A Short Article on Elbow as Pipe Fitting
Steel pipe elbow (sometimes also referred to as bends) is a key part of a pressure piping system used to change the fluid flow direction. It is used to connect two pipes with the same or different nominal diameters, and to make the pipe and thus the fluid direction turn to a certain direction of 45 degrees or 90 degrees. This change in fluid flow direction adds pressure losses to the system due to impact, friction, and re-acceleration.
Classification of Steel Pipe Elbows
Types of Elbows based on Direction Angle
According to the fluid flow direction of the pipes, elbows can be divided into different degrees, such as 45 degrees, 90 degrees, and 180 degrees, which are the most common elbows. Also, there are 60-degree and 120-degree elbows for some special pipelines. This degree is just a representation of the angle by which the fluid flow is going to change after flowing through the said elbow.
Types of Elbows based on Length and Radius
Elbows are split into two groups which define the distance over which the flowing fluid change direction; the centerline of one end to the opposite face. This is known as the “Center to Face” distance and is equivalent to the radius through which the elbow is bent.
If the radius is the same as pipe diameter (Center-to-Face dimension of 1.0 X diameter ), it is called Short Radius Elbow (SR elbow) used normally for low pressure and low-speed pipelines or in tight areas where clearance is the main issue. If the radius is larger than the pipe diameter (Center-to-Face dimension of 1.5 X diameter) then we call it a Long Radius Elbow (LR Elbow) used for high pressure and high flow rate pipelines.
Types of Elbows based on Connection with Pipe
As per the connection with pipe, elbows could be classified as Butt Welded elbows, Socket Welded elbows, and Threaded elbows.
Butt Welded Elbow
A buttweld elbow is a steel elbow formed by hot pressing or forging. Its connection form is to directly weld the elbow and steel pipe. Butt-welded elbows have beveled ends to allow for ease of welding. This bevel allows for full penetration weld in most cases. Butt-welded elbows are mainly used for elbows with higher pressure and temperature.
Socket Welded Elbow
Socket weld elbow is also welded to the pipe and fittings end. Unlike the butt weld elbow, the socket weld elbow has a trapezoidal area at the end. We can insert the pipe end into this area (the diameter of the SW elbow is matched with the outer diameter of the pipe), then do welding work to connect them together. Therefore, the actual diameter of the SW elbow end is greater than the elbow diameter.
The shape of the threaded elbow is similar to the SW elbow, except that the inner surface of the trapezoidal area has been machined into thread. It is easier to install and remove, good for pipeline repair and maintenance.
The 90 degree elbows are used to connect tubes at a 90° angle. As the name suggests, the elbow is always a right-angle in shape. Such type of elbow is also known as “90 bends or 90 ells”. This is a pipe fitting device that is bent in such a way to produce a 90° change in the direction of flow of the fluid/gas in the pipe. The elbow is used to change the direction in piping and is also sometimes called a “quarter bend”.
A 90° elbow attaches readily to pipes of various materials like plastic, copper, cast iron, steel, lead, rubber, etc. In other words, the 90° elbows are used to provide a joint between two pipes at right angles to each other. They are used as railing ends or corners on a level installation.
Types of 90° elbows:
90° elbows are manufactured as SR (Short Radius) elbows and LR (Long Radius) elbows:
SR (Short Radius) Elbows:
These elbows have a Center-to-Face dimension of 1.0 X diameter. They are typically used in tight areas where clearance is the main issue.
LR (Long Radius) Elbows:
These elbows have a Center-to-Face dimension of 1.5 X diameter. They are the most common type of elbow and are used when space is available and flow is more critical.
Application of 90° elbows:
90 Degree ElbowThe main application area of a 90° elbow is to connect hoses to valves, water pressure pumps, and deck drains. 90° elbows help to make the dust hose take that quick turn at the corner. These elbows can be used on instrumentation, process and control systems, and equipment employed in chemical, petroleum, fluid power, electronic, and pulp and paper plants.
45 Degree Elbow is also known as “45 bends or 45 ells”. The 45° pipe elbow is used to connect tubes at a 45° pipe angle. As the name suggests, this is a pipe fitting device that is bent in such a way to produce a 45° change in the direction of flow of the fluid/gas in the pipe.
Like a 90° elbow, the 45° pipe elbow also attaches readily to pipes of various materials like plastic, copper, cast iron, steel, lead, rubber, etc. They are typically made as LR (Long Radius) elbows. These types of elbows are available in various sizes (in mm or inches). They are available with different male-to-female BSP thread connections. Providing a wide choice of colors, these 45° elbows can be manufactured to meet different specifications, in terms of size and diameter.
Applications of 45° elbows:
45° elbows are used in a wide variety of applications like:
Water supply facilities
Food industrial pipelines
Chemical industrial pipelines
Electronic industrial pipelines
Air conditioning facility pipelines
Agriculture and garden production transportation
Pipeline network for solar energy facility
180 degree Long Radius Elbow
The 180 Degree Elbows are used for connecting pipes of different diameters and find wide applications in various chemicals, construction industries, paper, cement & shipbuilders.
We have adopted advanced production equipment to make our 180-degree Long Radius Elbow(1D D711.2～D1219.2), which can not only improve product quality but also save raw materials. An elbow is a pipe fitting installed between two lengths of pipe or tubing to allow a change of direction, usually a 180° or 90° angle, though 45° elbows are also made. The ends may be machined for butt welding (SW) or socketed welding(SW) etc. Most elbows are available in short radius or long radius variants. When the two ends differ in size, the fitting is called a reducing elbow or reducer elbow.
Elbows are categorized based on various design features as below:
Long Radius (LR) Elbow is also called LR elbow – which means the radius is 1.5 times the pipe diameter
L/R 180°Elbow: Long Radius 180 degree return bend allows complete reversal of flow.
Short Radius (SR) Elbow is also called SR elbow, – means the radius is 1.0 times the pipe diameter
Short radius 180° Elbow: Short Radius 180° return bend allows complete reversal of flow
Butt Weld fitting Tee
Tees straight and reducing
The primary purpose of a Tee is to make a 90° branch from the main run of pipe. Standard, there are 2 possibilities, on behalf of the equal tee and reducing tee. The equal tee (or straight tee) is used as the branch has the same diameter as the run-pipe. The reducing tee is used as the branch has a smaller diameter than the run-pipe.
Dimensions and Standards
When we talk about a tee NPS 3, an equal or straight tee is intended. With a tee, NPS 3 x 2 a reducing tee is intended. Although, officially a reducing tee will be indicated by 3 diameters, namely 3 x 3 x 2 (A x B x C). The A and B measure stands for the Nominal Pipe Size of Run-Pipe, C measure stands for Nominal Pipe Size of Outlet.
This designation actually is superfluous but comes from the time that tees were available in 3 different ends of diameters, such as
4 x 3 x 2 (A x B x C). In this implementation of course it is necessary, to specify 3 different sizes.
That kind of tee is probably no longer available. Applying an equal tee with a concentric or eccentric reducer is now the usual practice.
A straight or equal buttwelding Tee is available for all common diameters.
A Reducing Tee not, because many diameters are not produced, or can not be produced.
As an example.. a reducing tee NPS 6 x 4 is a standard item for most suppliers, but a reducing tee NPS 16 x 2 is probably not available by any supplier.
It would also not be economical to use an NPS 16 tee with an NPS 2 outlet; in such situations, a Branch Fitting will be used or a Branch Connection will be made.