NEK TS 606 · IEC 60092 · Offshore cable designations
RFOU and BFOU are NEK TS 606 offshore cable designations. In the common constructions compared here, RFOU provides flame-retardant performance; BFOU adds a fire-resistant insulation system for specified circuit-integrity requirements. Check the complete designation, sheath grade and test evidence: RFOU-FR and RFOU-HCF are distinct fire-resistant variants, and an SHF2 sheath alone does not establish mud resistance.
B = fire-resistant insulation system
(c) collective
150/250 (300) V
0.6/1 kV
Confirm mud-resistance grade
What RFOU and BFOU cables are
RFOU and BFOU are type designations used in NEK TS 606, the technical specification published by Norsk Elektroteknisk Komite for cables on offshore oil and gas installations. They are not IEC type codes and they are not brand names. They are a shorthand in which each letter names one physical layer of the cable, read from the conductor outwards.
A designation such as RFOU(i) identifies a construction family. Decoding it helps compare the basic layers; the complete datasheet and test evidence are still needed to compare ratings, dimensions and suitability for the project.
- NEK TS 606
- Norwegian technical specification covering halogen-free and/or mud-resistant cables for offshore installations. Built on the IEC 60092 series, with additional requirements for the specified cable types.
- RFOU
- An EPR-insulated, halogen-free cable family with a copper braid and SHF2 sheath. The ordinary construction compared here is flame retardant; check any additional fire-resistance or mud-resistance designation.
- BFOU
- A fire-resistant construction commonly using mica tape beneath EPR insulation. Its circuit-integrity claim is limited to the applicable test conditions, duration and supporting evidence.
- Mud resistance
- Resistance to the drilling fluids and exposure conditions covered by the specified test. Confirm a mud-resistant sheath grade and supporting NEK TS 606 test evidence.
- (i) and (c)
- Screening arrangement on instrumentation types: each pair or triad screened separately, or one screen over the whole lay-up.
The letter code, layer by layer
Published construction tables for NEK 606 cables map the designation letters directly onto layers. Reading RFOU from the inside out:
| Letter | Layer | What it is |
|---|---|---|
| — | Conductor | Tinned annealed stranded copper, IEC 60228 class 2 |
| R | Insulation | EP rubber (EPR) to IEC 60092-360 |
| B | Insulation | Mica tape plus EP rubber — the fire-resistant alternative to R |
| F | Inner covering | Flame-retardant, halogen-free thermoset bedding |
| O | Braid | Tinned annealed copper wire braid |
| U | Outer sheath | Halogen-free thermoset sheath, SHF2 to IEC 60092-360; confirm mud resistance from the complete designation and test evidence |
The common RFOU construction uses EPR insulation, halogen-free bedding, copper braid and an SHF2 outer sheath. A common BFOU construction adds mica tape beneath the EPR insulation. R and B identify the insulation position in the designation; the full datasheet still determines dimensions, ratings and environmental performance.
What the U does not mean
The U is not “unarmoured”. U identifies the SHF2 thermoset outer sheath in the constructions discussed here; mud resistance needs a separate check. Unarmoured instrumentation families include RU and BU. Confirm the full code and construction record instead of inferring armour or environmental performance from U alone.
The distinction matters commercially. If a specification calls for RFOU and a quotation offers RU, the difference is not a naming preference — a copper braid and a bedding layer have been removed. That changes screening performance, mechanical robustness and price. Comparing the two codes letter by letter surfaces the substitution immediately. What a copper braid does that a served wire layer does not is explained in braided vs spiral cable shields.
RFOU vs BFOU: flame retardant is not fire resistant
This is the single most consequential distinction in the whole family, and the two terms are routinely used as if they were interchangeable. They describe opposite expectations of a cable during a fire.
Flame-retardant performance limits flame spread under the specified test conditions; it does not establish circuit integrity. Fire-resistant performance demonstrates circuit integrity for the conditions and duration of the applicable test. Neither term means that a cable will survive every real fire.
| Attribute | RFOU | BFOU |
|---|---|---|
| Insulation system | EPR | Mica tape + EPR |
| Fire behaviour | Flame retardant, self-extinguishing | Flame retardant and fire resistant |
| Circuit integrity | Not claimed for the ordinary RFOU construction compared here | Demonstrated only for the specified test conditions and duration |
| Flame spread tests | IEC 60332-1-2, IEC 60332-3-22 | IEC 60332-1-2, IEC 60332-3-22 |
| Circuit integrity test | No circuit-integrity claim for the ordinary RFOU construction compared here | Applicable IEC 60331 test and project requirements; confirm voltage, cable diameter, test conditions and duration |
| Halogen free / low smoke | IEC 60754, IEC 61034 | IEC 60754, IEC 61034 |
| Mud resistance | Confirm specified mud-resistant variant and tests | Confirm specified mud-resistant variant and tests |
| Typical duty | General power, control and instrumentation | Circuits that must survive: ESD, fire and gas, emergency lighting, shutdown valves |
Use the project fire strategy to decide which circuits require a defined period of circuit integrity. Specify a construction with matching test evidence for those circuits. Ordinary RFOU should not replace a specified fire-resistant construction; separately assess any RFOU-FR or RFOU-HCF variant.
(i) or (c): screening arrangement and S-codes
The bracketed suffix applies to instrumentation types rated 150/250 (300) V. It states how the screens are arranged, and it changes the cable’s behaviour against interference rather than its fire performance.
(i) — individually screened. Every pair, triad or quad gets its own screen and drain wire, then a barrier tape so adjacent elements do not make contact. Signals in one pair are isolated from the others. This is the arrangement for mixed-signal multicore runs and for low-level analogue instrumentation.
(c) — collectively screened. The elements are laid up and a single screen is applied over the whole assembly. Interference from outside is handled; crosstalk between pairs inside the cable is not. Cheaper, smaller, and entirely adequate when every element in the cable carries the same class of signal.
| Type | Screening | 2025 code |
|---|---|---|
| RFOU(i) | Individual | S101 |
| RFOU(c) | Collective | S102 |
| BFOU(i) | Individual | S103 |
| BFOU(c) | Collective | S104 |
| RU(i) | Individual | S105 |
| RU(c) | Collective | S106 |
| BU(i) | Individual | S107 |
| BU(c) | Collective | S108 |
Older catalogues use labels such as S1/S5, S2/S6, S3/S7 and S4/S8. These are legacy catalogue references, not the code list used in the 2025 table above. Confirm the edition, full type designation and construction before treating an old reference as equivalent to a current code.
Quoting the S-code alongside the type designation removes almost all ambiguity from an enquiry, because the code fixes insulation, screening and braid in a single token.
Which IEC 60092 part applies
A recurring confusion is treating IEC 60092 as one document. It is a series, and the part number that belongs on a datasheet is decided by circuit duty and voltage — not by screening, and not by fire class.
| Part | Scope | Applies when |
|---|---|---|
| IEC 60092-350 | General construction and test methods for shipboard and offshore power, control and instrumentation cables, up to 18/30 (36) kV | Always — the umbrella document |
| IEC 60092-352 | Choice and installation of electrical cables | Installation design, not cable manufacture |
| IEC 60092-353 | Non-radial field power cables with extruded solid insulation, 1 kV and 3 kV | 0.6/1 kV power cables — RFOU and BFOU power types |
| IEC 60092-354 | Power cables 6 kV (Um 7.2 kV) to 30 kV (Um 36 kV) | Medium-voltage runs, including MV RFOU types |
| IEC 60092-360 | Insulating and sheathing materials | Defines EPR and the SHF2 sheath compound |
| IEC 60092-376 | Cables for control and instrumentation circuits, 150/250 V (300 V) | All (i) and (c) instrumentation types |
| IEC TR 60092-370 | Guidance on selecting telecommunication and data cables | Data and RF routes — a technical report, not a construction standard |
So a 0.6/1 kV BFOU power cable sits under IEC 60092-353, while a BFOU(i) 150/250 V instrumentation cable sits under IEC 60092-376. Same fire class, same manufacturer, different part number — because the circuit duty differs. A datasheet that cites the wrong part is usually a copy-paste error rather than a construction problem, but it is worth querying before approval.
For offshore drive-to-motor circuits, compare the BFOU VFD 1.8/3 kV cable construction and size table alongside the drive’s cable and termination requirements.
For fixed medium-voltage feeders, compare the RFOU P-series and BS 6883 MVA cable tables by voltage class, screen, armour and sheath. The RFOU and MVA ranges use separate voltage selections and dimensions; retain the specified family when preparing the cable schedule.
Working the other way round: if you know the voltage and the circuit duty, you already know which part to demand on the test certificate. A 150/250 V instrumentation cable submitted without an IEC 60092-376 reference is an incomplete submission.
Where NEK TS 606 goes beyond IEC 60092
NEK TS 606 is built on the IEC 60092 series, but a cable that satisfies IEC 60092 does not automatically satisfy NEK TS 606. The specification adds requirements shaped by the North Sea drilling environment.
| Requirement | IEC 60092 baseline | NEK TS 606 position |
|---|---|---|
| Oil resistance | Standard resistance requirements | Stricter enhanced oil resistance requirements and tests |
| Mud resistance | Not a dedicated requirement | Dedicated drilling-fluid resistance requirement and test |
| Hydrocarbon fire | Not covered | Test methods for hydrocarbon (HC) fire-resistant cables |
| Jet fire | Not covered | Test methods for jet fire (JF) resistant cables |
Hydrocarbon and jet fire are worth separating in your own mind from ordinary fire resistance. A standard IEC 60331 circuit-integrity test uses a flame far cooler than a pressurised hydrocarbon release. Where a fire risk assessment identifies HC or jet fire exposure, an ordinary BFOU is not the answer — the HC and JF variants exist precisely because the base test does not represent that scenario.
Check the edition on the datasheet
NEK 606 was first published in 1993 and has been revised repeatedly. The current issue is NEK TS 606:2025, edition 7, which replaced NEK TS 606:2022. The instrumentation standard beneath it has moved too: IEC 60092-376 reached edition 4 in 2025, superseding the 2017 third edition and the 2003 second edition.
NEK TS 606:2025 removed IEC 60331-21 and IEC 60331-25 and introduced IEC 60331-4. Its references include IEC 60331-1 and -2 for cables up to 0.6/1.0 kV, selected by overall diameter, and -4 for cables above 1 kV up to 30 kV. An older datasheet is not proof of a defect or of compliance with a newer edition: compare its test evidence with the edition and conditions required by the project.
Corrected on 8 October 2026 using NEK’s official 2025 preview: the code list and fire-test references above follow its pages 5, 7 and 9; legacy catalogue labels are shown separately.
A short diligence sequence that catches most problems: which edition of NEK TS 606 does the test report cite · which IEC 60092 part matches the voltage and duty · was circuit integrity tested to IEC 60331 if the type letter is B · does the sheath compound test to SHF2 · is the S-code stated, not just the type name.
Choosing between them
The choice is rarely free. On a live installation it is usually already made by the fire and gas philosophy, the safety case, and the requirements of the classification or verification body. What follows is how the decision decomposes, not permission to make it unilaterally.
Start with the circuit, not the cable. Ask whether this circuit must keep operating during a fire. Emergency shutdown, fire and gas detection, emergency lighting and safety-critical valve actuation normally must. General lighting, small power and routine process instrumentation normally need not.
Then set the voltage and duty, which fixes the IEC 60092 part and separates power types from instrumentation types.
Then choose screening. Mixed signal levels in one cable, or low-level analogue measurement, points to (i). Uniform signals point to (c).
Then confirm the environment. Drilling fluid exposure makes the mud-resistant SHF2 sheath non-negotiable. HC or jet fire exposure escalates the requirement beyond ordinary BFOU.
What an enquiry should state
Most delay in offshore cable enquiries comes from missing information rather than difficult requirements. Stating the following turns a quotation round trip into a single exchange.
| Item | Why it changes the answer |
|---|---|
| Type designation and S-code | Fixes insulation, screening and braid in one token |
| Voltage rating | Decides the IEC 60092 part and the construction family |
| Number of pairs, triads or cores, and cross-section | Drives dimensions, weight and price |
| Fire requirement | Flame retardant only, circuit integrity, or HC / JF |
| Edition of NEK TS 606 named in the project specification | Determines which test evidence is acceptable |
| Length per drum and total length | Affects drumming and delivery planning |
| Sheath colour and required marking text | OEM and ODM sheath printing is available on request |
| Documentation required at delivery | Test reports and traceability are prepared to order |
TEBAOFLEX manufactures marine and offshore cable designed to NEK TS 606 and the IEC 60092 series, with a minimum order quantity of 50 m and a production lead time of 7 to 45 working days depending on construction and quantity.
Common questions
What does RFOU stand for?
For the common construction discussed here, R identifies EPR insulation, F the inner covering, O a tinned copper wire braid, and U an SHF2 thermoset outer sheath. Confirm mud resistance and other additional requirements from the complete designation and datasheet.
What is the difference between RFOU and BFOU cable?
The ordinary RFOU and common BFOU constructions differ chiefly in their fire-performance requirements: BFOU incorporates a fire-resistant insulation system, commonly mica tape beneath EPR, with circuit-integrity test evidence. Other dimensions and ratings can differ. RFOU-FR and RFOU-HCF must be assessed as separate variants.
What does BFOU mean?
BFOU is the fire-resistant counterpart of RFOU under NEK TS 606. The B denotes mica tape combined with EP rubber at the insulation layer; F, O and U carry the same meanings as they do in RFOU.
Does the U in RFOU mean unarmoured?
No. U identifies an SHF2 thermoset outer sheath in these constructions. It does not identify the armour or prove mud resistance. Check the complete designation and test evidence; RU and BU are unarmoured instrumentation families.
Is NEK 606 the same as IEC 60092?
No. NEK TS 606 is built on the IEC 60092 series but adds stricter enhanced oil resistance and mud resistance requirements, plus test methods for hydrocarbon fire and jet fire resistance that the IEC parts do not cover. Compliance with IEC 60092 alone does not demonstrate compliance with NEK TS 606.
Which edition of NEK TS 606 is current?
NEK TS 606:2025, edition 7, which replaced the 2022 edition. Many datasheets in circulation still reference the 2009 edition, so it is worth confirming which edition the type test evidence was produced against.
Can RFOU be substituted for BFOU?
Ordinary RFOU should not replace a specified fire-resistant BFOU construction where circuit integrity is required. BFOU is not an automatically acceptable substitute in the other direction: confirm the complete electrical, dimensional, installation and approval requirements against the project specification.
Related cable routes
Where this guide ends, the product records begin. Each of the following carries construction detail, dimensions and the standards referenced for that specific type.
- Marine and offshore cables — the full range, organised by type and voltage
- 0.6/1 kV RFOU cable for marine and offshore projects — flame-retardant power construction
- 5G 35 mm² RFOU cable — product record with separate power and instrumentation construction references
- NEK 606 BFOU cable — separate power, BFOU(i) and BFOU(c) construction references
- NEK 606 P108 UX offshore earth cable — earthing and equipotential bonding
- TCu/MGT/EPR/ZH/GSWB/ZH 0.6/1 kV SW4 marine cable — braided armour with mica glass tape construction
For the wider selection logic across a facility, the oil and gas cable selection guide works through circuit duty, environment and armour together. If your scope also covers onshore instrumentation to British specifications, the PAS 5308 instrumentation cable guide covers the equivalent pair and triad decisions under a different standard family. Project-level requirements are set out under marine and offshore solutions and subsea and marine cable engineering.
Refinery and petrochemical instrument loops on tray, trunking or conduit that keep to the British polyethylene-insulated, unarmoured construction are covered by the PAS5308 Part 1 Type 1 instrumentation cable with collective or individual and collective screening.
The flame-retardant versus fire-resistant distinction also decides building voice-alarm cables. A two-core speaker cable enquiry from the Philippines that named a fire-resistant reference and was supplied as a screened PVC cable is worked through in the screened speaker cable record for the Philippines, with the IEC and British tests behind each term.
Send the type code, get a specific answer
Quote the designation and S-code, the voltage, the element count and the NEK TS 606 edition named in your specification. That is enough for a construction-level response rather than a price range.
Sources and review status
Standard identity, edition history and the scope of NEK TS 606 were taken from Norsk Elektroteknisk Komite, the body that publishes the specification. IEC 60092 part scopes and current edition status were taken from the IEC webstore. Designation letters, S-codes and layer construction were cross-checked against published manufacturer construction tables for cables built to NEK TS 606.
This guide explains designations and standards. It is not a substitute for the project specification, the fire and gas philosophy, or the requirements of the classification or verification body governing your installation. Where those documents conflict with anything written here, they govern.
Written 2026-09-03. Technical references and designation guidance corrected 2026-10-08.