API Specification 5CT, Casing and Tubing (11th Edition, December 2023) is the latest global standard for seamless and welded steel pipes used in oil and gas wells, including casing, tubing, pup joints, coupling stock, couplings, and accessories.

• Publication Date: December 2023

• Effective Date (Monogram): January 1, 2025

• Addendum 1: May 2025 (Monogram effective June 1, 2026)

• Key Updates: Structural overhaul, new steel grades, enhanced testing, and modernized inspection requirements

 2. Major Changes from 10th Edition

2.1 PSL System Reorganization

• Eliminated the traditional PSL‑1/2/3 classification

• Requirements previously under PSL‑2/3 are integrated into the main text or moved to Appendix A (Supplemental Requirements)

2.2 New Steel Grades

• L80 3Cr: Added for mildly corrosive downhole environments

• C125: Ultra‑high‑strength grade (min. yield 862 MPa / 125 ksi) for ultra‑deep, high‑pressure wells (introduced in Addendum 1)

2.3 Performance & Testing Enhancements

• High Collapse (HC) Product Rating: New provisions for enhanced collapse‑resistance casing

• Automated Inspection: Mandates advanced automated NDE and straightness measurement systems with updated calibration rules

• Charpy Impact: Simplified requirements for thick‑walled pipesEnd Sizing & Thermal Recovery: New requirements for pipe‑end sizing and high‑temperature service

• Welded Pipe Retest: Clarified retest rules for failed flattening tests

2.4 Other Key Updates

• Thread Protectors: Strengthened quality and performance requirements

• Chemical Reporting: Mandatory reporting of Niobium (Nb) content for all grades.

• Reference Standards: Updated to latest ASTM/ISO norms (e.g., MT per ASTM E3024).

3. Standard Steel Grades (11th Ed. + Addendum 1)

4. Key Dimensions & Threads

4.1 Outside Diameter (OD)

• Tubing: 2‑3/8" to 4‑1/2" (60.3 mm to 114.3 mm)

• Casing: 4‑1/2" to 20" (114.3 mm to 508 mm)

4.2 Length Ranges

• R1: 6.10 m – 7.32 m

• R2: 8.53 m – 9.75 m

• R3: 11.58 m – 12.80 m

4.3 API Thread Types

• Short Thread Casing (STC)

• Long Thread Casing (LTC)

• Buttress Thread Casing (BTC)

• Premium connections (e.g., VAM TOP, FOX) are non‑API but widely used.

5. Ordering & Specification (Key Elements)

1. Standard: API 5CT 11th Ed. (2023) + Addendum 1 (2025)

2. Steel Grade (e.g., L80 3Cr, C110, C125)

3. Size: OD × Wall Thickness × Length Range (e.g., 5‑1/2" × 11.99 mm × R2)

4. Thread Type: STC, LTC, BTC, or premium

5. Supplemental Requirements (Appendix A, e.g., HC rating, NDE levels)

6. End Finish: Plain end, threaded & coupled (T&C), etc.

6. Compliance & Monogram

• Products manufactured on or after January 1, 2025 must comply with the 11th Edition to bear the API Monogram

• Addendum 1 requirements become mandatory for Monogrammed products on June 1, 2026.