Technical Specification: API 5CT L80-1 API Tubing
1. Core Specification & Product Type
| Specification | Description |
|---|---|
| Governing Standard | API Specification 5CT - Casing and Tubing |
| Product Type | Tubing - Innermost pipe string for fluid production/injection |
| Grade Designation | L80 Type 1 - "L" designates restricted yield strength, "-1" indicates Quenched & Tempered |
2. Material Properties & Mechanical Requirements
| Property | Requirement / Specification | Critical Notes |
|---|---|---|
| Yield Strength | 80,000 - 95,000 psi (552 - 655 MPa) | Narrow range - Unlike N80/V80 (min 80,000 psi only) |
| Tensile Strength | Min. 95,000 psi (655 MPa) | Balanced with yield strength |
| Yield-to-Tensile Ratio | Maximum 0.85 (for all sizes ≤ 4½") | Ensures material ductility and SSC resistance |
| Hardness Limit | Maximum 23 HRC (Rockwell C scale) | Critical for SSC resistance |
| Heat Treatment | Quenched & Tempered (Q&T) | Type 1 specifically denotes Q&T condition |
3. Chemical Composition Requirements
API 5CT specifies strict chemical limits for L80 to ensure sour service compatibility:
| Element | Maximum % | Purpose / Rationale |
|---|---|---|
| Carbon (C) | 0.43% | Controlled for weldability and SSC resistance |
| Manganese (Mn) | 1.90% | Limited to prevent excessive hardness |
| Phosphorus (P) | 0.030% | Impurity - kept low for toughness |
| Sulfur (S) | 0.030% | Impurity - kept low to minimize SSC susceptibility |
| No Alloying Restrictions | - | Can include Cr, Mo, Ni as needed for properties |
4. Sour Service Designation
L80-1 is the primary sour service grade within the 80 ksi yield strength category:
| Aspect | L80-1 Qualification for Sour Service |
|---|---|
| NACE MR0175/ISO 15156 | Fully compliant when hardness ≤ 23 HRC is maintained |
| Testing Requirements | Typically requires SSC testing per Method A (NACE TM0177) |
| Application Limit | Suitable for moderate to severe H₂S environments |
| Key Advantage | Maintains 80 ksi strength while offering SSC resistance |
5. Comparison with Other 80-ksi Grades
| Grade | Yield Strength (psi) | Max Hardness | Heat Treatment | Sour Service Suitability | Primary Use Case |
|---|---|---|---|---|---|
| L80-1 | 80,000 - 95,000 | 23 HRC | Q&T | Excellent - Designed for H₂S | Sour wells, CO₂ injection |
| N80-1/Q | Min. 80,000 | 23 HRC | Q&T | Conditional (if ≤23 HRC) | General non-sour production |
| V80-Q | Min. 80,000 | 23 HRC | Q&T | Conditional (if ≤23 HRC) | Standard Q&T value grade |
| C90 | 90,000 - 105,000 | 25.4 HRC | Q&T | Type 1 only (with restrictions) | Higher strength with SSC limits |
6. Manufacturing Process Control
Critical production aspects for L80-1:
Quenching & Tempering: Must be performed to achieve uniform microstructure
Hardness Control: Entire pipe body must be ≤ 23 HRC
Yield Strength Control: Must fall within 80-95 ksi range (not just minimum)
Traceability: Full heat/lot traceability required for sour service applications
7. Typical Applications
| Application | Reason for Using L80-1 |
|---|---|
| Sour Gas Wells | H₂S resistance with 80 ksi strength |
| CO₂ Injection/Storage | Resistance to carbonate cracking |
| Geothermal Wells | Moderate corrosion resistance |
| High-Pressure Wells | Where SSC risk exists with H₂S/CO₂ |
| Workover/Completion | Reliable performance in corrosive environments |
8. Ordering Information (Typical)
When ordering L80-1 tubing, specify:
Size: e.g., 2-7/8", 3-½" OD
Weight/Wall: e.g., 6.50 lb/ft (0.217" WT), 9.20 lb/ft (0.300" WT)
Connection: API EUE, or premium connections (VAM, Atlas Bradford, etc.)
Length: Range 2 (20-24 ft) or Range 3 (38-42 ft)
Certification: EN10204 3.2 with full traceability for sour service
9. Important Limitations
Not for Severe Corrosion: While SSC-resistant, L80 is not a corrosion-resistant alloy (CRA)
Temperature Limits: Generally suitable for temperatures up to 175°C (350°F) in sour service
Not for Clad/Lined Pipe: Base grade only - cladding requires different specifications
Key Takeaway
API 5CT L80-1 Tubing is the standard, reliable choice for sour service applications requiring 80 ksi yield strength. Its controlled chemistry, strict hardness limit (23 HRC), and Q&T heat treatment make it predictably resistant to Sulfide Stress Cracking while maintaining good mechanical properties for downhole service.
