In pipeline system installation and maintenance, pipe nipples serve as the “bridge components” connecting pipes, valves, and equipment. Despite their compact size, they directly impact the system’s sealing integrity, pressure resistance, and service life. Many engineers often select incorrect models due to unfamiliarity with classification standards, leading to issues like leaks and insufficient pressure support. This article details common types of pipe nipples and provides application-specific selection recommendations to help you precisely match your requirements.
What is a Pipe Nipple?
A pipe nipple can be simply understood as a short section of threaded pipe. Its primary function is to serve as a transition connector, bridging two components (such as elbows, tees, valves, etc.) that need to be connected within a piping system. Due to its short length and threaded ends, it is highly convenient when adjusting connection distances or altering connection methods.
Types of Pipe Nipples
1. Close Pipe Nipples
Features: Threads run the entire length of the pipe fitting, with the threads at both ends nearly touching. There is no threadless shoulder or barrel section in the middle, enabling extremely compact installation in pipe connections.
Applications: Used to tightly connect two female-threaded fittings together, leaving no exposed body of the pipe fitting. Once installed, removal is nearly impossible without specialized tools such as pipe wrenches. Commonly employed in space-constrained applications, particularly suited for short-distance connections between equipment and piping systems.
2. Hexagon Nipples
Features: The pipe fitting features a hexagonal nipple (resembling a nut) at its center, with threads at both ends.
Applications: The hexagonal design facilitates installation or removal using a wrench, providing a better grip point and leverage surface. It serves as a common transition piece for connecting different fittings. Used in pipe connections requiring frequent maintenance or disassembly.
3. Long Pipe Nipples
Features: The long pipe nipple is longer than the ordinary nipple, which can effectively extend the distance between pipes. It has threads at both ends and a non-threaded barrel part in the middle.
Applications: Used when a longer connection span is required between two connection points or when bridging obstacles. Examples include building plumbing systems and industrial pipeline networks.
4. Reducing Pipe Nipples
Features: The pipe fitting features threads of different diameters at both ends.
Applications: Used to connect two pipe fittings or pipes of different sizes, enabling gradual reduction or expansion of pipe diameter. Commonly found in petroleum, chemical, and water supply systems.
5. Barrel Nipples
Features: Threaded at both ends with a distinct smooth, unthreaded section in the middle, resembling a small barrel or featuring a “shoulder.”
Applications: This is the most common type of pipe fitting. The unthreaded section in the middle provides a grip area after connection, facilitating wrench operation and allowing some adjustment of the connection distance. Widely used in general industrial and civil piping systems, it is one of the most common types of short sections.
6. Swage Nipples
Features: Resembling a reducer, it connects two pipes of different diameters. These can be concentric (with aligned axes) or eccentric (with offset axes). Typically, one end features internal/external threads, while the other end is either a straight end or a beveled end (for welding).
Applications: Primarily used to change pipe diameters, they also serve as transitions from threaded to welded connections.Particularly suited for high-pressure or high-temperature environments, they are widely used in power generation, petrochemical, and boiler systems.
7. Welded Pipe Nipples
Features: Welded pipe nipple feature welded ends without threads. Typically consisting of short, beveled pipe sections, they are used to connect to other components or pipes within a piping system via welding, providing a stronger, leak-proof connection.
Applications: Suitable for high-pressure, high-temperature environments or situations requiring permanent connections.
8. Threaded Pipe Nipples
Features: Refers broadly to pipe fittings with external threads at both ends, enabling direct connection to internally threaded pipe components. This is the most universal classification, encompassing types such as fully threaded, barrel-shaped, and hexagonal.
Applications: The most common connection method, linking threaded fittings to internally threaded pipe components, valves, and similar equipment. Widely used in medium- and low-pressure fluid piping systems.
9. Threaded Nipple with Thread one End
Features: External threads on one end only, with a smooth end on the other.
Applications: Typically used at pipe ends, with one end threaded for connection and the other smooth end suitable for welding or as an outlet.
10. Seamless Pipe Nipples
Features: Manufactured by cutting and processing seamless steel pipes, featuring no weld seams on the pipe body. Offers superior strength and enhanced pressure resistance.
Applications: Suitable for high-pressure applications or scenarios demanding exceptional pipe integrity, as seamless pipes deliver greater strength and reliability than welded pipes. A common choice in the power, petrochemical, and energy industries.
11. Galvanized Nipple
Features: Made of carbon steel with a hot-dip galvanized or electrogalvanized surface treatment, effectively preventing corrosion and rust.
Applications: The galvanized coating provides excellent corrosion protection. Commonly used in water pipes, fire protection systems, and general low-pressure non-corrosive medium piping systems.
12. Hose Nipple
Features: Typically features an external threaded end for connecting to piping systems, and a stepped barb connector (commonly known as a “pagoda head”) at the other end for inserting and securing hoses.
Applications: Used to connect rubber or plastic hoses, widely employed in agricultural irrigation, water systems, and machinery equipment for hose connections.
13. Stainless steel nipples
Features: Manufactured from various grades of stainless steel (e.g., 304, 316).
Applications: Offers exceptional corrosion resistance and high-temperature tolerance. Widely used in chemical processing, food manufacturing, pharmaceutical production, marine environments, and other applications demanding high cleanliness or corrosion resistance.
14. Alloy Steel Nipple
Characteristics: Manufactured from steel containing alloying elements other than carbon, such as chromium, molybdenum, nickel, etc.
Applications: Suitable for demanding conditions involving high temperatures, high pressures, or low temperatures, offering higher strength and specific corrosion resistance compared to carbon steel. Commonly used in power plants, refineries, and similar facilities.
15. Carton Steel Nipple
Characteristics: Made from carbon steel (primarily composed of iron and carbon). Offers lower cost and higher strength.
Applications: The most common material for pipe fittings. Widely used in low- and medium-pressure industrial and commercial piping systems for non-corrosive fluids such as water, oil, and gas.
Note: Prone to rusting without surface treatment (e.g., galvanization).
Pipe Nipple Sizes
Standard Sizes
Pipe nipples typically range in diameter from 1/8 inch to 12 inches. Lengths vary from short to extra-long, with the longest reaching up to 72 inches. The most commonly used sizes fall between 1/2 inch and 2 inches, accounting for 70% of industrial applications. When selecting pipe nipples, note that the actual outside diameter is approximately 1/8 inch larger than the nominal size.
Pipe Nipple Length and Diameter
Pipe fitting length refers to the measurement from one end to the other (from one threaded end to the other). Tube fitting sizes range from short tubes (1/8 inch to 1/4 inch) to long tubes (up to 72 inches). Diameter plays a vital role in matching with other components.
| TABLE 2 Pipe Nipples by Length and Nominal Pipe Size | ||||||||||||||||||
| Type of Nipple | NPS Designator | |||||||||||||||||
| 1/8 | 1/4 | 3/8 | 1/2 | 3/4 | 1 | 1 1/4 | 1 1/2 | 2 | 2 1/2 | 3 | 3 1/2 | 4 | 5 | 6 | 8 | 10 | 12 | |
| Pipe Nipple Lengths,in.AB | ||||||||||||||||||
| Close(cl) | 3/4 | 7/8 | 1 | 1 1/8 | 1 3/8 | 1 1/2 | 1 5/8 | 1 3/4 | 2 | 2 1/2 | 2 5/8 | 2 3/4 | 2 7/8 | 3 | 3 1/8 | 3 1/2 | 3 7/8 | 4 1/2 |
| 1 1/2 | 1 1/2 | 1 1/2 | 1 1/2 | 1 1/2 | ||||||||||||||
| 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | |||||||||||
| 2 1/2 | 2 1/2 | 2 1/2 | 2 1/2 | 2 1/2 | 2 1/2 | 2 1/2 | 2 1/2 | 2 1/2 | ||||||||||
| 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | ||||||||
| 3 1/2 | 3 1/2 | 3 1/2 | 3 1/2 | 3 1/2 | 3 1/2 | 3 1/2 | 3 1/2 | 3 1/2 | 3 1/2 | 3 1/2 | ||||||||
| 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | ||||||
| 4 1/2 | 4 1/2 | 4 1/2 | 4 1/2 | 4 1/2 | 4 1/2 | 4 1/2 | 4 1/2 | 4 1/2 | 4 1/2 | 4 1/2 | 4 1/2 | 4 1/2 | 4 1/2 | 4 1/2 | ||||
| 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | ||
| 5 1/2 | 5 1/2 | 5 1/2 | 5 1/2 | 5 1/2 | 5 1/2 | 5 1/2 | 5 1/2 | 5 1/2 | 5 1/2 | 5 1/2 | 5 1/2 | 5 1/2 | 5 1/2 | 5 1/2 | 5 1/2 | 5 1/2 | ||
| 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | |
| 7 | 7 | 7 | 7 | 7 | 7 | 7 | 7 | 7 | 7 | 7 | 7 | 7 | 7 | 7 | 7 | 7 | 7 | |
| 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | 8 | |
| 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | 9 | |
| 10 | 10 | 10 | 10 | 10 | 10 | 10 | 10 | 10 | 10 | 10 | 10 | 10 | 10 | 10 | 10 | 10 | 10 | |
| 11 | 11 | 11 | 11 | 11 | 11 | 11 | 11 | 11 | 11 | 11 | 11 | 11 | 11 | 11 | 11 | 11 | 11 | |
| 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 | 12 | |
| 13 | 13 | 13 | 13 | 13 | 13 | 13 | 13 | 13 | 13 | 13 | 13 | 13 | 13 | 13 | 13 | 13 | 13 | |
| 14 | 14 | 14 | 14 | 14 | 14 | 14 | 14 | 14 | 14 | 14 | 14 | 14 | 14 | 14 | 14 | 14 | 14 | |
| 15 | 15 | 15 | 15 | 15 | 15 | 15 | 15 | 15 | 15 | 15 | 15 | 15 | 15 | 15 | 15 | 15 | 15 | |
| 16 | 16 | 16 | 16 | 16 | 16 | 16 | 16 | 16 | 16 | 16 | 16 | 16 | 16 | 16 | 16 | 16 | 16 | |
| 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | 17 | |
| 18 | 18 | 18 | 18 | 18 | 18 | 18 | 18 | 18 | 18 | 18 | 18 | 18 | 18 | 18 | 18 | 18 | 18 | |
| 19 | 19 | 19 | 19 | 19 | 19 | 19 | 19 | 19 | 19 | 19 | 19 | 19 | 19 | 19 | 19 | 19 | 19 | |
| 20 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | |
| 21 | 21 | 21 | 21 | 21 | 21 | 21 | 21 | 21 | 21 | 21 | 21 | 21 | 21 | 21 | 21 | 21 | 21 | |
| 22 | 22 | 22 | 22 | 22 | 22 | 22 | 22 | 22 | 22 | 22 | 22 | 22 | 22 | 22 | 22 | 22 | 22 | |
| 23 | 23 | 23 | 23 | 23 | 23 | 23 | 23 | 23 | 23 | 23 | 23 | 23 | 23 | 23 | 23 | 23 | 23 | |
| 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | 24 | |
| Right and left | … | … | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | … | … | … | … | … · | … | … |
| A Nipples shorter than close are not recommended for pressure application. B 1 in.=25.4mm. | ||||||||||||||||||