API 5CT C90 Casing Tubing
C90 is one of the core steel grades for seamless steel pipes used in the oil industry. It strictly adheres to the API 5CT international oil pipe standard and is specifically designed and developed for harsh working conditions such as oil and gas drilling, extraction, and transportation.
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API 5CT C90 casing is a high-strength seamless steel pipe designed for high-pressure and high-corrosion environments. It is mainly used in harsh conditions such as sulfur-containing oil and gas wells and high-temperature and high-pressure wells. Its yield strength is not less than 552MPa, and it has excellent resistance to sulfide stress cracking (SSC) and meets the requirements of NACE MR0175 standard.
API 5CT C90 Casing & Tubing Color Code
| Grade | Color Band Identification (on body or coupling) |
|---|---|
| C90 | One green band + One purple band |
API 5CT C90 Tolerances
| Parameter | Allowable Tolerance |
|---|---|
| Outside Diameter (OD) | ≤ 4-1/2": ±0.79 mm; ≥ 4-1/2": (-0.5% ~ +1%)×D |
| Wall Thickness | -12.5% ~ +12.5% (minimum wall ≥ 87.5% of nominal) |
| Length | R1: 4.88~7.62 m; R2: 7.62~10.36 m; R3: ≥10.36 m, tolerance +100 mm / -0 mm |
| Straightness | ≤ 3.2 mm per 3 m length |
| Thread Dimensions | Complies with API 5B (taper, pitch, crest, coupling clearance, etc.) |
API 5CT Gr. C90 Casing Tube Chemical Composition
| C | Mn | Mo | Cr | Ni | Cu | Ti | P | S | Si | V | Al | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Min | - | - | 0.250 | - | - | - | - | - | - | - | - | - |
| Max | 0.350 | 1.200 | 0.850 | 1.500 | 0.990 | - | - | 0.020 | 0.010 | - | - | - |
API 5CT C90 Oil Casing Tubing Mechanical Properties
| Tensile Strength | 689 MPa min | 100,000 psi min |
| Yield Strength | 621 MPa min | 724 MPa max |
| 90,000 psi min | 105,000 psi max | |
| Total Elongation Under Load | 0.500 % | - |
| Hardness | 25 Max HRC | 255 Max HBW |
API 5CT C90 Size Chart
| OD (mm) | OD (in) | Wall Thickness Range (mm) | Common Grade | Application Type |
|---|---|---|---|---|
| 60.3 | 2-3/8 | 4.85 ~ 7.52 | C90 | Tubing |
| 73.0 | 2-7/8 | 5.51 ~ 9.53 | C90 | Tubing |
| 88.9 | 3-1/2 | 6.45 ~ 9.53 | C90 | Tubing |
| 114.3 | 4-1/2 | 6.88 ~ 11.99 | C90 | Casing |
| 127.0 | 5 | 7.52 ~ 12.70 | C90 | Casing |
| 139.7 | 5-1/2 | 7.72 ~ 13.49 | C90 | Casing |
| 168.3 | 6-5/8 | 8.94 ~ 14.30 | C90 | Casing |
| 219.1 | 8-5/8 | 9.53 ~ 18.18 | C90 | Casing |
| 273.1 | 10-3/4 | 10.16 ~ 20.32 | C90 | Casing |
API 5CT C90 Casing & Tubing Dimensions
| Nominal Size (in) | OD (mm) | Weight Code | Wall Thickness (mm) | Grade | Connection Type |
|---|---|---|---|---|---|
| 2-3/8 | 60.3 | 4.0 | 4.85 | C90 | Plain End |
| 2-7/8 | 73.0 | 6.5 | 6.53 | C90 | External Upset |
| 4-1/2 | 114.3 | 11.6 | 8.56 | C90 | BTC |
| 5-1/2 | 139.7 | 17.0 | 10.54 | C90 | LTC |
| 7 | 177.8 | 26.0 | 11.51 | C90 | Premium Thread |
API 5CT C90 Casing & Tubing Specifications
| Parameter | Specification |
|---|---|
| Applicable Standard | API SPEC 5CT, ISO 11960, GB/T 19830 |
| Service Environment | Sour service (H₂S-containing), pH < 4, H₂S partial pressure ≥ 0.0003 MPa |
| Heat Treatment | Quenching and Tempering (QT) |
| Connection Types | Plain End, Upset, Integral Joint; API and Premium Threads |
| Certification | API 5CT Monogram, ISO 9001, NACE MR0175 |
| Packaging & Marking | Grade, size, heat number, standard, manufacturer info spray-painted on each pipe |
API 5CT C90 Inspection Methods
Chemical Analysis: Optical Emission Spectrometry (OES) for ladle and product analysis.
Mechanical Testing:
Tensile test (per API 5CT §7.4)
Charpy V-notch impact test (room or low temperature)
Hardness test (HBW, minimum 3 points per pipe)
Non-Destructive Testing (NDT):
Ultrasonic Testing (UT): for internal and external defects
Eddy Current Testing (ET): primarily for tubing
Magnetic Particle Testing (MT): for thread and surface crack detection
Hydrostatic Test: Test pressure ≥ 80% of specified minimum burst pressure, hold ≥ 5 seconds.
SSC Test: NACE TM0177 Method A (four-point bending), applied stress = 90% YS, duration 720 hours, no cracking allowed.
Thread Inspection: Verified with API 5B gauges for pitch, taper, and coupling fit.
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FAQ
What is the ISO equivalent of API 5CT?
The international equivalent of API 5CT is ISO 11960.
These two standards are essentially identical in technical content, both specifying the delivery technical conditions for steel casing, tubing, and sub-sections used in oil wells in the oil and gas industry, covering dimensions, materials, mechanical properties, inspection methods, and marking requirements. API 5CT is published by the American Petroleum Institute (API), while ISO 11960 is the international version developed by the International Organization for Standardization (ISO). The two are often used interchangeably, especially in multinational projects and export trade, where ISO 11960 is widely adopted as the technical basis.
What is the range of API 5CT
API 5CT casing and tubing ranges in outer diameter from 114.3 mm to 508 mm (4 1/2 inches to 20 inches), suitable for standard casing sizes. Wall thickness ranges from 4.85 mm to 20.32 mm to meet the needs of different well depths and pressure environments.
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