API 5CT Tubing & Casing Couplings: High-Strength Connections for Oilfield Operations.
Precision-Engineered Tubing Couplings: EUE vs. NUE Designs
Tubing couplings (max OD 4.5”) are critical for connecting API 5CT J55-P110 grade oil tubing used in sucker rod pumping systems. Two primary designs dominate the market:
- EUE (External Upset End) Couplings:
- UPTBG Threads with 6.25” length and 8.05 lbs weight (4.5” OD).
- 50-65 ksi yield strength – 35% higher fatigue resistance vs. NUE.
- Tapered threads (2°30’ per side) reduce stress concentration by 18% (ISO 13679 CAL IV tested).
- NUE (Non-Upset End) Couplings:
- Buttress threads (STC/LTC) for shallow wells (<8,000 ft).
- Matching wall thickness (0.2–0.5”) to pipe body.
- Cost-efficient solution for low-pressure applications (<5,000 psi).
Casing Couplings: BTC, LTC & STC for Heavy-Duty Wells
Designed for casing OD ≥4.5”, these couplings meet API 5B/5CT standards with three configurations:
| Type | Length (in) | Torque (ft-lb) | Collapse Pressure (psi) |
|---|---|---|---|
| BTC | 6.25 | 12,000 | 6,500 |
| LTC | 7.75 | 15,500 | 8,200 |
| STC | 4.875 | 9,800 | 5,100 |
Key Features:
- Seamless/ERW manufacturing (YS up to 125 ksi).
- Anti-galling coatings (Zn-Ni or Cu) for sour service (H₂S 0.3 psi partial pressure).
- Thread tolerances: ±0.003” pitch diameter (API RP 5B1 verified).
Technical Specifications
Materials:
- Grades: K55, N80, L80 (13Cr/SS), C95, P110, Q125.
- Composition:
- C: 0.15–0.35% | Mn: 0.75–1.35% | Cr: 0.80–1.20% (for corrosion resistance).
Performance Metrics:
| Parameter | Tubing Couplings | Casing Couplings |
|---|---|---|
| Max Temp | 250°F | 350°F |
| Thread Engagement | 85–92% | 88–95% |
| Hydrostatic Test | 7,500 psi | 10,000 psi |
| Torque Turn Rate | 2.5–3.5 turns | 3.0–4.0 turns |
Applications
- Tubing Systems:
- EUE: Deep vertical wells (>10,000 ft), geothermal extraction.
- NUE: Coalbed methane wells, water injection lines.
- Casing Systems:
- BTC/LTC: Offshore drilling risers, HPHT reservoirs.
- STC: Surface casing in shale gas formations.
Certifications & Quality Assurance
- API 5CT Monogram: Full traceability from billet to finished product.
- NACE MR0175 Compliance: For H₂S environments (up to 15% NaCl).
- Ultrasonic Testing: Detects flaws >0.5% wall thickness (ASTM E213).
Competitive Advantages
- Lead Time: 18–25 days (MOQ 50 couplings).
- Customization: VAM TOP, Hydril Phoenix, and Wedge Thread options.
- Durability: 15–30 year service life in abrasive formations.
Logistics & Compliance
- Packaging: Wooden crates with anti-rust VCI paper.
- Certifications: API Q1, ISO 9001:2015, IATF 16949.
- Export Docs: Mill test reports, NACE certificates, COO.
Logical Connectors:
- Comparison: While STC suits shale gas, LTC excels in offshore HPHT.
- Example: For instance, P110 couplings are used in Permian Basin wells.
- Cause-Effect: Zn-Ni coating prevents sulfide stress cracking in sour wells.
Technical Comparison
| Connection Type | Max Depth (ft) | Cost Index | Key Markets |
|---|---|---|---|
| EUE Tubing | 15,000 | 1.8x | Geothermal, Offshore |
| NUE Tubing | 8,000 | 1.0x | Onshore Shale |
| LTC Casing | 20,000 | 2.5x | Deepwater Drilling |
Request Thread Gauging Reports or Custom Quotes Today!
Packing And Delivery
