API 5CT Coupling Stock

The API coupling is mainly applicable in the manufacture of pipe couplings. With a threaded cylinder, coupling stock is
used for connecting two thread pipes. Our company supplies tubing coupling and casing coupling. As a kind of oilfield
drilling tools, tubing coupling is mainly used for connecting tubings. While casing coupling is utilized for connecting
two casings. Compared to integral connections, our API couplings are much simpler and cheaper to produce. Besides,
coupling stock is with less risk of leakage due to less geometric errors in the connection parts.

Classifications1. According to its grade, it can be divided into J55, K55, N80-1, N80-Q, L80-1, C90, T95, P110, Q125 and
other grade API couplings.

2. According to its specifications, coupling stock can be classified into (Label 1) 4-1/2, 5, 5-1/2, 6-5/8, 7, 7-5/8, 8-
5/8, 9-5/8, 10-3/4, 11-3/4, 13-3/8, 16, 18-5/8, 20 types, etc. Among these specifications, 5-1/2, 7, 9-5/8 and 13-3/8
type are commonly used.
3. Based on the thread type, there are long round thread, short round thread, buttress thread and special thread
type API couplings.
4. We are able to supply special coupling stocks as per customer’s requirement.

Features
1. It enjoys the advantages of big mechanical strength and good overall performance.
JST API coupling is produced through tube rolling, heat treatment, threading and other procedures. We own two
heat treatment production lines. The large heat treatment production line possesses two sets of high-pressure
water descalers. After tempering, there are three sizing mills configured with two sets of online fast straightening
machines that can realize online measuring the thickness. For achieving coupling stock, this line is also equipped
with imported British UNICORN joint inspection machine that can check the quality of pipe head and pipe end.
The small heat treatment production line for API coupling has quenching and tempering, and normalizing
process routes. Fitted with two inspection machines, it can check raw materials and finished products. Before
quenching, it carries out high pressure water descaling.
2. Thread is made through special CNC processing, resulting in high manufacturing precision, reliable use and
long service life.
JST coupling stock thread production line is configured with two advanced QK1319-G CNC casing coupling
thread lathes and three Q1334H CNC tubing coupling thread lathes. The line for API coupling features high
precision and high stiffness. It has the tool nose radius compensation function (TNRC function), which
prolonging the service life of coupling.
3. Coupling adopts parkerising or copper treatment, resulting in good wear resistance and strong thread block
resistance.
The main purpose of coupling stock parkerising is to realize the block resistance of coupling thread and rust
prevention treatment for coupling and coupling threads. Currently, coupling parkerising uses immersion
phosphating. The API coupling also uses the copper treatment. The copper coating has a high melting point, low
hardness, good toughness, ductility and adhesion.
4. JST coupling stock features strict dimension control.
JST coupling pipes are manufactured in strict accordance with API 5CT standards. Our API couplings are of good
quality of the internal and outer surface, high dimension precision and good straightness. The control standards
are as follows:
Allowable Dimension
Technical Deviation Surface
Grade of Steel Tortuosity
Standard Wall Quality
Outer Diameter Length
Thickness
 J55 (A658 Ⅱ) -0.10%, +0.80% -5%, +9% ≥3m Higher 2‰
API 5CT
N80 (30Mn) -0.10%, +0.80% -5%, +10% ≥3m Higher 2‰
5. Tubing pup point complies with API specification 5CT, 5B and relevant standards, and gains API logo using
license. Our company is able to produce J, N, L and other grades of flat or external upset tubing pup points with
various specifications in accordance with API standards.
6. Our coupling stock products have passed the non-destructive testing.
JST makes use of advanced equipment to inspect API couplings according to the requirements of customers
and product standard. There are three advanced hydrostatic pressure equipment with the test specifications of
φ60 mm to 406 mm, and with the maximum test pressure reaching 120 MPa. Two sets of pipe end magnetic
particle inspection machine are available for coupling stock. They are used for inspecting inner and outer
surfaces and near-surface cracks in any direction. For J55 and N80-1 steel grades of API couplings, we can
adopt ultrasonic, magnetic flux leakage or eddy current method, or choose the combination of several methods
to realize non-destructive testing for tubing with plain ends one by one. For N80-Q, L80 and P110 steel grades of
coupling stock, we use electromagnetic and ultrasonic methods to achieve non-destructive testing for tubing with
plain ends one by one. The inspection class is in accordance with the requirements of API 5CT. The inspection or
testing results are stated in the “Product Quality Certificate”. We need to do demagnetization after
electromagnetic inspection.

Parameters Data

1. Dimension of Tubing API Coupling

The coupling dimension of flat tubing and upsetting tubing, and the recommended dimension respectively refers
to Table 1 and Table 2.
Table 1 Flat Tubing API Coupling
Outer Diameter Outer Diameter of Min. Length of Piece Suggested Size (Outer Diameter ×
Size
of Tubing Coupling Coupling Weight (kg) Wall Thickness)

1.900 48.26 55.88 95.25 0.56 55.9 × 8

2-3/8 60.32 73.02 107.95 1.28 73 × 11

2-7/8 73.02 88.90 130.18 2.34 88.9 × 12.5

3-1/2 88.90 107.95 142.88 3.71 108 × 15

4 101.60 120.65 146.05 4.35 120.7 × 15.5

4-1/2 114.30 132.08 155.58 4.89 132 × 15

Table 2 Upsetting Tubing API Coupling

Outer Diameter Outer Diameter of Min. Length of Piece Suggested Size (Outer Diameter ×
Size
of Tubing Coupling Coupling Weight (kg) Wall Thickness)

1.900 48.26 63.50 98.42 0.84 63.5 × 9.5

2-3/8 60.32 77.80 123.82 1.55 77.8 × 11.5

2-7/8 73.02 93.17 133.35 2.40 93.17 × 13

3-1/2 88.90 114.30 146.05 4.10 114.3 × 15.5

4 101.60 127.00 152.40 4.82 127 × 16

4-1/2 114.30 141.30 158.75 6.02 141.3 × 17

2. Dimension of Casing API Coupling 
Standard coupling dimension of round thread casing and buttress thread casing and weight refer to Table 3.
Table 3 Standard Coupling Dimension and Weight of Casing
Round Thread
Casing Buttress Thread
Outer Diameter of Short Round Thread Long Round Thread
Specification
Coupling (mm)
(mm) Min. Length Weight Min. Length Weight Min. Length Weight
(mm) (kg) (mm) (kg) (mm) (kg)

114.30 127.00 158.75 3.62 177.80 4.15 225.42 4.55

127.00 141.30 165.10 4.66 196.85 5.75 231.78 5.85

139.70 153.67 171.45 5.23 203.20 6.42 234.95 6.36

177.80 194.46 184.15 8.39 228.60 10.83 154.00 10.54

193.68 215.90 190.50 12.30 234.95 15.63 263.52 15.82

244.48 269.88 196.85 18.03 266.70 25.45 269.88 23.16

273.05 298.45 203.20 20.78 ― ― 269.88 28.03

339.73 365.12 203.20 25.66 ― ― 269.88 31.77

3. Dimension of API Coupling
0 0
  Size Type Outer Diameter Wall Thickness
1% 2.5%

2 3/8 NU 73.00 12

2 3/8 EU 77.80 12

2 7/8 NU 88.90 13

2 7/8 EU 93.20 14

3 1/2 NU 108.00 14
API Tubing
3 1/2 EU 114.30 15

4 NU 120.70 15

4 EU 127.00 15

4 1/2 NU 132.10 15

4 1/2 EU 141.30 16

API Casing 4 1/2 STC 127.00 12

4 1/2 LC 127.00 12
4 1/2 BC 127.00 12

5 STC 141.30 13

5 LC 141.30 14

5 BC 141.30 13

5 1/2 STC 153.70 13

5 1/2 LC 153.70 14

5 1/2 BC 153.70 13

6 5/8 STC 187.70 17

6 5/8 LC 187.70 17

6 5/8 BC 187.70 16

7 STC 200.03 15

7 LC 200.03 16

7 BC 200.03 15

7 5/8 STC 215.90 18

7 5/8 LC 215.90 19

7 5/8 BC 215.90 18

8 5/8 STC 244.50 20

8 5/8 LC 244.50 21

8 5/8 BC 244.50 20

9 5/8 STC 269.90 21

9 5/8 LC 269.90 22
 9 5/8 BC 269.90 20

10 3/4 STC 298.50 21

10 3/4 BC 298.50 20

11 3/4 STC 323.90 21

11 3/4 BC 323.90 21

13 3/8 STC 365.10 22

13 3/8 BC 365.10 21

2 7/8   92.00 18

Special Thread Tubing 3 1/2   112.00 24

4 1/2   135.00 21

5   144.00 19.5

5 1/2   158.00 20

6 5/8   190.00 23

7   200.00 24

Special Thread Casing 7   200.00 24

7 5/8   219.00 28

9 5/8   274.00 29

10 3/4   302.00 30

13 3/8   368.00 28
4. Pipe Stenciling
Spray colors on the outer surface of coupling stock and then spray chromatic circles as follows:
 Coupling Color
Grade Oil Casing Chromatic Circle
Integrated Coupling Color Bar

J55 Tubing One Bright Green Line Bright Green ―

J55 Casing One Bright Green Line Bright Green One White Line

K55 Two Bright Green Lines Bright Green ―

N80-1 One Red Line Red ―

N80-Q One Red Line, One Bright Green Line Red Green

L80-1 One Red Line, One Brown Line Red One Brown Line

P110 One White Line White ―

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