A technical overview of the ABS Rules for Building and Classing Single Point Moorings, July 2026, covering classification scope, mooring system design, structural and stability considerations, equipment, construction testing and surveys after construction.
The American Bureau of Shipping (ABS) Rules for Building and Classing Single Point Moorings, July 2026, establish classification requirements applicable to the design, construction, equipment, testing and survey of single point mooring (SPM) systems within the scope of the Rules.
An SPM is an offshore mooring arrangement that enables a vessel to connect at a single point and, where applicable, weathervane in response to environmental conditions. The configuration may include a buoy or platform, anchoring and mooring components, cargo transfer equipment, hoses or flexible risers, swivels, product piping and associated safety systems.
The July 2026 edition is arranged in five Parts. Together, these address conditions of classification, materials and welding, mooring system design, equipment and systems, and testing and surveys. The Rules should be read as a coordinated technical framework rather than as a stand-alone design checklist.
The Foreword to the July 2026 edition identifies specific changes to the annual survey requirements. These changes place additional emphasis on the review of maintenance and replacement records and extend the listed annual survey scope to further SPM components and systems.
The annual survey requirements include review and verification of maintenance and replacement records for specified SPM equipment and systems, with reference to the approved Information Booklet and Maintenance Manual.
Marine Breakaway Couplings (MBCs) are expressly included in the annual survey list of equipment and records to be reviewed as applicable to the SPM arrangement.
Safety device testing is included in the annual survey requirements where such devices are provided.
The annual review of mooring system maintenance and replacement records expressly includes the connection points to the SPM hull.
The July 2026 requirements clarify that PLEM testing is included in the annual survey list when the PLEM forms part of the classification scope.
The approved Information Booklet and Maintenance Manual are to be available to the attending Surveyor, and the maintenance and replacement records are reviewed against the approved documentation.
The July 2026 Rules are divided into five main Parts. Each Part addresses a different stage or technical aspect of the SPM classification process.
Addresses SPM-specific classification conditions, symbols and notations, plans and design data to be submitted, and the Information Booklet and Maintenance Manual. Part 1 is used together with the ABS Rules for Conditions of Classification – Offshore Units and Structures (Part 1B).
Refers to the applicable ABS materials and welding requirements. For structures and connections typical of offshore structures, such as towers, jackets and similar steel non-buoyant structures, the Rules direct the reader to the relevant offshore materials and welding provisions.
Covers general design matters, site and environmental conditions, material selection, design loads, structural design, weld design, stability, anchoring and mooring equipment.
Addresses cargo or product transfer systems, ancillary systems and equipment, hazardous areas and electrical installations, safety provisions and offshore charging connections.
Covers testing during construction, surveys after construction, drydocking surveys or equivalent examinations, annual surveys, special periodical surveys and the requirements for offshore charging stations.
The design of an SPM depends on the site conditions, the intended operating concept, the vessel characteristics and the loads transmitted through the mooring arrangement. The ABS Rules address site and environmental conditions in Part 3, Chapter 1, and design loads and structural design in Part 3, Chapter 2.
The design basis should establish the environmental conditions and operating cases relevant to the installation. These provide the engineering basis for assessing the buoy or platform, mooring components, anchoring system and associated structural connections.
Site-specific conditions and environmental data form part of the design information used to establish the SPM's design conditions and operating limits.
The Rules address design loads in Part 3, Chapter 2. The applicable load cases are to be considered in the design assessment of the SPM structure and mooring arrangement.
Structural design provisions address the strength and integrity of the relevant SPM structural components and connections under the applicable design conditions.
Part 3, Chapter 3 addresses stability and watertight or weathertight integrity. The Rules include intact and damage stability considerations for the SPM buoy.
The design basis should be documented and traceable to the calculations, drawings, specifications and supporting technical information submitted for the classification review.
The anchoring and mooring arrangement is a fundamental part of SPM integrity. Part 3, Chapter 4 addresses anchoring and mooring equipment, including anchor points, anchor legs, anchors and chains, mooring between the vessel and the SPM, structural components and buoyancy elements.
Anchors are to have adequate holding capacity. For drag anchor systems, the Rules refer to seabed soil characteristics when determining anchor holding capacity and require the anchorage type to be selected with regard to seabed conditions and maximum design anchor load.
The design and arrangement of anchor legs are to be assessed against the applicable design conditions and mooring system requirements. The Rules also address the testing of deployed mooring lines.
The vessel connection may use flexible hawsers or rigid mooring structures such as rigid arms and yokes. The relevant equipment and structural connections are addressed by the Rules.
Chains, accessories, synthetic mooring lines, wire ropes and associated components are subject to the applicable certification, recognized standards and survey requirements referenced by the Rules.
The Rules describe pull testing of deployed mooring lines in the presence of an ABS Surveyor, using the applicable approved procedure and design load criteria. The specific test basis and acceptance requirements must be taken from the relevant Rule provisions and approved project documentation.
Part 4 of the ABS Rules addresses the equipment and systems installed on the SPM. The actual arrangement depends on the SPM type, cargo or product service, operating concept and approved design.
Cargo or product transfer systems are addressed in Part 4, Chapter 1. The Rules include requirements relevant to the transfer arrangement and its associated equipment.
Hoses and flexible risers form part of the cargo transfer arrangement. Their design, installation, testing and associated documentation are addressed in the applicable provisions.
Swivels, valves, flex joints, expansion joints, seals and associated product piping are among the equipment items addressed by the Rules and their survey provisions.
Part 4, Chapter 2 addresses ancillary systems and equipment required for the SPM arrangement and its intended service.
Part 4, Chapter 3 addresses hazardous areas and electrical installations. The Rules also include survey attention to the maintenance of electrical equipment in hazardous locations.
Part 4, Chapter 4 addresses safety provisions. The wider system includes safety and shutdown equipment relevant to the SPM's cargo and operational arrangement.
Part 5, Chapter 1 addresses testing during construction. The provisions include surveys of buoy structures, buoyancy elements, PLEM structures and other structures, together with materials, welding, nondestructive examination, tank and bulkhead testing, mooring equipment, cargo transfer systems, control and safety systems, and hoses or flexible risers.
The construction quality control programme is to address material quality, suitability and traceability, together with the relevant certification and inspection records.
Welding procedure qualifications, welder qualifications, production welding, preparation, fit-up, alignment and inspection of fabricated components form part of the construction control process.
Nondestructive testing is addressed within the construction requirements. The applicable type and extent of NDT are determined by the relevant Rule provisions and approved construction documentation.
Tank, bulkhead and fitting tightness tests, hydrostatic testing and tank tests for structural adequacy are included in the construction testing provisions.
Fabrication and installation testing provisions address anchor legs, mooring equipment between the vessel and SPM, tower moorings, piles and anchors.
The cargo transfer system, control and safety equipment, hoses and flexible risers are subject to the applicable examination and testing requirements.
Part 5, Chapter 2 addresses surveys after construction. The Rules distinguish annual classification surveys, drydocking surveys or equivalent examinations, underwater survey in lieu of drydocking (UWILD), and special periodical surveys.
Annual classification surveys are to be made within three months either way of each annual anniversary date of the crediting of the previous Special Periodical Survey or the original construction date.
The Rules require examination of the underwater parts of each SPM and associated mooring hardware at intervals not exceeding five years, aligned with the Special Survey due date, subject to the applicable provisions.
An underwater survey in lieu of drydocking may be accepted subject to the Rule conditions, including prior submission of the inspection procedure, attendance under the surveillance of the attending Surveyor, and use of an in-water survey company recognized by ABS.
A Special Periodical Survey is to be completed within five years after build or after the crediting date of the previous Special Periodical Survey, subject to the detailed provisions of the Rules.
The Special Periodical Survey includes examination of the SPM buoy or platform structure, mooring components, foundations and supporting structure, underwater parts, corrosion protection, thickness measurements, mooring hardware, cargo hoses or flexible risers, safety equipment, swivel and cargo transfer equipment, and electrical installations, as applicable.
The July 2026 annual survey provisions require the maintenance and replacement records of the SPM system to be reviewed and verified. The attending Surveyor is to confirm compliance with the approved Information Booklet and Maintenance Manual.
The listed records include the following equipment and systems:
Swivels and the main bearing, including their maintenance and replacement records.
Mooring system records, including connection points to the SPM hull, together with the relevant anchoring and mooring equipment.
Maintenance and replacement records for the corrosion protection system.
Maintenance and replacement records for hawsers and associated vessel-to-SPM mooring components.
Records for hoses and flexible piping, together with applicable pressure testing and product or cargo riser checks.
Marine Breakaway Couplings and safety device testing where provided, as specified in the annual survey provisions.
The annual survey list also includes pressure testing, PLEM when part of the class scope, product valves, product or cargo risers, personnel protection, loading guidance and stability data as applicable, mooring chain tensions, hazardous-area electrical equipment, product lines and cargo equipment, shutdown devices, bilge pumping, ventilation, gauges and indicators, corrosion-prone structural areas, lights and navigational aids where applicable.
Underwater components are an important part of the SPM survey regime. The Special Periodical Survey provisions address underwater parts of the buoy, underbuoy hoses or risers and the PLEM when it forms part of the class scope.
Where underwater parts are inaccessible to the Surveyor, the Rules provide for examination by a qualified diver using two-way audio and visual communication, or by remotely operated vehicle (ROV). The examination is to be carried out in the presence of the Surveyor and in accordance with an accepted procedure.
The underwater examination addresses the relevant accessible portions of the SPM and associated equipment within the scope of the survey.
Underbuoy hoses or risers are included in the underwater survey scope as specified by the Rules and applicable class arrangements.
The PLEM is included in the relevant survey provisions when it forms part of the classification scope. The July 2026 annual survey clarification also specifies PLEM testing when it is part of class scope.
Any scour identified around the PLEM or foundation is to be investigated, documented and referred to ABS Engineering, with remedial actions applied as necessary.
Protective systems are to be verified as effective in accordance with the applicable provisions, including cathodic protection readings in the circumstances specified by the Rules.
Thickness gauging is addressed where wastage is evident or suspected, with representative gauging requirements at subsequent Special Surveys as specified in the Rules.
SPM classification depends on the relationship between the approved design, construction records, equipment certification, testing evidence, maintenance history and surveys after construction. Technical documentation should be maintained in a form that allows the condition and history of the SPM system to be reviewed.
An independent technical review can help an owner or project team examine whether the SPM design basis, engineering documentation, equipment interfaces, construction evidence and maintenance arrangements are coherent with the intended service and applicable classification requirements.
The review may consider the design assumptions, environmental criteria, mooring arrangement, structural connections, cargo transfer systems, safety functions, inspection access and the documentation needed to support construction, commissioning and in-service survey activities.
The scope and depth of any review should be agreed against the specific SPM configuration, project stage, available documentation and classification basis. An independent consultancy review does not replace approval, certification or survey functions reserved to ABS or another authorized organization.
The following PAMS pages provide additional information on SPM engineering design basis and independent single point mooring technical consultancy.
They are ABS classification rules addressing SPM-specific conditions of classification, materials and welding, mooring system design, equipment and systems, testing during construction and surveys after construction.
This article reviews the July 2026 edition of the ABS Rules for Building and Classing Single Point Moorings.
Part 1 covers Conditions of Classification; Part 2 covers Materials and Welding; Part 3 covers Mooring System Design; Part 4 covers Equipment and Systems; and Part 5 covers Testing and Surveys.
The Rules state that they are mainly applicable to SPM systems designed for temporarily moored vessels. For vessels permanently moored to an SPM, the Rules refer to Part 3B and Part 3C of the ABS Rules for Building and Classing Offshore Units.
The Foreword identifies updates to annual survey requirements, including review of replacement records, expanded coverage of Marine Breakaway Couplings, safety devices and hull mooring connections, and clarification that PLEM testing applies when the PLEM is part of the class scope.
Yes. Marine Breakaway Couplings are expressly listed in the annual survey provisions of the July 2026 edition, within the applicable SPM survey scope.
The July 2026 Rules clarify that PLEM testing is included when the PLEM forms part of the classification scope. The applicable class scope should be checked for the particular installation.
The Rules state that a Special Periodical Survey is to be completed within five years after the date of build or after the crediting date of the previous Special Periodical Survey, subject to the detailed provisions and any applicable authorization.
UWILD can be accepted subject to the conditions in the Rules. These include prior submission of the inspection procedure for review, an in-water survey company recognized by ABS, attendance under the surveillance of the attending Surveyor and an acceptable SPM condition.
As applicable, the survey addresses the SPM buoy or platform structure, mooring components, foundations and supporting structure, underwater parts, corrosion protection, thickness measurements, mooring hardware, cargo hoses or flexible risers, safety equipment, swivel and cargo transfer equipment, and electrical installations.
No. An independent technical consultancy review does not replace classification approval, certification or survey functions reserved to ABS or another authorized organization.
PAMS Pacific Admiralty Maritime Services provides independent marine surveying, offshore technical engineering and maritime compliance consultancy. SPM-related assignments are undertaken within an agreed technical consultancy scope.
November 2026
ABS Rules for Building and Classing Single Point Moorings, July 2026 edition. The article is intended as a technical overview and should be read together with the complete Rules and applicable referenced ABS publications.
This article provides a general technical overview of selected provisions in the ABS Rules for Building and Classing Single Point Moorings, July 2026. It is not a substitute for the complete ABS Rules, project-specific design calculations, approved drawings, classification review, survey instructions or applicable regulatory requirements. The applicability of individual provisions depends on the SPM configuration, classification scope, operating concept and approved project documentation. Where a requirement is to be applied to a particular installation, the complete Rule text and relevant referenced publications should be consulted.
PAMS Pacific Admiralty Maritime Services provides independent marine surveying, offshore technical engineering and SPM technical consultancy. Discuss your SPM design basis, engineering documentation, technical review or survey-related requirements within an agreed consultancy scope.
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