ClassNK Class Notations Explained: A Complete Guide

Introduction: how ClassNK describes a ship in a few letters

A ClassNK class line is a short code that tells you what a ship is, where she may trade and which extra standards she meets. Nippon Kaiji Kyokai (ClassNK) adds this code to the ship’s classification characters when she is registered. Every item in it marks either a special requirement the ship has met or a relaxation she has been granted.

This guide follows the ClassNK Notation Handbook, 2026-2 Edition (July 2026), in the handbook’s own order. It starts with the characters of class, moves through the six families of class notations, and then covers the environmental, comfort, safety and digital notations that owners add by choice. Near the end you will find class lines to decode yourself.

How a class line is built. The handbook gives the pattern as NS* followed by up to six groups, each in its own brackets. Each group has a fixed job.

Group	What it covers	Where it is defined
1	Restricted services	1.2.2, Part A
2	Structural materials for the main hull	1.2.3, Part A
3	Hull construction and equipment	1.2.4, Part A
4	Strengthening for navigation in ice, etc.	1.2.5, Part A
5	Application of hull structural analysis	1.2.6, Part A
6	Application of special survey scheme	1.2.7, Part A

Groups 2 and 3 share one bracket, so a class line such as NS*(FRP, YACHT) holds a hull material and a ship type together. A line such as NS*(CS)(TOB)(ESP) reads as a restricted service, a tanker type and an enhanced survey programme. In practice, the handbook’s own examples show survey schemes such as ESP, HCM-GBS, IWS and PSCM each in a bracket of their own.

One caution before you start. The handbook is a summary built to make notations easy to find. It takes account of the Rules up to July 2026, and any later amendment still applies. For the full requirements, go to the Regulations for the Classification and Registry of Ships and Part A of the Rules for the Survey and Construction of Steel Ships.

Characters of class: the foundation of every class line

Before any notation comes the basic character of class. ClassNK has two, and they show whether the Society watched the ship being built.

• NS* is the class of a ship whose plans ClassNK approved under the Ship Rules and which was built while under survey by ClassNK surveyors.
• NS is the class of a ship that was not built under ClassNK survey but has since been surveyed for classification.

Main propulsion machinery. When a ship with NS* or NS has main propulsion machinery installed, a matching machinery character follows.

• MNS* goes with ships that hold NS*.
• MNS goes with ships that hold NS.

Installation characters. These are separate characters, given when a ship’s installations have been surveyed under their own rules and found to comply. A star can be added if ClassNK approved the plans and surveyed the installation during construction. The handbook says the star applies only to cargo refrigerating installations, as in RMC*·CA. Since 1 July 2019 these characters are shown on the Certificate of Classification, because the old separate registration certificate was abolished.

• RMC and RMC·CA mark cargo refrigerating installations. The CA version adds a controlled atmosphere system.
• CHG marks cargo handling appliances.
• MPP marks marine pollution prevention installations.
• LSA marks safety equipment.
• CAA marks crew accommodation. It is for Japanese-flag ships only.
• RCF marks radio installations.
• MC marks a centralized monitoring and control system for main propulsion and essential auxiliary machinery.
• M0 marks operating systems for machinery spaces that are periodically unattended.
• M0·A, M0·B, M0·C and M0·D mark the Class A, B, C and D specific automation equipment of ships with those marks.
• BRS marks the bridge layout, bridge working environment and navigational equipment.
• BRS1 adds accident prevention systems to BRS.
• BRS1A adds bridge work assist systems to BRS1.
• DVS marks diving systems.
• PMM marks preventive machinery maintenance systems.
• IFC·M marks integrated fire control for category A machinery spaces and cargo areas.
• IFC·A marks integrated fire control for accommodation and service spaces.
• IFC·AM covers all of those spaces together.
• HMS marks a hull monitoring system. HMS·R adds continuous recording.
• AFS marks anti-fouling systems on ships.
• AFS·C is for ships where a barrier coat covers an existing non-compliant anti-fouling system.
• CCM marks centralized cargo monitoring and control systems.
• BWM marks ballast water management installations.
• IHM marks Part I of the Inventory of Hazardous Material, under the Rules for Ship Recycling.

One detail from the revision record: IHM joined this list in the 2025-3 revision and was removed from its earlier place under “Inventory of Hazardous Materials” in the same revision.

Class notations versus descriptive notes

A class notation is a formal part of the class line. A descriptive note is only extra information about the ship. The difference matters when you read a certificate, because a note never changes what the ship has to comply with.

When a class notation is added. ClassNK adds one when any of these four situations applies.

1. The ship is approved for a limited service area.
2. The ship is approved for a particular purpose.
3. The ship’s hull is strengthened for a particular purpose.
4. The ship falls outside the first three but ClassNK sees a need. The handbook gives five examples: a main hull made of a material other than steel, scantlings approved through detailed structural analysis such as advanced direct calculation, class granted on condition that a special scheme is used for class maintenance surveys, novel design features not covered by the current Rules, and corrosion prevention measures to specified standards.

Owners can also apply for notations that recognize measures taken to protect the marine environment, improve the crew’s working environment or serve other specific purposes. These follow separate ClassNK guidelines.

What a descriptive note does. Items such as special construction and the kind of cargo are entered in the Classification Register as descriptive notes when ClassNK thinks it necessary. They also appear on the Certificate of Classification. The handbook’s examples fall into five kinds.

Kind	Typical content
Restricted services	A distance limit or named waters, such as service up to 30 miles off the coast of Singapore, or service in the Philippines
Design condition	Compliance with the harmonized Common Structural Rules for bulk carriers and oil tankers (Part CSR-B&T); which holds may be empty on a bulk carrier (2 and 4 for a handy size, 2, 4 and 6 for a Panamax, 2, 4, 6 and 8 for a Cape size); double hull in all holds; design pressure and minimum temperature for gas carriers
Cargo	The cargo the ship was designed for, such as oils, chemicals and molasses, or cement
Purpose	The ship’s role, such as a high speed escort ship or a training ship
Others	Fatigue crack arrestors at hatch corners, a helicopter deck, the edition of the Environmental Guidelines used, and which engines are fitted with NOx or SOx control equipment

The gas carrier figures in the handbook show how a note looks in practice. An LPG carrier of the pressure type is listed with a design maximum pressure of 1.77 MPa and a minimum temperature of 0 degrees C. A low temperature LPG carrier is listed at 0.028 MPa and minus 46 degrees C. An LNG carrier is listed at 0.025 MPa and minus 163 degrees C. These are examples of how the note is worded, not fixed values for every ship.

Restricted services and structural materials (groups 1 and 2)

The first two groups answer two simple questions. Is the ship limited to certain waters, and is her hull made of something other than ordinary steel?

Restricted services. A ship classed for limited service gets one of these notations.

• CS (Coasting Service) is for ships that stay in coastal areas, generally within 20 miles of the nearest land, or in areas ClassNK treats as equivalent.
• SWS (Smooth Water Service) is for ships that work only in calm waters generally sheltered from the open sea by land, or equivalent areas.
• DSA (Designated Service Area) is for ships classed on the strength of their link to shore support facilities and operating in a specific sea area that support can reach. It also covers ships that work while moored or positioned in a specific sea area. The details of the area go in a descriptive note.
• RS (River Service) is for ships restricted to inland waterways such as rivers, or equivalent areas. Its rules sit in the Rules for the Survey and Construction of Inland Waterway Ships.

Structural materials for the main hull. A ship built of a material other than steel carries a notation for it.

• AL (Aluminium Alloy) is for ships made of aluminium alloy.
• FRP is for fibreglass reinforced plastic ships. It follows the Rules for the Survey and Construction of Ships of Fibreglass Reinforced Plastics, and is placed in the class line in the same way as the High Speed Craft rules describe.

Hull protection by highly ductile steel. The HP-HDS family is for ships that use ClassNK-approved highly ductile steel to improve hull protection after a collision or grounding. The plain HP-HDS notation covers the general case. The longer forms add two pieces of information: a letter for the area protected and a number for the steel grade.

Area protected	HD20 steel	HD35 steel	HD50 steel
Cargo area (C)	HP-HDS/C20	HP-HDS/C35	HP-HDS/C50
Machinery area (E)	HP-HDS/E20	HP-HDS/E35	HP-HDS/E50
Fuel oil tank (F)	HP-HDS/F20	HP-HDS/F35	HP-HDS/F50

Where highly ductile steel is used in several areas, ClassNK gives a combined notation that names those areas and the grades. The related guidance is the Guidelines for Use of Highly Ductile Steel.

Hull construction and equipment, part 1: structural rules, tankers and gas carriers (group 3)

Group 3 is the largest and the one most people read first. It tells you what kind of ship you are looking at. A ship with two functions, such as a combination carrier, is given the notation for her primary characteristic. The handbook’s examples are OC / TOB for ore and oil carriers, and BC with EQ C LB for a bulk carrier fitted to carry lumber.

Which structural rules apply

• ASR (Advanced Structural Rules) is for ships that fall under Part C of the Rules and were contracted on or after 1 July 2023. Sister ships of vessels built to the earlier Part C can still use that earlier version if their own contract date is before 1 January 2025.
• CSR is for bulk carriers on unrestricted international voyages of 90 m or more, and double hull oil tankers on unrestricted international voyages of 150 m or more, contracted on or after 1 July 2015. They must comply with Part CSR-B&T, and anything that Part does not cover follows the other Parts of the Rules. A descriptive note shows that CSR-B&T was applied.

Tankers (T)

• Tanker (T) is for ships that carry liquid cargo in tanks built into the hull structure.
• FLB is for liquid cargoes other than oils with a flash point on or below 60 °C.
• FLA is for the same kind of cargoes with a flash point above 60 °C.
• OB is for oils with a flash point on or below 60 °C.
• OA is for oils with a flash point above 60 °C.

The suffix joins the type letter in a class line, so you will meet TOB, TOA, TFLB and TFLA. For ships built for specific cargoes, the details go in descriptive notes.

Chemical tankers (CT)

• CT is for ships that carry dangerous chemicals in bulk under Part S. The type is chosen from the types defined in Part S.
• Type I is for products with very severe environmental and safety hazards. It needs the maximum preventive measures to stop an escape.
• Type II is for products with appreciably severe hazards. It needs significant preventive measures.
• Type III is for products with sufficiently severe hazards. It needs a moderate degree of containment to improve survival in a damaged condition.
• Type II&III is for ships that meet both the Type II and the Type III requirements.

A chemical tanker’s specific cargoes, and the design pressure and temperature of her cargo spaces, are entered as descriptive notes.

Liquefied gas carriers (LGC)

• LGC is for ships that carry liquefied gases in bulk under Part N, with a type chosen under Part N.
• 1G is for products that call for the maximum preventive measures against escape.
• 2G is for products that call for significant preventive measures.
• 2PG is for a gas carrier of 150 m or less in length, with independent type C tanks designed for a maximum allowable relief valve setting of at least 0.7 MPa gauge and a containment design temperature of minus 55 °C or above. A ship of that description over 150 m is treated as a type 2G ship.
• 3G is for products that call for moderate preventive measures.

A second notation names the cargo containment system, as in LGC 2G, IPT Type A.

• IPT Type A and IPT Type B are for independent prismatic tanks of type A or type B.
• IST Type B is for independent spherical tanks of type B.
• IT Type C is for independent tanks of type C, as in LGC 2PG, IT Type C.
• MT is for membrane tanks.
• OT is for other tank types.

Tank carriers (TC)

• TC is for ships that carry liquid cargo in independent tanks, other than chemical carriers and liquefied gas carriers. It uses the same four flash point suffixes as tankers: FLB, FLA, OB and OA.

Hull construction and equipment, part 2: ore carriers, bulk carriers and cargo ships

Ore carriers and special cargoes

• OC (Ore Carrier) is for ships that carry ore or similar high density cargoes. They generally have two longitudinal watertight bulkheads and a double bottom throughout the cargo spaces, and meet Part 2-3 of Part C.
• SCCS (Specially Constructed Cargo Ship) is for ships that carry cargoes whose moisture content can exceed the transportable moisture limit. The cargo details go in a descriptive note.

Bulk carriers (BC)

• BC (Bulk Carrier) is for ships that carry dry cargo in bulk. They generally have a single deck, a double bottom, and bilge hopper and topside tanks in the cargo spaces.
• BC-A is for bulk cargo of 1.0 t/m3 density and above, with specified holds empty at the designed maximum load draught and all ballast tanks empty.
• BC-B is for the same density range, loaded homogeneously at the designed maximum load draught with ballast tanks empty.
• BC-C is for bulk cargo below 1.0 t/m3, loaded homogeneously at the designed maximum load draught with ballast tanks empty.
• BCM (Bulk Carrier modified) is for a single deck ship with a double bottom and double-side skin along the cargo length, but without bilge hopper or topside tanks. It meets Part 2-2 of Part C.
• BC-XII is added for bulk carriers to which SOLAS chapter XII applies.
• NO MP (No Multi-port loading/unloading) is added to BC-A, BC-B or BC-C for ships that were not assessed for loading or unloading in several ports, as in BC-A, NO MP.
• GRAB is for ships that meet the grab operation requirements of Part 2-2 of Part C.
• GRAB [X] is for ships with a strengthened inner bottom for grab loading and discharging, designed for an unladen grab weight X of 20 tons or more under Part CSR-B&T. GRAB20 is the handbook’s example.

A bulk carrier whose maximum cargo density is limited to below 3.0 t/m3, or whose empty hold assignment at maximum draught is restricted, has the details written into a descriptive note. The handbook also says that GRAB, IWS and PSCM are not mandatory but are typically added as options.

Other cargo ships

• CNC (Container Carrier) is for ships that carry containers, generally with a double bottom in the cargo spaces, under Part 2-1.
• CPC (Chip Carrier) is for wood chip carriers. They are generally single-side skin ships with a single deck, a double bottom and bilge hopper tanks, under Part 2-4.
• HDCA (Heavy Deck Carrier) is for ships that carry heavy cargo on the upper deck and have no cargo holds below it.
• VC (Vehicles Carrier) is for ships that carry unoccupied motor vehicles, with several decks, under Part 2-6.
• RORO (Roll on-Roll off) is for ships whose cargo spaces are not normally subdivided and run over a substantial length or the whole length, with cargo loaded and unloaded horizontally. It also falls under Part 2-6.

Equipment for particular cargoes (EQ C)

These notations say a ship is equipped, not purpose-built, for a cargo.

• EQ C DG is for the carriage of dangerous goods.
• EQ C V is for motor vehicles with fuel in their own tanks.
• EQ C CNGPMV is for vehicle carriers equipped to carry motor vehicles powered by compressed natural gas.
• EQ C CHPMV is for vehicle carriers equipped to carry motor vehicles powered by compressed hydrogen.
• EQ C C is for the carriage of coal.
• EQ C LB is for the carriage of lumber.
• EQ LNG Bunkering is for liquefied gas carriers built to supply LNG, as propulsion fuel or otherwise, to other ships.

Hull construction and equipment, part 3: work ships, offshore units, barges and submersibles

Work ships (Part O)

• D (Dredger) is for dredgers.
• CV (Crane Vessel) is for ship-type crane ships. FC (Floating Crane) is for barge-type crane ships.
• TUG (Tug) is for tugs. TV (Towing Vessel) is for ocean tugs.
• EV (Escort Vessel) is for escort tugs that steer, brake and otherwise control an assisted ship during ordinary or emergency manoeuvring.
• P (Pusher) is for pusher tugs.
• UV (Utility Vessel) is for ships supporting a wide range of light duty work, such as carrying equipment, buoy laying, survey and research, fire-fighting and ferrying offshore workers within an oil field.
• SUL (Self-unloader) is listed beside the work ships, but it is a bulk cargo type. It is for ships with a single deck, a double bottom and hopper side and topside tanks in the cargo length, fitted with self-unloading facilities for dry bulk cargo.
• FFV (Fire Fighting Vessel) comes in three types, FFV1, FFV2 and FFV3, matched to the fire fighting equipment installed.
• OSV is for offshore supply vessels and AHV for anchor handling vessels.
• CL (Cable Layer) and PL (Pipe Layer) are for vessels that lay cables or pipes on the seabed.
• ORV is for oil recovery vessels.
• WTIS and WTIB are for ship-type and barge-type wind turbine installation vessels. SEWTIS and SEWTIB are the self-elevating versions. CSWTIU is for a column-stabilized wind turbine installation unit.
• WFSV-SOV is for wind farm support service operation vessels. WFSV-CTV is for wind farm crew transfer vessels.
• IP (Industrial Personnel) is for ships other than passenger ships, of 500 gross tonnage or more on international voyages (self-propelled), with large embarkation capacities that include industrial personnel.

Extra marks for fire fighting and wind farm vessels. An FFV line can carry marks for the equipment fitted, as in Fire Fighting Vessel Type 1 with WSS and FMS3.

• WSS is a water-spray system.
• MFG is a mobile high expansion foam generator.
• FMS1 to FMS4 are foam monitor systems with capacities of more than 1,000, 3,000, 6,000 and 12,000 litres a minute. FMS5 is two fixed low expansion foam monitors, with capacities above 5,000 litres a minute.
• HDC is added to WFSV-SOV or WFSV-CTV for heavy deck cargo.

Mobile offshore drilling units

• SEDU is for self-elevating units, CSDU for column-stabilized units, DV for ship-type drilling vessels and DB for drilling barges.
• MODU is added for units that comply with the 2009 MODU Code (IMO Resolution A.1023(26)), as in MODU/SEDU.

Special purpose barges. SB (Storage Barge) is for storage; where oil is stored, the notation is Oil Storage Barge with its flash point added. FH (Floating Hotel), PPB (Power Plant Barge) and AB (Accommodation Barge) are for hotel ships, electricity generation and accommodation.

Mooring systems for these units

• AM is for anchor mooring, where the force comes mainly from the net weight of the catenary lines.
• TM is for tension mooring, where straight upright lines hold the unit down and limit heave, roll and pitch.
• SPM is for single point mooring, where the force is taken at a single point of the hull.
• DM is for dolphin mooring, where fixed dolphins react the force through fenders.
• OM is for any other mooring system.

Dynamic positioning (DPS). The class depends on what the worst single failure is allowed to do.

• Class 1 may lose position keeping after a single failure.
• Class 2 must keep position after a single failure of any active component or system, and of any normally static component that is not properly documented with respect to protection.
• Class 3 must keep position after a single failure in all components or systems. It also assumes the loss of everything in any one watertight compartment or fire sub-division.

Design criteria such as water depth and wave height are entered as descriptive notes.

Floating offshore facilities for crude oil and petroleum gas

• FPSO produces, stores and offloads crude oil. FPO produces and offloads. FSO stores and offloads.
• ST is for a ship-shaped facility, CST for a column-stabilized facility and OTH for other shapes, such as cylindrical facilities.
• CM and TM are the catenary and tension mooring marks. CALM and SALM are for a buoy moored to the seabed, which the facility is moored to in turn. TRM is for a facility fitted with a turret that lets her weathervane.

Barges (B). B is for barges that carry cargo in holds, on deck or in integrated tanks and are not propelled by machinery. P is for pontoon barges that carry cargo on deck only. T is for tank barges, with the same flash point suffixes as tankers. CT and LGC are for chemical and liquefied gas barges, with the same type numbers as the ships.

Submersibles. SBM is for submersibles. EQ SS SBM is for mother ships or support ships equipped with support systems for submersibles. The maximum diving depth and similar conditions go in descriptive notes.

Hull construction and equipment, part 4: propulsion, coatings, special ship types and fuels

Wind-assisted propulsion. These notations follow the Guidelines for Wind-Assisted Propulsion Systems for Ships and say which kind of system is installed.

• EQ WAPS-S is for rigid or soft sails.
• EQ WAPS-R is for rotor sails.
• EQ WAPS-T is for turbo sails.
• EQ WAPS-K is for towing kites.

Coatings and corrosion protection of tanks

• PSPC-WBT is for ships that comply with the performance standard for protective coatings in dedicated seawater ballast tanks of all ship types, and in the double-side skin spaces of bulk carriers.
• PSPC-COT is for crude oil tankers whose cargo oil tanks are coated to IMO Resolution MSC.288(87).
• PSCRS-COT is for crude oil tankers that use corrosion resistant steel under IMO Resolution MSC.289(87).
• PSPC/PSCRS-COT is for tankers that combine both methods.

Special cargo arrangements

• OPEN-TOP is for container carriers, general cargo ships and other cargo ships that omit hatch covers on one or more holds. Its guidance is the Guidelines for Open-top Ships.
• DC (Deck Cargoes) is for ships intended to carry cargo on their upper decks or hatch covers. UD means the upper deck, CD the cross deck and HC a hatch cover.
• HELIDK is for ships with a helicopter deck as defined in Part R and subject to the helideck provisions of Part C.

Noise, hull form and passengers

• NC (Noise Code) is for ships that comply with the Code on Noise Levels On Board Ships, IMO MSC.337(91).
• NC J (Noise Code J) is for ships that comply with the same Code except for its noise level limits. It reflects a Japanese special regulation for non-international ships, and it is available in the Japanese version only.
• CAT (Catamaran) and TRI (Trimaran) are placed after the notation for the main hull material.
• PS (Passenger Ship) is for ships that carry more than twelve passengers. A passenger is anyone other than the master and crew, or other persons working on the ship’s business, and a child under one year old. A passenger ship with general cargo spaces is written PS/GC.
• HS (High Speed) is for craft that comply with the Rules for High Speed Craft. Craft that also meet the Part 14 requirements for international voyages carry HSC for the International Code of Safety for High Speed Craft. The handbook’s example is (HS CAT P)(HSC) for a high speed catamaran passenger craft.
• FD (Floating Dock) is for docks that comply with the Rules for Floating Dock.

Machinery and design features

• 1C (Propeller Shaft Kind 1C) is for ships fitted with a Kind 1C propeller shaft that meets the Part D provisions.
• ARD (Anti-rolling Device) is for ships that comply with the Guidelines for Anti-rolling Devices. The device used is named in a descriptive note, for example an anti-rolling tank.
• CybR (Cyber Resilience) is for ships that have taken particular cyber resilience measures under Chapters 4 and 5 of Part X.

Inland waterway ships. The inland waterway rules carry a few notations of their own, and they also use others such as BTFLB and GRAB. PTC is for tanker convoy pushers. BD is for dry cargo barges.

Gas floating offshore facilities. These follow the Guidelines for Floating Offshore Facilities for LNG/LPG Production, Storage, Offloading and Regasification.

• LNG FPSO and LPG FPSO produce, store and offload gas drawn from the seabed.
• LNG FPO and LPG FPO produce and offload it.
• LNG FSO and LPG FSO store and offload gas received from carriers or other liquefied gas production facilities.
• LNG FSRU stores and regasifies LNG and sends gas to onshore facilities.
• GPF (Gas Processing Facility) marks acid gas removal, dehydration and mercury removal from raw gas.
• LF (Liquefaction Facility) marks liquefaction of the refined gas by heat exchange with a refrigerant.
• RGF (Regasification Facility) marks gasification of liquefied gas by heating with water, air or steam.

These facilities also need a mooring system mark, in the same way as an FPSO.

Ships that use gas or other low-flashpoint fuels

• GLF (Gas or Low-flashpoint Fuel) is for ships that use gas or another low-flashpoint fuel.
• CF (Cargo as Fuel) is for gas carriers that use their cargo as fuel.
• MRS (Machinery Room Safety for Ammonia) is for machinery rooms with extra safety measures for ammonia.
• NG FR, ML FR, EL FR, PG FR, AM FR and HY FR are the fuel ready notations. They mark ships designed for later conversion to natural gas, methanol, ethanol, petroleum gas, ammonia or hydrogen.

The handbook ends this group with a catch-all. Where ClassNK considers it necessary, it may add an appropriate notation that is not listed above.

Strengthening for navigation in ice (group 4)

Group 4 shows how a ship is built for ice and cold. It has four parts, and two of them look alike, so read the letters and numbers closely. PC1 to PC7 are polar classes. PC A, PC B, PC C and PC O are Polar Code categories. They are different things.

Polar classes. These follow Chapter 1 of Part I and Annex 1 of Part I.

Notation	Operation the class is meant for
PC1	Year-round operation in all polar waters
PC2	Year-round operation in moderate multi-year ice
PC3	Year-round operation in second-year ice, which may include multi-year ice
PC4	Year-round operation in thick first-year ice, which may include multi-year or second-year ice
PC5	Year-round operation in medium first-year ice, which may include multi-year or second-year ice
PC6	Summer and autumn operation in medium first-year ice, which may include multi-year or second-year ice
PC7	Summer and autumn operation in thin first-year ice, which may include multi-year or second-year ice

ICB (Icebreaker) is an additional notation for ships whose power and dimensions allow aggressive operations in ice-covered waters and that meet the relevant requirements. It is added to the polar class notation.

Ice classes. These are the ice strengthening notations for ships outside the polar classes. The handbook ties each one to a Baltic class and to a type under the Arctic Shipping Pollution Prevention Regulations.

ClassNK notation	Finnish-Swedish Ice Class Rules 2010	Arctic Shipping Pollution Prevention Regulations
IA SUPER IS	IA Super	Type A
IA IS	IA	Type B
IB IS	IB	Type C
IC IS	IC	Type D
ID IS	II	Type E
(No IS), no ice class	II	Type E

Polar Code categories. These notations apply to ships that operate in polar waters.

• PC A (Polar Code Category A) is for polar waters in at least medium first-year ice, which may include old ice.
• PC B (Polar Code Category B) is for polar waters in at least thin first-year ice, which may include old ice.
• PC C (Polar Code Category C) is for open water or ice conditions less severe than those in categories A and B.
• PC O is for ships navigating in polar waters that are not certified under SOLAS Chapter I. The handbook lists fishing vessels of 24 m overall length and above, pleasure yachts of 300 gross tonnage and above that are not in trade, and cargo ships of 300 gross tonnage and above but below 500.

Design temperature (TD). For steel ships built for cold regions such as Arctic or Antarctic waters, TDa, TDb, TDc, TDd and TDe show the design temperature level the ship was built for. The steel used in the hull must suit that design temperature, whatever the ordinary steel grade tables say. For ships that carry cold cargoes, the steel for longitudinals in the cargo hold follows the Part C table for such cargoes, and the cargo hold’s own design temperature is set. The handbook does not give the temperature behind each letter, so look in 3.2.2.2 of Part 1 of Part C for the values.

Hull structural analysis (group 5): the PrimeShip notations

Group 5 is for ships whose scantlings or structural details were checked with direct strength analysis or fatigue assessment in a way approved by ClassNK. All of these notations carry the PrimeShip name.

• PS-DA (PrimeShip – Direct Assessment) is for ships where yield and buckling strength were assessed by direct strength calculation, following Chapter 8 of Part C.
• PS-DA-CNC (PrimeShip – Direct Assessment – Container Carrier) is for container carriers assessed under 32.9 of Part C as it stood before the comprehensive revision. Ships under the revised Part C use the ASR notation instead.
• PS-DA-DLA (PrimeShip – Direct Assessment – Direct Load Analysis) is for ships where yield and buckling strength of primary members in all cargo spaces were assessed by direct strength calculation, using individual design regular waves taken from a direct load analysis.
• PS-FA (PrimeShip – Fatigue Assessment) is for ships where fatigue strength was assessed by finite element analysis, following Chapter 9 of Part C.
• PS-FA-S (PrimeShip – Fatigue Assessment – Superior) is for ships with independent prismatic tanks of type A or type B, where fatigue strength of the optional structural details listed in Part C was also assessed.
• PS-FA-DLA (PrimeShip – Fatigue Assessment – Direct Load Analysis) is for ships where fatigue strength of the structural details of primary members in all cargo spaces, wherever ClassNK finds it necessary, was assessed with loads taken from a direct load analysis.

Reading the brackets. The fatigue notations carry two details, as in PS-FA(WW, 25).

Part	Meaning
WW	Worldwide loads were used
NA	North Atlantic Ocean loads were used
The number (TDF)	The fatigue design life in years

So PS-FA(WW, 25) means a fatigue assessment with worldwide loads for a 25 year design life, and PS-FA-S(NA, 25) means the Superior assessment with North Atlantic loads for 25 years. The PS-FA-DLA(WW, TDF) and PS-FA-DLA(NA, TDF) forms were added in the July 2026 edition.

Special survey schemes (group 6)

Group 6 does not change how the ship is built. It changes how she is surveyed once she is in service. These notations matter most to owners and superintendents because they shape the drydock and survey plan.

• ESP (Enhanced Survey Programme) is for oil tankers, chemical tankers, bulk carriers and self-unloading ships that receive enhanced surveys as part of class maintenance surveys under Part B.
• HCM (Hull Construction Monitoring) is for ships whose surveys of critical structural areas follow a construction monitoring plan, under 1.1.12 of Part B.
• HCM-GBS is HCM with the Goal-based Ship Construction Standards suffix. It is for ships that are subject to SOLAS Chapter II-1 Regulation 3-10.
• IWS (In Water Survey) is for ships approved for in-water surveys under 6.1.2 of Part B.
• PSCM (Propeller Shaft Condition Monitoring System) is for ships whose propeller shaft is surveyed on the basis of a preventive maintenance system, under 8.1.2 of Part B.
• PSCM-1A is the same idea for a water lubricated propeller shaft of Kind 1A, under 8.1.2-2 of Part B.
• EDD (Extended Drydock) is for ships whose in-water surveys are carried out consecutively in place of docking surveys, under 6.1.2-2 of Part B.
• HIDROVIA is for ships surveyed to the “HIDROVIA Parana – Paraguay” standards, which ClassNK accepts as appropriate for inland waterway ships.
• RMSV (Remote Survey) is for ships prepared in advance for remote surveys. They have the procedures ready and reliable communication equipment installed.

In the handbook’s representative class lines, IWS and PSCM are often present for ocean-going ships. The handbook describes them as optional, though, so their absence on a certificate does not mean a ship is non-compliant.

Environmental notations

The notations from here on are added at the owner’s request. ClassNK attaches them when particular measures for the marine environment, the crew’s working environment or other specific purposes have been taken.

EA (Environmental Awareness) is for ships that have taken particular environmental measures under the ClassNK Environmental Guideline. Marks for individual measures are added, as in EA + BILGE CONTROL, FOTP.

Mark	What it shows
BILGE CONTROL	An integrated bilge water treatment system; bilge discharge below 5 ppm oil content; or all bilge water sent ashore
FOTP	Fuel oil tanks kept at a specified minimum distance from the outer shell
LOTA	High level alarms on lubricating oil and hydraulic oil tanks
STS	Stern tube air seals
EAL	Environmentally acceptable lubricants
GW	A sewage treatment system (greywater)
GB	All garbage sent ashore
N2	Nitrogen generating equipment
NOx	NOx emissions reduced, to 80% or below
NOx-Tier III	NOx emissions reduced to Tier III level or below
SOx	Fuel oil sulphur content of 0.1% or below
LEV	Low emission vessel: reduced CO, HC, NOx, PM and PN
R	Refrigerant with a global warming potential below 1500
F	Fire extinguishing agents with a global warming potential below 1500
VOC	A volatile organic compound emission control system
SPC	A high voltage shore power connection
BFM	Biofouling management
CRP	A contra rotating propeller

The edition of the Environmental Guidelines used is recorded in a descriptive note. The handbook’s example refers to Edition 4.0.

a-EA (Advanced Environmental Awareness) is for ships with advanced measures under the same Guideline. Its marks include:

• SCELL, FCELL, WINDG, ORCWHR and EGWHR are for solar cells, fuel cells, wind generators, organic Rankine cycle waste heat recovery and exhaust gas waste heat recovery. When these supply onboard power, the mark is added if the system has at least 1% of the capacity of a single main generator. A -PA suffix is added where the system assists main propulsion.
• GRS (Green Steel Products) is for ships that use green steel products in the hull structure or elsewhere. The share by weight, against the lightweight of the ship, can be put in a descriptive note. The minimum figure is 10, and fractions under 10 are rounded down.
• CFP (Carbon Footprint) is for a calculated carbon footprint of the ship’s construction. It is shown in the handbook as a-EA(CFP) and is new in July 2026.
• ALS (Air Lubrication System) is for bottom air lubrication systems.
• ESA (Energy Saving Additives) is for fins, fin caps, rudder bulbs, ducts and similar devices.
• MPC (Micro Plastics Collection) is for systems that collect microplastics.

Emissions and energy efficiency

• EEDI-pX (Energy Efficiency Design Index, phase X) is for ships whose index meets a required value calculated with a stricter phase reduction factor than the one that applies. X is the phase adopted. For ro-ro cargo and ro-ro passenger ships it applies only where the required value really is stricter. EEDI-p1 suits ships subject to phase 0 that meet phase 1. EEDI-p2 suits ships subject to phase 0 or 1 that meet phase 2. EEDI-p3 suits ships subject to phase 0, 1 or 2 that meet phase 3.
• NOx-III (Nitrogen Oxides Emission, Tier III) is for ships with marine diesel engines that meet the maximum NOx limit and are permitted to operate in NOx emission control areas. A descriptive note names the engines, with M/E for the main engine and G/E for the generator engines, and the technology. The handbook’s technology labels are SCR, EGR, DFE (dual fuel engines using pre-mixed lean burned gas) and GOE (gas only engines).
• SOx(EGCS) is for ships that meet the sulphur content requirements through an exhaust gas cleaning system as an equivalent compliance method. The descriptive note says which engines and boilers are connected.
• EGCSR-F (Exhaust Gas Cleaning System Ready-Full) is for ships designed for later installation of a cleaning system that meets both class and convention requirements. EGCSR-G (Ready-General) meets the class requirements.
• HVSS (High Voltage Shore supply System) is for ships fitted with a high voltage shore supply as a pollution abatement measure in port.

Onboard carbon dioxide capture and storage (OCCS)

• OCCS-Full is for ships with both CO2 capture and storage systems installed.
• OCCS-Capture and OCCS-Storage are for ships with only the capture system or only the storage system installed.
• OCCS-Ready-Full, OCCS-Ready-Capture and OCCS-Ready-Storage are for ships designed so those systems can be installed later.
• OCCS-Ready-C-Full, OCCS-Ready-C-Capture and OCCS-Ready-C-Storage are for ships where that design has been done only at concept level. These three were added in July 2026.

Underwater noise. SUN-C (Silent Underwater Noise-Controlled) and SUN-A (Silent Underwater Noise-Advanced) are for ships that take special measures to reduce underwater noise under the Guidelines for Underwater Noise from Ships. Each is tied to the noise levels in 5.6 of the Guidelines.

Comfort, safety, container and digital notations

Noise and vibration comfort (NVC)

• NVC·A, ·B, ·B’ and ·C are for ships that apply the Noise and Vibration Guideline provisions for accommodation spaces and similar areas.
• NVC·A+, ·B+ and ·C+ are for ships that meet those provisions and also the Code on Noise Levels On Board Ships (MSC.337(91)).
• MVA (Mechanical Vibration Awareness) is for ships that meet the Guideline provisions on the vibration of machinery room installations.

Batteries. LiB (LiBattery) is for ships with accumulator battery systems of lithium-ion batteries, with total capacity of 20 kWh or more.

Container stowage and lashing

• CSSA (Container Stowage and Securing Arrangements) is for ships that keep a lashing calculation program on board that can check strength against the container stowage and securing arrangements, or whose container stowage strength was evaluated on that basis without regard to specific sea routes.
• CSSA-R adds service on specific sea routes to that evaluation.
• CSSA-RS adds specific sea routes and seasons.
• CSSA-WF adds weather forecasts, with the Guidelines for the Safety of Maritime Cargo Based on Weather Forecasts.
• SDCL (Safe Design for Container Lashing) is for ships whose keels were laid, or which were at a similar stage of construction, on or after 1 January 2015, and whose construction and equipment fully comply with Annex 14 of the CSS Code.
• SDCL-E is for existing containerships that were built before that date. They comply with Sections 4.4, 7.1, 7.3 and 8, and with the principles of CSS Code Annex 14 in Sections 6 and 7.2 as far as practical.
• DACA (Designed by Application of Brittle Crack Arrest Concept) is for ships that use a brittle crack arrest design in the region of the upper deck.

Parametric rolling. The three PRPM notations are for ships that deal with parametric rolling under the Guidelines on Preventive Measures against Parametric Rolling.

• PRPM (Design) is for ships that comply with the Second Generation Intact Stability Criteria.
• PRPM (Device) is for ships with devices and systems that prevent or reduce parametric rolling.
• PRPM (Operation) is for ships with operational measures to avoid it.

Digital Smart Ships (DSS). DSS covers ships with a technical solution that collects and processes data for operational support. Each mark names a function.

• DSS(EE) is for energy consumption monitoring or energy efficiency analysis using voyage data. DSS(EE2) adds support for energy efficient route planning or trim optimization with weather and ocean forecasts.
• +Sn (+Sensor) is added where sensor data is also acquired automatically and periodically.
• DSS(HM) is for hull monitoring that reports stress levels, cumulative damage and acceleration.
• DSS(SLOSH) is for systems that detect or predict sloshing in cargo or fuel tanks.
• DSS(MM) is for machinery monitoring with sensors that diagnose machinery condition.
• DSS(CNS) is for a connected ship that transfers processed data to a shore-based office.
• DSS(SM) is for sensor data sent ashore for monitoring by specialists.
• DSS(LAN) is for a fixed onboard local area network available almost everywhere in designated spaces and on open decks.
• DSS(RCSM) is for automatic shore monitoring of refrigerated cargo spaces and containers.
• DSS(ESM) is for automatic shore monitoring of emissions to the atmosphere from engines, boilers and similar sources.

Advanced safety (a-SAFE). These are navigation aids.

• a-SAFE(Rxx) is for a radar-based system that shows extra information. The letters replace xx, with RSW for sea waves, RFI for floating ice and RSP for spilled oil.
• a-SAFE(CRI) is for a collision risk indication system that predicts and warns about likely collision areas.
• a-SAFE(XRD) is for an extended reality display that overlays navigation information on camera or virtual 3D images.
• a-SAFE(FUOD) is for a forward underwater obstacle detection system.
• a-SAFE(BSS) is for a berthing support system that combines distance to the wharf, vessel speed, wind and other data.

Excellent Living and Working Environment (ELW)

• ELW(IA) is for internet access from smartphones in crew cabins. +M adds mobile phone lines and +S adds satellite communication, each with contracted services.
• ELW(IT) is for independent temperature control in each cabin.
• ELW(GE) is for a separate sanitary facility and laundry room for a small number of seafarers of a different sex from the rest.
• ELW(IC) is for infection control installations such as isolation rooms.
• ELW(FP) is for equipment that extends the freshness of food beyond ordinary refrigeration and freezing.
• ELW(HP) is for hydroponic vegetable growing for the crew.
• ELW(WM) is for fixed water mist on exposed decks to prevent heat stroke during cargo work.

Cyber security. CybR-G (Cyber Resilience-Guideline) is for ships that took cyber security measures for onboard computer-based systems under the Guidelines for Designing Cyber Security Onboard Ships. It is not the same as CybR in the hull construction group, which follows Part X.

Additional fire-fighting on container carriers (AFC). The mark in brackets says which measure is fitted.

• AFC(G) is for the general measures in 4.2 of the Guidelines.
• AFC(DH) is for added fire detection in cargo holds.
• AFC(DD) is for added detection in weather deck cargo spaces, with DD-VM for video monitoring and DD-OT for other detection measures.
• AFC(WH) is for water spray in cargo holds. WH-WD stops fire spreading to weather deck cargo spaces, and WH-HS stops spread to other holds and adjacent spaces.
• AFC(WD) is for water-based systems on weather deck cargo spaces. WD-FC is a fixed water curtain, WD-FM is a fixed water monitor system, WD-MM is extra mobile water monitors and WD-PF is portable fire-fighting equipment.
• AFC(FH) is for measures to flood cargo holds.

Additional fire-fighting on vehicle carriers (AFVC). These cover electric vehicles under the Guidelines for Safe Transportation of Electric Vehicle.

• AFVC(FD)(EV) is for added fire detection.
• AFVC(PS)(EV) is for preventing secondary fires.
• AFVC(PFS)(EV) is for preventing fire spread.
• AFVC(FF)(EV) is for fire-fighting.
• AFVC(EFF)(EV) is for better operational reliability of the fixed fire-extinguishing system.
• AMEVC(EV) is for measures that improve escape from a vehicle carrier cargo hold in a fire.

Autonomous navigation. AUTO-NavY(Z) is for ships with autonomous navigation systems under the Guidelines for Automated/Autonomous Operation on ships. Y is the level of autonomy. Z is the phase of navigation: either all phases, or a limited set chosen from berthing and unberthing (Be), harbour (Ha), coastal (Co) and open sea (Os).

Worked examples: reading real class lines

The handbook lists representative class lines for the main ship types. They show which notations normally travel together. Treat them as typical patterns, not as the full list for any one ship.

Ship type	Representative class line
Bulk carrier	NS*(CSR, BC-A, BC-XII, GRAB 20, PSPC-WBT, NC, 1C)(ESP)(HCM-GBS)(IWS)(PSCM)
Oil tanker, flash point above 60 °C	NS*(CSR, TOA, PSPC-WBT, NC)(ESP)(IWS)(PSCM)
Oil tanker, flash point on and below 60 °C	NS*(CSR, TOB/CT II&III, PSPC-WBT, NC, 1C)(ESP)(HCM-GBS)(IWS)(PSCM)
Container carrier	NS*(ASR, CNC, EQ C DG, PSPC-WBT, NC, GLF/NG, ML FR(C), CybR, 1C)(PS-DA)(PS-FA(WW, 25))(IWS)(PSCM)
Ore carrier	NS*(ASR, OC, BC-XII, GRAB, PSPC-WBT, NC)(ESP)(IWS)(PSCM)
Oil / chemical tanker	NS*(CSR, TOB / CT II&III, PSPC-WBT, NC)(ESP)(IWS)(PSCM)
Pure chemical tanker	NS*(ASR, CT II&III, PSPC-WBT, NC)(ESP)(IWS)(PSCM)
Liquefied gas carrier	NS*(ASR, LGC 2G, PSPC-WBT, NC)(PS-DA)(PS-FA(WW, 25))(IWS)(PSCM)
Liquefied gas carrier, direct load analysis	NS*(ASR, LGC 2G, PSPC-WBT, NC, 1C)(PS-DA-DLA)(PS-FA-DLA)(IWS)(PSCM)
Pure car and truck carrier	NS*(ASR, VC, PSPC-WBT, NC)(IWS)(PSCM)

Three notes from the handbook sit under that table. Ships approved for in-water survey carry IWS. Ships equipped for dangerous goods carry EQ C DG. Ships that follow the Environmental Guideline carry EA. IWS, PSCM and GRAB are not mandatory, but they are typically added.

Decoding a bulk carrier. Take NS*(CSR, BC-A, BC-XII, GRAB 20, PSPC-WBT, NC, 1C)(ESP)(HCM-GBS)(IWS)(PSCM).

• NS* says the plans were approved and the ship was built under ClassNK survey.
• CSR says she follows the Common Structural Rules, Part CSR-B&T.
• BC-A says she is a type A bulk carrier, designed to carry dense cargo with specified holds empty.
• BC-XII says SOLAS chapter XII applies.
• GRAB 20 says her inner bottom is strengthened for a 20 ton grab.
• PSPC-WBT says the ballast tank coatings meet the performance standard.
• NC says she complies with the Noise Code.
• 1C says her propeller shaft is Kind 1C.
• (ESP) says she gets enhanced surveys.
• (HCM-GBS) says her critical structural areas were surveyed during construction to a monitoring plan, under the goal-based standards.
• (IWS)(PSCM) say in-water surveys and shaft condition monitoring are approved.

In the handbook’s appendix, a Cape size version also carries a descriptive note. It says the ship is strengthened for heavy cargo loading where holds 2, 4, 6 and 8 may be empty.

Decoding a container carrier. Take NS*(ASR, CNC, EQ C DG, PSPC-WBT, NC, GLF/NG, ML FR(C), CybR, 1C)(PS-DA)(PS-FA(WW, 25))(IWS)(PSCM).

• ASR says she was built to the Advanced Structural Rules, so her contract date is on or after 1 July 2023 (or she is an eligible sister ship).
• CNC says she is a container carrier, and EQ C DG says she is equipped for dangerous goods.
• GLF/NG says she uses gas or another low-flashpoint fuel, apparently natural gas. The handbook does not spell out the slash form.
• ML FR(C) says she is methanol fuel ready. The handbook’s example does not explain the (C), so check the Guidelines for Ships Using Alternative Fuels before relying on it.
• CybR says she meets the cyber resilience requirements of Part X.
• (PS-DA) says yield and buckling strength were checked by direct assessment.
• (PS-FA(WW, 25)) says fatigue strength was assessed with worldwide loads for a 25 year design life.

Decoding an FPSO. The appendix gives (DSA)(FPSO)(ST)(CM) with a descriptive note that reads “Operation at XXXXX”.

• DSA says she is classed for a designated service area, which the note then names.
• FPSO says she produces, stores and offloads crude oil.
• ST says she is ship-shaped.
• CM says she is moored by catenary mooring lines.

What changed recently, and points to check

The July 2026 edition adds new notations for deck cargoes, fatigue direct load analysis, carbon footprint, concept-level carbon capture readiness and container ship fire-fighting. The table below covers the revisions since the start of 2025.

Edition	What changed
2025-1 (January 2025)	HELIDK and DACA revised. GRS and MPC added under advanced environmental awareness. +Sn added to the digital smart ship marks. +M and +S added to ELW(IA).
2025-2 (June 2025)	AFC revised. AMEVC added.
2025-3 (July 2025)	IHM added to the installation characters and removed from its earlier place. PC O added to the Polar Code notations.
2025-4 (August 2025)	AUTO-NavY(Z) added for autonomous navigation.
2025-5 (October 2025)	ARD added. CSSA-WF added. The carbon capture marks were renamed from SCCS-… to OCCS-….
2026-1 (January 2026)	HDCA added to the cargo ship notations.
2026-2 (July 2026)	DC-UD, DC-CD and DC-HS added. PS-FA-DLA(WW, TDF) and PS-FA-DLA(NA, TDF) added. a-EA(CFP) added. OCCS-Ready-C-Capture, OCCS-Ready-C-Full and OCCS-Ready-C-Storage added. Four AFC marks added, four changed and three deleted.

The October 2025 rename is easy to miss. The old SCCS-Full, SCCS-Capture and related names were for carbon capture and storage. They are not the same as SCCS, the Specially Constructed Cargo Ship notation, which still exists.

Points to check before you rely on a detail

• The 2026-2 revision record lists the new fire-fighting marks as AFC(WH-MM) and AFC(WH-PF). The notation table itself shows WD-MM and WD-PF. This guide follows the table. Confirm the final names with ClassNK.
• The handbook gives the TDa to TDe design temperature levels without the temperatures themselves. They are in 3.2.2.2 of Part 1 of Part C.
• The container carrier example uses GLF/NG and ML FR(C). The handbook does not explain the slash form or the (C), so this guide reads them only as far as the notation tables allow.
• The handbook gives the same Part A paragraph, 1.2.4-33, for both NC and HELIDK. One of them may be a typographical slip.
• The handbook is a summary. The Rules, Guidance and any amendment issued after July 2026 are the authority for any real project.

Source: ClassNK, Notation Handbook, 2026-2 Edition, July 2026 (the PDF supplied). All descriptions in this guide are paraphrased from that handbook.