Longitudinal Submerged Arc Welded (LSAW) Steel Pipe

LSAW (Longitudinal Submerged Arc Welded) steel pipes are manufactured using the advanced JCOE cold-forming process, ensuring superior structural integrity for the world’s most demanding engineering environments. The production process involves progressively forming a heavy steel plate into a "J", "C", "O" shape, followed by high-precision double-sided submerged arc welding (inside and outside) and full-body mechanical expansion.

Characterized by large diameters, heavy wall thicknesses, and high pressure resistance, LSAW pipes serve as the primary choice for long-distance oil and gas pipelines, offshore piling foundations, and massive steel structures.

Key Features & Advantages

Advanced JCOE Technology: Unlike conventional bending methods, JCOE progressive forming ensures uniform stress distribution across the pipe body and delivers significantly higher dimensional accuracy.

Heavy Wall Thickness Capacity: We specialize in producing thick-walled pipes with thicknesses up to 60mm, engineered specifically to withstand extreme subsea pressures and heavy structural loads.

100% Double-Weld Non-Destructive Testing: To guarantee zero-defect welds, every single pipe undergoes both automatic Ultrasonic Testing (UT) and Radiographic (X-Ray) testing over the entire weld seam length.

Integrated Anti-Corrosion Solutions: We offer complete online coating services, including 3PE, FBE, and Coal Tar Epoxy, designed to provide comprehensive corrosion barrier protection and extend project service life up to 50+ years.

Technical Specifications & Material Grades

To ensure compliance with international oil, gas, and heavy infrastructure projects, our LSAW steel pipes are produced strictly to the following parameters:

Parameter	Specification Details
Standard Compliance	API 5L (PSL1/PSL2), ASTM A671, ASTM A672, EN10210, EN10219, GB/T 9711
Material Grade	Gr.B, X42, X52, X60, X65, X70, X80, S355JR
Outer Diameter (OD)	406 mm to 1422 mm (16" to 56")
Wall Thickness (WT)	8 mm to 60 mm
Length Options	6.0 m to 12.5 m (Standard or Customized lengths)
Welding Process	Double-sided Submerged Arc Welding (DSAW)
Surface Treatment	Bare (uncoated), Black Paint, 3PE (Three-Layer Polyethylene), FBE (Fusion Bonded Epoxy) Coating, Galvanized

Quality Control & Inspection (NDT)

Given that LSAW pipes operate under extreme pressure and structural loads, we enforce a rigorous, multi-stage testing regime to ensure zero-defect compliance with project specifications:
· 100% X-Ray Radiographic Inspection: Performed along the full length of the longitudinal weld seam to detect any potential internal defects, including porosity, slag inclusion, or lack of fusion.
· Automatic Ultrasonic Testing (UT): Applied to the weld seam to monitor joint integrity and scanned across the plate body to check for laminations and wall thickness consistency.
· Magnetic Particle Testing (MT): Conducted on pipe ends to ensure the absence of surface or near-surface cracks in the critical bevel zones.
· Hydrostatic Pressure Test: Every pipe is subjected to a mandatory water-pressure test, held for at least 5 to 10 seconds, to verify structural seal integrity under maximum design pressures.
· Mechanical & Metallurgical Testing: Comprehensive destructing testing is executed on test coupons, including tensile, flattening, and Charpy V-Notch impact tests.
· Full Product Traceability: Supplied with a certified EN 10204 3.1 Mill Test Certificate (MTC). Third-party inspections by agencies such as SGS or Bureau Veritas (BV) are welcomed.

Dimensional Control & Mechanical Expansion

To guarantee hassle-free on-site welding fit-up, we utilize a critical Full Mechanical Expansion process after the double-sided submerged arc welding is completed.

Mechanical expansion physically stretches the pipe body from the inside out using a series of segmented dies. This process optimizes the final geometric dimensions, relieving internal residual welding stress while ensuring excellent ovality (out-of-roundness tolerances) and straightness along the entire length of the pipe.

Processing & Customization Services

End Preps: Beveled ends are cut to an angle of 30° (+5°, -0°) for butt welding, protected with plastic end caps. Threaded ends are supplied with couplings to ANSI/API standards.

Anti-Corrosion Coatings: 3-Layer Polyethylene (3PE) coating is executed to protect underground line pipes from chemical and environmental soil corrosion. Galvanizing services provide long-term rust prevention for outdoor structural use.

Frequently Asked Questions (FAQ)

Q: What forming processes do you use for LSAW pipe, and how do you ensure dimension control?

A: We primarily utilize advanced JCOE forming technology (and UOE for specific mass orders). JCOE processes ensure that the steel plate is progressively bent with high precision, maintaining minimal residual stress. After double-sided submerged arc welding (inside and outside), the entire pipe body undergoes Full Mechanical Expansion. This crucial step significantly optimizes the geometric dimensions, ensuring excellent ovality and straightness for seamless site fit-up.

Q: What non-destructive testing (NDT) procedures are implemented for LSAW steel pipes?

A: Given that LSAW pipes are widely used in high-pressure applications, our quality control is absolute. 100% of our LSAW pipes undergo a comprehensive testing regime: X-ray Radiographic Inspection and Automatic Ultrasonic Testing (UT) for the entire weld seam length, Magnetic Particle Testing (MT) for pipe ends, and a mandatory Hydrostatic Test held for at least 5-10 seconds to guarantee zero-leakage security under extreme pressure.

Q: What is your available size range for LSAW pipes, especially for heavy-wall thickness?

A: Our JCOE production line specializes in large-diameter and heavy-wall configurations. We supply Outside Diameters (OD) from 16″ to 56″ (406mm to 1422mm) with Wall Thicknesses (WT) up to 60mm. We can also source custom steel plates to meet specific high-yield heavy structural or piling project specifications.

Q: Which international standards and steel grades can your LSAW pipes meet?

A: Our LSAW pipes comply strictly with international oil, gas, and structural standards. We offer API 5L (PSL1 & PSL2, grades from Gr.B up to X80), ASTM A672/A671 (for atmospheric and lower temperatures), and EN 10210 / EN 10219 / ASTM A572 for heavy structural piling. All products are fully traceable and supplied with an EN 10204 3.1 Mill Test Certificate (MTC). Third-party inspection (SGS, BV) is also welcomed.

Q: Why should I choose LSAW pipes over SSAW (Spiral) pipes for critical pipelines?

A: Compared to SSAW (Spiral Welded) pipes, LSAW (Longitudinal Welded) pipes feature a much shorter weld seam length per pipe, significantly reducing the potential risk area for defects. LSAW pipes offer superior stress distribution, tighter dimensional tolerances, and are much less prone to stress corrosion cracking under high-pressure line pipe transmission or heavy dynamic structural loading, making them the safest choice for critical infrastructure.