API 5L PSL1 Grade X42 Double-Sided Submerged Arc Welding (DSAW) Steel Pipe
Basic Overview
API 5L PSL1 Grade X42 DSAW (Double-Sided Submerged Arc Welding) steel pipe is a medium-strength carbon steel line pipe manufactured to the American Petroleum Institute specification for pipeline transportation systems. The "X42" designation indicates a minimum yield strength of 42,000 psi (290 MPa), representing a significant strength increase over Grade B (35,000 psi) .
X42 is the entry-level "X-grade" in the API 5L family, offering approximately 17% higher yield strength than Grade B. It is widely used for medium-pressure oil and gas transmission, gathering lines, and water pipelines where higher strength than Grade B is required but the enhanced properties of PSL2 are not necessary .
The DSAW manufacturing process-also known as LSAW (Longitudinal Submerged Arc Welding)-is a high-integrity welding method where both inside and outside welds are applied, forming a single high-quality weld nugget. This process is specifically designed for large-diameter, thick-wall pipes used in oil and gas transmission, water mains, and structural applications .
Name Explanation
| Part | Meaning |
|---|---|
| API | American Petroleum Institute |
| 5L | Specification for line pipe used in pipeline transportation systems |
| PSL1 | Product Specification Level 1 – standard quality level with basic requirements (no mandatory impact testing) |
| X42 | Grade designation: "X" indicates pipeline grade, "42" represents minimum yield strength in ksi (42,000 psi / 290 MPa) |
| DSAW | Double-Sided Submerged Arc Welding – both inside and outside welds are applied; the welding arc is submerged in granular flux during welding |
| Also Known As | LSAW (Longitudinal Submerged Arc Welding) – when the weld seam runs longitudinally along the pipe |
Key Specifications
| Attribute | Description |
|---|---|
| Standard | API 5L (46th Edition, aligned with ISO 3183) |
| Product Specification Level | PSL1 – standard quality level |
| Grade | X42 (L290 in ISO notation) |
| Minimum Yield Strength | 290 MPa (42,000 psi) |
| Minimum Tensile Strength | 414 MPa (60,000 psi) |
| Manufacturing Process | DSAW (Double-Sided Submerged Arc Welding) / LSAW (Longitudinal Submerged Arc Welding) |
| Forming Methods | JCOE (progressive J-C-O forming) or UOE (U-ing, O-ing, Expanding) |
| Size Range (DSAW/LSAW) | 406 mm to 1829 mm (16" to 72") OD – typical for DSAW; up to 84" available |
| Wall Thickness | 6.0 mm to 50 mm (up to 75 mm for special applications) |
| Length | 6 m to 12 m standard; up to 18 m available |
| End Finishes | Plain ends, beveled ends (30° bevel angle) |
| Coating Options | Black paint, varnish, anti-rust oil, FBE, 3LPE, coal tar epoxy |
Chemical Composition (API 5L PSL1 Grade X42 Welded Pipe)
| Element | Maximum % | Notes |
|---|---|---|
| Carbon (C) | 0.26% | Low carbon for good weldability |
| Manganese (Mn) | 1.30% | Provides strength; higher than Grade B |
| Phosphorus (P) | 0.030% | Controlled for weldability |
| Sulfur (S) | 0.030% | Controlled for toughness |
| Silicon (Si) | Not specified for PSL1 | Typically ≤ 0.40% |
Note: PSL1 has no requirement for maximum yield strength, carbon equivalent, or mandatory impact testing . For each reduction of 0.01% below the specified maximum carbon content, an increase of 0.05% above the specified maximum manganese is permitted, up to a maximum of 1.65% .
Mechanical Properties (API 5L PSL1 Grade X42)
| Property | Requirement |
|---|---|
| Yield Strength (min) | 290 MPa (42,000 psi) |
| Yield Strength (max) | Not specified for PSL1 |
| Tensile Strength (min) | 414 MPa (60,000 psi) |
| Tensile Strength (max) | Not specified for PSL1 |
| Elongation | Per API 5L formula (varies by wall thickness) |
| Charpy Impact | Not required for PSL1 – only PSL2 requires mandatory impact testing |
X42 vs. Adjacent Grades Comparison
| Grade | Yield Strength (min) | Tensile Strength (min) | Relative Strength vs. X42 | Typical Application |
|---|---|---|---|---|
| Grade B | 241 MPa (35 ksi) | 414 MPa (60 ksi) | -17% | General pipeline service |
| X42 | 290 MPa (42 ksi) | 414 MPa (60 ksi) | Baseline | Medium-pressure transmission |
| X46 | 320 MPa (46 ksi) | 435 MPa (63 ksi) | +10% | Higher-pressure transmission |
| X52 | 359 MPa (52 ksi) | 455 MPa (66 ksi) | +24% | General transmission |
*X42 offers approximately 17% higher yield strength than Grade B, making it a cost-effective upgrade for medium-pressure applications where Grade B strength is insufficient .*
Dimensional Specifications
| Parameter | Range / Tolerance |
|---|---|
| Outside Diameter | 406 mm to 1829 mm (16" to 72") – typical DSAW range |
| Wall Thickness | 6.0 mm to 50 mm (up to 75 mm for special applications) |
| Diameter Tolerance (Pipe Body) | ±0.75% of specified OD |
| Diameter Tolerance (Pipe Ends, 219.1-273.1mm) | +1.6 mm / -0.4 mm |
| Diameter Tolerance (Pipe Ends, 274-457mm) | +2.4 mm / -0.8 mm |
| Wall Thickness Tolerance (508-610 mm) | +19.5% / -8% |
| Wall Thickness Tolerance (219.1-457 mm) | +15% / -12.5% |
| Length | 6 m to 12 m standard; up to 18 m available |
| Out-of-Roundness | ≤ 1% of specified OD |
Typical Size Availability (API 5L Grade X42 DSAW):
| OD (inch) | OD (mm) | Wall Thickness Range (mm) |
|---|---|---|
| 16" | 406 | 6.0 - 14.0 |
| 20" | 508 | 6.0 - 16.0 |
| 24" | 610 | 6.0 - 18.0 |
| 30" | 762 | 7.0 - 21.0 |
| 36" | 914 | 8.0 - 24.0 |
| 40" | 1016 | 8.0 - 26.0 |
| 48" | 1219 | 9.0 - 28.0 |
| 56" | 1422 | 10.0 - 29.0 |
| 60" | 1524 | 10.0 - 29.0 |
| 64" | 1626 | 10.0 - 30.0 |
| 72" | 1829 | 10.0 - 30.0 |
DSAW/LSAW Manufacturing Process
Double-Sided Submerged Arc Welding (DSAW), also known as Longitudinal Submerged Arc Welding (LSAW), is a high-efficiency process used primarily for large-diameter steel pipes.
Process Description
Welding arc is submerged in granular flux during welding, protecting the weld from atmospheric contamination
Both inside and outside welds are required, usually accomplished in separate processes
The separate welds consume a portion of the other, resulting in a single high-quality weld nugget
Forming Methods
| Method | Description | Typical Diameters |
|---|---|---|
| JCOE | Progressive J-C-O forming steps (J-shape → C-shape → O-shape), expanded after welding | 406-1626 mm (16"-64") |
| UOE | Plate pressed into U-shape, then O-shape, expanded after welding | 508-1118 mm (20"-44") |
Process Steps
Plate Selection – Steel plates meeting API 5L PSL1 X42 requirements
Edge Preparation – Edges are beveled to create a V-shaped groove
Forming – Steel plates are formed into cylindrical shapes using JCOE or UOE presses
Tack Welding – Formed plates are tack-welded to maintain shape
Double Submerged Arc Welding – Pipe seam welded on both interior and exterior surfaces
Cold Expansion – Pipe may be expanded up to 1.5% to achieve final OD dimension
Ultrasonic Inspection – Seam inspected by continuous ultrasonic automatic flaw detection
Hydrostatic Pressure Test – Each pipe undergoes hydrostatic pressure testing (when specified)
Finishing – End processing, beveling, coating, and marking according to specifications
Testing & Inspection Requirements (PSL1)
| Test Type | Requirement | Notes |
|---|---|---|
| Chemical Analysis | Per heat lot | Verifies composition limits per API 5L PSL1 |
| Tensile Test | Per lot | Verifies yield and tensile strength |
| Flattening Test | Required | Checks ductility and weld integrity |
| Bend Test | Required | Verifies weld integrity |
| Charpy Impact Test | Not required for PSL1 | Only PSL2 requires mandatory impact testing |
| Hydrostatic Test | Each pipe (when specified) | Pressure integrity verification |
| Ultrasonic Inspection | 100% of weld seam | Standard practice for DSAW |
| X-ray Inspection | For "T" joints | Where strip butt welds intersect spiral seams |
| Dimensional Inspection | 100% | Per standard tolerances |
| Mill Test Certificate | EN 10204 Type 3.1B | Provided with full test results |
PSL1 vs. PSL2 Comparison for X42
| Feature | PSL1 X42 | PSL2 X42 | Significance |
|---|---|---|---|
| Carbon (C) max | 0.26% | 0.22-0.24% | PSL2 has tighter control for better weldability |
| Sulfur (S) max | 0.030% | 0.015% | PSL2 has 50% reduction – critical for toughness |
| Phosphorus (P) max | 0.030% | 0.025% | PSL2 has stricter limits |
| Yield Strength | 290 MPa min only | 290-495 MPa range | PSL2 specifies maximum to prevent over-strength materials |
| Tensile Strength | 414 MPa min only | 414-655 MPa range | PSL2 specifies maximum for consistency |
| Yield-to-Tensile Ratio | Not specified | ≤ 0.93 | PSL2 ensures adequate ductility |
| Impact Testing | Not required | Mandatory | PSL2 guarantees low-temperature toughness |
| Carbon Equivalent | Not required | Calculated and controlled | PSL2 ensures good field weldability |
| NDT Requirements | Standard | More stringent | PSL2 provides better defect detection |
| Typical Use | General service, water lines, non-critical | Critical service, sour service, low temperature |
Common Applications
| Application | Description |
|---|---|
| Oil and Gas Transmission | Medium-pressure pipelines for crude oil, natural gas, and refined products |
| Natural Gas Gathering Lines | Connecting wells to processing facilities |
| Water Transmission Mains | Large-diameter municipal and industrial water pipelines |
| Gathering and Flow Lines | Upstream oil and gas operations |
| Structural Applications | Piling, bridge supports, construction |
| Industrial Process Piping | Refineries, chemical plants, power generation |
Key Advantages
| Advantage | Description |
|---|---|
| Higher Strength than Grade B | 17% higher yield strength allows higher operating pressures or reduced wall thickness |
| Cost-Effective | PSL1 is more economical than PSL2 – suitable for general service applications |
| Excellent Weldability | Low carbon content ensures good field weldability |
| Large Diameter Capability | DSAW produces pipes from 16" to 72" OD – ideal for large-diameter applications |
| High Weld Integrity | Double-sided welding creates a single high-quality weld nugget with 100% UT inspection |
| Wide Availability | Commonly stocked by manufacturers globally |
| JCOE/UOE Forming | Precise dimensional accuracy through advanced forming methods |
International Approximations
| Standard | Equivalent Grade | Notes |
|---|---|---|
| ISO 3183 | L290 | International standard equivalent |
| GB/T 9711 | L290 | Chinese equivalent |
| EN 10208-2 | L290MB | European equivalent |
| ASTM A53 | Grade B (similar strength) | A53 Grade B has 35 ksi yield vs. X42's 42 ksi |
Coating Options
API 5L PSL1 X42 DSAW pipe can be supplied with various coatings for corrosion protection:
| Coating Type | Best For | Key Features |
|---|---|---|
| 3LPE (3-layer polyethylene) | Buried pipelines | Most common; excellent corrosion protection, high impact resistance |
| FBE (Fusion Bonded Epoxy) | Oil & gas pipelines | Strong adhesion, chemical resistance |
| Coal Tar Epoxy | Marine environments | Heavy-duty protection |
| Varnish / Anti-rust oil | Temporary protection | Short-term corrosion protection during transport |
| Bitumen Coating | Buried service | Cost-effective protection |
| Black Oil Coating | Standard mill finish | Temporary protection |
End Finishes
Available end treatments include:
Plain ends (PE) – standard for most applications
Beveled ends (BE) – for field welding (30° bevel angle)
Threaded ends – for mechanical connections
Important Considerations
1. PSL1 vs. PSL2 Selection
PSL1: Suitable for general service, water lines, non-critical applications where low-temperature toughness is not required
PSL2: Required for low-temperature service (below 0°C), sour service (H₂S environments), regulated pipelines (FERC, DOT), and critical applications
2. X42 vs. Grade B Selection
X42: Choose when higher strength than Grade B is needed for medium-pressure applications
Grade B: Standard choice for general pipeline service where 35 ksi yield is sufficient
3. DSAW Size Limitations
DSAW manufacturing for X42 is typically available from 16" to 72" OD
Smaller diameters (under 16") are typically produced by ERW or seamless methods
4. Impact Testing
PSL1 does not require Charpy impact testing by the standard . If low-temperature service is anticipated, consider:
Specifying impact testing as a supplementary requirement
Upgrading to PSL2 (which mandates impact testing)
5. Temperature Limitations
Maximum recommended service temperature: 350°C (662°F)
No guaranteed low-temperature toughness under PSL1 – not suitable for sub-zero applications without evaluation
6. Third-Party Inspection
Available inspection services include SGS, BV, Lloyds
7. Mill Test Certificate
Typically provided as EN 10204 Type 3.1B with full test results
Third-party inspection available upon request
8. Weldability
Low carbon content (≤0.26%) ensures excellent weldability
Suitable for all standard welding methods (SMAW, GTAW, GMAW, SAW)
No post-weld heat treatment required for most thicknesses
Summary
API 5L PSL1 Grade X42 Double-Sided Submerged Arc Welded (DSAW/LSAW) steel pipe is the entry-level "X-grade" line pipe for medium-pressure pipeline applications. With minimum yield strength of 42,000 psi (290 MPa) – approximately 17% higher than Grade B – and tensile strength of 60,000 psi (414 MPa), this material offers a cost-effective upgrade for applications requiring higher strength than Grade B without moving to higher X-grades .
Key features:
Material standard: API 5L PSL1 X42 – entry-level X-grade for medium-pressure service
Yield strength: 290 MPa (42,000 psi) minimum – 17% higher than Grade B
Tensile strength: 414 MPa (60,000 psi) minimum
PSL1 quality level: No mandatory impact testing; standard requirements for general service
DSAW manufacturing produces pipes from 16" to 72" OD with wall thickness up to 50 mm
Double-sided welding creates a single high-quality weld nugget
JCOE or UOE forming methods ensure precise dimensional accuracy
100% ultrasonic inspection of weld seam ensures quality
Excellent weldability with low carbon content (≤0.26%)
Cost-effective upgrade from Grade B for medium-pressure applications
Common applications include:
Medium-pressure oil and gas transmission pipelines
Natural gas gathering and distribution networks
Water transmission mains
Gathering and flow lines
Structural applications (piling, bridge supports)
Industrial process piping
When ordering, specify: API 5L PSL1 Grade X42, DSAW/LSAW (Double-Sided/Longitudinal Submerged Arc Welded), Size (OD x WT), Length, End Finish (plain/beveled), Coating Requirements, and Mill Test Certificate to EN 10204 Type 3.1B .
For applications requiring guaranteed low-temperature toughness, tighter chemistry controls, or sour service capability, specify API 5L PSL2 Grade X42 instead . For most medium-pressure applications, X42 PSL1 offers an excellent balance of strength and economy .
