In industrial pipeline connection systems, pipe couplings are an indispensable type of pipe fitting used to connect two sections of pipeline, enabling the continuous transportation of fluids or gases. As a critically important type of pipe fitting in pipeline connections, pipe couplings are widely used in high-pressure pipeline systems with diameters of 4 inches or less. They offer advantages such as easy installation, safety and stability, excellent sealing performance, corrosion resistance, and high-temperature resistance, and are extensively applied in industries such as petroleum, natural gas, chemicals, and water treatment.
Different Types of Pipe Couplings
Socket weld pipe couplings
Pipe couplings that connect pipes using a socket-welded joint are called socket-welded pipe couplings. This connection method involves inserting a steel pipe into a socket hole and welding it in place. This connection method does not require complex threading or welding operations, making installation convenient and ensuring reliable sealing. It features a compact structure, strong pressure resistance, and excellent sealing performance, and is commonly used in high-pressure and high-temperature environments. They are widely applied in fields such as water supply and drainage, and municipal engineering. Depending on the number of sockets, socket weld pipe couplings can be classified into single-socket pipe couplings and fullsocket pipe couplings.
Socket Weld Half Couplings
Socket Weld Half Coupling have a socket on one end, while the other end is typically a flat end or features other connection structures. They are primarily used to connect a pipe with a socket to another pipe with a flat end, or as transition connectors when changing direction or branching within a pipe system.
Socket Weld Full Coupling
Socket weld full coupling have sockets on both ends and are specifically designed to connect two pipes with sockets, enabling the two pipes to be aligned in a straight line. In long-distance pipe laying, double socket pipe couplings play a particularly important role. The connection method of double socket pipe couplings effectively resists axial displacement caused by thermal expansion and contraction of the pipes, ensuring the stability of the pipe system, while also facilitating maintenance and replacement in the future.
Socket Weld Coupling Dimension
| Nominal Size | Socket Bore Dia. | Bore Dia. of Fittings | Socket Wall Thickness | Depth of Socket | Laying Lengths | Laying Lengths | ||||||||
| DN | NPS | B | D | C | J min | E | F | |||||||
| 3000 | 6000 | 9000 | 3000 | 6000 | 9000 | |||||||||
| ave | min | ave | min | ave | min | |||||||||
| 6 | 1/8 | 10.9 | 6.1 | 3.2 | 3.18 | 3.18 | 3.96 | 3.43 | 9.5 | 6.5 | 16 | |||
| 8 | 1/4 | 14.3 | 8.5 | 5.6 | 3.78 | 3.30 | 4.6 | 4.01 | 9.5 | 6.5 | 16 | |||
| 10 | 3/8 | 17.7 | 11.8 | 8.4 | 4.01 | 3.50 | 5.03 | 4.37 | 9.5 | 6.5 | 17.5 | |||
| 15 | 1/2 | 21.9 | 15 | 11 | 5.6 | 4.67 | 4.09 | 5.97 | 5.18 | 9.53 | 8.18 | 9.5 | 9.5 | 22.5 |
| 20 | 3/4 | 27.3 | 20.2 | 14.8 | 10.3 | 4.9 | 4.27 | 6.96 | 6.04 | 9.78 | 8.56 | 12.5 | 9.5 | 24 |
| 25 | 1 | 34 | 25.9 | 19.9 | 14.4 | 5.69 | 4.98 | 7.92 | 6.93 | 11.38 | 9.96 | 12.5 | 12.5 | 28.5 |
| 32 | 11/4 | 42.8 | 34.3 | 28.7 | 22 | 6.07 | 5.28 | 7.92 | 6.93 | 12.14 | 10.62 | 12.5 | 12.5 | 30 |
| 40 | 11/2 | 48.9 | 40.1 | 33.2 | 27.2 | 6.35 | 5.54 | 8.92 | 7.8 | 12.7 | 11.12 | 12.5 | 12.5 | 32 |
| 50 | 2 | 61.2 | 51.7 | 42.1 | 37.4 | 6.93 | 6.04 | 10.92 | 9.5 | 13.84 | 12.12 | 16 | 19.0 | 30 |
| 65 | 21/2 | 73.9 | 61.2 | 8.76 | 7.62 | 16 | 19.0 | 43 | ||||||
| 80 | 3 | 89.9 | 76.4 | 9.52 | 8.30 | 16 | 19.0 | 44.5 | ||||||
| 100 | 4 | 115.5 | 100.7 | 10.69 | 9.35 | 19 | 19.0 | 48 | ||||||
Threaded Pipe Couplings
Threaded pipe couplings rely on the interlocking of internal and external threads to connect pipes, offering high connection strength and easy disassembly. They are suitable for pipe systems that require frequent maintenance or disassembly and are commonly used in industrial equipment, household water supply, and other fields. Depending on the number of threads, threaded pipe couplings can be divided into half threaded pipe couplings and full threaded pipe couplings.
Threaded Half Coupling
One end of this coupling has threads, while the other end is typically a socket or welded end. It is commonly used to connect threaded pipes to non-threaded pipes or equipment, offering flexibility in connection methods. The design of the half threaded pipe coupling allows for greater flexibility when connecting different types of pipes or equipment, compensating for differences in connection forms between pipes and equipment interfaces.
Threaded Full Coupling
Both ends of the double threaded pipe coupling have threads machined on the inner walls, used to connect two pipes with external threads, enabling the two pipes to be securely connected in a straight line. This type of pipe coupling is widely used in industrial pipeline systems, especially in high-pressure pipelines transporting gases, liquids, and other media. It is most commonly used to connect two threaded pipes, simply by screwing the pipes into both ends of the coupling. Due to its ease of installation and disassembly, it is highly convenient in pipeline systems requiring frequent maintenance or modifications. Additionally, full threaded pipe couplings can be selected with different thread specifications to accommodate pipeline connections of varying diameters and pressure ratings.
Threaded Pipe Couplings Dimension
| Nominal Size | End-to-End | Outside Diameter | Length of Thread | |||
| DN | NPS | W | D | L5 min | L2 min | |
| 3000 & 6000 | 3000 | 6000 | ||||
| 6 | 1/8 | 32 | 16 | 22 | 6.4 | 6.7 |
| 8 | 1/4 | 35 | 19 | 25 | 8.1 | 10.2 |
| 10 | 3/8 | 38 | 22 | 32 | 9.1 | 10.4 |
| 15 | 1/2 | 48 | 28 | 38 | 10.9 | 13.6 |
| 20 | 3/4 | 51 | 35 | 44 | 12.7 | 13.9 |
| 25 | 1 | 60 | 44 | 57 | 14.7 | 17.3 |
| 32 | 1 1/4 | 67 | 57 | 64 | 17.0 | 18.0 |
| 40 | 1 1/2 | 79 | 64 | 76 | 17.8 | 18.4 |
| 50 | 2 | 86 | 76 | 92 | 19.0 | 19.2 |
| 65 | 2 1/2 | 92 | 92 | 108 | 23.6 | 28.9 |
| 80 | 3 | 108 | 108 | 127 | 25.9 | 30.5 |
| 100 | 4 | 121 | 140 | 159 | 27.7 | 33.0 |
Carbon Steel Pipe Coupling
ASTM A105 / A105N
ASTM A350 LF2 / LF3
ASTM A694 F42 / 46 / 52 / 56 / 65 / 70
Carbon steel pipe couplings, which use carbon as the primary alloying element, offer high strength, good ductility, and relatively low cost, making them a commonly used connection component in industrial and residential piping systems. They are suitable for low-pressure pipelines transporting non-corrosive or weakly corrosive media such as water, steam, and air, and are widely applied in building plumbing and heating systems. However, carbon steel has poor corrosion resistance and is prone to rusting in humid or corrosive environments. Therefore, it typically requires corrosion-resistant treatments such as galvanization to extend its service life.
Alloy Steel Pipe Coupling
ASTM / ASME A/SA 182 & A 387 F1, F5, F9, F11, F12, F22, F91
Alloy steel pipe couplings are made by adding alloy elements such as chromium, nickel, and molybdenum to carbon steel. The addition of these elements significantly improves the mechanical properties and corrosion resistance of the pipe couplings. They can withstand higher pressures and temperatures and are suitable for use in industries such as petroleum, chemical, and power, where they are used in pipeline systems that transport high-temperature, high-pressure media or media containing certain corrosive components.
Stainless Steel Pipe Coupling
ASTM A182, A240 F304, 304L, 304H, 316, 316L, 316Ti, 310, 310S, 321, 321H, 317, 347, 347H, 904L
ASTM A182 F44, F45, F51, F 53, F 55, F 60, F61
Stainless steel pipe couplings contain a high proportion of chromium and nickel, forming a dense oxide film that provides excellent corrosion resistance and oxidation resistance, enabling long-term use in corrosive environments such as humid or acidic/alkaline conditions. They are widely used in pipeline systems requiring high hygiene standards or exposure to strong corrosive media, such as food processing, pharmaceutical manufacturing, and chemical industries. Additionally, stainless steel pipe couplings have a smooth surface, are easy to clean, and do not require additional corrosion protection, resulting in low maintenance costs. They are an ideal choice for those seeking high-quality and long-lasting pipe connections.
How to choose?
Selecting the appropriate pipe coupling structure is critical based on different pipeline application requirements:
For high-temperature, high-pressure, or corrosive environments, we recommend using socket weld pipe couplings to ensure welding strength and sealing safety.
For medium – to – low – pressure applications, non-permanent connections, or systems requiring easy maintenance, threaded pipe couplings can be used for quick disassembly and replacement.
In special scenarios, such as when only one side of the pipe or equipment needs to be connected, half socket or half threaded pipe couplings can be used, offering a more compact structure and saving space.