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.

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What is a union?

A union, also known as a union joint, is a component used for removable connections between pipes. It typically consists of three parts: a male end, a female end, and a gasket. The male and female ends are connected to the two pipes to be joined, achieving a tight seal through threaded connections, while the gasket serves as a seal to prevent leakage of the medium inside the pipes.

Compared to traditional welding or flange connections, the most significant feature of union is their removability. This feature makes pipeline installation, maintenance, and replacement more convenient, eliminating the need for destructive operations on the pipeline, significantly improving work efficiency, and reducing maintenance costs.

MSS SP-83 Pipe Union Specification

ZIZI offered range of MSS SP-83 Union Pipe Fittings is intended and developed in accordance with the international quality standards at our infrastructure facility to achieve the very best benchmarks of quality. Our modernized infrastructure is crowned by means of recent tools and advanced machines that enable us to satisfy the large demands of customers in a dexterous manner. Our products are can further be made-to-order as per the detailed requirements given by our valuable Client..

Types of Unions

Socket Weld Union:

Socket welding involves inserting a steel pipe into a socket hole for welding, hence the term socket weld union. A socket coupling consists of a socket, a spigot, and a socket groove, with the distinctive feature of a socket groove on the spigot, and the spigot and socket located at opposite ends. Socket unions can be widely applied to pipes of various diameters and are also suitable for water meters and valves. Due to the socket structure, pipe joints reduce costs and offer extremely convenient installation, use, and maintenance, while also providing excellent leak prevention capabilities, making them highly promising in the market.

Threaded Union:

Threaded connections involve screwing steel pipes into threaded holes for connection, hence the term threaded union.Threaded unions are the most common type of joint, characterized by using a threaded connection method for pipe connections. They primarily consist of three parts: a male end with external threads, a female end with internal threads, and a nut. By rotating the nut, the sealing surfaces of the male and female ends can be tightly aligned, thereby achieving connection and sealing. Thread forms can include BSP, NPT, G, etc., and the connection is further secured using a locking nut and a seal ring. Suitable for small-diameter pipes, threaded connections achieve pipe sealing. They are easy to install and commonly used in water pipes, gas pipes, and other applications.

MSS SP-83 Union Dimension and Weight

Class 3000 Socket Weld Union Dimension

Dimensions in inches

Class 6000 Socket Weld Union Dimension

Dimensions in inches

CLASS 3000 Threaded Union Dimensions

Dimensions in inches

CLASS 6000 Threaded Union Dimensions

Dimensions in inches

Weight List

SW & THD Union volume

If you want to know more about the weight and volume of forged pipe fittings, please click on the following keywords

• ASME B16.11 Socket Weld Fitting Weight and Volume Chart
• ASME B16.11 Threaded Fitting Weight and Volume Chart

Union Pipe Fittings Applications

Water treatment systems

Petrochemical pipelines

Heating, ventilation, and air conditioning (HVAC) systems

Pharmaceutical and food industry piping

Laboratory and research piping systems

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Goods List

Inspection Photos:

Specifications of Forged Fittings 

Chemical Composition of Stainless Steel Forged Fittings

Mechanical Properties of ASTM A182 Forged Fittings

Chemical Composition of Carbon Steel Forged Fittings

Mechanical Properties of ASTM A105 Forged Fittings

Class 3000 Socket Weld Fittings

Class 3000 Socket weld fittings are widely used in piping systems. They feature an end with a socket-like opening, into which the pipe is inserted and then welded. 316L stainless steel socket weld fittings provide a secure and sealed connection. These fittings are typically used in applications where pipe sizes are relatively small and high-integrity connections are required, such as in chemical and petrochemical plants.

Types of Socket Weld Fittings

Socket Weld Cap

Socket Weld Elbow

Socket Weld Tee

Socket Weld Cross

Socket Weld Coupling

Socket Weld Union

Class 3000 Threaded Fittings

Class 3000 Threaded fittings have internal or external threads machined at their ends. They adhere to different thread standards, such as NPT and BSP. Threaded fittings are commonly used in medium-to-low-pressure applications and in systems that may require frequent modifications or maintenance.

Types of Threaded Fittings

Threaded Elbow

Threaded Tee

Threaded Cross

Threaded Coupling

Threaded Cap

Threaded Union

Threaded Nipple

Threaded Hex Nipple

Threaded Swage Nipple

Threaded Plug

Threaded Bushing

Material & Grades of Forged Fittings:

Carbon Steel Forged Fittings :
Carcon Steel: ASTM A105 / A105N,ASTM A350 LF2 / LF3, A694 F42 / 46 / 52 / 56 / 65 / 70

Alloy Steel Forged Fittings :
ASTM / ASME A/SA 182 & A 387 F1, F5, F9, F11, F12, F22, F91

Stainless Steel Forged Fittings :
ASTM A 182, A 240 F 304, 304L, 304H, 316, 316L, 316Ti, 310, 310S, 321, 321H, 317, 347, 347H, 904L

Duplex & Super Duplex Steel Forged Fittings :
ASTM / ASME A/SA 182 F 44, F 45, F51, F 53, F 55, F 60, F 61

Copper Alloy Steel Forged Fittings :

 ASTM SB 61 , SB62 , SB151 , SB152 UNS No. C 70600 (Cu-Ni 90/10), C 71500 (Cu-Ni 70/30), UNS No. C 10100, 10200, 10300, 10800, 12000, 12200

Nickel Alloy Forged Fittings:
ASTM SB564, SB160, SB472, SB162 Nickel 200 (UNS No. N02200), Nickel 201 (UNS No. N02201), Monel 400 (UNS No. N04400), Monel 500 (UNS No. N05500), Inconel 800 (UNS No. N08800), Inconel 825 (UNS No. N08825), Inconel 600 (UNS No. N06600), Inconel 625 (UNS No. N06625), Inconel 601 (UNS No. N06601), Hastelloy C 276 (UNS No.N10276), Alloy 20 (UNS No. N08020)

Applicable industries

Oil & Gas Industry

Chemical and Fine Chemical Plants

LNG / Cryogenic Engineering

Energy & Power (Thermal, Nuclear)

Food & Pharmaceutical Machinery Piping Systems

Offshore Platforms & Offshore Equipment

You can get an offer for products in below material forms:

-Pipe and Tube (EN 10216-5, ASTM A213, ASTM A249, A312, A790,)

-Forged Fitting and Flange (ASTM A182 , ASTM A105,ASTM B564 )

-Butt Weld Fittings (ASTM A234, ASTM A403,ASTM A815)

-Round bar , Billet (ASTM A276, ASTM A479)

– Plate, Sheet, Strip(ASTM A240, EN 10028-7, A480)

-Bolting, Nuts（ASTM A193, A194, A320）

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What are NPT Threaded Fittings?

NPT Threaded Fittings are pipe fittings manufactured in accordance with the NPT tapered pipe thread standard established by the American National Standards Institute (ANSI). The NPT thread is a U.S. standard tapered thread, distinguished by its taper angle, typically 3/4 inch per foot. It is this taper that allows male and female threads to fit tightly together when screwed together, forming a mechanical seal. Threaded fittings include various types such as elbows, tees, pipe clamps, pipe caps, and plugs, used for connecting, redirecting, branching, or sealing off pipeline systems.

Threaded Fittings are commonly used in water gas pipes, small-diameter water pipes, compressed air pipes, and low-pressure steam pipes. They are connected to threaded pipe ends to form a pipeline. A suitable adhesive can be applied to the threads to ensure sealing. This design not only provides excellent connection strength but also reduces the risk of fluid leakage, making it an ideal choice for low- to medium-pressure pipeline systems.

Material & Grades of Forged Threaded Fittings 

Carbon Steel :
ASTM A105 / A105N,ASTM A350 LF2 / LF3, A694 F42 / 46 / 52 / 56 / 65 / 70

Alloy Steel :
ASTM / ASME A/SA 182 & A 387 F1, F5, F9, F11, F12, F22, F91

Stainless Steel :
ASTM A 182, A 240 F 304, 304L, 304H, 316, 316L, 316Ti, 310, 310S, 321, 321H, 317, 347, 347H, 904L

Duplex & Super Duplex Steel :
ASTM / ASME A/SA 182 F 44, F 45, F51, F 53, F 55, F 60, F 61

Copper Alloy Steel :

 ASTM SB 61 , SB62 , SB151 , SB152 UNS No. C 70600 (Cu-Ni 90/10), C 71500 (Cu-Ni 70/30), UNS No. C 10100, 10200, 10300, 10800, 12000, 12200

Nickel Alloy :
ASTM SB564, SB160, SB472, SB162 Nickel 200 (UNS No. N02200), Nickel 201 (UNS No. N02201), Monel 400 (UNS No. N04400), Monel 500 (UNS No. N05500), Inconel 800 (UNS No. N08800), Inconel 825 (UNS No. N08825), Inconel 600 (UNS No. N06600), Inconel 625 (UNS No. N06625), Inconel 601 (UNS No. N06601), Hastelloy C 276 (UNS No.N10276), Alloy 20 (UNS No. N08020)

ASME B16.11 Threaded Fittings Types

Threaded fittings include elbows, tees, crosses, couplings, caps, unions, plugs, bushings, hexagonal nipples, etc.

	Threaded Elbow A threaded elbow is a pipe fitting used to change the direction of a pipe, with threads on one or both ends. It usually consists of an elbow body and a threaded part. The bending part of the elbow body is generally 90° or 45°.
	Threaded Tee Threaded Tee is usually used in some low-pressure small-diameter pipeline systems. It can divide the pipeline into three branches and form a 90-degree angle between the three branches.
	Threaded Cross Threaded Cross is a pipe connector with four openings, usually used to divide the pipe system into four different directions to achieve the diversion of the medium.
	Threaded Coupling The threaded coupling is a simple but important pipe connection fitting. Its main structure is a hollow cylinder with threads inside. The threads at both ends of the couplings are usually of the same specification so that it can be connected to threaded pipes of the same diameter.
	Threaded Cap A threaded cap is a pipe fitting used to close the end of a pipe. It is mainly composed of a cap body and a threaded part. The cap body is a hemispherical or flat-top structure with a hollow interior to fit the outer diameter of the pipe.
	Threaded Bushing Thread bushing is a technique used to repair damaged or worn threads by installing thread inserts made of special metals or alloys into the original thread holes to restore the dimensions and load-bearing capacity of the threads. This method not only extends the service life of parts, but also improves the strength and wear resistance of connections.
	Threaded Nipple A threaded nipple is a short pipe fitting with internal and external threads at both ends, used to connect two sections of threaded pipes to extend or transition the pipeline. It enables quick and reliable pipeline connections while facilitating maintenance and replacement.

Advantages of NPT Threaded Fittings

1. The primary reasons for choosing NPT threaded fittings over other connection methods are their significant advantages:
2. Easy Installation: No specialized welding equipment or technical expertise is required; installation and removal can be easily accomplished using a wrench. This significantly reduces construction costs and time.
3. Reusability: As a mechanical connection, NPT threaded fittings can be repeatedly disassembled and reassembled without damage, facilitating maintenance and adjustments to the piping system.
4. Excellent Sealing Performance: The tapered thread design creates compression when tightened, forming a reliable leak-proof seal. When installed with PTFE tape or thread sealant, the sealing effect can be further enhanced.
5. Cost-Effective: Compared to welded fittings, NPT threaded fittings typically have lower installation costs, especially for small-scale pipeline systems that require frequent adjustments or maintenance.

Advantages of NPT Thread

The tapered design provides strong sealing performance, making it suitable for high-pressure applications.

The NPT thread design is specifically engineered to achieve sealing through thread contact, eliminating the need for additional O-rings or gaskets.

It prevents sealant contamination of the medium, making it suitable for sensitive applications such as fuel and lubricants.

Strict dimensional parameters ensure good interchangeability between products from different manufacturers, making them widely compatible in North America and regions adhering to related standards.

Threaded Sealing Method

Teflon tape

A thin, white tape that fills the microscopic gaps between threads when tightened, preventing leaks. When using, it should be wound clockwise around the male thread, ensuring the winding direction aligns with the insertion direction.

– First, wrap the Teflon tape around the external threads in a clockwise motion.

– Overlap the tape halfway between each wrap to ensure a tight seal and complete coverage of the thread surface.

– Apply enough layers of Teflon tape to ensure a good seal on the threads without excessive residue that could prevent proper tightening.

Thread sealant

A liquid or paste-like sealant that cures after application to the threads, forming a stronger, more pressure-resistant seal. Suitable for high-pressure applications.

– Use a brush or applicator to evenly apply a thin layer of pipe sealant to the external threads.

– Ensure that the sealant is evenly applied to the entire thread surface, without clumps or excess residue.

– Use a pipe sealant that is suitable for the application and the type of fluid being conveyed through the fitting.

Difference Between BSP & NPT Threads

BSP and NPT are two different thread standards, with their primary differences lying in geographical region, thread angle, and sealing method. NPT (American Standard Tapered Pipe Thread) is primarily used in the United States and Canada, featuring a thread angle of 60 degrees. Sealing is achieved through the compression created by tightening the tapered thread, typically requiring the use of PTFE tape or sealant. BSP (British Standard Pipe Thread) is primarily used in Europe, Asia, and Commonwealth countries. It has a thread angle of 55 degrees and is divided into two types: tapered (BSPT) and parallel (BSPP). BSPT achieves sealing through the thread itself, while BSPP requires gaskets or O-rings for sealing at the end face. Due to differences in design and dimensions, these two thread types are incompatible.

How to Choose the Right NPT Threaded Fittings?

Material: Select the appropriate material based on the nature of the fluid, temperature, and pressure. For example, stainless steel (304/316) is suitable for corrosive media, while carbon steel or copper is suitable for general fluids.

Size: Ensure that the size of the fittings (e.g., 1/2 inch, 3/4 inch) matches your piping system perfectly.

Pressure Rating: Select the appropriate pressure rating (e.g. Class 3000) based on the system’s operating pressure to ensure the threaded fittings can withstand the pipeline’s working pressure and prevent leaks or damage.

Pipeline Layout: Use couplings for straight connections, elbows for direction changes, and tees for branching or merging.

Application of NPT Threaded Fittings

Oil and gas pipelines

Chemical equipment pipelines

Water treatment systems

Firefighting pipelines

Pharmaceutical industry

Food processing equipment

Air conditioning and refrigeration systems

Shipbuilding and marine engineering

Hydraulic and pneumatic systems

Building pipeline installation

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ASTM A105 carbon steel, as the most common material for forged pipe fittings, has long been one of our company’s most familiar and common products.

ZIZI can offer a full range of A105 threaded fittings, covering pressure ratings such as Class 2000, 3000, and 6000. All products are manufactured in accordance with ASME B16.11 standards and undergo rigorous dimensional and pressure testing to ensure reliable application in industries such as oil, gas, chemicals, and power.

Our customers have long relied on us for our advantages in timely delivery, consistent quality, and customization capabilities. This inquiry once again demonstrates their trust in our brand.

Inspection of ASTM A105 Threaded Fittings

Visual and Dimensional Inspection

Inspect threaded elbows, tees, pipe clamps, pipe caps, etc., for cracks, pores, burrs, or deformation.

Thread precision is inspected using a thread gauge to ensure a tight and reliable connection with the corresponding pipe or fitting.

Dimensions are verified against ASME B16.11 standards, including outer diameter, inner diameter, wall thickness, thread depth, etc.

Material and Chemical Composition Testing

Spectral analysis or chemical analysis is used to confirm that material composition meets ASTM A105 standard requirements.

Particular attention is paid to the content of elements such as carbon, manganese, sulfur, and phosphorus to ensure that the material possesses the specified mechanical properties and pressure resistance.

Mechanical property testing

Tensile, impact, and hardness tests are conducted to ensure that the fittings have sufficient strength and toughness under pressure and low-temperature conditions.

Inspection Photos

Threaded Fitting Specification

Threaded Length:

The length of the threaded portion must comply with NPT standards for a tight, secure fit.

Nominal Pipe Size (NPS):

The NPS is used to designate the size of the forged threaded fittings. For example, a 1/2” fitting has a 1/2” NPS.

Wall Thickness:

The threaded elbows and threaded tees wall thickness must comply with the class designation (2000, 3000, or 6000) to handle the pressure rating associated with that class.

ASTM A105 Carbon Steel Chemical Composition

ASTM A105 Carbon Steel Mechanical Property

Threaded Elbow & Tee Dimension

Threaded Coupling & Cap Dimension

Common Types of Threaded Fittings

Elbows (90° and 45°) – Used to change pipe direction.

Tees – Allow branching of the pipeline.

Couplings – Connect two pipes together.

Unions – Provide easy disconnection for maintenance.

Bushings – Reduce pipe size.

Nipples – Short sections of threaded pipe.

Caps & Plugs – Seal pipe ends.

Crosses – Four-way connection.

Advantages of ASTM A105 Threaded Fittings

Easy and Quick Installation: No specialized welding equipment or technicians are required; installation can be completed using simple tools, significantly reducing construction time and labor costs.

Removable and Reusable: Threaded connections allow fittings to be easily disassembled when necessary, facilitating maintenance, inspection, or modification of the piping system, thereby enhancing system flexibility.

Reliable Sealing Performance: Through the tight fit of threads and the use of thread sealants or sealing tapes, reliable leak-proof sealing is achieved, making them suitable for medium to low-pressure fluid transportation.

Cost-effective: Compared to welded fittings that require complex welding processes and non-destructive testing, ASTM A105 threaded fittings typically offer a cost advantage.

Common Application Scenarios

Oil and Gas Transportation

Chemical and Petrochemical Industries

Power and Water Conservancy

Construction and Fire Protection

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Manufacturing Process of Stainless Steel Elbow

Pushing Process

This is a commonly used process. First, the stainless steel tube blank is heated to the appropriate temperature, then a specialized pushing machine is used to shape the tube blank into a 90-degree elbow using a die. The pushing process has high production efficiency, enabling large-scale production, and produces elbows with high dimensional accuracy and good surface quality.

Stamping Process

For smaller stainless steel 90 degree elbows, the stamping process can be used. Stainless steel sheets are cut into the appropriate shape, placed into a stamping die, and then pressed into the rough shape of an elbow using a stamping machine. Subsequent welding and finishing processes are then performed. The stamping process is suitable for mass production of elbows with relatively simple shapes.

Welding Process

First, the stainless steel sheet is rolled into two 90 degree curved sections, which are then welded together to form a 90 degree elbow. The welding process can produce large-diameter elbows but requires high-quality welding techniques to ensure the strength and sealing of the welds.

Classification by Bending Radius

Long Radius (LR) 90° Elbow:

The radius of curvature (R) is 1.5 times the nominal pipe size (NPS) or outside diameter (D). (R = 1.5D). This provides a smoother turn, reducing friction, turbulence, and pressure drop. It’s generally preferred when space allows and flow efficiency is critical.

Short Radius (SR) 90° Elbow:

The radius of curvature (R) is equal to the nominal pipe size (NPS) or outside diameter (D). (R = 1.0D). This results in a sharper turn, increasing turbulence and pressure drop, but it is more compact and suitable for tight spaces where a smaller bend is necessary.

Classification by Material:

Based on the different grades of stainless steel used, stainless steel 90 degree elbows can be categorized into 304 stainless steel 90 degree elbows, 316 stainless steel 90 degree elbows, 321 stainless steel 90 degree elbows, etc. Elbows made from different materials exhibit variations in corrosion resistance, high-temperature resistance, and other properties, making them suitable for different operational environments. The following chemical composition and mechanical properties are provided as examples for 304 and 316.

Butt Weld Stainless Steel Elbow Chemical Composition

Butt Weld Stainless Steel Elbow Mechanical Property

Socket Weld & Threaded Elbow Chemical Composition

Socket Weld & Threaded Elbow Mechanical Property

Classification by Connection Type

Butt Weld Elbow

Stainless steel 90-degree elbows are welded to tightly connect pipes, offering high strength and excellent sealing. They are the most common type in industrial piping systems. They can withstand high pressure and high temperature operating environments with virtually no leakage, making them particularly suitable for large-diameter, high-pressure, or high-temperature piping systems. However, this connection is not removable, requiring pipe cutting for repair or replacement.

Socket Weld Elbow

Socket-weld elbows are constructed by inserting the pipe into the socket of the elbow and then welding the elbow externally. They are commonly used for small-diameter, high-pressure pipes. They provide a secure connection, strong sealing, and are unlikely to leak, making them particularly suitable for high-pressure applications. Installation is relatively simple, making them particularly suitable for small-diameter pipes. However, the internal socket structure does introduce some fluid resistance.

Threaded Elbow

Threaded elbows connect pipes via threads, with both internal and external threads being common. They are primarily used for small-diameter, low-pressure pipes. They offer advantages such as easy installation and multiple disassembly capabilities, making them particularly suitable for pipe systems that require frequent disassembly or maintenance. However, the sealing performance is relatively weak and leakage is likely to occur under high pressure or vibration conditions, so it is not suitable for high temperature and high pressure environments.

Stainless Steel 90 Degree Elbow Applications

1. Oil and Gas Industry: Used for transporting crude oil, natural gas, and in refinery pipeline systems, suitable for high-temperature and high-pressure environments.

2. Chemical Industry: Suitable for conveying corrosive media such as acids, alkalis, and salts in pipeline systems.

3. Power Industry: Commonly used in boilers, cooling water pipelines, and high-pressure steam systems.

4. Water Treatment and Supply Systems: Suitable for potable water, wastewater, and industrial water pipelines, ensuring long-term corrosion resistance.

5. Pharmaceutical and Food Processing: Ensures pipeline hygiene, corrosion resistance, and suitability for conveying pure fluids.

6. Marine Engineering: Used in ship and offshore platform pipeline systems, resistant to salt fog and seawater corrosion.

7. Air Conditioning and HVAC Engineering: Used in hot and cold water, refrigerant, and circulation system pipelines.

Conclusion

Stainless steel 90 degree elbows can be classified into different types based on manufacturing processes, connection methods, and structural forms. Selecting the appropriate elbow type is critical for ensuring pipeline efficiency, safety, and durability. With our expertise and advanced production equipment, we provide high-quality stainless steel elbows that meet international standards for various industrial applications.

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Specification For Threaded 90 Degree Elbow

Long Radius (LR) 90° Elbow:

The radius of curvature (R) is 1.5 times the nominal pipe size (NPS) or outside diameter (D). (R = 1.5D). This provides a smoother turn, reducing friction, turbulence, and pressure drop. It’s generally preferred when space allows and flow efficiency is critical.

Short Radius (SR) 90° Elbow:

The radius of curvature (R) is equal to the nominal pipe size (NPS) or outside diameter (D). (R = 1.0D). This results in a sharper turn, increasing turbulence and pressure drop, but it is more compact and suitable for tight spaces where a smaller bend is necessary.

Material & Grades of Threaded Elbow :

Carbon Steel :
ASTM A105 / A105N,ASTM A350 LF2 / LF3, A694 F42 / 46 / 52 / 56 / 65 / 70

Alloy Steel :
ASTM / ASME A/SA 182 & A 387 F1, F5, F9, F11, F12, F22, F91

Stainless Steel :
ASTM A 182, A 240 F 304, 304L, 304H, 316, 316L, 316Ti, 310, 310S, 321, 321H, 317, 347, 347H, 904L

Duplex & Super Duplex Steel :
ASTM / ASME A/SA 182 F 44, F 45, F51, F 53, F 55, F 60, F 61

Copper Alloy Steel :

 ASTM SB 61 , SB62 , SB151 , SB152 UNS No. C 70600 (Cu-Ni 90/10), C 71500 (Cu-Ni 70/30), UNS No. C 10100, 10200, 10300, 10800, 12000, 12200

Nickel Alloy :
ASTM SB564, SB160, SB472, SB162 Nickel 200 (UNS No. N02200), Nickel 201 (UNS No. N02201), Monel 400 (UNS No. N04400), Monel 500 (UNS No. N05500), Inconel 800 (UNS No. N08800), Inconel 825 (UNS No. N08825), Inconel 600 (UNS No. N06600), Inconel 625 (UNS No. N06625), Inconel 601 (UNS No. N06601), Hastelloy C 276 (UNS No.N10276), Alloy 20 (UNS No. N08020)

ASME B16.11 Threaded 90 Degree Elbow  Dimension

Threaded Elbow Weight Chart in KG

Installation and Sealing Guidelines

Clean the threads and inspect for burrs or damage

Select appropriate PTFE tape or specialized thread sealant (chemical compatibility must match the medium)

After hand-tightening to the correct position, use a wrench to tighten at the specified angle to avoid over-tightening, which can cause cracking or thread failure

Align the direction before final tightening to prevent seal surface damage caused by backlash

After passing pressure leakage testing (airtight/water pressure), put into operation and conduct regular re-inspections

How to Calculate Weight of 90 Degree Elbow

The weight formula is W=0.0387 * S*(D – S) * R / 1000, the unit is kg/piece. What’s the meaning of each letter? Let’s explain to you.

W means Weight.

S means Thickness in mm.

D means Outside Diameter in mm.

R means Radius that LR=1.5D, SR=1D.

Now we take “90 Degree Elbow LR Seamless 6″ Sch 40 BW ASTM A234 WPB” as sample. From above diameter and thickness chart, we know the outside diameter is 168.3mm and thickness is 7.11mm. The weight will be 0.0387 x 7.11 x ( 168.3 – 7.11 ）x 1.5 x 168.3 / 1000 = 11kg/piece.

How to Inspect Forged Elbows

Inspect the surface of A182 forged elbows for defects such as cracks, wrinkles, or scale. Cracks may be caused by stress concentration during the forging process or defects in the raw material, while wrinkles and scale may affect the uniformity of wall thickness and strength of the elbow.

Measure the dimensional parameters of the elbow. For example, for a 90° forged elbow, the angular deviation should be within the specified range, typically not exceeding ±1°.

Inspect the end port shape of the elbow, which should be flat and perpendicular to the axis to ensure proper alignment with adjacent pipes.

Frequently Asked Questions (FAQ)

Q1: Are 90° threaded elbows more prone to leaks than butt-welded elbows?

A: When properly selected and sealed and tightened according to specifications, they can reliably meet the requirements of medium and low pressure applications. For high temperature, high pressure, or highly corrosive environments, butt-welded or flanged connections are recommended.

Q2: Can NPT and BSPT be directly connected?

A: Not recommended. Differences in thread angle, pitch, and taper may cause leakage or damage if forced to connect.

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Product List

Inspection Photos

ASME B16.9 Concentric Reducer Specification

Stainless steel 316 concentric reducers are fittings used to connect two pipes of different diameters. Their primary function is to alter the pipe diameter and flow velocity, ensuring smooth fluid flow within the piping system.

ASTM A403 WP316L Pipe Fittings Chemical Composition

ASTM A403 WP316L Pipe Fittings Mechanical Property

MSS SP-83 Threaded Union Specification

The threaded union is the most widely used type of union, characterized by its use of threaded connections for piping. It consists of three main components: a male end with external threads, a female end with internal threads, and a nut. By rotating the nut, the sealing surfaces of the male and female ends can be tightly aligned to achieve connection and sealing. The thread forms can be BSP, NPT, G, etc., and the connection is further secured by a locking nut and seal ring.

Class 3000 Threaded Union Dimensions

Specification of Weld Neck Flange

316L weld neck flanges are pipe connectors made from 316L stainless steel. They achieve a secure connection by butt-welding the pipe and are commonly used in applications involving high pressure, high temperature, and highly corrosive media. The high structural strength and excellent sealing properties of 316L weld neck flanges ensure the long-term safe operation of pipeline systems.

ASTM A182 F316L Flanges Chemical Composition

ASTM A182 F316L Flanges Mechanical Property

Advantages of SS316L

1. Excellent Corrosion Resistance

SS316L contains 2-3% molybdenum in its chemical composition, which gives it significantly better corrosion resistance than 304 stainless steel in chloride environments. It effectively resists pitting and crevice corrosion, making it ideal for marine environments, coastal areas, and applications involving chloride-containing media.

2. Excellent Welding Performance

“L” stands for “Low Carbon.” SS316L has a carbon content below 0.03%, significantly reducing the risk of carbide precipitation (also known as “sensitization”) during welding. This property prevents intergranular corrosion near the weld seam, ensuring the integrity and long-term stability of the welded joint in corrosive environments. Therefore, in pipeline systems requiring extensive welding, SS316L is a superior choice over 316.

3. High strength at high temperatures

SS316L maintains high tensile strength and creep strength even at high temperatures. This makes it suitable for high-temperature, high-pressure piping systems, such as heat exchangers and pressure vessels.

Applications of SS316L Fittings and Flanges

Petroleum and Natural Gas Industry

Chemical and Pharmaceutical Industry

Marine Engineering and Shipbuilding

Food and Beverage Processing

Power and Nuclear Energy

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Its structural features include an external thread on the male end, an internal thread on the female end, and a threaded connection between the two, with a gasket placed in between to ensure sealing. Union fittings are available in various materials, including copper, stainless steel, cast iron, and plastic. Selection should be based on factors such as the pipeline medium, pressure, and temperature.

MSS SP-83 Pipe Union Specification

Different Types of Pipe Unions 

A pipe union is a type of detachable pipe fitting connection consisting of two end joints and a locking nut in the middle, enabling quick assembly and disassembly without rotating the pipe body. Depending on the connection method, pipe unions are mainly divided into two categories: socket weld unions and threaded unions. These two types differ significantly in terms of structural design, installation method, sealing performance, and applicable scenarios.

Socket Weld Unions

Socket weld unions are primarily used in piping systems that require a more secure and reliable connection. Unlike threaded unions, the ends of socket weld unions feature sockets, into which the pipes are inserted and then welded along the socket edges. The two ends of the unions are secured together using nuts or clamps, and metal or non-metal seals are installed at the connection surfaces to ensure reliable sealing. Similar to threaded unions, they also include a nut for connection and sealing.

Advantages of Socket Weld Unions:

Reliable and secure connection: Welded connections have significantly higher strength than threaded connections, capable of withstanding higher pressures and vibrations.

Excellent leak prevention: Welding provides a permanent leak-proof seal, suitable for applications with extremely high sealing requirements.

Easy installation: Socket weld unions do not require precise alignment during installation, making the process relatively simple.

Disadvantages of Socket Weld Unions:

Welding construction is required, resulting in longer installation and disassembly times.

The heat-affected zone from welding may alter metal properties, necessitating strict welding procedures.

Class 3000 Socket Weld Union Dimension

Threaded Union

The threaded union is the most widely used type of union, characterized by its use of threaded connections for piping. It consists of three main components: a male end with external threads, a female end with internal threads, and a nut. By rotating the nut, the sealing surfaces of the male and female ends can be tightly aligned to achieve connection and sealing. The thread forms can be BSP, NPT, G, etc., and the connection is further secured by a locking nut and seal ring.

Advantages of Threaded Unions

Easy to install, no welding required, suitable for quick on-site construction.

Facilitates disassembly, maintenance, and replacement of pipeline systems.

Suitable for applications where welding is not feasible.

Disadvantages of Threaded Unions

Threaded connections are prone to loosening due to thermal expansion and contraction and vibration, resulting in slightly lower sealing performance compared to welded types.

Not suitable for long-term use in high-pressure, high-temperature, or highly corrosive environments.

CLASS 3000 Threaded Union Dimensions

Material & Grades of Forged Unions:

Carbon Steel Threaded Flanges :
Carcon Steel: ASTM A105 / A105N,ASTM A350 LF2 / LF3, A694 F42 / 46 / 52 / 56 / 65 / 70

Alloy Steel Threaded / Screwed Flanges :
ASTM / ASME A/SA 182 & A 387 F1, F5, F9, F11, F12, F22, F91

Stainless Steel Threaded Flanges :
ASTM A 182, A 240 F 304, 304L, 304H, 316, 316L, 316Ti, 310, 310S, 321, 321H, 317, 347, 347H, 904L

Duplex & Super Duplex Steel Threaded Flanges :
ASTM / ASME A/SA 182 F 44, F 45, F51, F 53, F 55, F 60, F 61

Copper Alloy Steel Threaded Flanges :

 ASTM SB 61 , SB62 , SB151 , SB152 UNS No. C 70600 (Cu-Ni 90/10), C 71500 (Cu-Ni 70/30), UNS No. C 10100, 10200, 10300, 10800, 12000, 12200

Nickel Alloy Threaded Flanges :
ASTM SB564, SB160, SB472, SB162 Nickel 200 (UNS No. N02200), Nickel 201 (UNS No. N02201), Monel 400 (UNS No. N04400), Monel 500 (UNS No. N05500), Inconel 800 (UNS No. N08800), Inconel 825 (UNS No. N08825), Inconel 600 (UNS No. N06600), Inconel 625 (UNS No. N06625), Inconel 601 (UNS No. N06601), Hastelloy C 276 (UNS No.N10276), Alloy 20 (UNS No. N08020)

Socket Weld Union VS Threaded Union

Threaded union are mainly used in low-pressure, normal-temperature pipeline systems that require frequent disassembly and maintenance. Their core advantage lies in their ease of installation and disassembly.

Socket weld union are suitable for high-pressure, high-temperature pipeline systems with strict sealing requirements. Their core advantage lies in their secure and reliable connection.

Applications of Pipe Unions

Civil and building water supply and drainage systems

Industrial piping systems

Food and pharmaceutical industries

Oil, gas, and energy sectors

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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

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

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.

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