Approval in Principle (AiP)

In recent years, the maritime industry has been developing and implementing various new technologies in response to environmental regulations, digitalization, and technological innovations in related areas. On the other hand, in the implementation of technologies with novel concepts, as the installation of technologies on ships needs to be ensured to have the level of safety equivalent to those required by international conventions and classification rules, the Society inspects technologies to confirm their safety from such point of view.
Design inspections of the Society are usually carried out at the stage in which the product design of the new technology has been completed. However, if a critical issue from the viewpoint of international conventions and classification rules is found at the stage of design completion, it may cause backward progress in the design, which in turn may greatly impede the speed of product development. In order to prevent such situations, the Society provides a service for checking the design of a product in its early design stage or before a specific ship that will implement the product is determined, prior to the final ship classification design review.

What is AiP?

AiP, which stands for Approval in Principle, is a scheme for the examination of plans and documents based on the rules for products in the early design stage to confirm their technical feasibility from the viewpoint of the rules.

The AiP is generally applied to technologies that are newly developed or have little experince in the maritime industry. The product concepts, including but not limited to the following examples, may be subject to an AiP.

    Examples of ships
  • Ships using alternative fuels (LNG, LPG, methanol, ammonia, hydrogen, etc.)
  • Ships carrying special liquefied gases (liquefied hydrogen, liquefied CO2, etc.)
  • Automated/autonomous ships
  • Offshore floating facilities (FPSO, FLNG, FSRU, offshore plants, etc.)
    Examples of equipment and systems
  • Liquefied gas cargo/fuel containment systems
  • Wind assisted propulsion systems
  • Fuel supply systems
  • Gas reforming systems

Under the scheme, the applicant submits the design documents at approximately the basic design level to the Society, and the Society reviews them based on the framework agreed upon with the applicant and issues an AiP Certificate for the product whose feasibility is confirmed.

As an AiP is focused on "feasibility" in the initial design stage, it does not directly lead to the final plan approval. Through this stage, the applicant can identify issues based on the philosophy of the rules and regulations in the early stages, and can clarify the key points of the design that need to be cleared in order to obtain the final approval of the drawings. Therefore, it is a practical scheme for efficiently performing design work to achieve final plan approval.

Fig. 1 Example of AiP Certificate

Approval Framework

As the AiP does not certify complete conformity to rules, its framework is decided upon consultation with reference to the provisions of relevant rules, taking into consideration the design stage of the concerned product and the applicant's requirements. The framework for the AiP is generally determined by the following procedure.

(1) Confirmation of the product specifications

(2) Determination of referenced rules

(3) Determination of the scope of approval

Required Documents

The documents that need to be checked in the AiP scheme are determined according to the approval framework agreed upon with the applicant. The required documents will vary according to the details of the agreement, but in general, they should include the following.

(1) Documents pertaining to product specifications

(2) Documents pertaining to technical validation of the product

(3) Documents pertaining to risk assessment

For reference, specific examples of the documents required for the AiP are shown below, using several products as examples.

Table 1 Examples of basic design approval documents for alternative fuelled ships

1 Basic specifications for the vessel
2 Basic specifications for alternative fuel related equipment
3 General arrangement drawings
4 Engine room layout diagram
5 Alternative fuel piping system diagram
6 Hazardous location identification diagram
7 Ventilation system diagram
8 Fire extinguishing and fire protection system diagram
9 Longitudinal strength and non-damage restoration calculations
10 Documents relating to risk assessment

Table 2 Examples of basic design approval documents for battery propelled ships

1 Basic specifications for ship
2 Basic specifications for battery equipment
3 Basic specifications for energy management system
4 General arrangement drawings
5 Engine room layout drawings
6 Battery room layout diagram
7 Power system diagram
8 Hazardous location identification diagram
9 Fire extinguishing and fire protection equipment diagram
10 Longitudinal strength and non-damage restoration calculations
11 Documents for risk assessment

Table 3 Examples of basic design approval documents for offshore floating facilities

1 Basic specifications for floating facilities
2 General arrangement drawing
3 Central cross-sectional drawing
4 Structural analysis method for hull and mooring equipment
5 Longitudinal strength and non-damage restoration calculations
6 Basic design clauses for topside equipment
7 Equipment list for topside facilities
8 Process flow diagram for topside equipment
9 Hazardous location identification diagram
10 Fire fighting and fire protection equipment diagram
11 Normal and emergency operating concept
12 Documents for risk assessment

Table 4 Examples of basic design approval documents for wind propulsion equipment

1 Basic specifications of the equipment
2 Overall assembly drawing
3 Detailed structural drawing
4 Structural analysis method (including trial analysis results for typical loading conditions)
5 Drive unit structural drawing
6 Power system diagram
7 Normal and emergency operating concept
8 Material for risk assessment (including discussion of effects on the vessel)

For other details on the AiP scheme, see Guidelines for Basic Design Approval and General Design Approval (Edition 1.0). The Guidelines can be downloaded from “ClassNK MyPage” after the registration.

ClassNK MyPage Login > Guidelines

Trends of AiP and approval records

LNG/LPG/methanol fuelled ships

For alternative fuels, such as LNG/LPG/methanol fuels, where the ships fuelled with them have already been in service, the development from basic design to detailed design has progressed relatively smoothly, and design approval is often granted without going through the stage of obtaining an AiP as an implementation project. For methanol fuels, designs are planned not only for methanol carriers using methanol cargo as fuel but also for methanol fuelled bulk carriers and container ships.

Ammonia-fuelled ship

In parallel with the ongoing development of ammonia-fuelled engines, systems for supplying ammonia fuel to engines and the design of ships equipped with these engines and systems are underway. Ammonia is highly toxic and corrosive, so in order to confirm the feasibility from the initial design stage, an AiP is issued based on the Society's Guidelines for Alternative Fuelled Ships (methanol/ethanol/LPG/ammonia) after checking safe handling on board and identifying issues to be considered in the detailed design. We also issue AiP for 'Ammonia Fuel Ready' for ships using conventional fuels, in which a conceptual design is prepared in advance in anticipation of future conversion to ammonia fuels for zero-emission ships.

Hydrogen-fuelled ships and fuel-cell-powered ships

The use of hydrogen fuel has already been realized in small coastal vessels equipped with fuel cells. Hydrogen-fuelled engines are also being developed for the future use of decarbonized fuels in larger ships. Due to the physical properties of hydrogen, safety measures are required, particularly against hydrogen embrittlement of materials, leakage, and fire. In addition, when hydrogen is liquefied for use on board to store large quantities of fuel, safety measures are also required to ensure the resistance of materials to cryogenic temperatures of -253°C and to the liquefaction of the surrounding air (nitrogen, oxygen, etc.). As the development of hydrogen-fuelled engines progresses, applications of AiP certification are expected to increase in order to confirm the feasibility of ships equipped with hydrogen-fuelled engines.

CO2 carriers and Carbon Capture

Projects for marine transportation of CO2 captured from onshore power plants and other sources are gaining momentum, and the number of AiPs issued for liquefied CO2 carriers is increasing accordingly. A system has also been developed to capture CO2 emitted from ships on board, based on land-based CO2 capture technology. In the future, we expect to see an increase in the application of AiP to confirm the feasibility of ships equipped with liquefaction and storage systems on board, in addition to the CO2 capture system.

Wind-assisted propulsion ship

As one of the technologies for reducing GHG emissions, devices have been developed and are already being put into practical use to assist ship propulsion by utilizing the power of wind, a renewable energy source. Rigid sails, kites, rotor sails, and other systems have been developed for these wind-assisted propulsion systems, and AiPs have been issued for ships equipped with these systems on deck after confirming their feasibility based on the Society's 'Guidelines for Wind-assisted Propulsion Systems for Ships.' Ships combining the use of the above-mentioned alternative fuels with wind-assisted propulsion systems are also being planned.

The table below shows the AiP results published to date.

(As of 22 March 2024)
No. Applicant Subject Link Date of publication
1 Namura Shipbuilding Co., Ltd. Minimal Ballast Water VLCC Design
6 March 2013
2 Mitsubishi Heavy Industries, Chiyoda Corporation H2/CO2 FPSO
12 November 2014
3 Maritime Innovation Japan Corporation (MIJAC). LNG-fueled bulk carrier
17 November 2015
4 Hanjin Heavy Industries & Construction Co., Ltd. LNG Bunkering Vessel
20 October, 2016
5 Nippon Yusen Kabushiki Kaisha, Japan Marine United LNG-fuelled 200K DWT bulk carrier
5 July 2018
6 Kawasaki Heavy Industries LNG-fuelled 207K DWT bulk carrier
31 January 2019
7 Osaka Gas, Daihatsu Diesel LPG Reformer for marine engines
24 September 2019
8 Mitsui O.S.K. Lines, Ltd.,Oshima Shipbuilding Co.,Ltd. Wind Challenger Project
3 October 2019
9 NS United Kaiun Kaisha, Ltd.,Imabari Shipbuilding Co., Ltd. LNG-fueled capesize bulker
17 December 2019
10 Kawasaki Heavy Industries, Ltd. LPG Fuel Supply System
5 February 2020
11 Daihatsu Diesel, Iino Gas Transport, Osaka Gas, Izumi Steel Works, Miura Shipbuilding LPG reformed gas fueled coastal LPG carrier
13 March 2020
12 SHIN KURUSHIMA DOCKYARD CO., LTD LNG-fueled chemical tanker
1 April 2020
13 Imabari Shipbuilding Co., Ltd.,Mitsubishi Shipbuilding Co., Ltd 180,000 DWT LPG dual fuelled bulk carrier
27 April 2020
14 Nippon Yusen Kabushiki Kaisha,MTI Co., Ltd. autonomous ship framework (development code “APExS”)
14 May 2020
15 Kawasaki Kisen Kaisha, Ltd., AIRSEAS SAS Automated kite system “Seawing”.
19 August 2020
16 Sumitomo Heavy Industries Marine & Engineering Co., Ltd. Methanol dual-fueled tanker
22 March 2021
17 Kawasaki Heavy Industries, Ltd. Cargo Containment System for Large Liquefied Hydrogen Carrier
7 May 2021
18 Eco Marine Power Renewable energy system for ships, “Aquarius Marine Renewable Energy with EnergySail”
26 May 2021
16 June 2021
20 Kawasaki Kisen Kaisha, Ltd., Shin Kurushima Dockyard Co. Ltd. Ammonia-fuelled PCC
8 December 2021
21 Planning and Design Center for Greener Ships (GSC) Ammonia-fueled Panamax bulk carrier
20 January 2022
22 Nippon Yusen Kabushiki Kaisha, MTI Co., Ltd., Japan Marine Science Inc. Fully autonomous ship framework (development code “APExS-auto”)
15 March 2022
23 Hitachi Zosen Corporation, Mitsui O.S.K. Lines, Ltd., Yanmar Power Technology Co., Ltd. Methane Oxidation Catalyst System
16 March 2022
24 GTT’ LNG fuel tank with 2 bar gauge design pressure
31 March 2022
25 Japan Offshore Design & Engineering Platform Technology & Engineering Research Association (J-DeEP). Floating offshore hydrogen production plant
4 April 2022
26 Planning and Design Center for Greener Ships (GSC) Ammonia-ready LNG-fueled Panamax Bulk Carrier
21 April 2022
27 Kawasaki Heavy Industries, Ltd. Large Liquefied Hydrogen Carrier "Following AiPs for CCS, CHS, and Dual-fuel Main Boilers"
28 April 2022
28 Mitsubishi Shipbuilding Co., Ltd., Nippon Yusen Kabushiki Kaisha Large Liquefied CO2 (LCO2) Carrier
16 May 2022
29 Mitsubishi Shipbuilding Co.,Ltd Ammonia-ready VLGC
9 June 2022
30 Nippon Yusen Kabushiki Kaisha,IHI Power Systems Co., Ltd. Ammonia-fueled tugboat (A-Tug)
12 July 2022
31 Mitsui O.S.K. Lines, Ltd. Large-scale Liquefied CO2 (LCO2) Carrier
23 August 2022
32 Nippon Yusen Kabushiki Kaisha, Japan Engine Corporation, IHI Power Systems Co., Ltd., Nihon Shipyard Co., Ltd. Ammonia-fueled ammonia gas carrier (AFAGC)
7 September 2022
33 Nippon Yusen Kabushiki Kaisha Ammonia Bunkering Vessel (ABV)
28 September 2022
34 ITOCHU Corporation, Nihon Shipyard Co.,Ltd., Mitsui E&S Machinery Co., Ltd., Kawasaki Kisen Kaisha, Ltd., NS United Kaiun Kaisha, Ltd. Ammonia fueled 200,000 DWT type bulk carrier
28 November 2022
35 Kawasaki Heavy Industries, Ltd Dual fuel generator engine using hydrogen gas as fuel and related machinery systems & arrangements for 160,000m3 Liquefied Hydrogen Carrier
30 November 2022
36 Nippon Yusen Kabushiki Kaisha, Nihon Shipyard Co., Ltd., IHI Corporation Ammonia Floating Storage and Regasification Barge (A-FSRB)
5 January 2023
37 Mitsui O.S.K. Lines, Ltd.,MITSUI & CO., LTD large ammonia fueled 210,000 DWT bulk carrier
27 January 2023
38 GTT - Concept of 12,500m3 LNG Dual-fuelled VLCC fitted with Mark III Flex system
- Concept of LNG Fuel Tanks with NH3 ready notation that includes material compatibility with NH3, risk assessment and Boil-off gas management
- Concept of 8,000 CEU PCTC LNG Dual-fuelled with NH3 ready notation
- Recycool™ system applied to LNG fuelled vessels which is designed for allowing the reliquefaction of LNG evaporation in order to reduce greenhouse gas emissions and economic losses
7 March 2023
39 TOA Corporation,NIHON SHIPYARD CO.,LTD.,Japan Marine United Corporation Conversion plan of the medium-sized self-elevating platform (SEP) vessel
14 April 2023
40 Mitsui O.S.K. Lines, Ltd.,TSUNEISHI SHIPBUILDING Co., Ltd.,Mitsui E&S Shipbuilding Co., Ltd. Ammonia Fuelled Gas Carrier
14 April 2023
41 Mitsubishi Shipbuilding Co., Ltd.Nippon Yusen Kabushiki Kaisha Ammonia and Liquefied CO2 Carrier
29 June 2023
42 GTT Cargo Containment System (CCS) and Cargo Handling System (CHS) for liquefied hydrogen carrier
25 July 2023
43 Samsung Heavy Industries (SHI) Ammonia fuel supply system for oil tanker and container ship
14 August 2023
44 China Shipbuilding Power Engineering Institute Co., Ltd. (CSPI), a member of CSSC Power (Group) Co. Ltd. (CPGC) Onboard CO2 capture and storage (OCCS) system
7 September 2023
45 Mitsui O.S.K. Lines, Ltd., MOL Drybulk Ltd., Onomichi Dockyard Co., Ltd., Kawasaki Heavy Industries, Ltd., Japan Engine Corporation Parcel layout concept for hydrogen-fueled multi-purpose vessel
19 October 2023
46 Shanghai Merchant Ship Design & Research Institute (SDARI) - Ammonia ready LNG dual fueled 7,000CEU vehicle carrier
- Ammonia dual fueled 10,000CEU vehicle carriers
- Methanol dual fueled 10,000CEU vehicle carriers
6 December 2023
47 Marine Design & Research Institute of China (MARIC) - 210k methanol dual-fueled bulk carrier
- 210k ammonia dual-fueled bulk carrier
- 210k LNG dual-fueled bulk carrier
- 88k LPG dual-fueled very large gas carrier
7 December 2023
48 Kawasaki Kisen Kaisha, Ltd., Kawasaki Kinkai Kisen Kaisha, Ltd., Japan Radio Co., Ltd., YDK Technologies Co., Ltd. Advanced Maneuvering Assistant System
12 December 2023
49 Mitsui O.S.K. Lines, Ltd., Mitsubishi Shipbuilding Co., Ltd. Ammonia FSRU (Ammonia Floating Storage and Regasification Unit)
22 December 2023
50 YANMAR Power Technology Co., Ltd. Maritime hydrogen fuel cell system
17 January 2024
51 Planning and Design Center for Greener Ships (GSC) Prismatic ammonia fuel tank (IMO Type B independent tank) for container ships
6 February 2024
52 “K” Line Wind Service, Ltd., Japan Marine United Corporation, Nihon Shipyard Co., Ltd. Multi-functional floating offshore windfarm support vessel (MFSV)
28 February 2024

For applications and service enquiries

Nippon Kaiji Kyokai, Technical Division, Technical Solution Department
Tel: +81-3-5226-2042
Fax: +81-3-5226-2736