Offshore Oil & Gas Platform Structural Steel-Tsisco

Offshore Oil & Gas Platform Structural Steel

1) Overview

Offshore structural steel is specially designed for offshore oil & gas platforms, featuring high strength, excellent toughness, low-temperature impact resistance, corrosion resistance in seawater, and good weldability.
It is widely used in fixed platforms, semi-submersibles, FPSOs, subsea structures, and piling systems.

2) Manufacturing Process
   •   Melting: BOF / EAF + LF / AOD / VOD refining
   •   Casting: continuous casting slabs/billets
   •   Rolling: hot rolled heavy plates, sections, linepipe grades
   •   Heat treatment: normalizing, TMCP, quenching & tempering (QT)
   •   Surface: shot blasting, primer coating

3) Key Features
   •   High strength: yield strength 355–690 MPa
   •   Low-temperature toughness: excellent impact properties at -40℃ to -60℃
   •   Seawater corrosion resistance: alloying with Ni, Cu for durability
   •   Good weldability: low CE, suitable for offshore welding
   •   Heavy plate capability: thickness up to 150 mm with through-thickness (Z-quality)

4) Standards
   •   API / ASTM: API 2H Gr.50, API 2W Gr.50 / Gr.60
   •   EN / DIN: EN 10225 (S355G7, S355G10, S420G2, S460G2, S460ML, S690QL)
   •   BS: BS 7191 (50D, 355EM, 420EM)
   •   GB/T: GB/T 714, GB/T 1591, GB/T 5313

5) Grades
   •   API grades: API 2H Gr.50, API 2W Gr.50/60
   •   EN grades: S355G7, S355G10, S420G2, S460G2, S460ML, S690QL
   •   Chinese grades: Q355GJ, Q420GJ, Q460GJ
   •   Corrosion-resistant alloys: Ni, Cu alloyed steels

6) Applications
   •   Fixed platforms (Jacket): piles, legs, deck beams
   •   Semi-submersibles: pontoons, columns, decks
   •   FPSO hulls: hull plating, decks, storage tanks
   •   Subsea structures: manifolds, riser supports, subsea frames
   •   Piling: foundation piles, port piles
   •   Topside modules: drilling, production, crane foundations

7) Quality & Testing
   •   Chemical analysis (spectrometer, C, Mn, Ni, Mo, Cu)
   •   Mechanical tests (yield, tensile, elongation, impact at -20/-40/-60℃)
   •   NDT: UT, MT, PT, RT
   •   Z-direction properties: Z15/Z25/Z35 against lamellar tearing
   •   Corrosion tests: salt spray, seawater immersion
   •   Third-party certifications: ABS, DNV, BV, LR, CCS, SGS, TÜV

8) Supply & Packaging
   •   Forms: hot rolled heavy plates, medium-thick plates, sections, tubular piles
   •   Dimensions: thickness 6–150 mm, width ≤ 4200 mm, length ≤ 18000 mm
   •   Surface: shot blasted, primer coated, or bare
   •   Packaging: strapped, loose, or export-specific racks
   •   Traceability: MTC (EN 10204 3.1/3.2) with offshore certifications

Materials & Dimensions of Structural Steel for Offshore Oil & Gas Platforms

1. Carbon Structural & Shipbuilding Plates
   •   Standards: ASTM A36, API 2H Gr.50, API 2W, CCS/ABS/DNV/BV
   •   Dimensions:
   •   Thickness: 8 – 150 mm
   •   Width: 1500 – 4000 mm
   •   Length: 6 – 20 m
   •   Applications: Deck plating, deck girders, leg plating, platform hull structures

2. High-Strength Low Alloy Steel (HSLA)
   •   Standards: API 2Y, API 2MT1, ASTM A572 Gr.50/60
   •   Dimensions:
   •   Thickness: 10 – 120 mm
   •   Width: 1500 – 3500 mm
   •   Length: 6 – 18 m
   •   Applications: Offshore piles, main girders, stiffeners for deepwater platforms

3. Structural Sections
   •   Types: H-beams, I-beams, angle steel, channel steel
   •   Dimensions:
   •   H-beams: H200 – H900
   •   Angles/Channels: 50 × 50 mm – 300 × 300 mm
   •   Applications: Platform legs, support beams, truss frameworks

4. Pipes for Offshore Platforms
   •   Carbon Steel Pipes: API 5L X42–X70, ASTM A106 Gr.B/C
   •   Alloy Steel Pipes: ASTM A335 P11, P22, P91
   •   Stainless Steel Pipes: ASTM A312 304/316L, Duplex 2205/2507
   •   Dimensions:
   •   OD: ½” – 1200 mm
   •   WT: 3 – 80 mm
   •   Length: 6 m, 12 m
   •   Applications: Offshore pipelines, seawater cooling lines, firewater systems, drilling mud lines

5. Special Steels & Corrosion-Resistant Alloys
   •   Weathering Steel (Corten): External structures, marine atmospheric resistance
   •   Low-Temperature Steel (ASTM A333, 9%Ni): LNG tanks and cryogenic pipelines
   •   Cu-Ni Alloys (70/30, 90/10): Seawater cooling and firewater piping
   •   Duplex Stainless Steel (2205/2507): Chloride-rich offshore service
   •   Dimensions:
   •   OD: ½” – 36”
   •   Thickness: 2 – 50 mm
   •   Applications: Seawater systems, LNG projects, sour oil & gas transport

6. Typical Applications
   •   Topsides: Deck plates, deck girders, equipment supports
   •   Jackets & Legs: High-strength plates, H-beams, tubular piles
   •   Seawater & Firewater Systems: Cu-Ni alloy pipes, duplex stainless steel
   •   LNG & Cryogenic Systems: 9%Ni steels, low-temp carbon steels
   •   Corrosion-Resistant Components: Corten steel, 316L/2205 fittings

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