API 5CT H40 is a grade of steel casing pipe specified in the API (American Petroleum Institute) Specification 5CT. It is a low-strength, non-upset grade primarily used for shallow wells and less demanding applications. Its key characteristics are its cost-effectiveness and suitability for benign environments.
Key Features & Typical Applications
Grade: H40 is one of the lowest strength grades in the API 5CT standard.
Type: It is typically supplied as NU (Non-Upset) pipe, meaning the ends of the pipe are not thickened. H40 is not commonly available as EU (External Upset) or IEU (Integral External Upset).
Application: Due to its lower mechanical properties, it is mainly used for:
Surface Casing: The first string of pipe run in a well to protect freshwater aquifers and stabilize the wellbore near the surface.
Conductor Casing: Very large-diameter pipe used to prevent the top of the well from caving in.
Shallow Wells: Low-pressure oil and gas wells where high strength is not required.
Non-Critical Applications: Such as pilings or structural supports in non-ofield contexts.
Product Parameters & Technical Data
The following tables summarize the key requirements as per API 5CT.
Table 1: Mechanical Properties - API 5CT H40
| Property | Requirement | Notes |
|---|---|---|
| Yield Strength (min) | 40,000 psi (276 MPa) | This is the defining property. "H" stands for the minimum yield strength in ksi (kilo-pounds per square inch). 40 = 40,000 psi. |
| Yield Strength (max) | 80,000 psi (552 MPa) | API 5CT sets a maximum limit to ensure adequate ductility and hardness control. |
| Tensile Strength (min) | 60,000 psi (414 MPa) | - |
| Hardness (HRC) | ≤ 22.0 (Typical) | Maximum hardness is specified to reduce the risk of Sulfide Stress Cracking (SSC), but H40 is not recommended for sour service (H₂S environments) unless specifically tested and qualified. |
| Elongation | As per API 5CT formula | The minimum elongation required depends on the specified diameter of the pipe. |
Table 2: Chemical Composition (Product Analysis) - Typical Ranges
API 5CT does not mandate a strict chemical composition for H40, J55, and K55 grades, focusing instead on mechanical properties. However, the composition must be reported, and it is typically a carbon-manganese steel.
| Element | Typical Range (%) |
|---|---|
| Carbon (C) | 0.20 - 0.35 |
| Manganese (Mn) | 0.60 - 1.40 |
| Phosphorus (P) | ≤ 0.030 |
| Sulfur (S) | ≤ 0.030 |
| Silicon (Si) | 0.20 - 0.35 |
Table 3: Dimensional Ranges (API 5CT Standard)
H40 casing is available in a wide range of sizes, defined by Outside Diameter (OD) and Wall Thickness (Weight per foot).
| Parameter | Common Range |
|---|---|
| Outside Diameter (OD) | 4.5 inches (114.3 mm) to 13.375 inches (339.7 mm) and larger. Common sizes start from 4.5" and 9.625". |
| Wall Thickness | Defined by the nominal weight (e.g., 9.5 lb/ft, 11.0 lb/ft, 13.0 lb/ft). This determines the internal diameter. |
| Length Range | API R1: 16 - 25 ft (4.88 - 7.62 m) API R2: 25 - 34 ft (7.62 - 10.36 m) API R3: > 34 ft (> 10.36 m) |
Comparison with Similar Grades
H40 is often compared to J55 and K55, which have a higher minimum yield strength.
| Feature | H40 | J55 | K55 |
|---|---|---|---|
| Min. Yield Strength | 40,000 psi (276 MPa) | 55,000 psi (379 MPa) | 55,000 psi (379 MPa) |
| Max. Yield Strength | 80,000 psi (552 MPa) | 80,000 psi (552 MPa) | 80,000 psi (552 MPa) |
| Coupling Material | Can be same pipe body or higher grade. | Typically requires a higher grade coupling (e.g., J55 pipe with N80 coupling). | Same as J55. |
| Key Difference | Lowest strength, most economical. | Higher strength than H40, very common for shallow/intermediate casing. | Chemically similar to J55 but with stricter impurity control. |
Important Notes
Sour Service: API 5CT H40 is not classified as a sour service grade. Its use in environments containing Hydrogen Sulfide (H₂S) requires extensive testing and qualification by the manufacturer and end-user.
Standard Reference: All manufacturing, testing, and inspection must comply with the latest edition of API Specification 5CT.
Purchasing: When ordering, the product is specified as, for example: "Casing 9-5/8", 40.0 lb/ft, H40, NU, API R3".
This information is based on the API 5CT standard and is intended for general reference. For critical applications, always consult the full API specification and the mill's test certificates (MTC) for the specific pipe lot.
