Casing and Tubing Coupling
Our high-quality Casing and Tubing Couplings are essential components designed to connect two joints of pipe securely in oil and gas wells. Manufactured in strict accordance with API 5CT and API 5B specifications, our couplings ensure maximum joint tightness, prevent fatigue fracture, and maintain the integrity of the pipe string.
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Tubing Couplings: OD up to 4-1/2″. Available in External Upset End (EUE / UPTBG) and Non-Upset End (NUE / TBG).
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Casing Couplings: OD 4-1/2″ to 20″. Available in Short Buttress (STC), Long Buttress (LTC), and Buttress Thread (BTC).
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Standards: API 5CT, API 5B
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Grades: H40, J55, K55, N80, L80, C90, T95, C110, P110, Q125, and Special Grades for sour services.
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Features: Precise tapered threads, rigorous NDT and hydrostatic testing, exact color-code identification.
Description
1. Product Overview
About Tubing Coupling
Normally, tubing coupling OD maximum is 4 1/2″. As the tubing pipe is applied for drilling activities (inside the tubing is the sucker rod to drill/pump the oil), coupling types are more various and rigorous than casing. The most favorable type in tubing connections is the thickened type upset coupling (Internal upset and external upset), short for EUE coupling. Tubing with EU end (EUE) coupling connection is also called UPTBG. Because the end of the tubing is thickened (upset), the connecting stress is better than buttress coupling.
Another type used for tubing connections is the buttress coupling, which has the same thickness as the pipe body, called NU end (NUE) tubing or TBG.
Features: The oil tubing coupling can effectively solve the problem of fatigue fracture in existing couplings due to stress concentration. The oil tubing end is connected to the inside wall of the coupling via a tapered thread. The coupling body end and oil tubing are connected with the same thread pitch flat thread. This makes the coupling highly resistant to fatigue fracture and provides an excellent connection effect, effectively preventing oil well pipe string break accidents.
About Casing Coupling
Casing coupling is for dimensions greater than 4 1/2 inches. Different from tubing coupling, casing coupling normally does not need to be thickened (Non-upset), which means no upset casing coupling. It features the following types:
- BTC: Buttress coupling
- LTC: Long buttress coupling
- STC: Short buttress coupling
All three types have the same thickness as the casing pipe body but differ in lengths. The oil casing coupling is a necessary piece used to connect two casings. The manufacturing method is the same as seamless pipe. In order to ensure joint tightness, the precision of the screw thread is strictly required.
2. General Specifications
Seamless and ERW Casing
- Specification: API 5CT
- Grades: K55, N80, L80, C95, P110, Chrome, J55(Modified), J55 (API), PS80
- Special Grades: For sour services and for deep wells with high collapse properties
- Dimensions: OD 4″ – 26″ WT – 0.2 -0.5″
- Length Range: 1, 2 or 3
- Thread Connections: API (STC and LTC), BTC, extreme line, etc.
Seamless and ERW Tubing
- Specification: API 5CT
- Grades: J55 (API), J55(Modified), N80, L80, L80 13Cr, P110, Q125, H40 (API)
- Thread Connections: API 5B – Last Edition or Premium, EUE, NUE, special seal, metal-to-metal seal and VAGT
3. Coupling Dimensions & Specifications
Casing Couplings (Short Thread, Long Thread & Buttress)
| Casing Size OD (in) | Coupling Size OD (in) | Short Thread Length (in) | Long Thread Length (in) | Buttress Length (in) |
|---|---|---|---|---|
| 4-1/2 | 5.000 | 6.250 | 7.000 | 8.875 |
| 5 | 5.563 | 6.500 | 7.750 | 9.125 |
| 5-1/2 | 6.050 | 6.750 | 8.000 | 9.250 |
| 6-5/8 | 7.390 | 7.250 | 8.750 | 9.625 |
| 7 | 7.656 | 7.250 | 9.000 | 10.000 |
| 7-5/8 | 8.500 | 7.500 | 9.250 | 10.375 |
| 8-5/8 | 9.625 | 7.750 | 10.000 | 10.625 |
| 9-5/8 | 10.625 | 7.750 | 10.500 | 10.625 |
| 10-3/4 | 11.750 | 8.000 | * 10.500 | 10.625 |
| 11-3/4 | 12.750 | 8.000 | * 10.500 | 10.625 |
| 13-3/8 | 14.375 | 8.000 | * 10.500 | 10.625 |
| 16 | 17.000 | 9.000 | * 11.000 | 87.56 (Weight) |
| 18-5/8 | 20.000 | 9.000 | – | 10.625 |
| 20 | 21.000 | 9.000 | * 11.500 | 10.625 |
* NOT API SPECIFICATIONS. (Weights and Carton Qty available upon request)
Tubing Couplings (EUE & NUE)
| Casing Size OD (in) | Coupling Size OD (in) | Threads per inch | EUE Length (in) | NUE Length (in) |
|---|---|---|---|---|
| 1.90 | 2.500 (EUE) / 2.200 (NUE) | 10 Round | – | 3.750 |
| 2-3/8 | 3.063 (EUE) / 2.875 (NUE) | 8 Round (EUE) / 10 Round (NUE) | 4.875 | 4.500 |
| 2-7/8 | 3.668 (EUE) / 3.500 (NUE) | 8 Round (EUE) / 10 Round (NUE) | 5.500 | 5.500 |
| 3-1/2 | 4.500 (EUE) / 4.250 (NUE) | 8 Round | 5.750 | 5.625 |
| 4 | 5.000 (EUE) / 4.750 (NUE) | 8 Round | – | 5.750 |
| 4-1/2 | 5.563 (EUE) / 5.200 (NUE) | 8 Round | 6.500 | 6.500 |
4. API 5CT & 5B Standards
Casing coupling and tubing coupling are manufactured according to API 5CT and API 5B specifications.
- API 5CT: Specifies the technical delivery conditions for steel pipes, coupling stock, coupling material, and accessory material. Establishes requirements for three Product Specification Levels (PSL-1, PSL-2, PSL-3).
- API 5B: The standard specification for threading, gauging, and inspection of Casing, Tubing, and line pipe threads. Covers dimensions and marking requirements for API Master thread gauges, and procedures for measuring taper, lead, height, and angle of thread.
Chemical Composition (%)
| Grade | C | Mn | Mo | Cr | Ni | P (Max) | S (Max) |
|---|---|---|---|---|---|---|---|
| H40 / J55 / K55 | – | – | – | – | – | ≤0.03 | ≤0.03 |
| N80-1 / N80Q | – | – | – | – | – | ≤0.03 | ≤0.03 |
| L80-1 | ≤0.15 | 0.30~0.60 | 0.90~1.10 | 8.00~10.0 | – | ≤0.03 | ≤0.03 |
| L80-13Cr | 0.15~0.22 | 0.25~1.00 | – | 12.0~14.0 | ≤0.25 | ≤0.03 | ≤0.03 |
| C90 | ≤0.35 | ≤1.20 | 0.25~0.85 | ≤1.50 | ≤0.5 | ≤0.02 | ≤0.01 |
| T95 | ≤0.35 | ≤1.20 | 0.25~0.85 | 0.40~1.50 | ≤0.5 | ≤0.02 | ≤0.01 |
| P110 | – | – | – | – | ≤0.99 | ≤0.02 | ≤0.01 |
| Q125 | ≤0.35 | 1.35 | ≤0.85 | ≤1.50 | ≤0.99 | ≤0.02 | ≤0.005 |
Mechanical Properties
| Grade | Total Elongation Under Load (%) | Yield Strength (Mpa) | Tensile Strength (Mpa) | Hardness (HRC) |
|---|---|---|---|---|
| H40 | 0.5 | 276~552 | 414 | – |
| J55 / K55 | 0.5 | 379~552 | 517 / 655 | – |
| N80-1 / N80Q | 0.5 | 552~758 | 689 | – |
| L80 (1, 9Cr, 13Cr) | 0.5 | 552 | 655 | 23.0 |
| C90 | 0.5 | 621 | 689 | 25.4 |
| T95 | 0.5 | 655 | 724 | 25.4 |
| P110 | 0.6 | 758 | 862 | – |
| Q125 | 0.65 | 862 | 931 | b |
5. Coupling Pipe Grade Identification By Paint Color
| Grade | Colour(s) for Entire Coupling | Band(s) Color |
|---|---|---|
| H40 | None | Same as for pipe (None/black band) |
| J55 Tubing | Bright Green | None |
| J55 Casing | Bright Green | One White |
| K55 | Bright Green | None |
| M65 | Uses L80 Type 1 Couplings | One Bright Green, One Blue |
| N80 1 | Red | None |
| N80 Q | Red | One Green |
| L80 1 | Red | One Brown |
| L80 9Cr | None | Two Yellow (One Red, One Brown, Two Yellow for product) |
| L80 13Cr | None | One Yellow (One Red, One Brown, One Yellow for product) |
| C90 1 | Purple | None |
| T95 1 | Silver | None |
| C110 | White | Two Brown |
| P110 | White | None |
6. Manufacturing Process & Inspection
Process Flow of API 5CT Couplings
Round Pipe → Pipe Inspection → NDT inspection MPI → End Threading → Thread Inspection → Coupling Threading Inspection → NDT inspection MPI (coupling) → Phosphating (for coupling) → Coupling power Make up → Hydrostatic test → Drift test → Doping and Protectors Application → Coating → Measurement of Length and Weight → Colour Identification → Marking → Packing → Warehousing.
Test & Inspection
According to API 5CT, API 5B, or customer specified standards, a strict inspection and test system is utilized before shipping. This includes appearance inspection, dimension inspection, chemical composition inspection, performance test, strength test, tensile test, hardness test, NDT, and hydrostatic tests. The highest quality products will be supplied to ensure zero worry about operational integrity.
