API 5CT N80 Casing And Tubing
What is API 5CT N80 Casing and Tubing?
Grade Level: It is a mid-range steel grade, stronger than J55/K55 but lower in strength than P110.
N80-1: Usually delivered in a Normalized condition. It is more economical but has lower impact resistance.
N80-Q: Delivered in a Quenched and Tempered (Q&T) condition. It has superior strength and toughness compared to N80-1 and is more suitable for wells with higher pressure and temperature requirements.
Application: Used in medium-depth wells where higher tensile and burst strength is required than what J55 can provide. It is not specifically designed for sour service (H2S).
Submit your requirements, and we will customize an N80 casing solution for you that complies with API 5CT standards!
Chemical Composition Table (Mass Fraction %)
API 5CT defines maximum limits for Phosphorous and Sulfur. The specific alloying elements are chosen by the manufacturer.
| Grade | Carbon (C) | Manganese (Mn) | Phosphorous (P) | Sulfur (S) | Silicon (Si) |
| N80-1 | - | - | ≤ 0.030% | ≤ 0.030% | ≤ 0.45% |
| N80-Q | - | - | ≤ 0.030% | ≤ 0.030% | ≤ 0.45% |
Note: While C and Mn are not strictly limited by the API 5CT table for N80, manufacturers typically use 0.20-0.40% Carbon and 1.2-1.5% Manganese to reach the required properties.
Mechanical Property Table (Mechanical Analysis)
| Property | Units | Value |
| Yield Strength | psi (MPa) | 80,000 - 110,000 (552 - 758) |
| Tensile Strength | psi (MPa) | ≥ 100,000 (689) |
| Elongation | % | Calculated based on specimen area |
| Hardness (N80-Q) | HRC | Typically 18 - 24 (not strictly mandated like L80) |
Specification & Size Chart: N80 Tubing
Tubing is used to transport oil/gas to the surface.
| Outer Diameter (inch) | OD (mm) | Nominal Weight (lb/ft) | Wall Thickness (mm) |
| 2-3/8" | 60.3 | 4.60 - 5.80 | 4.83 - 6.45 |
| 2-7/8" | 73.0 | 6.40 - 8.60 | 5.51 - 7.82 |
| 3-1/2" | 88.9 | 9.20 - 12.70 | 6.45 - 9.50 |
| 4-1/2" | 114.3 | 12.60 - 15.10 | 6.88 - 8.56 |
Specification & Size Chart: N80 Casing
Casing lines the wellbore to provide structural integrity.
| Outer Diameter (inch) | OD (mm) | Nominal Weight (lb/ft) | Wall Thickness (mm) |
| 4-1/2" | 114.3 | 9.50 - 15.10 | 5.21 - 8.56 |
| 5-1/2" | 139.7 | 14.00 - 23.00 | 6.22 - 10.54 |
| 7" | 177.8 | 20.00 - 35.00 | 6.91 - 12.65 |
| 9-5/8" | 244.5 | 36.00 - 53.50 | 7.92 - 13.84 |
| 13-3/8" | 339.7 | 48.00 - 72.00 | 8.38 - 13.06 |
| 20" | 508.0 | 94.00 - 133.00 | 11.13 - 16.13 |
API 5CT N80 Tolerance Table
| Item | Tolerance |
| Outside Diameter (OD) | OD < 4-1/2": ±0.031"; OD ≥ 4-1/2": +1.00% / -0.50% |
| Wall Thickness | -12.5% |
| Weight (Single Joint) | +6.5% / -3.5% |
| Weight (Group/Lot) | -1.75% |
| Inside Diameter (ID) | Limited by OD, Weight, and Wall Thickness tolerances |
| Straightness | < 0.2% of total length |
API 5CT N80 Color Code Table
| Grade | Color Band (on Pipe Body) | Coupling Color |
| N80-1 | One Red band | Entire coupling Red |
| N80-Q | One Red band + One Green band | Entire coupling Red + Green band |
Testing for API 5CT N80 OCTG
To ensure quality and compliance, N80 undergoes several tests:
Chemical Analysis: Verifying P, S, and alloying elements.
Tensile Test: Ensuring yield and tensile strength fall within the 80k-110k psi range.
Flattening Test: Checking for ductility and potential weld defects (for ERW pipe).
Hydrostatic Test: Every joint is pressurized to ensure there are no leaks.
NDT (Non-Destructive Testing):
Ultrasonic (UT) or Magnetic Particle (MPI) to find cracks and wall thickness variations.
Hardness Test (Specifically for N80-Q): To verify the success of the Quench & Temper process.
Impact Test (Charpy V-Notch): Mandatory for N80-Q to ensure toughness; optional/supplementary for N80-1.
Drift Test: Passing a mandrel through the pipe to ensure the internal diameter is clear for tools.
API 5CT N80 Casing test equipments
API 5CT N80 OCTG Factory
API 5CT N80 Casing Tubing Certificate
FAQ
What is the difference between N80 and L80?
N80 and L80 are two casing/tubing grades under the API SPEC 5CT standard, with main differences in strength control, corrosion resistance, and applicable environments. L80 has more stable strength, contains chromium, and offers resistance to hydrogen sulfide corrosion, making it suitable for sour gas fields; N80 is used in conventional medium-depth wells, has lower cost, but weaker corrosion resistance.
What is the latest edition of API 5CT?
The latest edition of API 5CT is the 11th Edition, published in December 2023. This edition updates non-destructive testing (NDT) requirements, expands the product scope, and establishes more rigorous standards for chemical composition, mechanical properties, and quality control applicable to casing and tubing used in oil and gas extraction.
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