Sanitary Butt-Weld Elbows (DIN 11852 / 3A / SMS)
In high-purity process lines, the elbow is the primary source of flow turbulence and pressure drop. Inferior hydroforming can lead to wall thinning at the extrados (outer radius) and “orange peel” surface defects that compromise sterility.
Our Sanitary Weld Elbows are cold-formed from annealed stainless steel tubing, strictly adhering to DIN 11852 and 3A sanitary standards. We prioritize tangent straightness and wall thickness consistency. This ensures that when paired with automatic orbital welding heads, the alignment is perfect, eliminating the “high-low” misalignment that creates internal crevices (bio-traps). These fittings are designed to maintain laminar flow and facilitate full drainability in CIP/SIP cycles.
- Orbital Weld Ready: Squareness tolerance < 0.5°.
- Dead Leg Free: Full-flow radius minimizes turbulence.
- Controlled Ra: Internal finish < 0.8μm (Standard).
- Heat Treated: Solution annealed to restore corrosion resistance.
- Consistent Wall: Uniform thickness prevents burn-through.
- Material Traceability: Heat numbers marked on every fitting.
Technical Specifications
Product Name
Sanitary Weld Elbow / Hygienic Butt-Weld Bend
Configuration
45° Elbow, 90° Elbow, 180° Return Bend (U-Bend)
Design Standards
DIN 11852, 3A (63-03), SMS 1145, ISO 2037, ASME BPE (DT-4.1.1)
Material Grades
AISI 304 (1.4301) / AISI 316L (1.4404)
Wall Thickness
1.5mm, 1.65mm, 2.0mm (Standard dependent)
Size Range
1/2″ – 6″ (Imperial) / DN10 – DN150 (Metric)
Surface Finish
ID: Ra ≤ 0.8μm (Mechanical) or Ra ≤ 0.38μm (Electropolished)
OD: Ra ≤ 1.6μm (Satin/Brushed) or Mirror Polish
Radius Type
Long Radius (1.5D) standard; Short Radius (1.0D) on request
Optimized for Automatic Orbital Welding Manual welding often compensates for poor fit-up, but orbital welding requires perfection.
The Pain Point: Variations in wall thickness or ovality at the weld ends cause the tungsten electrode to maintain a constant arc gap on one side while grounding out or losing penetration on the other.
Our Solution: We machine the tangent ends (the straight section before the curve) to ensure perfect circularity and squareness. This guarantees a consistent weld bead profile, critical for passing borescope inspections in pharmaceutical loops.
Surface Integrity & Passivation Cold forming creates stress in the crystalline structure of stainless steel, which can reduce corrosion resistance.
The Pain Point: Micro-cracks or “orange peel” surfaces inside the bend become nucleation sites for pitting corrosion and bacterial biofilm.
Our Solution: All our elbows undergo solution annealing after forming, followed by pickling or electropolishing. This restores the passive oxide layer and ensures the internal roughness (Ra) meets hygienic limits throughout the entire curve, not just the straight ends.
Flow Dynamics (Long Radius)
The Benefit: Our standard Long Radius (1.5 x Diameter) design minimizes pressure drop compared to short-radius steam fittings. This gentler sweep reduces fluid shear, which is critical when transporting shear-sensitive media like cell cultures or dairy proteins.
Note: The dimensions below apply to DIN 11852 Series 2 (Metric). Please verify against the “Tube OD” of your existing system.
| DN Size | Tube OD x Wall (mm) | Center-to-Face Dimension (90°) | Center-to-Face Dimension (45°) |
| DN 10 | 13.0 x 1.5 | 26 mm | 13 mm |
| DN 15 | 19.0 x 1.5 | 35 mm | 17 mm |
| DN 20 | 23.0 x 1.5 | 40 mm | 20 mm |
| DN 25 | 29.0 x 1.5 | 50 mm | 25 mm |
| DN 40 | 41.0 x 1.5 | 60 mm | 30 mm |
| DN 50 | 53.0 x 1.5 | 70 mm | 35 mm |
| DN 65 | 70.0 x 2.0 | 80 mm | 40 mm |
Welding Best Practices for Sanitary Elbows
Preparation (Facing): Even with high-quality fittings, always face the tube ends. The gap between the elbow and the tube should be 0.0mm (Zero gap) for autogenous orbital welding.
Purge Gas (Back-gassing): Oxygen inside the tube ruins the weld (sugaring/oxidation).
Purge the line with 99.999% Argon until oxygen levels are < 10 ppm before striking the arc.
Maintain purge pressure until the weld has cooled below 150°C.
Tacking: If manual tacking is required, use minimal heat input to avoid disturbing the orbital weld path. Ideally, use an orbital clamp with alignment blocks.
Heat Input: 316L requires controlled heat input to prevent the precipitation of chromium carbides (sensitization). Ensure the amperage program is dialed in for the specific wall thickness (e.g., 40A for 1.65mm wall is a baseline reference only).
Post-Weld Cleaning: Mechanical polishing or chemical passivation is mandatory on the heat-affected zone (HAZ) to remove discoloration and restore the passive layer.
Related Products
FAQ
What is the difference between 3A and DIN 11852 weld elbows?
The primary difference is the Tube Outside Diameter (OD) and Wall Thickness. A 3A 1.5″ elbow has an OD of 38.1mm, whereas a DIN DN40 elbow typically has an OD of 41mm (Series 2) or 40mm (Series 1). They are not compatible; mixing them causes “steps” in the flow path that fail hygienic inspection.
When should I use a 45-degree elbow instead of a 90-degree elbow?
Use 45-degree elbows to minimize pressure loss and flow turbulence. A 90-degree turn creates significant fluid impact forces and head loss. Two 45-degree elbows separated by a straight pipe run create a smoother flow profile than a single hard 90-degree turn, which is beneficial for viscous liquids.
What does "Tangents" mean on a sanitary weld elbow?
Tangents are the straight sections of pipe extending from the ends of the curved radius. These straight extensions are crucial for orbital welding heads, allowing the clamp to grip the fitting without interfering with the arc, and providing material for future re-welding if a repair is needed.
Why is 316L required for sanitary elbows instead of 304?
316L contains Molybdenum, which provides superior resistance to chloride-induced pitting (common in salted food products) and withstands harsh Clean-in-Place (CIP) chemicals like sodium hydroxide and nitric acid better than 304 stainless steel.
What surface finish (Ra) is required for food grade elbows?
For general food and dairy (3A standard), a maximum roughness average (Ra) of 32μin (0.8μm) is required. For pharmaceutical applications (ASME BPE), finer finishes like 20μin (0.5μm) or 15μin (0.38μm) with electropolishing are standard to ensure sterility.