的NEK 606電纜類型。這些電纜設計用於承受全球石油和天然氣工業的嚴苛和危險操作條件，對導體、絕緣、屏蔽、編織鎧裝、墊層和電纜護套化合物有嚴格要求。NEK 606要求使用SHF2（熱固性無鹵素）額定護套以確保耐泥漿性能。
2. NEK 606 Cable Code Designation
NEK 606 uses a systematic 2-4 letter code to describe the construction and properties of offshore cables. Understanding this code designation is essential for engineers, procurement specialists, and installation personnel working in the offshore oil and gas industry.
🔤 NEK 606 Cable Code System
| Position | Letter | Meaning | Description |
|---|---|---|---|
| 1st Letter Insulation | B | Fire Resistant + Halogen Free | EPR insulation with mica glass tape (MGT) fire barrier |
| R | Ethylene Propylene Rubber (EPR) | Flame retardant, excellent low-temp flexibility (-40°C) | |
| T | Cross-linked Polyethylene (XLPE) | Better electrical properties, higher ampacity | |
| 2nd Letter Bedding | F | Halogen Free Bedding | Inner sheath/bedding present between cores and armour |
| 3rd Letter Armour/Screen | O | Wire Braid (Copper) | Tinned copper wire braid (TCWB) armour |
| C | Wire Braid (Steel) | Galvanized steel wire braid armour | |
| 4th Letter Outer Sheath | U | Halogen Free + MUD Resistant | SHF2 or SHF MUD thermosetting compound |
| Suffix Screening | (i) | Individual Screen | Each pair/triple separately screened (for 4-20mA analog) |
| (c) | Collective Screen | Single screen over all pairs (for digital signals) |
2.1 Cable Type Examples
| Code | Breakdown | Full Description |
|---|---|---|
| BFOU | B + F + O + U | Fire resistant EPR insulation + bedding + copper braid + MUD resistant sheath |
| RFOU | R + F + O + U | EPR insulation + bedding + copper braid + MUD resistant sheath |
| TFOU | T + F + O + U | XLPE insulation + bedding + copper braid + MUD resistant sheath |
| BU | B + U | Fire resistant EPR + MUD resistant sheath (unarmoured) |
| RU | R + U | EPR insulation + MUD resistant sheath (unarmoured) |
| UX | U + X | Earth cable with halogen-free MUD resistant sheath |
3. BFOU vs RFOU — Critical Selection Criteria
The distinction between BFOU (fire resistant) and RFOU (flame retardant) cables is critical for offshore safety. Incorrect selection can compromise life safety systems during emergencies.
| Property | BFOU Fire Resistant | RFOU Flame Retardant |
|---|---|---|
| Fire Barrier | Mica glass tape (MGT) over conductor | None |
| Circuit Integrity | Maintained during fire (2-3 hours) | NOT maintained during fire |
| Test Standard | IEC 60331-21, IEC 60331-31 | IEC 60332-3-22 |
| Fire Temperature | 750-830°C sustained, 1000°C for 180 min | Self-extinguishing only |
| Construction | TC/MGT/EPR/SHF2/TCWB/SHF2 | TC/EPR/SHF2/TCWB/SHF2 |
| Application | Emergency systems, fire alarms, evacuation | General power, non-critical circuits |
| Cost | Higher (mica tape layer) | Standard |
3.1 Application Selection Guide
| Application | Cable Type | Reason |
|---|---|---|
| BFOU Required (Fire Resistant) | ||
| Emergency shutdown systems (ESD) | BFOU | Must function during fire |
| Fire and gas detection systems | BFOU | Critical safety function |
| Emergency lighting | BFOU | Evacuation visibility |
| Public address and alarm systems | BFOU | Evacuation communication |
| Fire pump power supply | BFOU | Firefighting capability |
| Life safety systems | BFOU | Personnel protection |
| RFOU Acceptable (Flame Retardant) | ||
| General power distribution | RFOU | Non-critical during fire |
| Non-critical instrumentation | RFOU | Can be isolated in emergency |
| Lighting in safe areas | RFOU | Not evacuation critical |
| HVAC systems | RFOU | Can be shut down in fire |
4. NEK 606 Power Cables
NEK 606 power cables supply electromechanical and electrical equipment on offshore platforms, including emergency and critical systems such as lighting systems. Available in low voltage (0.6/1kV) and medium/high voltage (3.6/6kV to 18/30kV) ratings.
| Code | Type | Voltage (U₀/U) | Construction | Fire Rating | Application |
|---|---|---|---|---|---|
| Low Voltage Power Cables (0.6/1kV) | |||||
| P101 RFOU | Flame Retardant | 0.6/1kV | TC/EPR/SHF2/TCWB/SHF2 | IEC 60332-3-22 | General power distribution |
| P101 TFOU | Flame Retardant XLPE | 0.6/1kV | TC/XLPE/SHF2/TCWB/SHF2 | IEC 60332-3-22 | Higher ampacity applications |
| P105 BFOU | Fire Resistant | 0.6/1kV | TC/MGT/EPR/SHF2/TCWB/SHF2 | IEC 60331 | Emergency systems |
| P108 UX | Earth Cable | 0.6/1kV | TC/SHF2 (Green/Yellow) | IEC 60332-1 | Earthing and bonding |
| P110 BU | Fire Resistant Unarmoured | 0.6/1kV | TC/MGT/EPR/SHF2 | IEC 60331 | Emergency (no armour) |
| Medium/High Voltage Power Cables | |||||
| P102 RFOU | MV Flame Retardant | 3.6/6kV | TC/EPR/SHF2/TCWB/SHF2 | IEC 60332-3-22 | MV power distribution |
| P103 RFOU | MV Flame Retardant | 6/10kV | TC/EPR/SHF2/TCWB/SHF2 | IEC 60332-3-22 | MV power distribution |
| P104 RFOU | MV Flame Retardant | 8.7/15kV | TC/EPR/SHF2/TCWB/SHF2 | IEC 60332-3-22 | MV power distribution |
| P112 RFOU | HV Flame Retardant | 12/20kV | TC/EPR/SHF2/TCWB/SHF2 | IEC 60332-3-22 | HV power distribution |
| P113 RFOU | HV Flame Retardant | 18/30kV | TC/EPR/SHF2/TCWB/SHF2 | IEC 60332-3-22 | HV power distribution |
Construction Key: TC = Tinned Copper conductor, MGT = Mica Glass Tape fire barrier, EPR = Ethylene Propylene Rubber, XLPE = Cross-linked Polyethylene, SHF2 = Thermosetting Halogen Free sheath, TCWB = Tinned Copper Wire Braid armour.
5. NEK 606 Instrumentation Cables
NEK 606 instrumentation cables are designed for control and instrumentation systems on offshore platforms. They feature excellent screening properties to reduce electromagnetic interference (EMI) and are available with individual (i) or collective (c) screening options.
| Code | Type | Voltage | Screen | Fire Rating | Application |
|---|---|---|---|---|---|
| Flame Retardant Instrumentation Cables | |||||
| S101 RFOU(i) | Individual Screen | 150/250V | Each pair screened | IEC 60332-3-22 | 4-20mA analog signals |
| S102 RFOU(c) | Collective Screen | 150/250V | Overall screen | IEC 60332-3-22 | Digital signals |
| Fire Resistant Instrumentation Cables | |||||
| S103 BFOU(i) | Individual Screen + Fire Barrier | 150/250V | Each pair screened | IEC 60331 | Emergency instrumentation |
| S104 BFOU(c) | Collective Screen + Fire Barrier | 150/250V | Overall screen | IEC 60331 | Emergency control circuits |
| Unarmoured Instrumentation Cables | |||||
| S105 RU(i) | Individual Screen Unarmoured | 150/250V | Each pair screened | Flame Retardant | Protected routes |
| S106 RU(c) | Collective Screen Unarmoured | 150/250V | Overall screen | Flame Retardant | Protected routes |
| S107 BU(i) | Fire Resistant Unarmoured | 150/250V | Each pair screened | IEC 60331 | Emergency (no armour) |
| S108 BU(c) | Fire Resistant Unarmoured | 150/250V | Overall screen | IEC 60331 | Emergency (no armour) |
6. MUD Resistance Requirements
NEK TS 606 imposes significantly more stringent oil and mud resistance requirements compared to IEC 60092-360, reflecting real-world offshore conditions where cables are exposed to drilling mud, hydraulic fluids, crude oil, and various chemical treatments.
| Property | SHF1 | SHF2 | SHF2 MUD |
|---|---|---|---|
| Halogen Content | <0.5% | <0.5% | <0.5% |
| Thermosetting | Yes | Yes | Yes |
| Oil Resistance (ISO 1817) | Basic | Enhanced (Category b) | Enhanced (Category b) |
| Drilling Mud Resistance | No | No | Yes (Category c) |
| Hydraulic Oil Resistance | No | Optional | Yes (Category d) |
| UV Resistance | Basic | Enhanced | Enhanced |
| Temperature Range | -40°C to +90°C | -40°C to +90°C | -40°C to +90°C |
6.1 Sheath Code Designations
| Code | Description | Oil Resistance | Application |
|---|---|---|---|
| (no marking) | Minimum requirements | Basic | General offshore |
| E | Enhanced Oil Resistant | Category b | Oil exposure areas |
| M | Enhanced Oil + MUD Resistant | Category b + c | Drilling areas |
| H | Enhanced Oil + Hydraulic Oil | Category b + d | Hydraulic systems |
| H-M | Enhanced Oil + Hydraulic + MUD | Category b + c + d | All drilling areas |
7. Key Technical Parameters
Voltage Range
Conductor
Temp Range
Fire Test
Insulation
Armour
7.1 Typical Cable Construction
| Conductor | Tinned annealed stranded copper, Class 2 per EN 60228 |
| Fire Barrier (BFOU) | Mica glass tape (MGT) wrapped around conductor |
| Insulation | EPR (flame retardant) or XLPE (higher ampacity) |
| Inner Sheath/Bedding | SHF2 halogen-free thermosetting compound |
| Screen (Instrumentation) | Aluminium/polyester tape + tinned copper drain wire |
| Armour | Tinned copper wire braid (TCWB), 85%+ coverage |
| Outer Sheath | SHF2 or SHF MUD thermosetting halogen-free compound |
| Sheath Colour | Black (power), Grey/Blue (instrumentation), Green/Yellow (earth) |
8. Certifications and Approvals
NEK 606 cables manufactured for the offshore industry require certification from classification societies to ensure compliance with safety and quality standards.
| Certification Body | Abbreviation | Region | Scope |
|---|---|---|---|
| Det Norske Veritas | DNV | Norway (International) | Marine & offshore classification |
| Lloyd’s Register | LR | UK (International) | Marine certification |
| American Bureau of Shipping | ABS | USA (International) | Marine & offshore |
| Bureau Veritas | BV | France (International) | Marine classification |
| Germanischer Lloyd | GL (now DNV GL) | Germany | Marine classification |
| China Classification Society | CCS | China | Marine certification |
NEK 606 cables are also designed to comply with related IEC standards including IEC 60092-350 (general construction), IEC 60092-353 (1kV/3kV power cables), IEC 60092-354 (6-30kV power cables), and IEC 60092-376 (instrumentation cables).
9. Complete Cable Model Summary
| Code | Type | Voltage | Armour | Fire | Application |
|---|---|---|---|---|---|
| Power Cables | |||||
| P101 RFOU/TFOU | Flame Retardant | 0.6/1kV | TCWB | FR | General power |
| P105 BFOU | Fire Resistant | 0.6/1kV | TCWB | Fire Res | Emergency power |
| P102 RFOU | Flame Retardant | 3.6/6kV | TCWB | FR | MV power |
| P103 RFOU | Flame Retardant | 6/10kV | TCWB | FR | MV power |
| P104 RFOU | Flame Retardant | 8.7/15kV | TCWB | FR | MV power |
| P112 RFOU | Flame Retardant | 12/20kV | TCWB | FR | HV power |
| P113 RFOU | Flame Retardant | 18/30kV | TCWB | FR | HV power |
| P108 UX | Earth Cable | 0.6/1kV | No | FR | Earthing |
| P110 BU | Fire Res Unarmoured | 0.6/1kV | No | Fire Res | Emergency |
| P111 RU | Flame Ret Unarmoured | 0.6/1kV | No | FR | Protected routes |
| Instrumentation Cables | |||||
| S101 RFOU(i) | Individual Screen | 150/250V | TCWB | FR | Analog signals |
| S102 RFOU(c) | Collective Screen | 150/250V | TCWB | FR | Digital signals |
| S103 BFOU(i) | Fire Res Individual | 150/250V | TCWB | Fire Res | Emergency inst. |
| S104 BFOU(c) | Fire Res Collective | 150/250V | TCWB | Fire Res | Emergency control |
| S105 RU(i) | Unarmoured Individual | 150/250V | No | FR | Protected routes |
| S106 RU(c) | Unarmoured Collective | 150/250V | No | FR | Protected routes |
| S107 BU(i) | Fire Res Unarm. (i) | 150/250V | No | Fire Res | Emergency |
| S108 BU(c) | Fire Res Unarm. (c) | 150/250V | No | Fire Res | Emergency |
Legend: FR = Flame Retardant (IEC 60332), Fire Res = Fire Resistant (IEC 60331), (i) = Individual screen, (c) = Collective screen, TCWB = Tinned Copper Wire Braid
Authoritative External References
https://www.elandcables.com/…/nek-606-cable
https://www.elandcables.com/cables/bfou-and-rfou-cables
https://www.habia.com/…/bfou-and-rfou-cables
https://www.incore-cables.com/nek-606-standard
https://www.clevelandcable.com/…/nek606-cable
https://www.nek.no/…/Preview_NEKTS6062022en.pdf
https://cmc-cable.com/…/offshore-cable
https://www.powerandcables.com/…/offshore-marine-cables
https://www.powerandcables.com/…/Prysmian-Draka-NEK606
https://kvcable.com/nek606-cable
Contact Feichun Cable
For technical support with NEK 606 offshore cables, BFOU/RFOU power cables, instrumentation cables, or oil & gas industry cable applications, please contact our engineering team.
