Views: 12 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).
This larger bend radius is better than standard short-radius elbows (R=1.0D). It lets fluids change direction more smoothly. This change reduces flow resistance, pressure loss, turbulence, and wear.
They are commonly used in high-pressure and high-speed transport of fluids and solids. This is true in industries like chemicals, power, and pharmaceuticals. 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 type. It has a 90° bend angle and a bend radius that is 1.5 times the pipe diameter.
It is used to achieve right-angle directional changes in piping systems. Its gentle curve lowers flow resistance, pressure drop, turbulence, and erosion. This makes it great for high-speed flows, uses with particles, or when low energy loss is needed.
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 need smooth transitions. This is useful when there is space for longer bends or when specific angles are needed.
180° Long Radius Elbow: This elbow completely changes direction. It has a centerline bend radius of 1.5D. It is mainly used for tight U-shaped loops.
This includes heat exchanger manifolds, pump bypasses, or when pipes need to go back to their original direction. The long radius improves flow better than the short radius 180° elbow. However, it takes up more space.
The core characteristic of long radius elbow is a constant bend radius of 1.5 times the nominal pipe diameter.
The key installation measurement is the center-to-end (C-E) distance. This is the straight distance from the elbow's centerline to the end plane. The center-to-end (C-E) distance of a 90° long radius elbow is 1.5D. For a 45° elbow, the C-E distance is 0.625 times 1.5D, which is about 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
A long-radius elbow has a centerline radius of 1.5 × the pipe diameter (1.5D). This makes a gentle bend and greatly reduces fluid turbulence.
In contrast, a short-radius elbow has a bend radius of only 1.0 times the nominal pipe diameter (1.0D). Its sharper turn is more abrupt and can easily cause fluid shock and a sudden rise in pressure drop.
2. Fluid Dynamics
Long-radius elbows feature a gentle turn that minimizes flow resistance and pressure drop. This makes them ideal for high-velocity fluids carrying solids or susceptible to scaling.
Short radius elbows create strong turbulence and high pressure drop from their abrupt directional change. Consequently, they are suitable only for clean, low-pressure, low-flow fluids like 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 tight curve of a short-radius elbow focuses flow on the outer bend. In abrasive conditions, this can increase wear by more than 2 times, resulting in a need for frequent replacement.
5. Application Scenarios
Long-radius elbows: Reserved for high-pressure, high-temperature, or corrosive services, complying with stringent codes (e.g., ASME B31.3).
Short-radius elbows: Suited only for low-pressure piping or drainage, such as in building water systems or ventilation.
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 cost more upfront, but they save money in the long run.
Q: Are long radius elbows piggable?
A: Yes, Long radius elbows are piggable because their gradual curve prevents pigs from 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.
