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Always up to date. In this column you can find the steel pipe related articles, including industry trends, product standards and materials, and some technical guidelines.
The API Spec 5CT is the key international standard governing seamless casing pipes used in oil and gas operations. It outlines detailed technical specifications to ensure quality, safety, and compatibility across the industry.
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Scope of Application
This standard covers the delivery requirements for casing, tubing, and pup joints, including coupling materials and accessories. It defines three Product Specification Levels (PSL-1, PSL-2, PSL-3) and applies to casing connections such as:
STC (Short Threaded Coupling)
LC (Long Threaded Coupling)
BC (Buttress Thread)
XC (Special Clearance)
NU (Non-Upset Tubing)
EU (External-Upset Tubing)
IJ (Integral Joint Tubing)
These connection types follow threading standards outlined in API Spec 5B.
Dimensional Specifications
Outer Diameter: 6.0 mm – 219.0 mm
Wall Thickness: 1.0 mm – 30.0 mm
Maximum Length: 12,000 mm
Steel Grades and Chemical Composition
1. J55 / K55
C: 0.34–0.39
Si: 0.20–0.35
Mn: 1.25–1.50
P ≤ 0.020, S ≤ 0.015
Cr ≤ 0.15, Ni ≤ 0.20, Cu ≤ 0.20
Als ≤ 0.020
2. N80
C: 0.34–0.38
Mn: 1.45–1.70
V: 0.11–0.16
Other elements similar to J55
3. L80
C: 0.15–0.22
Si ≤ 1.00, Mn: 0.25–1.00
Cr: 12.0–14.0
P ≤ 0.020, S ≤ 0.010
4. P110
C: 0.26–0.35
Cr: 0.80–1.10
Mo: 0.15–0.25
V: ~0.08
Mechanical Properties
|
Grade |
Yield Strength (MPa) |
Tensile Strength (MPa) |
|
J55 |
379–552 |
≥517 |
|
K55 |
≥655 |
≥517 |
|
N80 |
552–758 |
≥689 |
|
L80 |
552–655 |
≥655 |
|
P110 |
758–965 |
≥862 |
Surface Requirements
Roughness: Must comply with international standards to maintain proper sealing and lubrication.
Cleanliness: Surface should be free of rust, scale, and contaminants.
Coating: If required, coatings must adhere well and offer long-term protection.
Hardness: Sufficient to resist environmental wear and corrosion.
Conclusion
The API Spec 5CT standard ensures that seamless casing pipes meet high-performance and safety benchmarks required in energy and industrial applications. Adherence to these specifications supports efficient drilling, reliable operation, and long-term infrastructure stability.
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