Difference Between A Pipe Elbow And A Pipe Bend

What is a pipe bend?

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pipe bend is the generic term for what is called in piping as an “offset” – a change in direction of the piping. A bend is usually meant to mean nothing more than that there is a “bend” – a change in direction of the piping (usually for some specific reason) – but it lacks specific, engineering definition as to direction and degree. Bends are usually custom-made (using a bending machine) on site and suited for a specific need.

Pipe bends typically have a minimum bending radius of 1.5 times pipe radius (R). If this bending radius is less than 1.5R, it is called Elbow. Reference to any international / industry standard need to be traced. 1.5, 3 and 4.5 R are the most common bending radii in industry.

A pipe bend typically flows smoother since there are not irregular surfaces on the inside of the pipe, nor does the fluid have to change direction abruptly.

The most basic difference of them is the elbow relatively short than bend, R = 1D to 2 D is elbow More than 2D is bend. In the production process, cold bends can use Bending Machine to bend by ready-made straight bend. One-time completed also don’t need second corrosion. But elbow need manufacturers make to order, to do anti-corrosion, order cycle is long. Elbow price is higher than bend. But cost performance is much higher than bend. It is well-known that bend do not have anticorrosive processing is easy damaged, but the price is cheap so are  used very much in some demand which not very high engineering.

In the west-east gas transmission of course, cold bends cost is low. elbow need manufacturers make to order, needs corrosion, order cycle is long,but cold bends can use ready-made straight bend by Bending Machine to bend. One-time completed also don’t need second corrosion. The cold bend construction technology need follow oil standard .west-east gas transmission have the enterprise standard,but we can use either elbow nor bend in open area.  Sunny Steel Enterprise warn broad customers betweenness elbow and bend performance price is differ ,please carefully choose after consider it.

The pipe bends should be as per the standard of  ANSI/ASME B16.49 which did not specific the bending radius and angle , the regular pipe bend radius are 2.5D, 3D ,5D ,7D or 8D , but it can be any other bending radius according to the design need, and bending angle can be in any degree, 5 ,10 ,15, 90 degree or any other. People said “All bends are elbows but all elbows are not bend”, it is not true . Actually “All elbows are pipe bends but not all bends are elbows”  is more reasonable.

Industrial Processes 
Bending, squeezing, pressing, forging, machining and more
Industries Served
Our pipe elbows are widely used in many industries, such as power generation, petroleum, natural gas, chemicals, shipbuilding, heating, papermaking, metallurgy and so on.

The production process of stainless steel pipe bend

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According to the different manufacturing methods, the stainless steel pipe bend can be divided into three types, namely, the bending pipe, the punching pipe and the welded pipe. Which can be divided into two types of bending bending and bending. When the stainless steel tube for bending the pipe along the longitudinal direction under pressure, leading to pipe wall thickness of the pipe is shortened, the lateral pipe subjected to tensile, elongation, wall thinning and tube; center without force, deformation will not occur. The cross section of stainless steel tube is changed from round to oval. Bend in the production of the need to pay attention to, when the piping system, when the bending radius design does not require the minimum bending radius of the bend to meet certain standards.

Cold bending of stainless steel pipe bend. Bending pipe in the heating process, the heating process should be slow and uniform, so as to ensure the thermal conductivity of the pipe, we should pay attention to avoid overheating and carburizing.

Bending technology is widely used in the field of boilers and pressure vessels. In many industries, such as aerospace, shipbuilding and other industries, the quality of the pipe bend has a direct impact on the structural rationality, safety and reliability of the product. Therefore, bending the quality of the pipe is the most critical, and grasp the technical conditions of the pipe is the most important. In the cold bending of the pipe bend, the need to choose a reasonable mandrel formation and master the correct method of use.

Because the inner side of the bending tube in bending when wrinkling, core tube is when they bend the tube relative bending radius is small, in order to obtain high quality pipe fittings, pipe is in the bending process, in which are inserted into a suitable mandrel, thereby avoiding method of flattening and wrinkling phenomenon stainless steel pipe bending appears when arc. Because the tube has a certain elasticity, so when bending force is removed, a rebound angle of pipe bend. In the bending angle, should consider increasing the angle.

How to Calculate a Pipe Bend?

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Whether you are bending pipe for running electrical conduit or a metal project, calculating the bend for the start and end point can be an important factor. While there are different types of pipe benders on the market, they all share a common identification for the operation. Identified on all pipe benders is the size of pipe the unit will bend along with a number called the “take up.” The take up measurement is used for adding or deducting an allowance in the overall length of the bend. By following a basic process, you can calculate pipe bends regardless of the type of bender or the diameter of pipe.

Instructions

  1. Identify the take up measurement that is located on the pipe-bending shoe itself. This is the addition or deduction of measurement to the length of pipe from the front mark on the bending shoe. Also be aware that there is a second centre-of-bend mark located approximately in the centre of the bending shoe. Also located along the running length of the shoe are angle markings with lines. These numbers and lines correspond to actual angles that can be bent into the pipe by aligning the pipe with the angled line marked on the outside of the shoe.

  2. Bend a 90-degree angle on a ½-diameter pipe with a ½-inch bender. The process will remain the same for different sized pipes and benders, but only the take up measurement will be different. Identified on the shoe for the ½-inch pipe may be the wording “stub take up 5 inches from arrow or line.” The 5 inches is the amount you will deduct from the overall length of the 90-degree bend measurement.

  3. Use the measuring tape and pencil and place a mark at 12 inches from the end of the pipe. This will be the distance from the bend to the end of the pipe. By using the deduction measurement on the shoe, measure back 5 inches from the 12-inch mark and make a solid pencil line.

  4. Lay the pipe on a level surface and insert the pipe into the bender. The solid pencil mark should be placed 5 inches back from the 12-inch mark and should be aligned with the front mark or arrow on the bending shoe. Pull back on the handle in a smooth motion until the pipe sits at a 90-degree position to the level surface. Place the small level against the upright portion of the pipe and check for level. This will give you a perfect 90-degree bend. Check the height of the overall bend by placing the end of the tape measure on the level base and measure the end of the pipe. It should read 12 inches exactly.

  5. Practice with other angled bends by using the deduction measurement and the centre of the bend mark on the shoe. All pipe benders may have their own quirks and slight measurement adjustments that will have to be done. The actual end result also depends on how well and secure you hold the pipe in the bender, prior to the first bend you place on the pipe.

What is a pipe elbow?

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A pipe elbow, on the other hand, is a specific, standard, engineered bend pre-fabricated as a spool piece and designed to either be screwed, flanged, or welded to the piping it is associated with. An elbow can be 45o or 90o. There can also be custom-designed elbows, although most are catagorized as either “short radius” or long radius”.

A pipe bend can be an elbow; an elbow does not mean a bend. If you use the term elbow, it should also carry the qualifiers of type (45 or 90o) and radius (short or long) – besides the nominal size.

 The ends may be machined for butt welding (SW) or socketed welding(SW) etc.

Most pipe 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 – means the radius is 1.5 times the pipe diameter
    • L/R 45°Elbow: Long radius 45 degree elbow changes the direction by 45 degrees.
    • L/R 90°Elbow: Long radius 90 degree elbow changes the direction by 90 degrees.
    • 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 radiu 45°Elbow: Short radius 45° elbow changes the direction by 45 degrees.
    • Short radius 90°Elbow: Short Radius 90° elbow is same as LR90 except for the measurement between end of elbow to center line is 1 x NPS.
    • Short radius 180° Elbow: Short Radius 180° return bend allows complete reversal of flow


Processing:

The physical difference between Long Radius and Short Radius Elbows is graphically illustrated in the attached Workbook that I have put together for this thread.

The following is the criteria I use when deciding which to use:

Long Radius Elbows are used when:

there is a need to keep the frictional fluid pressure loss down to a minimum;
there is ample space and volume to allow for a wider turn and generate less pressure drop;
the fluid being transported is abrasive or has solids in it.


Short Radius Elbows are used when:

there is a need to reduce the cost of elbows;
there is a scarcity of space and volume to allow a Long Radius type.

Size range:

  • Seamless elbow: 1/2″-24″ DN15-DN600
  • Welding elbow: 6″-72″ DN150-DN1800
  • Wall thickness: Sch5-Sch160 XXS
Materials
  • Carbon steel: ASTM/ASME A234 WPB-WPC
  • Alloy steel: –WP 22-WP 5-WP 91-WP 911
    • ASTM A335 P22
    • ASME SA335 P91 elbow
    • ASTM A234 WP 11
  • Low temperature steel: ASTM/ASME A402 WPL 3-WPL 6
  • High performance steel: ASTM/ASME A860 WPHY 42-46-52-60-65-70
  • Stainless steel: ASTM/ASME A403 WP 304-304L-304H-304LN-304N
    • ASTM/ASME A403 WP 316-316L-316H-316LN-316N-316Ti
    • ASTM/ASME A403 WP 321-321H ASTM/ASME A403 WP 347-347H

What is a 45 Degree Elbow?

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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 which is bent in such a way to produce 45° change in the direction of flow of the fluid/gas in the pipe.

Like a 90° elbow, the 45 Degree 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 Degree Elbows can be manufactured to meet different specifications, in terms of size and diameter.

What is a 90 Degree Elbow?

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A 90 degree elbow is also called a “90 bend” or “90 ell”. It is a fitting which is bent in such a way to produce 90 degree change in the direction of flow in the pipe. It used to change the direction in piping and is also sometimes called a “quarter bend”. A 90 degree elbow attaches readily to plastic, copper, cast iron, steel and lead. It can also attach to rubber with stainless steel clamps. It is available in many materials like silicone, rubber compounds, galvanized steel, etc. The main application of an elbow (90 degree) is to connect hoses to valves, water pressure pumps, and deck drains. These elbows can be made from tough nylon material or NPT thread.

Butt Weld Pipe Fitting Bevel
  • All welded pipe fittings have bevelled end to allow for ease of welding.
  • This bevel allows for full penetration weld in most cases.
  • There are two types of bevels;
    Plain Bevel and Compound Bevel: according to the bevel of welding pipe fittings construction .
  • ASME B16.28, Buttwelding Short Radius Elbows and Returns

Industrial Processes: Bending, squeezing, pressing, forging, machining and more ANSI/ASME B16.25, Buttwelding Ends 
ANSI/ASME B16.25 Standard covers the preparation of butt welding ends of piping components to be joined into a piping system by welding.

Application of pipe elbows:

Petroleum, chemical, power, gas, metallurgy, shipbuilding, construction, etc.


How to calculate a 90 degree elbow center and 45 degree elbow center?

Pipe Elbow Center Calculator

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For standard degrees of pipe elbows such as 45° and 90°, elbow center to end dimensions are available in standard pipe charts. But many times, custom elbow angles are required at site which should be cut from standard 45° or 90° elbows.

Formula for calculating center to end distance of such elbows is as follows:

Elbow length in mm = Tan(Elbow Angle/2) X Elbow Radius in mm

Where:

For 90° Long Radius elbows, center to end dimension given in dimension tables of ASME B16.9 is same as radius of elbow. This is because Tan(90/2) i.e. Tan 45 is 1.

Normally custom elbow angles from 45 degree to 90 are cut from 90 degree standard elbow. But for custom elbow angles smaller than 45 degree, elbow is normally cut from existing standard 45 degree elbow. Center to end dimension given in dimension tables for 45 degree elbow must be divided by Tan(22.5) to get elbow radius for standard 45 degree elbow. Then we can use above formula to get elbow angle for custom degrees.

Same procedure applies to 3D elbows.

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Example 1:

Calculate elbow center to end dimension for 4 inch nominal pipe diameter elbow at 60 degree angle, cut from 90 degree LR elbow.

From ASME B16.9, center to elbow dimension for 4 in elbow is 152 mm.

Length = Tan (60/2) X 152

Length = 0.57735027 X 152

Length = 87.757 i.e. 88 mm Approx.

Example 2:

Calculate elbow center to end dimension for 2 inch nominal pipe diameter elbow at 30 degree angle, cut from 45 degree LR elbow.

From ASME B16.9, center to elbow dimension for 2 inch 45 degree elbow is 35 mm.

Radius of elbow = 35/Tan(22.5)

Radius of elbow = 35/0.4142 = 84.5 mm

Length = 0.26795 X 84.5

Length = 22.64 i.e. 23 mm Approx.


If your elbow is a short radius it is 1 times your nominal pipe diameter. If it is a long radius it is 1 1/2 times your nominal pipe diameter.show me the exact pattern of long radius.

(90/2tan*Dia*1.5*25.4)
(45/2tan*Dia*1.5*25.4)
u will obtain Ur answer in (mm)

For 90 degree elbow (Dia*38.1) this formula used for only 90 degree elbow.
For 45 degree elbow (45/2of tan*Dia*1.5*25.4) this answer obtained in (mm).

Difference between a pipe elbow and a pipe bend is as follows:

  1. Pipe Bend is a generic term for any offset or change of direction in the piping. It is a vague term that also includes elbows.
  2. An elbow is an engineering term and they are classified as 90 deg or 45 deg, short or long radius.
  3. Pipe elbows have industrial standards and have limitations to size, bend radius and angle. The angles are usually 45 deg or 90 degrees. All others offsets are classified as pipe bends.
  4. Bends are generally made or fabricated as per the need of the piping; however elbows are pre fabricated and standard, and are available off the shelf.
  5. Bends are never sharp corners but elbows are. Pipe bending techniques have constraint as to how much material thinning can be allowed to safely contain the pressure of the fluid to be contained.  As elbows are pre fabricated, cast or butt welded, they can be sharp like right angles and return elbows which are 180 degrees.
  6. Elbow is a standard fitting but bends are custom fabricated.
  7. In bends as the pipe is bent and there is no welding involved, there is less pipe friction and flow is smoother. In elbows, the welding can create some friction.
  8. All elbows are bends but all bends are not elbows.
  9. Bend has a larger radius then elbows.
  10. Generally the most basic difference is the radius of curvature. Elbows generally have radius of curvature between one to twice the diameter of the pipe.  Bends have a radius of curvature more than twice the diameter.

Source: China Pipe Fittings Manufacturer – Yaang Pipe Industry Co., Limited (www.pipelinedubai.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@pipelinedubai.com

Please notice that you might be interested in the other technical articles we’ve published:

  • Tips for selecting expansion joints

  • What is the difference between a steel pipe and a steel tube?

  • Engineering Specification for Pressure Test of Piping System

  • How to choose a valve and valve end connection type

  • How to test pipe fitting?

  • Manufacturing process of cold rolled steel pipe

  • Development trend of high pressure pipe fittings

  • How to get high quality flanges

  • How to get high quality alloy steel pipes

  • How to get high quality pipe fittings

  • How to get high quality bellow expansion joints

  • How to Calculate a Pipe Bend?

  • Stainless steel pipe bend

  • The production process of stainless steel pipe bend

  • Knowledge of Stamping Elbows

References:

  • https://www.yaang.com
  • https://www.marineinsight.com/tech/pipeing/pipes-and-bends-an-essential-guide-for-second-engineers-part-2/
  • http://www.pipingengineer.org/pipe-elbow-center-calculator/ 

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