Views: 3 Author: Monica Publish Time: 2025-09-15 Origin: Site
Long radius elbows are used to change the direction of pipes. Their bend radius is 1.5 times the nominal pipe diameter (R=1.5D). Compared to standard short-radius elbows (R=1.0D), this larger bend radius allows fluids to change direction more gradually as they pass through the elbow, significantly reducing flow resistance, pressure loss, turbulence, and wear. They are widely used in high-pressure, high-speed fluid and solid transport scenarios in industries such as the chemical, power, and pharmaceutical industries. Materials include stainless steel, carbon steel, and alloy steel.
In this article, JN will introduce you to all topics related to long radius elbows.
Long radius elbows are mainly classified according to their bending angle.
90° Long Radius Elbow: This is the most common and widely used type, with a 90° bend angle and a centerline bend radius of 1.5 times the nominal pipe diameter. It is used to achieve right-angle directional changes in piping systems. Its gentle curve effectively reduces flow resistance, pressure drop, turbulence, and erosion, making it particularly suitable for high-velocity flows, applications involving particulates, or where low energy loss is required.
45° Long Radius Elbow: This elbow has a 45° bend angle and also has a centerline bend radius of 1.5D. It is used when a gentler, more gradual directional change is required. Compared to a 90° elbow, it produces less pressure drop and flow resistance. It is often used in piping systems that require smooth transitions, when space allows for slightly longer bends, or when specific angles are required.
180° Long Radius Elbow: This elbow achieves a complete reversal of direction and also has a centerline bend radius of 1.5D. It is primarily used for tight U-shaped loops, such as heat exchanger manifolds, pump bypasses, or where pipes need to be routed back to their original direction. The long radius makes its flow characteristics better than the short radius 180° elbow, but it occupies a relatively larger space.
The core characteristic of long radius elbow is a constant bend radius of 1.5 times the nominal pipe diameter.
The critical installation dimension is the center-to-end (C-E) distance, which is the perpendicular distance from the elbow's centerline to the plane of any end. The C-E of a 90° long radius elbow is 1.5D, while the C-E of a 45° elbow is 0.625 × 1.5D, which is approximately 0.94D.
Dimensions are standardized according to ASME B16.9 and cover NPS sizes from ½" to 48".
ASME B16.9 / EN 10253 / GB/T 12459 90 Degree Long Radius Elbow Dimensions
Nominal Diameter (DN) | Nominal Pipe Diameter (NPS) | Outside Diameter (OD) (mm) | Center to End Dimension (A) (mm) | Bend Radius (R) (mm) | Wall Thickness (Sch 40) (mm) |
15 | ½ | 21.3 | 38 | 25 | 2.77 |
20 | ¾ | 26.7 | 38 | 29 | 2.87 |
25 | 1 | 33.4 | 48 | 38 | 3.38 |
32 | 1¼ | 42.2 | 57 | 48 | 3.56 |
40 | 1½ | 48.3 | 76 | 57 | 3.68 |
50 | 2 | 60.3 | 95 | 76 | 3.91 |
65 | 2½ | 73.0 | 114 | 95 | 5.16 |
80 | 3 | 88.9 | 152 | 114 | 5.49 |
100 | 4 | 114.3 | 191 | 152 | 6.02 |
125 | 5 | 141.3 | 238 | 190 | 6.55 |
150 | 6 | 168.3 | 286 | 229 | 7.11 |
200 | 8 | 219.1 | 381 | 305 | 8.18 |
250 | 10 | 273.0 | 476 | 381 | 9.27 |
300 | 12 | 323.9 | 572 | 457 | 10.31 |
ASME B16.9 / EN 10253 / GB/T 12459 45 Degree Long Radius Elbow Dimensions
Nominal Diameter (DN) | Nominal Pipe Diameter (NPS) | Outside Diameter (OD) (mm) | Center to End Dimension (A) (mm) | Bend Radius (R) (mm) | Wall Thickness (Sch 40) (mm) |
15 | ½ | 21.3 | 16 | 25 | 2.77 |
20 | ¾ | 26.7 | 16 | 29 | 2.87 |
25 | 1 | 33.4 | 20 | 38 | 3.38 |
32 | 1¼ | 42.2 | 24 | 48 | 3.56 |
40 | 1½ | 48.3 | 32 | 57 | 3.68 |
50 | 2 | 60.3 | 40 | 76 | 3.91 |
65 | 2½ | 73.0 | 48 | 95 | 5.16 |
80 | 3 | 88.9 | 64 | 114 | 5.49 |
100 | 4 | 114.3 | 80 | 152 | 6.02 |
125 | 5 | 141.3 | 100 | 190 | 6.55 |
150 | 6 | 168.3 | 120 | 229 | 7.11 |
200 | 8 | 219.1 | 160 | 305 | 8.18 |
250 | 10 | 273.0 | 200 | 381 | 9.27 |
300 | 12 | 323.9 | 240 | 457 | 10.31 |
ASME B16.9 / EN 10253 / GB/T 12459 180 Degree Long Radius Elbow Dimensions
Nominal Diameter (DN) | Nominal Pipe Diameter (NPS) | Outside Diameter (OD) (mm) | Center to End Dimension (A) (mm) | Bend Radius (R) (mm) | Wall Thickness (Sch 40) (mm) |
15 | ½ | 21.3 | 25 | 38 | 2.77 |
20 | ¾ | 26.7 | 29 | 38 | 2.87 |
25 | 1 | 33.4 | 38 | 48 | 3.38 |
32 | 1¼ | 42.2 | 48 | 57 | 3.56 |
40 | 1½ | 48.3 | 57 | 76 | 3.68 |
50 | 2 | 60.3 | 76 | 95 | 3.91 |
65 | 2½ | 73.0 | 95 | 114 | 5.16 |
80 | 3 | 88.9 | 114 | 152 | 5.49 |
100 | 4 | 114.3 | 152 | 191 | 6.02 |
125 | 5 | 141.3 | 190 | 238 | 6.55 |
150 | 6 | 168.3 | 229 | 286 | 7.11 |
200 | 8 | 219.1 | 305 | 381 | 8.18 |
250 | 10 | 273.0 | 381 | 476 | 9.27 |
300 | 12 | 323.9 | 457 | 572 | 10.31 |
350 | 14 | 355.6 | 533 | 667 | 11.13 |
400 | 16 | 406.4 | 610 | 762 | 12.70 |
1. Bend Radius
The center line radius of a long radius elbow is 1.5 times the nominal pipe diameter (1.5D), resulting in a gentle curve and significantly reducing fluid turbulence. A short-radius elbow, with a bend radius of only 1.0 times the nominal pipe diameter (1.0D), is more abrupt and can easily cause fluid shock and a sudden increase in pressure drop.
2. Fluid Dynamics
Long-radius elbows offer a gentle turn, resulting in low fluid resistance and pressure drop, making them suitable for high-velocity fluids containing solid particles or prone to scaling. Short radius elbows, due to their sudden change in direction, generate strong turbulence and a high pressure drop, making them suitable only for low-pressure, low-flow clean fluids such as room-temperature water and air.
3. Space Requirement
The compact design of short radius elbows saves installation space and is suitable for confined areas. Long-radius elbows require a longer layout distance and may not be suitable for space-constrained applications.
4. Wear and Lifespan
The gentle curve of long-radius elbows disperses fluid impact, reducing pipe wall erosion and extending service life. The sharp bend of short-radius elbows causes fluid to concentrate on the outer bend area, which can increase the wear rate by more than 2 times in abrasive media, necessitating frequent replacement.
5. Application Scenarios
Long-radius elbows are the preferred choice for high-pressure, high-temperature, and corrosive applications, complying with stringent standards such as ASME B31.3. Short-radius elbows are only used for low-pressure auxiliary piping or drainage, such as building water pipes and ventilation ducts.
6. Cost and Maintenance
Short-radius elbows have a lower unit price, but their higher wear rate may result in higher long-term maintenance costs. Long-radius elbows have a higher initial investment, but their low energy consumption, long life, and reduced downtime make them more cost-effective over time.
Q: Are long radius elbows piggable?
A: Yes, long radius elbows are generally piggable for pipeline inspection/maintenance, as their gradual curve allows pigs to pass without jamming.
Q: Are there different radii of long radius elbows?
A: No. By definition, "long radius" elbows have a fixed bend radius of 1.5 times the nominal pipe diameter. For example, a 6" NPS LR elbow always has a 9" bend radius. Variations would be classified as "short radius" or custom designs, which are not standard LR elbows.
Q: Do you need long radius elbow for sewer lines?
A: Not necessarily. Short radius (SR) elbows are common in sewer lines where space is constrained and flow velocities are low. LR elbows are preferred only in high-velocity sections to reduce turbulence, prevent solids deposition, and minimize pipe wear.
Q: How to measure long radius elbow?
A: Measure Center-to-End (A) and Outside Diameter (OD). For a 90° LR elbow:
1. Place the elbow upright on a flat surface.
2. Measure vertically from the surface to the center of the elbow’s curve.
3. Verify R = 1.5 × OD.
Note: For 45° elbows, A ≈ 0.621 × R.
Q: What is fillet radius for 16" long radius elbow?
A: The filler radius for a 16" LR elbow is not standardized. Typically, it ranges from 1/8" to 1/4". Critical applications require fillet radii to be defined in weld maps to avoid stress concentration.
Q: What is long radius and short radius elbow?
A:
l Long Radius (LR): Bend radius = 1.5 × pipe diameter (1.5D). Lower pressure drop, gentler flow, requires more space.
l Short Radius (SR): Bend radius = 1.0 × pipe diameter (1.0D). Compact, higher pressure loss, used in tight spaces.
Q: Which elbow has the longer tangent: 8R or 9R?
A: 9R elbows have longer tangents than 8R. Historically, "R" denoted bend radii multiples:
l 8R = Radius ≈ 8 × pipe diameter (obsolete, similar to modern Short Radius)
l 9R = Radius ≈ 9 × pipe diameter (obsolete, similar to modern Long Radius)
Note: Modern standards use 1.5D (LR) and 1.0D (SR)—avoid outdated "R" classifications.
