In which oil and gas scenarios can spiral welded pipes replace seamless pipes? Why?
Applicable scenarios:
Medium and low pressure gas/oil pipelines (such as gathering and transportation networks, urban gas)
Large diameter and long distance transportation (such as West-East Gas Transmission Φ1420mm pipeline)
Non-acidic environment (H₂S content <20ppm)
Reasons for substitution:
Cost advantage: The price of spiral welded pipes is 30%-50% lower than that of seamless pipes of the same specification, suitable for large-scale laying.
Diameter coverage: Pipe diameters of Φ219mm-Φ3000mm can be produced, and seamless pipes are difficult to break through Φ650mm.
Exception: Seamless pipes are still used for high-pressure trunk lines (such as above 10MPa) and acidic gas fields.
How can the pressure bearing capacity of spiral welded pipes meet the standards of the oil industry?
Material upgrade: Use X70/X80 high-grade steel plates (yield strength ≥485MPa) to improve toughness through controlled rolling and controlled cooling processes.
Weld reinforcement:
Multi-wire submerged arc welding (SAW) improves penetration and density
100% ultrasonic + radiographic testing of welds (in compliance with API 5L standard)
Post-weld expansion treatment eliminates residual stress
Pressure verification: Water pressure test reaches 1.25 times the working pressure, and some spiral welded pipes have achieved 12MPa pressure bearing (such as the Central Asian natural gas pipeline).
Comparison: Ordinary spiral welded pipes can withstand 6-8MPa, and seamless pipes can reach more than 15MPa.
How does spiral welded pipe solve the corrosion risk of traditional welds?
Anti-corrosion technology triple protection:
Inner coating: epoxy resin or liquid epoxy to prevent medium from corroding welds (thickness ≥ 200μm)
External protection: 3PE structure (epoxy powder + adhesive + polyethylene) or FBE (fused epoxy)
Cathode protection: sacrificial anode (magnesium alloy) or impressed current system is set along the line
Material selection:
HIC (hydrogen induced cracking) resistant steel plate (such as L245NS) is used in wet H₂S environment
Low carbon equivalent design reduces intergranular corrosion in welding area
Effect: After protection, the life of spiral welded pipe can reach 30 years (equivalent to seamless pipe).
What are the advantages of spiral welded pipe in construction efficiency?
Continuous production: Steel strip coiling and welding can produce pipes 24 hours a day (single unit produces 20,000-30,000 tons per month).
Easy on-site docking:
Spiral welded pipes have their own grooves, and the efficiency of girth welding is 20% higher than that of seamless pipes
Automatic welding machines can achieve rapid field construction (such as the average daily pipe laying of 1.5km on the China-Russia East Line)
Transportation optimization:
Can produce 12-18m ultra-long single pipes to reduce on-site welding points
Thin-wall design (such as D/S ≥ 100) reduces lifting weight
Case: The Central Asia pipeline project uses spiral welded pipes and was completed 4 months ahead of schedule.
What technological innovations promote the replacement of seamless pipes with spiral welded pipes?
Plate technology:
TMCP (thermomechanical control process) steel plate achieves high strength and high toughness (-40℃ impact energy ≥100J)
Welding technology:
Multi-wire submerged arc welding (4-wire welding) increases the welding speed to 2m/min
Laser tracking system controls weld deviation <0.5mm
Detection technology:
Fully automatic ultrasonic flaw detection (AUT) monitors weld quality in real time
Digital radiography (DR) replaces traditional film detection
Design breakthrough:
Large thickness spiral welded pipes (such as 25mm) have been used in deep-sea pipelines
Composite pipe design (lined with stainless steel spiral welded pipe) to cope with corrosive environments
Trend: X100 steel grade spiral welded pipes are being tested and may cover 15MPa high-pressure scenarios in the future.
