What are the different grades of pipe elbow?

Classification by Material

According to the valve body material, pipe elbows can be made from stainless steel, carbon steel, and alloy steel.

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Carbon Steel Elbow

Materials in carbon steel adhere to the following standards:
ASTM 234 WPB and WPC
ASTM A420 WPL6
MSS-SP-75 WPHY 42, 46, 52, 56, 60, 65, and 70

Stainless Steel Pipe Elbow

Stainless steel pipe elbows have higher strength and corrosion resistance compared to carbon steel elbows. For general surface treatment, they are used in high-corrosion environments like chemical plants, offshore, and gas pipelines. Surface treatments in 2B or mirror finishes are used in food industries and for sanitary purposes.

Materials in stainless steel adhere to the following standards:
ASTM A403 WP 304/304L, 316/316L
ASTM A270

Stainless Steel 90 Degree Elbow

The most common usage of pipe elbow for stainless pipelines is the stainless steel 90-degree elbow. Another common type is the stainless steel 45-degree elbow. Both types are widely needed for butt weld, socket weld, and threaded connections.

How to Make Steel Pipe Elbow – 2 Options

Creating steel pipe elbows involves many steps, but it is simpler compared to other production processes.

Option 1 to Manufacture Steel Pipe Elbow

First, weld the closed end of a polygonal circular or sector shell. When the pipe is filled with a pressure medium, its cross-section changes from a polygon to a circular shape. Under internal pressure, the section will form a circular shell. This ring can be cut into four 90-degree elbows, six 60-degree elbows, or other required sizes. Advances in technology have made it possible to weld and manufacture larger diameter steel pipe elbows, especially those with long radii.

Option 2

You can also directly purchase seamless or welded pipe as the steel elbow material. Heat the pipe body with a heating machine, then push the pipe into a mold to form the elbow shape. Generally, carbon steel has high carbon content, providing more strength and hardness but lower plasticity. Therefore, those without large amounts of alloy elements are often referred to as carbon steel or straight carbon steel.

Steel pipe elbows are crucial components in plumbing pipeline systems, used to change fluid directions. They vary in types based on materials, including stainless steel, carbon steel, and alloy steel; fluid direction, including 45, 90, and 180 degrees; length and radius, including short radius (SR) and long radius (LR); and connection types, including butt weld, socket weld, and threaded steel piping elbows.

If you find elbow descriptions confusing, like what is a butt weld elbow, SW elbow, or the meanings of LR and SR, keep reading. We will explain the specifications and applications for each type, helping you identify your exact needs before purchasing.

Steel Elbow Applications and Types

Simply put, a steel pipe elbow connects two pipes to change the flow direction. Steel elbows can be classified into different degrees, including 45, 90, and 180 degrees. Other degrees like 60° or 120° are also used for special requirements.

90 Degree Steel Pipe Elbow – The Most Common Type

The 90-degree steel pipe elbow changes fluid direction by 90 degrees. It's the most common type in pipeline systems, as it is easy to integrate with steel construction and structures.

• 90 Degree Elbow of Long Radius
This elbow is installed between different lengths of pipe or tubing to change the direction by 90 degrees. It’s often used for connections between hoses, water pumps, deck drains, and valves.
• 90 Degree Elbow of Short Radius
This type, similar to the long radius elbow, has a shorter diameter, making it suitable for use where space is limited.

45 Degree Steel Pipe Elbow

The 45-degree elbow changes the pipe direction by 45 degrees, making it the second most common type in industrial pipelines.

• 45 Degree LR Steel Elbow
This elbow changes the direction by 45 degrees and creates lower frictional resistance, resulting in lower pressure.
• 45 Degree SR Elbow
This elbow can be attached to various materials like copper, plastic, steel, cast iron, and lead. It’s widely used in chemical industries, food facilities, water supply, electronic industries, gardening, agriculture, solar power facilities, and air conditioning pipelines.

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180 Degree Steel Elbow

This elbow changes the direction by 180 degrees. It is typically used in systems with low pressure, minimum deposition, and low turbulence.

Butt Weld Elbow – Most Common Connection Type

The easiest way to connect an elbow to a pipe is by welding the elbow ends directly to the pipe ends, known as butt to butt weld (BW Elbow). Butt weld elbows are used in higher pressure and temperature applications than other elbow connection types like socket weld or threaded elbows.

Socket Weld Elbow – For Small Diameter Pipelines

Socket weld elbows are connected similarly but have a ladder-shaped area to insert the pipe ends, followed by welding to join them. This structure makes the welding process easier for small diameter elbows and pipes.

Threaded Elbow – Easy to Install

Similar in shape to the socket weld elbow, the main difference is that the ladder area's inner surface is threaded, making installation and uninstallation easier. This feature is beneficial for pipeline repair and maintenance.

Reducer Elbow

Also known as a decreasing elbow, it is used when the elbow and closures are different sizes. This allows for differing pipe sizes to be easily connected, enabling significant directional changes.

What is Elbow Radius

Elbow radius refers to the curvature radius. If the radius equals the pipe diameter, it is a short radius elbow (used in low pressure and low velocity pipelines). If the radius is larger than the pipe diameter (R ≥ 1.5 Diameter), it is a long radius elbow (used in high pressure and high flow velocity pipelines). Generally, if the buyer doesn't specify the radius specs, it is assumed to be an LR elbow.

Stainless Steel Pipe Elbow

Stainless steel elbows, made with added Cr and Ni chemicals in carbon steel, conform to standards like ASTM A403 WP 304/304L, 316/316L, ASTM A270, etc. They provide higher strength and corrosion resistance compared to carbon steel elbows.

Surface treatments in 2B or mirror finishes are typically used in food industries and sanitary applications. For general surface treatment, stainless steel elbows are mainly used in high-corrosion environments, such as chemical plants or offshore oil and gas pipelines.

Carbon Steel Elbow

Materials in carbon steel adhere to the following standards:
ASTM 234 WPB and WPC
ASTM A420 WPL6
MSS-SP-75 WPHY 42, 46, 52, 56, 60, 65, and 70

How to Make Steel Pipe Elbow – Manufacturing Processes

Manufacturing steel pipe elbows consists of several steps but is considered simple compared to other production processes.

First, we can weld a polygonal circular shell or a polygonal fan-shaped shell with closed ends. When the pipe body is filled with pressure mediums, its cross-section changes from a polygon to a circular shape. Under internal pressure, the section will form a round shell. This circular ring can be cut into four 90° elbows, six 60° elbows, or other required sizes. Thanks to advancements in technology, this welding process is now applied in various ways, enabling the manufacture of larger diameter steel piping elbows, especially those with long radii.

Alternatively, you can purchase seamless or welded pipe directly as the raw material. Then use a heating and forming machine to heat the pipe body and push it into a mold to form the elbow shape with different degrees.

Generally, carbon steel has a high amount of carbon, providing more strength and hardness but lower plasticity. Therefore, those without large amounts of alloy elements are usually referred to as carbon or straight carbon steel.

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