Long radius and short radius 90 degree, 45 degree and 180 degree butt weld elbows to ASME B16.9 in carbon steel, alloy steel and stainless steel, from 1/2 inch to 48 inch.
- Standard: ASME B16.9, ASME B16.25, ASTM A234, ASTM A403, MSS SP-43, MSS SP-75
- Grades: WPB, WPC, WP1, WP5, WP9, WP11, WP12, WP22, WP91, WP304, WP304L, WP316, WP316L, WP321, WP347
Specifications
| Outer diameter | 1/2" - 48" (DN15 - DN1200) |
|---|---|
| Wall thickness | SCH 10 - SCH XXS, or matching pipe wall thickness |
| Schedule | SCH 10, 20, 40, 80, 160, XXS, STD, XS |
| Length | Center to end per ASME B16.9, e.g. LR 90 deg 1.5 x NPS |
| Ends | Bevelled to ASME B16.25, 37.5 deg +/- 2.5 deg |
| Surface treatment | Black, varnish, galvanized, sand blasted, or epoxy coated |
| Manufacturing process | Seamless or welded, hot formed or cold formed |
| Pressure rating | Per ASME B16.9 wall thickness and ASME B31.3 design |
Long Radius versus Short Radius
The most common question about elbows is which radius to specify. A long radius elbow has a centerline radius of 1.5 times the nominal pipe size, while a short radius elbow has a radius of 1.0 times the nominal size. Long radius is the default because it gives a lower pressure drop and lower turbulence, and most process and pipeline specifications ask for it by default. Short radius is used where space is tight, for example inside a skid or a manifold, and it accepts a higher pressure loss as the trade-off. There is also a 3D radius elbow, with a centerline radius of 3 times the nominal size, used where the application requires minimal pressure drop or reduced erosion, for example in slurry or catalyst lines. Specifying the wrong radius is one of the most frequent ordering errors, so it should be stated explicitly rather than assumed.
Material Grades and Their Service
Butt weld elbow material is specified by the ASTM grade of the fitting, not the pipe. For carbon steel the standard grade is ASTM A234 WPB, which is the weldable carbon steel used for the vast majority of general service. WPC is a higher carbon variant for slightly higher strength, used less often. For low temperature service, low alloy grades in the A420 series are used. For high temperature service in refinery and power applications, the chrome-moly grades A234 WP5 (5Cr), WP9 (9Cr), WP11 (1-1/4Cr), WP22 (2-1/4Cr) and WP91 (9Cr-1Mo-V) are specified depending on temperature and hydrogen partial pressure. Stainless steel elbows are to ASTM A403, with WP304 and WP316 for general corrosion resistance, the L grades for welded construction where intergranular corrosion is a risk, and WP321 and WP347 for elevated temperature service. The fitting grade must be compatible with the pipe grade, and for alloy and stainless materials a PMI test is normally required to confirm the chemistry.
What is the difference between a long radius and short radius elbow?
A long radius elbow has a centerline radius of 1.5 times the nominal pipe size, and a short radius elbow has a radius of 1.0 times the nominal size. Long radius is the standard choice because it produces lower pressure drop and less turbulence. Short radius is used only where installation space is limited, and it accepts a higher pressure loss. For a 4 inch elbow, long radius means a 6 inch centerline radius, short radius means 4 inch.
How do I know whether an elbow will fit my pipe?
Match three things: outside diameter, wall thickness or schedule, and material grade. The butt weld end is bevelled to ASME B16.25 with a 37.5 degree bevel and a root face, so it is designed to butt against a pipe end prepared the same way. ASME B16.9 also sets tolerance limits: the wall thickness must not be less than 87.5 percent of the nominal value at any point, and outside diameter tolerances apply. If the fitting wall is thinner than the pipe wall, check the ASME B31.3 or project specification for the permitted mismatch before welding.
Materials
- Carbon steel
- Alloy steel
- Stainless steel
- Duplex stainless steel
Typical applications
- Oil and gas pipeline construction
- Petrochemical and refinery piping
- Power plant piping systems
- Water treatment and desalination
- Shipbuilding and marine piping
Inspection & testing
- Dimensional inspection per ASME B16.9
- Radiographic or ultrasonic weld examination
- PMI on alloy and stainless steel
- Hardness testing
- Hydrostatic test on request
- Third-party inspection (SGS, BV, TUV)
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