Key Applications of DNV Grade AH36 Shipbuilding Steel Plates in Offshore Engineering

I. Floating Oil and Gas Production Units (FPSO/FPU/FSU)

FPSOs float on the sea surface year-round and are subjected to alternating wave loads. DNV Grade AH36 shipbuilding steel plates are extensively used for the deck and key non-cryogenic structures in the topside:

1. Deck plates, deck stringers, and beam frames of the topside modules

These structures support drilling equipment, oil and gas processing skids, generator sets, and pipeline supports. Given the significant dead weight and dynamic loads from equipment, the high strength of DNV Grade AH36 shipbuilding steel plates allows for thinner plate thickness, thereby reducing weight and decreasing the draft of the floating unit. As these components are exposed to ambient temperatures and are not subject to sustained temperatures below -20°C, they only need to meet the impact test requirements at 0°C.

2. Upper freeboard area of FPSO sides, superstructure bulkheads, and platform walkways

These areas are subject only to wave splash impact, with no risk of underwater high pressure or low-temperature brittle fracture; DNV Grade AH36 shipbuilding steel plates are uniformly selected for compartment bulkheads, stair bases, and guardrail stiffeners.

3. Upper bulkheads of ballast tanks and auxiliary support structures for storage tanks

DNV Grade DH36/EH36 shall be used for the submerged sections of ballast tanks and the high-impact zone at the bow; DNV Grade AH36 shall be used for the above-water dry-dock section bulkheads and external tank supports to reduce costs.

4. Secondary load-bearing framework for mooring auxiliary platforms, boarding gangways, and helicopter decks

With the exception of high-impact primary load-bearing members such as helicopter deck main girders, deck plating, secondary girders, and walkway plating shall all be constructed using DNV Grade AH36 shipbuilding steel plates.

II. Fixed Offshore Oil and Gas Platforms (Jack-up Platforms, Self-elevating Drilling Rigs)

1. General-purpose structures for the entire series of topside modules

Equipment deck plating, grating support frames, pipe rack supports, and cable tray bases;

Exterior walls, floor slabs, and reinforced frames for doors and windows of living quarters, control rooms, and barracks;

Secondary supports for crane bases, fixed supports for fire protection piping, and tank saddles.

2. Jack-up platform above-water structures

Platform main deck, cantilever beam auxiliary stiffeners, and drilling deck plating;

Lifting mechanism machinery room shells, upper above-water section gusset plates for pile legs, and above-water maintenance platforms for pile boots;

Submerged sections of pile legs; in cold-water regions, the main body of pile legs is mandatorily constructed using DNV Grade DH36/EH36 shipbuilding steel plates, while the above-water sections use DNV Grade AH36 shipbuilding steel plates.

3. Jack-up Platforms (Above-Water Deck Levels)

Jack-up subsea legs and high-fatigue zones in tidal range areas require steel with higher toughness; all decks above sea level, auxiliary platforms, access walkways, and pipeline supports are core applications for DNV Grade AH36 shipbuilding steel plates, suitable for platforms in the South China Sea, the Middle East, and Southeast Asia—regions with year-round high temperatures.

III. Offshore Wind Power Projects (Nearshore Temperate Wind Farms)

Applicable only to offshore wind turbine foundations and supporting facilities in ice-free areas where winter temperatures remain above 0°C:

1. Above-water platforms, operating decks, ladder supports, and guardrail bases for jacket-type wind turbine foundations;

2. Turbine upper nacelle maintenance platforms, offshore substation decks, walls, and equipment supports;

3. Floating wind turbine (FVOWT) float above-water freeboard plates and upper equipment frames.

DNV Grade AH36 shipbuilding steel plates are prohibited for underwater and tidal-range structures of wind turbines in ice-prone areas and northern waters with low winter temperatures; DH36/EH36 must be used instead.

IV. Marine Auxiliary Vessels and Offshore Support Vessels

1. Main decks, superstructures, above-water bulkheads of ballast tanks, and cargo and oil tank tops on multi-purpose workboats, supply vessels, and floating cranes;

2. Deck planking, wave guards, and container mounting bases on offshore barges and crane barges;

3. Above-water hull structures and work platforms for dredgers and channel maintenance vessels.

V. Port, Coastal, and Offshore Marine Infrastructure

1. Main girder plating, pipeline supports, and operating platforms for offshore terminals and oil loading/unloading jetties;

2. Above-water load-bearing structures for intake and discharge structures at coastal power plants and desalination platforms;

3. Above-water deck sections for cross-sea access bridges, offshore observation platforms, and floating caissons of floating docks;

4. Steel structures for channel protection embankments, temporary offshore construction platforms, and formwork for precast components.

VI. Subsea and Pipeline Supporting Structures (Non-Deepwater High-Pressure Main Structures)

1. Support piers for the above-water landing sections of subsea pipelines and frames for pipeline ballast blocks;

2. Surface protective frames for subsea risers and pipeline maintenance and operation platforms.

DNV Grade AH36 shipbuilding steel plates shall not be used for deepwater risers, subsea manifolds, or the main bodies of cryogenic subsea equipment.

VII. Selection Criteria for DNV AH36 in Offshore Engineering

VIII. Key Advantages of Selecting DNV AH36

1. Mechanical Properties: Yield strength ≥355 MPa, significantly superior to standard Grade A/B ship plates; lightweight design reduces weight and enhances structural load-bearing capacity;

2. Fabrication: Low-carbon microalloy steel; no preheating required for cold bending, flame cutting, or conventional submerged arc welding, enabling high on-site prefabrication efficiency;

3. Certification: Certified by DNV, meeting global classification society compliance requirements for offshore oil and gas, wind power, and port engineering projects;

4. Cost-Effectiveness: Lower procurement and processing costs than DH36/EH36 at equivalent strength levels, offering the best cost-performance ratio under ambient temperature conditions;

5. Weather Resistance: Suitable for environments exposed to seawater spray and salt fog corrosion; when paired with anti-corrosion coatings, its fatigue life meets 25-year offshore engineering design standards.