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:

  Technical Standard	Grade of Steel	Allowable Dimension Deviation			Surface Quality	Tortuosity
  		Outer Diameter	Wall Thickness	Length
  API 5CT	J55 (A658 Ⅱ)	-0.10%, +0.80%	-5%, +9%	≥ 3 m	Higher	2‰
  	N80 (30Mn)	-0.10%, +0.80%	-5%, +10%	≥ 3 m	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

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

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

  Casing Specification (mm)	Outer Diameter of Coupling (mm)	Round Thread				Buttress Thread
  		Short Round Thread		Long Round Thread
  		Min. Length (mm)	Weight (kg)	Min. Length (mm)	Weight (kg)	Min. Length (mm)	Weight (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

• 	Size	Type	Outer Diameter	0	Wall Thickness	0
  				1%		2.5%
  API Tubing	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
  	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
  Special Thread Tubing	2 7/8		92.00		18
  	3 1/2		112.00		24
  	4 1/2		135.00		21
  Special Thread Casing	5		144.00		19.5
  	5 1/2		158.00		20
  	6 5/8		190.00		23
  	7		200.00		24
  	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:

• Grade	Oil Casing Chromatic Circle	Coupling Color
  		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	―