Comprehensive Guide to Norwegian Offshore & Marine Cable Standards
What is NEK TS 606:2025 Cable Code Designation?
Comprehensive Guide to Norwegian Offshore & Marine Cable Standards
NEK TS 606:2025 represents the most comprehensive technical specification for offshore and marine cables, developed by the Norwegian Electrotechnical Committee (NEK) to address the extreme demands of the oil and gas industry, offshore platforms, and marine vessels. This specification has become the global benchmark for cable performance in harsh offshore environments, superseding many regional standards through its rigorous requirements for fire resistance, halogen-free construction, and mud resistance.
According to Feichun Cable, NEK TS 606 cables are essential for critical safety systems on offshore installations where cable failure could result in catastrophic consequences. The standard mandates performance levels significantly exceeding IEC 60092-360:2014, particularly in oil resistance, mud resistance, and fire performance testing.
1. Understanding NEK TS 606: Purpose and Background
1.1 Historical Development
The NEK TS 606 specification originated from the “Recommended Practice for Specification of Cables” published by the Norwegian Oil Industry Association (OLF) in the late 1980s. The offshore industry recognized the critical need to standardize and limit cable types used in offshore operations, where cable diversity complicated maintenance, increased inventory costs, and created potential safety risks.
Evolution Timeline
- 1980s: OLF develops initial cable specifications to address offshore industry needs
- 1993: Norwegian Electrotechnical Committee (NEK) assumes responsibility and publishes first edition as NEK 606 national standard
- 2009: Redesignated as Technical Specification (TS) to distinguish from IEC standards, becoming NEK TS 606
- 2016: Major revision incorporating enhanced oil and mud resistance requirements
- 2025: Current edition with expanded cable types and updated test methodologies
1.2 Primary Applications
Offshore Oil & Gas Platforms
- Fixed production platforms (TLP, SPAR, jacket structures)
- Floating production systems (FPSO, FSO)
- Semi-submersible drilling rigs
- Jack-up drilling platforms
- Subsea production systems
Marine Vessels
- Drilling ships and drillships
- Oil tankers and chemical tankers
- Supply vessels and accommodation vessels
- Offshore construction vessels
- Pipe-laying barges
Critical Systems
- Emergency shutdown (ESD) systems
- Fire and gas detection systems
- Emergency lighting and alarms
- Process control and SCADA
- Power management systems
Industry leader Crane Cable emphasizes that NEK TS 606 compliance is increasingly specified by international oil companies and maritime regulatory bodies, making it a de facto requirement for offshore projects worldwide.
2. Key Characteristics and Performance Requirements
2.1 Fire Performance Classification
| Property | Fire Resistant (BFOU) | Flame Retardant (RFOU/TFOU) | Test Standard |
|---|---|---|---|
| Fire Resistance Test | ✓ Required | ✗ Not Required | IEC 60331-21, IEC 60331-31 |
| Test Temperature | 750-800°C (1,000°C enhanced) | N/A | IEC 60331 |
| Test Duration | Minimum 120 minutes (180 minutes for enhanced) | N/A | IEC 60331 |
| Circuit Integrity | Must maintain functionality during fire | Not required | IEC 60331-21 |
| Water Spray Test | 90 min fire + 15 min water spray | N/A | EN 50200 Annex E |
| Flame Propagation (Bundled) | ✓ Required | ✓ Required | IEC 60332-3-22 (Category A) |
| Flame Propagation (Single) | ✓ Required | ✓ Required | IEC 60332-1-2 |
| Halogen Content | ≤ 5 mg/g | ≤ 5 mg/g | IEC 60754-1, IEC 60754-2 |
| Light Transmittance (Smoke) | ≥ 60% | ≥ 60% | IEC 61034-1, IEC 61034-2 |
| Acidity (pH) | ≥ 4.3 | ≥ 4.3 | IEC 60754-2 |
| Conductivity (μS/mm) | ≤ 10 | ≤ 10 | IEC 60754-2 |
Source: NEK TS 606:2025, IEC 60331 series, IEC 60332 series, IEC 60754 series
Critical Distinction: Fire Resistant vs. Flame Retardant
BFOU (Fire Resistant): Contains mica glass tape fire barrier that maintains circuit integrity for minimum 2-3 hours during direct fire exposure at 750-830°C. The cable continues to function as an electrical circuit while burning, critical for emergency systems, evacuation alarms, and firefighting equipment.
RFOU/TFOU (Flame Retardant): Self-extinguishing cables that prevent fire propagation but do NOT maintain circuit functionality during fire. Suitable for non-critical power and control applications where circuit integrity during fire is not essential.
Application Rule: Emergency systems, fire detection, emergency lighting, and life safety circuits MUST use fire resistant (BFOU) cables. General power distribution and non-critical controls may use flame retardant (RFOU/TFOU) cables.
2.2 Oil and 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, and crude oil.
| Test Parameter | NEK 606 SHF2 | NEK 606 SHF2 MUD Resistant | Test Method |
|---|---|---|---|
| Enhanced Oil Resistance Tests | |||
| Test Oil IRM902 | Required | Required | IEC 60092-360 SHF2 |
| Temperature | 100°C ± 5°C | 100°C ± 5°C | — |
| Duration | 168 hours (7 days) | 168 hours (7 days) | — |
| Tensile Strength Change | ≤ ±25% | ≤ ±25% | — |
| Elongation at Break Change | ≤ ±25% | ≤ ±25% | — |
| Test Oil IRM903 | Required | Required | IEC 60092-360 Annex C |
| Temperature | 100°C ± 5°C | 100°C ± 5°C | — |
| Duration | 168 hours (7 days) | 168 hours (7 days) | — |
| Mud Resistance Tests (Mandatory for SHF2 MUD) | |||
| Base Oil EDC 95-11 | Not required | Required | NEK 606 proprietary |
| Temperature | — | 100°C ± 5°C | — |
| Duration | — | 168 hours (7 days) | — |
| Tensile Strength Change | — | ≤ ±30% | — |
| Elongation at Break Change | — | ≤ ±30% | — |
| Synthetic Drilling Mud | Not required | Required | NEK 606 proprietary |
| Temperature | — | 80°C ± 5°C | — |
| Duration | — | 168 hours (7 days) | — |
| Water-Based Drilling Mud | Not required | Required | NEK 606 proprietary |
| Temperature | — | 80°C ± 5°C | — |
| Duration | — | 168 hours (7 days) | — |
Source: NEK TS 606:2025 Table 1a, 1b, 1c – Enhanced requirements compared to IEC 60092-360:2014
Field-Specific Mud Testing
When project-specific drilling mud formulations deviate from the standard NEK 606 test fluids (EDC 95-11, synthetic mud, or water-based mud), special evaluation or additional testing must be agreed between manufacturer and end user. Offshore operators should provide actual mud samples for qualification testing before cable procurement.
3. Material Structure and Construction
3.1 Conductor Specifications
| Parameter | Power Cables (0.6/1 kV and above) | Instrumentation Cables (250V) |
|---|---|---|
| Material | Tinned copper (preferred) or bare copper | Tinned copper |
| Stranding Class | Class 2 (stranded) or Class 5 (flexible) | Class 5 (flexible) or Class 6 (extra flexible) |
| Standard Reference | IEC 60228 | IEC 60228 |
| Conductivity | ≥ 100% IACS (annealed copper) | ≥ 100% IACS (annealed copper) |
| Tinning Thickness | Minimum 1 μm (ASTM B33) | Minimum 1 μm (ASTM B33) |
| Typical Sizes (Power) | 1.5 mm² to 300 mm² | — |
| Typical Sizes (Instrumentation) | — | 0.75 mm², 1.0 mm², 1.5 mm², 2.5 mm² |
Amplex Mining reports that tinned copper conductors are essential for NEK 606 applications due to superior corrosion resistance in marine environments and improved solderability during terminations.
3.2 Insulation Materials
EPR (Ethylene Propylene Rubber)
- Type: Thermoset elastomer (EPDM)
- Temperature Rating: -40°C to +90°C continuous
- Dielectric Constant: 3.0-4.0 at 50/60 Hz
- Dielectric Strength: ≥ 20 kV/mm
- Tensile Strength: ≥ 12 MPa
- Elongation at Break: ≥ 300%
- Key Features: Excellent flexibility, ozone resistance, thermal aging resistance
- Applications: RFOU power cables, instrumentation cables
XLPE (Cross-Linked Polyethylene)
- Type: Thermoset polymer
- Temperature Rating: -20°C to +90°C continuous
- Dielectric Constant: 2.3 at 50/60 Hz
- Dielectric Strength: ≥ 25 kV/mm
- Tensile Strength: ≥ 15 MPa
- Elongation at Break: ≥ 350%
- Key Features: Superior electrical properties, moisture resistance, higher ampacity
- Applications: TFOU power cables, medium/high voltage applications
Mica Glass Tape (Fire Barrier)
- Composition: Mica flakes bonded to glass fabric with silicone
- Thickness: Typically 0.08-0.15 mm per wrap
- Application: Helically wrapped around conductor before insulation
- Overlap: Minimum 50% coverage
- Temperature Resistance: ≥ 1,000°C
- Function: Maintains electrical integrity during fire by forming ceramic barrier
- Applications: BFOU fire resistant cables only
3.3 Shielding and Armoring
| Component | Description | Specifications | Application |
|---|---|---|---|
| Bedding/Inner Covering (F) | Halogen-free thermoplastic elastomer tape or extruded layer | Thickness 0.5-1.5 mm depending on cable size SHF1 compound | Protects insulation from armor, provides cushioning |
| Tinned Copper Wire Braid (O) | Woven mesh of tinned copper wires | Wire size: 0.2-0.5 mm diameter Coverage: ≥ 80% optical Carriers: 16-32 depending on cable diameter | Electromagnetic shielding, mechanical protection, ground path |
| Galvanized Steel Wire Braid (C) | Woven galvanized steel wires | Wire size: 0.8-1.2 mm diameter Coverage: ≥ 85% Tensile strength: ≥ 1,400 N/mm² | Heavy mechanical protection, high tensile strength applications |
| Aluminum Laminate (L) | Aluminum foil laminated to outer sheath | Thickness: 0.2-0.4 mm aluminum Laminated to polymer film | Electromagnetic shielding, moisture barrier (lightweight) |
| Individual Screen (i) | Copper/polyester tape with drain wire per pair/triple | Coverage: ≥ 90% Drain wire: Tinned copper 0.5-1.0 mm² | Instrumentation cables requiring EMI protection per circuit |
| Collective Screen (c) | Single copper/polyester tape over all cores | Coverage: ≥ 90% Drain wire: Tinned copper 1.5-2.5 mm² | Instrumentation cables with common ground reference |
3.4 Sheathing Materials
SHF Compound Classifications
SHF1 (Thermoplastic Halogen-Free):
- Polyolefin-based compounds (PE, PP blends)
- Flame retardant additives (metal hydroxides)
- Suitable for bedding and inner coverings
- Temperature range: -20°C to +80°C
- Shore A hardness: 85-95
SHF2 (Thermoset Halogen-Free):
- EVA (Ethylene Vinyl Acetate) based elastomers
- LSZH (Low Smoke Zero Halogen) compounds
- Enhanced oil and chemical resistance
- Temperature range: -40°C to +90°C
- Shore A hardness: 80-90
- Standard for NEK 606 outer sheaths
SHF2 MUD (Mud Resistant Thermoset):
- Specially formulated EVA/elastomer blends
- Must pass enhanced oil and mud resistance tests
- Resistant to EDC 95-11, synthetic mud, water-based mud
- Required for drilling operations exposure
- Highest chemical resistance grade
4. NEK TS 606:2025 Cable Code Designation System
4.1 Code Structure Overview
NEK TS 606 employs a systematic 2-letter or 4-letter coding system to precisely describe cable construction. This standardized nomenclature enables rapid cable identification and ensures proper cable selection for specific applications.
Basic Code Format
2-Letter Code: Uses positions 1 and 4 only (Insulation + Outer Sheath)
4-Letter Code: Uses all positions (Insulation + Bedding + Armor/Screen + Outer Sheath)
Function: INSULATION BEDDING ARMOUR/SCREEN OUTER SHEATH
Example: R F O U
(EPR) (Bedding) (Cu Braid) (Thermoset)
4.2 Complete Code Letter Definitions
| Position | Letter Code | Material/Function | Technical Details |
|---|---|---|---|
| Position 1: INSULATION TYPE | |||
| 1 | B | Fire resistant tape + insulation | Mica glass tape (MGT) + EPR insulation. Fire resistant per IEC 60331 |
| R | Ethylene Propylene Rubber (EPR) | EPDM elastomer, -40°C to +90°C, flame retardant | |
| T | Cross-Linked Polyethylene (XLPE) | Thermoset XLPE, -20°C to +90°C, superior electrical properties | |
| I | Thermoplastic compound | PVC or halogen-free thermoplastic for low voltage applications | |
| A | Fiber, tight buffered | Optical fiber with tight buffer coating (fiber optic cables) | |
| Q | Fiber in loose tube | Optical fiber in gel-filled loose tube (fiber optic cables) | |
| Position 2: BEDDING / INNER COVERING | |||
| 2 | F | Bedding / Inner covering or taping | SHF1 thermoplastic layer or tape separating core from armor |
| (blank) | No bedding layer | Used for unarmored cables or cables with direct sheath over insulation | |
| Position 3: ARMOUR / SCREEN TYPE | |||
| 3 | L | Aluminum (laminated to outer jacket) | Aluminum foil/polymer laminate for EMI shielding |
| X | No armor | Unarmored construction for earth/bonding cables | |
| O | Tinned copper wire braid | Standard shielding for NEK 606 cables, ≥80% coverage | |
| A | Strength member of yarn | Aramid/glass fiber strength members (fiber optic cables) | |
| C | Galvanized steel wire braid | Heavy-duty mechanical protection, high tensile applications | |
| Position 4: OUTER SHEATH TYPE | |||
| 4 | I | Thermoplastic compound SHF1 | Halogen-free thermoplastic, typically for instrumentation cables |
| U | Thermoset compound SHF2 | EVA-based elastomer, standard NEK 606 sheath, oil resistant | |
| U | Mud resistant thermoset compound, SHF2 MUD | Enhanced formulation passing all mud resistance tests, for drilling operations | |
| Additional Abbreviations (Instrumentation Cables) | |||
| Suffix | (c) | Collective screen | Single shield over all pairs/triples with common drain wire |
| (i) | Individual pair or triple screen | Each pair/triple individually shielded with drain wire | |
4.3 Code Designation Examples
Example 1: RFOU
FLAME RETARDANT
- R = EPR insulation
- F = Bedding layer
- O = Tinned copper wire braid
- U = Thermoset outer sheath (SHF2)
Application: Most common NEK 606 power cable for offshore platforms. Flame retardant, halogen-free, oil resistant.
Example 2: BFOU
FIRE RESISTANT
- B = Mica glass tape + EPR insulation
- F = Bedding layer
- O = Tinned copper wire braid
- U = Thermoset outer sheath (SHF2)
Application: Fire resistant cable for emergency systems, fire alarms, emergency lighting. Maintains circuit integrity during fire.
Example 3: RFOU(i)
INSTRUMENTATION
- R = EPR insulation
- F = Bedding layer
- O = Tinned copper wire braid
- U = Thermoset outer sheath (SHF2)
- (i) = Individual pair screening
Application: Instrumentation cable with individual pair shields for maximum EMI protection in process control systems.
Example 4: TFOU
FLAME RETARDANT
- T = XLPE insulation
- F = Bedding layer
- O = Tinned copper wire braid
- U = Thermoset outer sheath (SHF2)
Application: Medium voltage power cable with XLPE insulation for superior electrical performance at 6/10 kV and above.
Example 5: UX
EARTH CABLE
- U = Thermoset sheath (direct on conductor)
- X = No armor
Application: Earth/ground cable with single conductor, no insulation required, flame retardant sheath only.
Example 6: BFOU-HCF
HYDROCARBON FIRE
- BFOU = Standard fire resistant construction
- -HCF = Hydrocarbon Fire resistant qualification
Application: Enhanced fire resistant cable for hydrocarbon fire scenarios (pool fires). Maintains circuit integrity at 1,100°C per ISO 22899-1.
4.4 Complete Cable Marking Example
Typical Cable Marking
Breakdown:
• Manufacturer: FEICHUN CABLE
• Cable Type Code: S101 (NEK 606 designation for instrumentation cable)
• Construction Code: RFOU(i) (EPR/Bedding/Cu Braid/Thermoset, Individual screening)
• Installation: E-M (Explosion risk and Mud resistant areas)
• Voltage Rating: 250V
• Configuration: 2 PAIR (4 conductors arranged as 2 twisted pairs)
• Conductor Size: 0.75 mm² per conductor
• Manufacturing Year: 2025
Installation Classification Codes:
- E = Explosion risk areas (Zone 1, Zone 2 per IEC 60079)
- M = Mud resistant (drilling operations exposure)
- S = Safe areas (no explosion risk)
5. Complete NEK TS 606:2025 Cable Types List
5.1 Power Cables (P-Series)
| Type Code | Construction | Voltage Rating | Key Features |
|---|---|---|---|
| P101 | RFOU / TFOU | 0.6/1 (1.2) kV | Low voltage power, flame retardant, most common offshore cable |
| P102 | RFOU / TFOU | 3.6/6 (7.2) kV | Medium voltage power distribution |
| P103 | RFOU / TFOU | 6/10 (12) kV | Medium voltage, common platform distribution voltage |
| P104 | RFOU / TFOU | 8.7/15 (17.5) kV | Medium voltage for large platforms |
| P105 | BFOU | 0.6/1 kV | Fire resistant, emergency power systems |
| P106 | BFOU | 3.6/6 (7.2) kV | Fire resistant, medium voltage emergency systems |
| P107 | BFOU | 6/10 (12) kV | Fire resistant, critical MV systems |
| P108 | UX | 0.6/1 kV | Earth/bonding cable, no armor, flame retardant |
| P109 | TFLI | 250 V | Lighting cable, thermoplastic insulation |
| P110 | BU | 0.6/1 kV | Fire resistant, unarmored, flexible installation |
| P111 | RU / TU | 0.6/1 kV | Flame retardant, unarmored, lightweight |
| P112 | RFOU / TFOU | 12/20 (24) kV | High voltage distribution |
| P113 | RFOU / TFOU | 18/30 (36) kV | High voltage, large platform main feeders |
| P113 | RFOU / TFOU | 76/132 (145) kV | Extra high voltage, platform-to-shore connections |
| P114 | RFOU-HCF / TFOU-HCF | 6/10 (12) kV | Hydrocarbon fire resistant, enhanced fire protection |
| P115 | RFOU-HCF / TFOU-HCF | 8.7/15 (17.5) kV | Hydrocarbon fire resistant, MV applications |
| P116 | RFOU-HCF / TFOU-HCF | 12/20 (24) kV | Hydrocarbon fire resistant, HV distribution |
| P117 | RFOU-HCF / TFOU-HCF | 18/30 (36) kV | Hydrocarbon fire resistant, HV feeders |
| P117 | RFOU / TFOU-HCF | 76/132 (145) kV | Hydrocarbon fire resistant, extra HV applications |
| P118 | BFOU-HCF | 0.6/1 kV | Fire + Hydrocarbon fire resistant, critical safety systems |
| P119 | RX / TX | 0.6/1 kV | Earth cable with EPR/XLPE insulation, no armor |
| P120 | RFOU / TFOU – FIRE RESISTANT | 3.6/6 (7.2) kV | Special fire resistant qualification (non-standard) |
| P121 | RFOU / TFOU – FIRE RESISTANT | 6/10 (12) kV | Special fire resistant qualification |
| P122 | RFOU / TFOU – FIRE RESISTANT | 8.7/15 (17.5) kV | Special fire resistant qualification |
| P123 | RFOU / TFOU – FIRE RESISTANT | 12/20 (24) kV | Special fire resistant qualification |
| P124 | RFOU / TFOU – FIRE RESISTANT | 18/30 (36) kV | Special fire resistant qualification |
| P125 | SFOU | 0.6/1 (1.2) kV | Silicone fire resistant, extreme temperature applications |
Source: NEK TS 606:2025 Annex A – Power Cable Specifications
5.2 Instrumentation Cables (S-Series)
| Type Code | Construction | Voltage | Screening | Application |
|---|---|---|---|---|
| S101 | RFOU(i) | 250 V | Individual pair | High EMI protection instrumentation |
| S102 | RFOU(i)c | 250 V | Individual + Collective | Maximum EMI protection, dual screening |
| S103 | BFOU(i) | 250 V | Individual pair | Fire resistant instrumentation, emergency systems |
| S104 | BFOU(c) | 250 V | Collective | Fire resistant, collective screen |
| S105 | RU(i) | 250 V | Individual pair | Unarmored, individual screening, flexible |
| S106 | RU(c) / TU(c) | 250 V | Collective | Unarmored, collective screen |
| S107 | BU(i) | 250 V | Individual pair | Fire resistant, unarmored, individual screen |
| S108 | BU(c) | 250 V | Collective | Fire resistant, unarmored, collective screen |
| S109 | BFOU-HCF(i) | 250 V | Individual pair | Hydrocarbon fire + fire resistant, individual screen |
| S110 | BFOU-HCF(c) | 250 V | Collective | Hydrocarbon fire + fire resistant, collective screen |
| S111 | RX / TX | 250 V | None | Signal/control cable, no armor, no screening |
| S112 | SFOU(i) | 250 V | Individual pair | Silicone fire resistant, individual screen |
| S113 | SFOU(c) | 250 V | Collective | Silicone fire resistant, collective screen |
Reeling Cable specialists note that instrumentation cable selection depends on the noise environment, with individually screened pairs (i) providing superior EMI rejection for 4-20mA analog signals and thermocouple circuits.
5.3 Fiber Optic Cables (F-Series)
| Type Code | Construction | Fiber Type | Application |
|---|---|---|---|
| F101 | QFCI | Loose tube, collective screen, thermoplastic sheath | Data communication, SCADA, general offshore networking |
| F102 | QFCI-HCF | Loose tube, hydrocarbon fire resistant | Critical communication systems requiring HCF protection |
| F103 | QFCB | Loose tube, fire resistant (mica tape barrier) | Emergency communication systems, fire detection networks |
| F104 | AICI | Tight buffered, aramid strength member | Compact installations, harsh environment data links |
5.4 DC Power Cables (D-Series)
| Type Code | Construction | Voltage Rating | Application |
|---|---|---|---|
| D101 | RU / TU | 1500 V DC | DC power distribution, battery systems, unarmored |
| D102 | RFOU / TFOU | 1500 V DC | DC power distribution, armored, mechanical protection |
| D103 | BU | 1500 V DC | Fire resistant DC, emergency DC systems, unarmored |
| D104 | BFOU | 1500 V DC | Fire resistant DC, critical safety systems, armored |
6. Compliance with International Standards
6.1 Primary Standards References
| Standard | Title | Application in NEK 606 |
|---|---|---|
| IEC 60092-350 | Shipboard power cables – general construction | Base standard for cable construction requirements |
| IEC 60092-353 | Shipboard power cables – single core non-radial field cables | Construction requirements for BFOU, BU cables |
| IEC 60092-354 | Shipboard power cables – single and multicore screened cables | Construction for RFOU, TFOU medium/high voltage cables |
| IEC 60092-360 | Shipboard insulated cables – materials and tests | Base material specifications (NEK 606 requirements more stringent) |
| IEC 60092-376 | Instrumentation and telecommunication cables | Requirements for S-series instrumentation cables |
| IEC 60228 | Conductors of insulated cables | Conductor sizing, stranding classes, resistance values |
| IEC 60331-21 | Fire resistance tests – cables ≥20mm diameter | Mandatory for BFOU fire resistant cables |
| IEC 60331-31 | Fire resistance tests – cables <20mm diameter | Mandatory for small diameter BFOU cables |
| IEC 60332-1-2 | Flame propagation – single vertical insulated wire/cable | Required for single core cables, earth cables |
| IEC 60332-3-22 | Flame propagation – bundled cables (Category A) | Mandatory for all NEK 606 power and control cables |
| IEC 60754-1 | Halogen content determination – halogen acid gas content | Required: ≤5 mg/g halogen for halogen-free claim |
| IEC 60754-2 | Halogen content determination – pH and conductivity | Required: pH ≥4.3, conductivity ≤10 μS/mm |
| IEC 61034-1, -2 | Smoke density measurement | Required: ≥60% light transmittance (low smoke) |
| EN 50200 | Fire resistance with water spray | Enhanced fire test for critical safety circuits |
| ISO 22899-1 | Hydrocarbon fire resistance test method | Required for all -HCF designated cables |
6.2 Third-Party Certification Bodies
DNV (Det Norske Veritas)
- Norwegian classification society
- Primary certification authority for NEK 606
- Type approval designation: DNV-CP-0417
- Factory production control audits
- Sample testing program
Lloyd’s Register (LR)
- UK-based classification society
- Widely accepted in North Sea operations
- Type approval for NEK 606 cables
- Material approval program
- Quality system certification
ABS (American Bureau of Shipping)
- US classification society
- Required for US flag vessels
- NEK 606 recognition program
- Quarterly production testing
- Material traceability requirements
Anhui Feichun Special Cable Certifications
Feichun Cable maintains comprehensive third-party approvals for NEK TS 606 cables:
- DNV Type Approval Certificate (CP-0417) for full NEK 606 product range
- Lloyd’s Register Type Approval for BFOU and RFOU cables 0.6/1 kV to 35 kV
- ABS Product Design Assessment for NEK 606 compliance
- ISO 9001:2015 Quality Management System certification
- ISO 14001:2015 Environmental Management System certification
- In-house IEC 17025 accredited testing laboratory
7. Safety Thresholds and Operating Parameters
7.1 Temperature Ratings
| Operating Condition | EPR Insulation | XLPE Insulation | SHF2 Sheath |
|---|---|---|---|
| Minimum Installation Temp | -25°C | -10°C | -15°C |
| Minimum Operating Temp | -40°C | -20°C | -40°C |
| Maximum Continuous Operating Temp | +90°C | +90°C | +90°C |
| Emergency Overload Temp (100h/year) | +130°C | +130°C | +105°C |
| Short Circuit Temp (5 seconds max) | +250°C | +250°C | N/A |
7.2 Voltage Ratings and Insulation Thickness
| Voltage Rating U₀/U (Um) | Insulation Thickness (mm) EPR/XLPE | Test Voltage AC (5 min) | Typical Applications |
|---|---|---|---|
| 150/250 (300) V | 0.6 – 0.7 | 1.5 kV | Instrumentation, control, signaling |
| 0.6/1 (1.2) kV | 0.7 – 2.0 (size dependent) | 3.5 kV | Low voltage power distribution, motors |
| 3.6/6 (7.2) kV | 2.5 – 3.4 | 13 kV | Medium voltage distribution, switchgear |
| 6/10 (12) kV | 3.4 – 4.5 | 20 kV | Primary distribution voltage offshore |
| 8.7/15 (17.5) kV | 4.5 – 5.5 | 30 kV | Large platform distribution |
| 12/20 (24) kV | 5.5 – 6.5 | 42 kV | High voltage platform feeders |
| 18/30 (36) kV | 6.5 – 8.0 | 60 kV | Platform main incoming supply |
| 76/132 (145) kV | 15 – 18 | 220 kV | Subsea transmission, platform interconnection |
Voltage notation: U₀ = phase-to-earth voltage, U = phase-to-phase voltage, (Um) = maximum system voltage
7.3 Current-Carrying Capacity (Ampacity)
Ampacity Calculation Factors for NEK 606 Cables
NEK TS 606 cables follow IEC 60287 ampacity calculation methodology with the following considerations:
- Conductor Temperature: 90°C maximum continuous for EPR and XLPE
- Ambient Temperature: 45°C air, 25°C seawater (offshore platforms)
- Grouping Factor: 0.80 for cables touching in trefoil, 0.70 for cables in ladder/tray
- Armor Loss Factor: Tinned copper braid adds ~3-5% loss, steel braid ~8-12% loss
- Sheath Loss Factor: Metallic shields/sheaths induce additional losses in AC applications
Example Ampacity (P101 RFOU 0.6/1 kV, 90°C conductor, 45°C ambient, single cable in air):
| Conductor Size | 1-Core | 2-Core | 3-Core | 4-Core |
|---|---|---|---|---|
| 1.5 mm² | 22 A | 20 A | 18 A | 16 A |
| 2.5 mm² | 30 A | 27 A | 24 A | 22 A |
| 4 mm² | 40 A | 36 A | 32 A | 28 A |
| 10 mm² | 70 A | 63 A | 56 A | 50 A |
| 25 mm² | 115 A | 104 A | 92 A | 82 A |
| 50 mm² | 168 A | 152 A | 134 A | 120 A |
| 95 mm² | 240 A | 217 A | 192 A | 172 A |
| 150 mm² | 315 A | 285 A | 252 A | 225 A |
Values are approximate and must be calculated for specific installation conditions per IEC 60287
8. Precautions for Use and Installation
8.1 Handling and Storage Requirements
Critical Pre-Installation Inspections
- Drum Condition: Inspect for shipping damage, moisture ingress, or cable end seal integrity. Reject drums with visible damage to flanges or core barrel
- Cable End Sealing: Verify factory-applied heat-shrink end caps are intact. Re-seal immediately if damaged. Moisture ingress voids warranty
- Insulation Resistance Testing: Perform IR test using 1000V DC megger before installation. Minimum acceptable: 100 MΩ·km at 20°C. Values <50 MΩ·km indicate moisture contamination
- Conductor Continuity: Verify continuity of all conductors, screens, and ground paths before pulling
- Identification: Confirm cable marking matches specification, voltage rating, and construction code
- Storage Duration: Cables stored >6 months require re-testing before installation. Maximum storage: 24 months in controlled conditions
8.2 Installation Guidelines
According to Mining Cable Chile, proper installation technique is critical for NEK 606 cable longevity in harsh offshore environments.
| Installation Parameter | RFOU/TFOU Cables | BFOU Cables | Notes |
|---|---|---|---|
| Minimum Bending Radius (Installation) | 8 × Cable OD | 10 × Cable OD | During pulling only |
| Minimum Bending Radius (Fixed) | 6 × Cable OD | 8 × Cable OD | After installation |
| Maximum Pulling Tension | 50 N/mm² conductor area | 40 N/mm² conductor area | Calculate per conductor CSA |
| Maximum Sidewall Pressure | 300 N per meter of bend radius | 250 N per meter of bend radius | In conduit bends |
| Installation Temperature (Minimum) | -10°C | -5°C | Warm cables if below minimum |
| Cable Lubricant | Water-based, non-corrosive | Water-based, non-corrosive | Verify compatibility with sheath |
| Support Spacing (Vertical) | Every 1.0 meter | Every 0.8 meter | Use non-metallic cleats |
| Support Spacing (Horizontal) | Every 0.3-0.5 meter | Every 0.3 meter | Prevent sagging |
8.3 Termination Requirements
Low Voltage (≤1 kV)
- Strip sheath and armor using appropriate tools
- Remove 40-60 mm armor, 80-100 mm sheath
- Bond tinned copper braid to ground terminal
- Use compression or mechanical lugs rated for tinned copper
- Apply shrink boots over termination for IP protection
- Minimum creepage distance: 10 mm per kV
Medium Voltage (>1 kV)
- Use only manufacturer-approved termination kits
- Clean insulation surface with 99% isopropanol
- Score semiconductor shield circumferentially before removal
- Apply stress control cone/boot per kit instructions
- Verify cone position aligns with shield termination ±5 mm
- Ground metallic shield at both cable ends
- Minimum strike distance per voltage rating
Instrumentation Cables
- Preserve pair twist to termination point
- Terminate drain wires to dedicated ground terminal
- Individual screens: ground one end only (signal reference)
- Collective screen: ground both ends
- Maintain shield continuity through connectors
- Use numbered ferrules matching cable identification
8.4 Testing After Installation
Mandatory Commissioning Tests
Before Energization:
- Insulation Resistance Test: 1000V DC megger, 1 minute soak time. Minimum IR: 100 MΩ·km
- Conductor Continuity: <1.0 Ω end-to-end for all conductors, screens, grounds
- Phase Identification: Verify correct phasing using phase rotation meter
- High Voltage Test (if specified): 80% of factory test voltage for 1 minute. Note: Not recommended for aged cables
- Functional Test: Energize at reduced voltage, verify connected equipment operates correctly
Annual Maintenance Testing:
- Insulation resistance (trending program, compare to baseline)
- Infrared thermography of terminations under load
- Visual inspection for mechanical damage, corrosion, jacket deterioration
- Partial discharge testing for MV cables (offline or online)
9. Common Problems and Troubleshooting
9.1 Installation-Related Failures
| Problem | Symptoms | Root Cause | Prevention/Solution |
|---|---|---|---|
| Low Insulation Resistance | IR <50 MΩ·km, may trip ground fault protection | Moisture ingress through damaged end seal or damaged sheath | Inspect end seals before installation, replace cable if IR cannot be restored by drying |
| Jacket Abrasion | Surface wear, exposed armor/bedding, reduced jacket thickness | Improper pulling technique, sharp cable tray edges, excessive friction | Use adequate lubrication, inspect cable path, apply protective sleeving at wear points |
| Armor Braid Damage | Broken braid wires, loss of screen continuity, EMI issues | Exceeding minimum bending radius, kinking during handling | Verify bending radius compliance, use appropriate pulling equipment, train personnel |
| Conductor Breakage | Open circuit, intermittent connection during vibration | Excessive pulling tension, sharp bends, conductor fatigue | Monitor pulling tension with load cell, respect minimum bend radii, replace damaged section |
| Shield Termination Errors | Circulating currents, overheating, ground loops, EMI problems | Incorrect grounding scheme (both ends grounded when should be single-point) | Follow manufacturer grounding diagram, use insulated glands when required, ground shields correctly |
9.2 Service-Related Issues
| Problem | Symptoms | Diagnostic Method | Corrective Action |
|---|---|---|---|
| Mud Attack on Sheath | Sheath softening, swelling, cracking, loss of mechanical properties | Visual inspection, Shore A hardness test, tensile/elongation testing | Verify cable has SHF2 MUD rating, replace if severely degraded, prevent mud contact with protective measures |
| Oil-Induced Degradation | Sheath swelling, plasticizer extraction, brittleness | Measure sheath diameter change, conduct oil resistance test per IEC 60092-360 | Confirm cable meets enhanced oil resistance requirements, replace with properly rated cable |
| UV Degradation (Exposed Cables) | Surface chalking, color fading, embrittlement, cracking | Visual examination, elongation at break test (should be >300%) | Install cables in conduit/tray, apply UV-resistant paint or tape, replace if mechanically compromised |
| Overheating at Terminations | Discoloration, melting of components, tripped overload protection | Infrared thermography (hot spots >15°C above ambient suspect), contact resistance measurement | De-energize, re-torque connections, clean oxidation, replace damaged lugs, verify proper conductor preparation |
| Partial Discharge Activity | Audible noise, ozone smell, progressive insulation degradation, eventual failure | Online or offline PD testing, locate discharge source, measure magnitude in pC | Investigate termination quality, check for moisture ingress, consider cable replacement if PD >50 pC |
| Ground Fault | Ground fault relay operation, loss of power, visible arcing | IR testing (phase-to-ground), time domain reflectometry for fault location | Locate fault using TDR or tracer, excavate/expose cable, cut out damaged section and splice, or replace cable |
9.3 Fire Performance Concerns
Post-Fire Cable Assessment
After a fire incident on an offshore platform, all cables in the affected zone must be assessed before returning to service:
Visual Inspection:
- Discoloration, charring, or melting of jacket material
- Deformation or sagging indicating excessive heat exposure
- Exposed conductor or insulation
- Damage to support systems or cable trays
Electrical Testing:
- Insulation resistance: must meet new cable standards (>100 MΩ·km)
- Dielectric withstand test at 80% factory voltage (consult with manufacturer)
- Continuity verification of all conductors and grounds
- Partial discharge testing to detect insulation damage
Decision Criteria:
- Replace: Any cable showing visible damage, IR <50 MΩ·km, or PD >10 pC
- Monitor: Cables passing electrical tests but in fire zone – implement enhanced surveillance program
- Return to Service: Only cables completely outside fire/smoke zone with normal test results
Critical Note: Fire resistant BFOU cables that maintained circuit integrity during fire should still be replaced after incident, as mica tape barrier may be compromised even if cable functioned during emergency.
10. Selecting the Correct NEK 606 Cable Type
10.1 Selection Decision Tree
Step-by-Step Cable Selection Process
Step 1: Determine Fire Performance Requirement
- Question: Must the cable maintain circuit integrity during fire?
- YES → Use BFOU (fire resistant) for: Emergency shutdown systems, fire/gas detection, emergency lighting, public address, fire pump power, life safety systems
- NO → Use RFOU/TFOU (flame retardant) for: General power distribution, non-critical instrumentation, lighting in safe areas
Step 2: Determine Voltage Level
- Instrumentation & Control: 250V (S-series)
- Low Voltage Power: 0.6/1 kV (P101, P105)
- Medium Voltage: 3.6/6 kV to 18/30 kV (P102-P104, P106-P107, P112-P113)
- High Voltage: 76/132 kV (P113)
Step 3: Assess Environmental Exposure
- Drilling Mud Exposure: Specify SHF2 MUD resistant sheath (all drilling areas)
- Hydrocarbon Pool Fire Risk: Specify -HCF designation (process areas, wellhead)
- Mechanical Damage Risk: Consider galvanized steel braid armor (C) instead of copper braid (O)
- Weight Constraints: Consider unarmored types (RU, BU, TU) where mechanical protection not essential
Step 4: Select Insulation Material
- EPR (R): Superior low-temperature flexibility (-40°C), preferred for instrumentation and arctic applications
- XLPE (T): Better electrical properties, higher ampacity, preferred for medium/high voltage power
Step 5: Determine Screening Requirements (Instrumentation Only)
- Individual (i): Each pair/triple separately screened, maximum EMI protection, 4-20mA analog signals
- Collective (c): Single screen over all pairs, adequate for digital signals, lower cost
- Combination (i+c): Individual plus collective screening, maximum protection in extreme EMI environments
10.2 Application-Specific Recommendations
| Application | Recommended Type | Rationale |
|---|---|---|
| Emergency Shutdown (ESD) System | S103 BFOU(i) 250V | Fire resistant, individual screening, maintains function during fire |
| Fire & Gas Detection | S103 BFOU(i) 250V | Fire resistant, EMI protected, life safety critical |
| Emergency Lighting | P105 BFOU 0.6/1 kV | Fire resistant power cable, maintains lighting during evacuation |
| Process Control (4-20mA) | S101 RFOU(i) 250V | Individual screening prevents signal interference, adequate fire performance |
| DCS Digital I/O | S102 RFOU(c) 250V or S102 RFOU(i)c 250V | Collective screening adequate for digital, double screening for noisy areas |
| Main Platform Power (10 kV) | P103 TFOU 6/10 kV | XLPE offers best electrical performance and ampacity for power feeders |
| Drilling Equipment Power | P101 RFOU 0.6/1 kV (SHF2 MUD) | Mud resistant rating essential, EPR flexibility advantage |
| Variable Frequency Drive (VFD) | P101 RFOU 0.6/1 kV + additional copper braid | Standard power cable with enhanced screening for VFD noise |
| Thruster Motor Power | P102 TFOU 3.6/6 kV | MV power, seawater environment, XLPE moisture resistance |
| Wellhead Control Panel | S101 RFOU(i) 250V (SHF2 MUD) | Instrumentation cable, mud resistant, hydrocarbon exposure |
| Helideck Lighting | P105 BFOU 0.6/1 kV | Fire resistant for life safety, outdoor UV exposure |
| Telecommunications/Data | F101 QFCI or F103 QFCB | Fiber optic, QFCB if fire resistance required for critical data |
| Cathodic Protection | D102 RFOU 1500V DC | DC rated, suitable for impressed current systems |
| UPS Battery Strings | D103 or D104 BFOU 1500V DC | Fire resistant DC cable for emergency power backup |
Expert Cable Selection Service
Feichun Cable provides comprehensive technical support for NEK TS 606 cable selection:
- Application-specific cable recommendations based on project specifications
- Ampacity calculations for actual installation conditions
- Cable schedule review and optimization
- Third-party certification coordination (DNV, LR, ABS)
- Factory acceptance testing witness services
- Installation supervision and commissioning support
Contact our technical team:
- Email: [email protected]
- Sales: [email protected]
- WhatsApp: +86 138 5512 3218
11. Conclusion
NEK TS 606:2025 represents the pinnacle of cable specifications for offshore and marine applications, providing comprehensive requirements that ensure safety, reliability, and performance in the world’s most challenging environments. The systematic code designation system enables precise cable identification and selection, while the rigorous testing requirements guarantee that cables will perform as expected when lives depend on them.
Understanding the NEK 606 cable code designation is essential for engineers, procurement specialists, and installation personnel working in the offshore oil and gas industry. The distinction between fire resistant (BFOU) and flame retardant (RFOU/TFOU) cables is particularly critical, as incorrect selection can compromise life safety systems during emergencies.
The 2025 edition of NEK TS 606 continues to evolve, incorporating lessons learned from decades of offshore operations and advancing cable technology. The addition of hydrocarbon fire resistant (-HCF) designations and enhanced mud resistance requirements reflects the industry’s commitment to continuous improvement in safety and reliability.
Key Takeaways
- NEK TS 606 is more stringent than IEC 60092 series, particularly for oil/mud resistance
- The 4-letter code system (e.g., RFOU, BFOU) precisely describes cable construction
- Fire resistant (B) cables must maintain circuit integrity for 2-3 hours during fire
- Flame retardant (R/T) cables prevent fire propagation but do not maintain circuit function
- All NEK 606 cables are halogen-free, low smoke, and either oil resistant or mud resistant
- Third-party certification (DNV, LR, ABS) is essential for offshore applications
- Proper installation technique and post-installation testing are critical for reliability
- Cable selection must consider application criticality, environmental exposure, and voltage requirements
12. References and Additional Resources
Standards and Specifications
- NEK TS 606:2025 – Cables for Offshore Installations (Norwegian Electrotechnical Committee)
- IEC 60092 series – Electrical installations in ships (Parts 350, 353, 354, 360, 376)
- IEC 60331-21, -31 – Fire resistance tests for electric cables
- IEC 60332-1-2, -3-22 – Flame propagation tests
- IEC 60754-1, -2 – Halogen content determination
- IEC 61034-1, -2 – Smoke density measurement
- IEC 60228 – Conductors of insulated cables
- IEC 60287 series – Calculation of current rating
- ISO 22899-1 – Determination of the resistance to fire of cables – Hydrocarbon fire
- EN 50200 – Method of test for resistance to fire for cables with water spray
Technical content compiled from NEK TS 606:2025, IEC standards, DNV certification guidelines, and manufacturer technical documentation
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