Overview
EN 10217 is a European standard titled "Welded steel tubes for pressure purposes." It specifies the technical delivery conditions for electric welded and submerged arc welded steel tubes, designed to convey pressurized fluids.
LSAW stands for Longitudinal Submerged Arc Welding. Therefore, an EN 10217 LSAW steel pipe is a longitudinally welded pipe manufactured according to the stringent quality and testing requirements of the EN 10217 standard, primarily for use in pressure systems.
1. The EN 10217 Standard
EN 10217 is divided into several parts, each covering different steel grades and manufacturing routes. The most relevant part for LSAW pipes is:
EN 10217-3: Welded steel tubes for pressure purposes - Technical delivery conditions - Part 3: Alloy fine grain steel tubes
This part specifically covers tubes made from alloyed fine grain steel and welded by the submerged arc welding (SAW) process-which includes both LSAW and HSAW (Helical/Spiral SAW).
It specifies requirements for chemical composition, mechanical properties, technological tests (e.g., flattening, flaring, bending), non-destructive testing, and inspection.
Other parts of the standard (like Part 1 for non-alloy steel) may also apply to certain LSAW pipes if the material and process fit, but Part 3 is the most directly applicable.
2. Manufacturing Process of LSAW Pipe (JCOE / UOE)
The typical process for manufacturing an EN 10217 LSAW pipe is as follows:
Plate Preparation: Steel plates (from fine grain steel) are cut to the required width and length based on the desired pipe diameter and length.
Bending (JCO or UO Forming):
JCOE: The plate is first pressed into a 'J' shape on both ends, then into a 'C' shape, and finally into an 'O' (open oval) shape. It is the most common method for large-diameter pipes.
UOE: The plate is first bent into a 'U' shape and then into an 'O' shape using large presses. This is common for very high-volume production.
Welding:
The open-seam "O" pipe is moved to the welding station.
Internal Welding: A multi-electrode submerged arc weld is made along the entire internal length of the seam.
External Welding: The pipe is rotated, and a subsequent multi-electrode submerged arc weld is made along the entire external length of the seam.
The submerged arc process uses a granular flux that completely covers the weld arc, preventing sparks and spatter and resulting in a very high-quality, clean, and strong weld.
Expansion (E): The welded pipe is mechanically expanded (e.g., using a mandrel). This critical step ensures perfect circularity, eliminates stress from the welding process, and improves mechanical properties uniformity.
Testing and Inspection: As per EN 10217, the pipe undergoes rigorous testing, including:
Non-Destructive Testing (NDT): 100% radiographic (X-ray) or ultrasonic testing (UT) of the weld seam to detect any internal defects.
Mechanical Tests: Tensile, impact (Charpy V-notch), and hardness tests on samples taken from the pipe body and weld.
Hydrostatic Test: Every pipe is tested to a pressure that induces a stress equal to a specified percentage of the yield strength of the steel.
Final Processing: Ends are bevelled (if required), pipes are measured, cleaned, painted (if required), and marked with the standard, grade, size, and manufacturer's info.
3. Common Steel Grades and Chemical Composition
EN 10217-3 specifies several grades based on minimum yield strength (e.g., P275NL2, P355NL2, P420NL2). The naming convention is:
P = Pressure purpose
XXX = Minimum specified yield strength in MPa (e.g., 355 MPa)
NL2 = Notified material for normalized delivery with Charpy V-notch impact energy at -40°C.
These are fine grain steels micro-alloyed with elements like Niobium (Nb) and Vanadium (V) to achieve high strength and toughness through grain refinement.
4. Key Applications
Due to their high strength, pressure integrity, and ability to be produced in large sizes, EN 10217 LSAW pipes are used in critical applications:
Oil & Gas Transmission: Main lines for long-distance transportation of oil and natural gas.
Petrochemical Plants: For process piping within refineries and chemical plants under high pressure.
Power Generation: Boiler tubes, high-pressure steam lines, and penstocks in power plants.
Offshore Engineering: Subsea pipelines, platform risers, and structural components.
Civil Engineering: Piling and foundation support in large construction projects.
5. Advantages of EN 10217 LSAW Pipes
High Pressure Resistance: The SAW process creates a robust, reliable weld capable of withstanding very high internal pressures.
Large Sizes: Can be manufactured in very large diameters (over 1.5 meters) and thick walls (over 40 mm), which ERW pipes cannot achieve.
Excellent Material Properties: Made from fine grain steel, offering a good combination of high strength and toughness, especially in low temperatures.
Stringent Quality Control: The EN 10217 standard mandates comprehensive testing, ensuring high and consistent quality for safety-critical applications.
Dimensional Accuracy: The expansion process ensures excellent roundness and straightness.
Comparison with Other Pipe Types
| Feature | EN 10217 LSAW Pipe | ERW Pipe (EN 10217-1) | SSAW/Spiral Pipe |
|---|---|---|---|
| Weld Seam | Longitudinal straight seam | Longitudinal straight seam | Helical seam |
| Size Range | Large Diameter & Thick Wall | Small to Medium Diameter | Large Diameter |
| Pressure Rating | Very High | High | High |
| Weld Quality | Excellent, fully NDT tested | Very Good | Good |
| Primary Use | High-pressure main lines | Process piping, lower pressure lines | Pilings, low-pressure fluid transport |
In summary, EN 10217 LSAW steel pipe represents a high-end product designed for demanding pressure applications. Its manufacture is governed by a strict European standard, ensuring its performance, safety, and reliability in some of the most critical industrial sectors.
