API 5CT C95 Casing Tubing
API 5CT C95 casing and tubing is a high-strength, sour-resistance steel grade designed for deep and ultra-deep wells in corrosive environments, particularly those containing hydrogen sulfide (H₂S). It meets the API SPEC 5CT standard with a minimum yield strength of 95,000 psi (655 MPa), offering excellent resistance to stress cracking and ensuring operational safety under high pressure and high temperature conditions.
Specification Of API 5CT C95 Casing Tube
Standard: API SPEC 5CT (Latest 11th Edition, 2023)
Grade: C95 (Controlled Yield Strength Grade)
Applicable Products: Casing, Tubing, Pup Joints
Connection Types: API Standard Threads (STC/LTC/BTC), Premium Connections
Product Specification Level (PSL): PSL-2 or PSL-3 depending on service conditions
Chemical Composition Of API 5CT C95 Casing Tube
| Element | Max Content (%) | Notes |
|---|---|---|
| C | 0.35 | Controlled carbon equivalent for weldability |
| Mn | 1.20 | Enhances strength and hardenability |
| P | 0.020 | Reduces cold brittleness |
| S | 0.010 | Minimizes hot cracking risk |
| Cr | 1.50 | Improves corrosion resistance |
| Ni | 0.99 | Enhances low-temperature toughness |
| Mo | 0.85 | Increases resistance to hydrogen-induced cracking |
| Cu | 0.030 | Impurity control |
| V | - | Optional for grain refinement |
| Ti | - | Optional for grain control |
Mechanical Properties Of API 5CT C95 Casing Tubing
| Property | Requirement |
|---|---|
| Yield Strength | 655 MPa min ~ 758 MPa max (95,000~110,000 psi) |
| Tensile Strength | 724 MPa min (105,000 psi) |
| Elongation | ≥10% (50mm gauge length) |
| Hardness | ≤25 HRC / ≤255 HBW (maximum) |
| Charpy V-notch Impact | As per API SR16 or customer specification (required for PSL-2 and above) |
| SSC Resistance | Must pass NACE TM0177 Method A test at ≥80% of minimum yield strength |
API 5CT C95 Casing Tube Sizes in MM
| Outer Diameter (mm) | Common Wall Thickness (mm) | Nominal Size (inches) |
|---|---|---|
| 114.3 | 6.35 ~ 12.70 | 4-1/2" |
| 127.0 | 7.52 ~ 15.88 | 5" |
| 139.7 | 7.72 ~ 18.19 | 5-1/2" |
| 168.3 | 8.94 ~ 20.32 | 6-5/8" |
| 177.8 | 9.19 ~ 22.23 | 7" |
| 219.1 | 10.16 ~ 25.40 | 8-5/8" |
| 244.5 | 11.05 ~ 28.58 | 9-5/8" |
| 273.1 | 12.19 ~ 31.75 | 10-3/4" |
| 339.7 | 14.27 ~ 38.10 | 13-3/8" |
| 406.4 | 16.51 ~ 44.45 | 16" |
API 5CT C95 Tolerance
| Parameter | Allowable Deviation |
|---|---|
| Outer Diameter (OD) | ±0.79 mm (≤101.6 mm); +1.0% / -0.5% (>114.3 mm) |
| Wall Thickness (WT) | -12.5% (minimum single point) |
| Length | R1: 4.88~7.62m; R2: 7.62~10.36m; R3: >10.36m |
| Straightness | ≤3 mm/m, total ≤12 mm |
| Thread Parameters | Complies with API SPEC 5B, strict control on taper, pitch, and thread height |
API 5CT C95 Dimensional Table
| Size (inches) | OD (mm) | Common WT (mm) | Weight (kg/m) | Thread Type |
|---|---|---|---|---|
| 4-1/2 | 114.3 | 6.35 / 8.56 / 10.92 | 17.7 / 23.5 / 29.8 | STC/LTC/BTC |
| 5-1/2 | 139.7 | 7.72 / 9.17 / 11.51 | 26.0 / 30.6 / 37.8 | LTC/BTC |
| 7 | 177.8 | 9.19 / 11.51 / 13.72 | 39.0 / 48.0 / 56.8 | LTC/BTC |
| 9-5/8 | 244.5 | 11.05 / 13.84 / 16.13 | 63.5 / 78.8 / 90.5 | LTC/BTC |
| 13-3/8 | 339.7 | 14.27 / 18.19 | 108.0 / 135.0 | BTC |
API 5CT C95 Casing Tube Manufacturing Process
- Raw Material Preparation: High-quality carbon or low-alloy steel billets with grain-refining elements (e.g., Al, V, Ti) are selected
- Heating & Piercing: Billets heated above 1200°C and pierced via skew-rolling to form hollow shells
- Tube Rolling & Sizing: Continuous rolling or extrusion to achieve precise outer diameter and wall thickness
- Heat Treatment: Full-body quenching and tempering (Q&T) to ensure uniform microstructure and mechanical properties
- Straightening & Cutting: Mechanical straightening followed by length cutting (R1/R2/R3)
- Threading & Coupling: Machining of API or premium threads; couplings attached
- Non-Destructive Testing (NDT): 100% UT (Ultrasonic), ET (Eddy Current), or MT (Magnetic Particle) inspection for defects
- Hydrostatic Testing: Each pipe undergoes pressure testing to verify sealing integrity
- Marking & Packaging: Laser marking of grade, heat number, dimensions; anti-rust coating and bundling
Testing & Inspection of API 5CT C95 Casing Tubes
| Test Item | Requirement |
|---|---|
| Hydrostatic Test | Performed on every pipe, pressure ≥ specified minimum internal yield pressure |
| Non-Destructive Testing (NDT) | UT + ET or MT; mandatory for PSL-2 and above |
| Dimensional Inspection | OD, WT, length, ovality within tolerance |
| Hardness Testing | Multiple points per heat batch, must not exceed 25 HRC |
| Chemical Analysis | Heat and product analysis to meet standard limits |
| Tensile Test | Sampled per heat treatment batch for yield, tensile, elongation |
| Impact Test | Required for PSL-2 and above (e.g., -20°C or lower) |
| SSCC Test | Mandatory for sour service per NACE TM0177 Method A |
| Traceability | Each pipe marked with unique ID for full traceability of heat number, batch, and test data |
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FAQ
What is the difference between API 5CT and API 5L
The core difference between API 5CT and API 5L lies in their application areas and pipe types: API 5CT is used for casing and tubing inside oil wells and belongs to downhole structural pipes; while API 5L is used for pipelines for surface oil and gas transportation and belongs to long-distance pipelines.
What are the different types of thread in API 5CT?
The API 5CT standard mainly includes three types of threads: short round thread (STC), long round thread (LTC), and truncate thread (BTC), all of which must meet the processing and inspection requirements of API SPEC 5B.
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