C90-1 OCTG Casing
API 5CT C90 Type 1 Casing is a high-strength, controlled-yield steel grade specifically engineered for Sour Service (H2S environments). It belongs to Group 2 of the API 5CT specification. The "Type 1" designation refers to a specific Cr-Mo (Chromium-Molybdenum) alloy that is Quenched and Tempered (Q+T) to achieve a fully martensitic structure. This ensures maximum resistance to Sulfide Stress Cracking (SSC), making it essential for deep, high-pressure, and sour oil and gas wells.
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API 5CT C90 Type 1 Casing Color Code
Identification is vital for field operations to prevent mixing grades.
| Grade | Pipe Body Paint Band | Coupling Paint Color | Band on Coupling |
| C90 Type 1 | One Purple Band | Purple | None (Solid Purple) |
API 5CT C90 Type 1 Oil Well Casing Pipe Chemical Composition (%)
C90 requires high hardenability to ensure uniform properties through the wall thickness.
| Element | Requirement (%) | Purpose |
| Carbon (C) | 0.15 – 0.35 | Strength and hardenability |
| Manganese (Mn) | 0.40 – 1.20 | Deoxidizer and strength |
| Chromium (Cr) | 0.80 – 1.50 | Corrosion and SSC resistance |
| Molybdenum (Mo) | 0.15 – 0.85 | Temper embrittlement resistance |
| Phosphorus (P) |
≤0.020 |
Minimize impurities |
| Sulfur (S) |
≤0.010 |
Critical for Sour Service |
| Nickel (Ni) |
≤0.25 |
Limited to prevent SSC sensitivity |
| Silicon (Si) |
≤0.45 |
Deoxidizer |
API 5CT C90-1 Casing & Tubing Tensile & Hardness Requirements
The yield strength window is narrow to ensure the material is strong yet ductile enough for sour service.
| Property | Imperial Units | Metric Units |
| Yield Strength (Min) | 90,000 psi | 621 MPa |
| Yield Strength (Max) | 105,000 psi | 724 MPa |
| Tensile Strength (Min) | 100,000 psi | 689 MPa |
| Max Hardness | 25.4 HRC | 255 HBW / 270 HV |
| Hardness Variation (Max) | 3.0 HRC | -- |
API 5CT C90 Type 1 Casing Tolerance Table
| Item | Tolerance |
| Outside Diameter (OD) |
≤≤ 4-1/2":±± 0.031" |>> 4-1/2": -0.5% to +1.0% |
| Wall Thickness | -12.5% (No upper limit) |
| Weight (Single Joint) | -3.5% to +6.5% |
| Inside Diameter (ID) | Governed by OD and Wall Thickness |
| Straightness |
≤≤ 0.2% of total length |
API 5CT C90 Type 1 Casing Connections
C90 is used in critical wells, often requiring high-integrity sealing.
| Connection Type | Abbreviation | Use Case |
| Short Round Thread | STC | Standard shallow wells |
| Long Round Thread | LTC | Most common for C90 casing |
| Buttress Thread | BTC | High tension/deep wells |
| Premium Connections | VAM / Tenaris / Fox | Gas-tight seals for high-pressure sour wells |
Grade C90 Type 1 Casing Dimensions and Weight Chart (Common Sizes)
| OD (Inches) | Weight (lb/ft) | Wall Thickness (in) | Drift Diameter (in) |
| 4-1/2" | 13.50 | 0.290 | 3.795 |
| 5-1/2" | 17.00 | 0.304 | 4.767 |
| 7" | 26.00 | 0.362 | 6.151 |
| 7" | 29.00 | 0.408 | 6.059 |
| 9-5/8" | 47.00 | 0.472 | 8.525 |
| 9-5/8" | 53.50 | 0.545 | 8.379 |
API 5CT C90 Type 1 Casing for Sour Service Specification
This table summarizes the technical standards for procurement.
| Technical Parameter | Specification Value |
| Standard | API Spec 5CT / ISO 11960 |
| NACE Compliance | MR0175 / ISO 15156-2 |
| Material Group | Group 2 (Controlled Yield Strength) |
| Heat Treatment | Quenched and Tempered (Q+T) |
| Process of Manufacture | Seamless (SML) Only |
| Product Spec Level | PSL-1 (Std), PSL-2, or PSL-3 (High Quality) |
| Impact Testing | Mandatory Charpy V-Notch (CVN) |
Testing & Inspection of API 5CT C90 Type 1 Casing
Quality assurance is much higher for C90 than for standard J55/K55 grades.
| Test Method | Requirement | Frequency |
| Hydrostatic Test | Verify leak-tight integrity | 100% of pipes |
| Hardness Testing | Mandatory Max 25.4 HRC | 100% of pipes (at ends) |
| SSC Testing | NACE TM0177 (Method A) | Per heat / Per lot |
| Ultrasonic (UT) | Full body wall thickness/defect scan | Mandatory (PSL2/PSL3) |
| Magnetic Particle | Surface defect inspection | Mandatory for ends/threads |
| Grain Size | ASTM E112 (Must be Fine Grain) | Once per heat |
GNEE API OCTG Pipe test and inspection
GNEE API OCTG Pipe factory
FAQ
What does octg pipe mean?
OCTG (oil country tubular goods) refers to a collection of rolled metal products, more commonly known as pipes, and the various accessories included. This can consist of drill, casing or tubing pipes, thread protectors, stabbing guides, bumper rings, and pipe chocks.
What is the difference between casing and tubing in Octg?
OCTG pipes consist of two main classifications of products: casing and tubing. Tubing is the pipe that carries oil and gas from the ground to the surface. Casing is the pipe that protects the integrity of the wellbore and protects sensitive underground structures.
What are the different types of Octg pipes?
OCTG typically includes three main types: casing, tubing, and drill pipe. Casing stabilizes the wellbore and isolates different underground formations, tubing transports oil and gas to the surface, and drill pipes connect the drill bit to the rig while transmitting torque and drilling fluids.
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