API 5L Welded Steel Pipe

API 5L steel line pipe is for oil and gas industries pipelines, developed for different working environments. The steel line pipe material is generally carbon steel and complies with API SPEC 5L specifications. Applied for petroleum and natural gas industries, oil industries requirements for transportation and are expected working in extreme situations, low and high temperatures, corrosion resistance for corrosive environments, and for sour services in H2S conditions.

• Common Class: API 5L Gr.B PSL1, PSL2, Sour Service pipe.
• Medium: X42, X46, X52.
• Medium and high: X56.
• High level: API 5L X60 PSL1, PSL2 LSAW line pipe.
• High: API 5L X65 PSL1, PSL2 LSAW/SSAW line pipe.
• Premium high: API 5L X70, API 5L X80.

PSL2 pipe comes with a suffix letter of N, Q, M, eg API 5L X52N, API 5L X60Q/M.

Sour service pipe with suffix letter NS, QS, MS, eg API 5L X65QS.

Suffix Letter N, Q, M, S

• R: As rolled.
• N: Normalizing rolled, Normalized formed, Normalized.
• Q: Tempered and quenched.
• M: Thermomechanical rolled or thermomechanical formed.
• S: Sour Service Use.

• Welded (ERW, LSAW, SSAW) steel line pipe: 1/2” to 60”.
• Range of Thickness: SCH 10 to SCH 160.
• Ends Type: Beveled ends, Plain ends.
• Range of length: 20FT, 40FT, or customized.
• Protection Caps in plastic or iron are available.
• Surface appearances: Natural, Varnished, Black painting, 3PE, FBE, etc.

There are 3 welding types: ERW (Electric Resistance Welding), LSAW (Longitudinally Submerged Arc Welding), and SSAW (Spirally Submerged Arc Welding) welding types.

• ERW pipe is a type of Resistance pipe that stands apart from welded pipe and DC welded pipe in two different manners as listed below. Based on the welding frequency, IF welding is for low frequency, and ultra-IF welding is for high frequency. In the case of thin-walled pipe, there is a high-frequency weld used typically in the case of contact welding and induction welding. When the usage is for a small-diameter pipe, they make use of DC welding. There is a high-frequency welding process used to manufacture comprehensive pipes and of ERW type. For oil and gas storage, the best-recommended type is ERW longitudinal, owing to its quality, ease of transport, and cost.
• Both LSAW pipe and SSAW pipe are SAW pipe (Submerged Arc Welding Steel Pipe), which is manufactured by making use of a submerged arc soldering process for preparing the steel and it results in a high-density pipe. Owing to the flux layer, there is no instant heat loss and it gets concentrated near the weld. It results in high-quality, highly efficient arc and smoke, which finds intensive usage in pressure vessels, pipe manufacturing, beams, fluids, steel works etc. SAW pipe finds its main usage in LSAW pipe, which is Longitudinally Submerged Arc Welding pipe.

ERW process is normally applied to the pipe below 24 in, 609 mm.

ERW/HFW Longitudinally Welding Steel Line Pipe (Electric Resistance Welding ) Manufacturing Flow Chart:

 - Uncoiling - Flattening - Shearing and Butt Welding - Loop Storing - Plate UT - Trimming - Forming - High-Frequency Welding - Removal of Inside and Outside Blurs - Ultrasonic Testing - Annealed by Medium Frequency - Air Cooling - Water Cooling - Sizing - Straightness - Cutting Off - Dimension and Initial Surface Inspection - Pipe Ends Beveling - Hydrostatic Test - Ultrasonic Testing of Entire Tube - Off Line Ultrasonic Testing - Ultrasonic Testing for Pipe Ends - Dimension and Final Surface Inspection - Corrosion Resistant Coating - Marking - Pipe Ends Protection - Inspection and Warehousing.

LSAW pipe applied to diameters from 20 in (508 mm) to 40 in (1016 mm), LSAW pipe also named JCOE pipe by manufacturing procedures, forms in J Shape - C Shape - O Shape and E Cold Expansion.

LSAW Welded Steel Line Pipe Manufacturing Flow Chart:

 - Plate UT - Vacuum Lifting - Ultrasonic Inspection - Edge Milling - Pre Bending - Type J Forming - Type C Forming - Type O Forming - Tack Welding By CO2 Gas Shield Arc Welding - Tab Welding - Inside Welding - Outside Welding - Removal of Tab Plate - Cleaning - Rounding - X Test - Ultrasonic Testing - Washing Before Expansion - Mechanical Expansion - Washing After Expansion - Straightness - Hydrostatic Test - Ultrasonic Testing - Weld Grinding for Pipe Ends - Mechanical Facing - X-Ray Test for Body and Both Ends - Ultrasonic Testing for Pipe Ends - Magnetic Particle Inspection For Both Ends - Weighing and Measuring Length - Product Inspection - Outside Coating - Inside Coating - Marking - Packing and Warehousing.

SSAW pipe applied for diameters up to 60 in (1524 mm).

SSAW Steel Pipe Manufacturing Flow Chart:

 - Uncoiling - Flattening - Shearing and Butt Welding - Edge Milling - Preliminary Rolling - Forming - Inside and Outside Welding - Cutting Off - Ultrasonic Testing - X-Ray Test - Weld Grinding for Pipe Ends - Expanding at Pipe Ends - Hydrostatic Test - Ultrasonic Inspection - Pipe Ends Beveling - X Test - Production Inspection - Marking - Warehousing.

As above manufacturing processes, we can see SAW (LSAW, SSAW) and ERW pipes are entirely different right from formation, welding, etc., and hence, the performance of both the pipes differ in the following aspects:

• The surface quality of ERW pipes is better when compared to SAW (LSAW, SSAW) pipes, as they are smooth and have a better finish. In most of the SAW pipes, it is mainly about the weld reinforcement internally and externally.
• The defects found in ERW pipes are lesser than in SAW pipes. As there is a solvent deposit in SAW pipes, it results in more defects apart from the defects in the volume. The defects found in ERW pipes are only confined to wire-line and straight welds and they can be inspected easily. The defects can be noticed easily and the ultrasonic reflection on the surface makes it easier to detect.
• The residual stress ratio in ERW is lower than in SAW pipes. As ERW pipe deformation happens more in ERW followed by a sizing of flat oval, it results in elliptical vertical changes and necking, thereby making the stress smaller. The displacement of ERW pipes was smaller when compared along the axial and transverse incisions for comparison with SAW pipes built using the same material and it was also easy to detect.
• Although the overall performance of both ERW and SAW pipes are the same, once the pipes have defects, the steel scrap and welding can be done on ERW, while it is not the same in the case of SAW, which would result in cracking or corrosion, making the ERW more durable.