Pipe Elbow Dimensions – Long & Short Radius Elbow Dimensions in mm

Pipe elbow dimensions & sizes are mainly determined by parameters such as nominal diameter (DN/NPS), bending radius (R), bending angle, wall thickness (Sch) and pressure level (Class/PN). The sizes of elbow fittings of different standards and types vary.

1. Main size parameters

Nominal diameter (DN): indicates the diameter size of the elbow (such as DN15, DN20, DN25, DN50, DN100), which needs to match the pipe.

American Standard (NPS, inches): 1/2", 3/4", 1", 1.5", 2", 3", 4", 6", 8", 10", 12", etc.

Bending radius (R): divided into short radius (SR) and long radius (LR)
- SR: R = 1.0 × DN (such as DN100 elbow R = 100mm)     Application: low pressure drop, high flow system (such as chemical, petroleum pipeline).

- LR: R = 1.5 × DN (such as DN100 elbow R = 150mm)     Application: space-constrained installation scenarios (such as equipment interface, compact pipeline).

Bending angle: Common 45°, 90°, 180° (U-bend), special angles can be customized.
Among them, 90° elbow is the most commonly used, changing the flow direction by 90 degrees. 45° elbow eases the change of flow direction and reduces turbulence. 180° elbow is used for reverse arrangement of pipelines.

Wall thickness (Sch): Select according to the pressure level, such as Sch5, Sch10, Sch20, Sch40, Sch80, Sch160 (refer to ASME B36.10 standard).
Among them, Sch40 elbow (standard wall thickness) and Sch80 elbow (thickened) are most commonly used.

Wall thickness effect: high pressure, high temperature or corrosive media need to choose a higher Sch number.

2. Pressure Rating Influence

● Class Series (American Standard):
For example, Class 150, Class 300. These grades define the dimensions and pressure-temperature ratings of flanges for weld neck fittings (see ASME B16.5). For elbows themselves, their pressure capacity is indicated by the wall thickness class (Sch), not directly by the Class grade. Click here to view the Pipe Elbow Pressure Rating and Selection Guide.

● PN Series (Chinese Standard/European Standard):
For example, PN10, PN16. These grades determine the dimensions and pressure-temperature ratings of flange connections. For weld neck fittings such as elbows, the PN grade guides wall thickness design, and pressure requirements are ultimately met by selecting the Sch wall thickness class or directly specifying the wall thickness value.

Pipe Elbow dimensions are covered in ASME B16.9. Refer to the table given below for the dimension of the elbow size 1/2″（21.3mm) to 48″(1220mm).

Dimensions of Pipe Elbow according to ASME B16.9:

Dimensions of Special Elbows:

Reducing elbows: The diameters of the large end (DN1) and the small end (DN2) must be marked. For example, for DN100×50, you need to check the dimension table separately.
Threaded elbows: The dimensions are based on the NPT or BSP thread standards (such as 1/2"NPT, 3/4"BSP).

Stamped elbows: Commonly used for small diameters (DN15-DN50), the dimensions may be slightly smaller than welded elbows.

Long Radius Elbow vs. Short Radius Elbow: A Comprehensive Comparison

Comparison Dimensions	Long Radius Elbow (LR)	Short Radius Elbow (SR)
Radius of Curvature	1.5D (Centerline Radius = 1.5 × Nominal Diameter)	1.0D (Centerline Radius = 1.0 × Nominal Diameter)
Turn Sharpness	Smooth turn, smoother fluid path	Sharp turn, abrupt change in fluid direction
Fluid Resistance	Lower pressure drop, lower pressure loss	Higher pressure drop
Erosion and Wear	Less severe, with minimal impact on the pipe wall.	More severe, with the back of the elbow susceptible to erosion.
Pipeline Cleaning Capability	Can be cleaned; pipeline cleaning equipment can pass through.	Cannot be cleaned; pipeline cleaning equipment cannot pass through.
Applicable Pressure	Applicable to high, medium, and low pressure	Only applicable to low pressure and low flow rate conditions
Applicable Flow Rate	Applicable to high, medium, and low pressure	Only applicable to low pressure and low flow rate conditions
Installation Space	Requires more space, large turning radius	Space-saving, small turning radius
Cost	Slightly higher price for the same specifications (more material usage)	Slightly lower price for the same specifications (less material usage)
Standard Basis	Preferred elbows in standards such as ASME B16.9 and GB/T 12459.	Allowed use as specified in the standards.
Application Frequency	Most commonly used, accounting for over 90% of elbow usage.	Less used, only when space is limited.

Long Radius Elbow vs. Short Radius Elbow: How to Choose Correctly?

Use Cases / Customer Needs	Recommended	Reasons
Conventional Pipeline Design (No Special Space Restrictions)	Long Elbow (LR)	Low fluid resistance, low pressure drop, high safety; the industry default standard.
High-Pressure Pipeline Systems (≥4.0MPa)	Long Elbow (LR)	Short elbows with sharp turns are prone to localized high pressure and erosion, posing safety hazards.
High-Speed Fluid Pipelines (Gas, Steam, etc.)	Long Elbow (LR)	Effectively reduces erosion and wear, extending elbow lifespan.
Pipelines Requiring Pigging (Long-Distance Oil and Gas Pipelines)	Long Elbow (LR)	Short elbows cannot pass through pigging equipment; long elbows are necessary.
Pulsating Flow or Vibrating Pipelines	Long Elbow (LR)	Smooth turns reduce fluid impact and pipeline vibration.
Extremely Limited Installation Space (e.g., densely populated equipment areas)	Short Elbow (SR)	Only used as an alternative when long elbows cannot be installed.
Temporary Pipelines or Low-Pressure Drainage Pipelines	Short Elbow (SR)	Low pressure, slow flow rate, controllable risk, saves space.
Customers Extremely Cost-Sensitive and Operating Conditions Allow	Short Elbow (SR)	Less material is used, resulting in slightly lower cost, but safety risks need to be assessed.

Note: Long elbows must be used unless installation space is severely limited. Short elbows are only used as a compromise in special situations where long elbows cannot be installed.

If you have specific operating parameters (pressure, flow rate, medium, whether pigging is required, space dimensions), please provide them to us at sales@hu-steel.com, and we will help you further confirm the appropriateness of your selection.

Manufacturing Process of Pipe Elbow:

How to choose elbow size?

Match pipe diameter: The DN/NPS of the elbow must be consistent with the pipe.
Select wall thickness according to pressure: Sch80 or higher for high pressure.
Space limitations: Use short radius (SR) for narrow areas and long radius (LR) for smooth turning.
Medium characteristics: Corrosive media require increased wall thickness or stainless steel (such as 304/316).

How to obtain specific dimensions?

Check standard manuals: such as ASME B16.9, GB/T 12459.
Manufacturer's catalog: Different manufacturers may provide slightly different size tables.

Online tools: Use pipe size calculator (e.g. PVC elbows and metal elbows have different sizes).

FAQs:

Q1. What are the main size specifications for elbows? How are they represented?
A: Elbow size specifications mainly involve three dimensions: angle (45°, 90°, 180°), radius of curvature (LR and SR), and nominal diameter.

Common elbow size ranges are: 1/2 inch to 48 inches (DN15 to DN1200); 

Pressure ratings: Sch5s, Sch10s, Sch20, Sch40, STD, Sch80, XS, Sch160, XXS, etc., among which STD and XS are the most commonly used.

Example of standard ordering representation:
LR STD 90° 8" = Long radius, pressure rating STD, 90°, 8-inch elbow
SR XS 45° 4" = Short radius, pressure rating XS, 45°, 4-inch elbow

Q2: What are the requirements for elbow dimensional tolerances in ASME B16.9 standard? 

A: ASME B16.9 is the core dimensional standard for welded pipe fittings, clearly defining the dimensional tolerances for elbows. Generally, the larger the size (±3.2~±4.8), the wider the allowable tolerance range; the smaller the size, the stricter the tolerance requirements (±0.8~±1.6). During acceptance, special attention should be paid to the wall thickness, using an ultrasonic thickness gauge to check the back arc of the elbow to ensure that the thinning does not exceed 12.5%.

Q3: How is the pressure rating of the elbow indicated? How to match it with the pipeline?
The pressure rating of an elbow is indicated by its wall thickness series number (Schedule No.), which must match the wall thickness of the connected pipe. 

Common wall thickness series:
STD: Standard – Most commonly used, suitable for normal pressures
XS: Extra Strong – Most commonly used, suitable for higher pressures
XXS: Double Extra Strong – For high-pressure applications

Selection Notes:
a. The pressure rating (wall thickness) of the elbow must not be lower than the wall thickness of the connected pipe;
b. Common combinations: STD wall thickness elbows with STD pipes, XS wall thickness elbows with XS pipes;
c. The wall thickness series should be clearly specified when purchasing, such as 90° LR Sch40. 6"

Q4: How to measure and accept the key dimensions of elbows?
A: When accepting elbows, customers are advised to focus on the following dimensional items:

Outer/Inner Diameter: The port is the key inspection area.
Wall Thickness: Focus on the back arc (outer arc), where it is the thinnest – ultrasonic thickness gauge
Bending Angle: Deviation ≤ ±1° – angle gauge, template
Radius of Curvature: 1.5D or 1.0D, tolerance ±2mm (NPS≤24) – template, coordinate measuring machine
Ellipticity: Ensure matching with the pipe – calipers to measure the maximum/minimum outer diameter
End Face Perpendicularity: Affects the quality of weld joints – right-angle ruler

Practical Experience: 

Assemble four 90° elbows into a circle to quickly check angle accuracy; 

Wall thickness must be measured at multiple points along the back arc, as measuring the port with calipers alone cannot detect thinning issues.

Q5: What are the dimensions of a DN40 elbow?

A: A DN40 elbow refers to a small-diameter pipe elbow with a nominal diameter (DN) of 40 mm. DN is an internationally recognized pipe size designation system; DN40 is approximately equal to 1.5 inches of pipe. The outer diameter of a DN40 elbow ranges from approximately 40.0 to 48.3 mm, with a center length of approximately 45-85 mm and a bending radius (typically 1.5D). Its main applications cover multiple industries including industrial manufacturing, food and pharmaceuticals, and construction and municipal engineering, and it is a key component in piping systems for changing the direction of connections.

Note: In actual engineering, when we say "DN40 elbow," if it is manufactured according to American Standard (ASME) or Chinese Standard (GB) for butt-welded pipe fittings, its interface outer diameter (OD) is always 48.3 mm, not 40 mm.

The dimensions of DN40 elbows also vary depending on the material and connection method. For example:
● Sanitary welded elbow: outer diameter approximately 40mm, center length approximately 60mm;
● Grooved ductile iron elbow: outer diameter 48.3mm, center length 45mm, bending radius 50mm;
● Aluminum elbow for compressed air: outer diameter 40.1mm, inner diameter 36.5mm.

Q6: What are the dimensions of 4-inch and 6-inch long radius elbows?

A:
● 4-inch long radius elbow dimensions (DN100): Outer diameter 114.3mm, 90° center distance 152mm, 45° center distance 64mm
● 6-inch long radius elbow dimensions (DN150): Outer diameter 168.3mm, 90° center distance 229mm, 45° center distance 95mm

● 8-inch long radius elbow dimensions (DN200): Outer diameter 219.1mm, 90° center distance 305mm, 45° center distance 127mm

Note: Engineers prioritize long-radius elbows (R=1.5D) whenever space permits, accounting for over 90% of applications. The reasons are as follows:

a. Lower flow resistance → Lower energy consumption
b. Less wear → Longer pipe life
c. Less stress → Safer system

Short-radius elbows are only considered when the equipment layout is extremely compact and long-radius elbows cannot be installed. This is why long-radius elbows dominate most elbow inventories and product catalogs.

Conclusion:

The actual selection of pipe elbows needs to be determined in combination with the pipe material (carbon steel, stainless steel, PVC, etc.), medium pressure/temperature and installation space!

Read more: Material Selection and Application of Pipe Elbows or ASTM A403 WP316 Stainless Steel Butt-weld Elbow