DIN 11850 and EN 10357 are the primary stainless steel standards governing hygienic tubing in food, dairy, beverage, and biotechnology processing. EN 10357 replaced DIN 11850 at the start of 2014 as the unified European standard for welded stainless steel tubes for the food and chemical industry. While both define the same metric dimensional logic for high-purity applications, EN 10357 is the active specification today, whereas DIN 11850 is officially withdrawn.
Our experience with hygienic process installations shows that DIN 11850 language still appears frequently in older project specifications and legacy supplier catalogues. Understanding the relationship between these two standards ensures that you select components with the correct wall thickness and internal surface finish—essential for maintaining structural integrity and preventing bacterial build-up in sensitive production environments.
TL;DR — key facts at a glance
- EN 10357 is the current active European standard for hygienic stainless steel tubing, having replaced DIN 11850 in 2014.
- The standard defines three tube series: A (standard), B (medium wall), and C (heavy wall) to suit different pressure requirements.
- Approved materials include stainless steel grades 304 and 316L, typically delivered with a 3.1 certificate in accordance with EN 10204.
- Internal surface finishes for the hygienic range are specified at Ra < 0.8 µm to ensure cleanability and corrosion resistance.
- UltraPure ranges for pharmaceutical use meet ASME BPE standards with internal finishes as smooth as Ra < 0.38 µm.
From DIN 11850 to EN 10357: what changed and why
The transition to EN 10357 was designed to harmonise technical requirements across Europe. The dimensional geometry of Series A and Series B remains largely identical between the two standards, ensuring that modern tubes are compatible with legacy DIN 11852 fittings and DIN 11851 unions. However, EN 10357 provides more specific surface roughness (Ra) values and introduces Series C for heavier-wall applications.
One notable difference is that EN 10357 explicitly references EN 10088 for material composition. While DIN 11850 historically provided some guidance on pressure ratings at 20 °C and 150 °C, many modern technical data sheets for hygienic fittings, such as those in the Alfa Laval range, provide specific service ratings based on connection type. For example, a 1-inch (25.4 mm) Tri-Clamp connection might have a service rating of 34.5 bar (500 psi) at 20 °C (70 °F) when using standard Buna-N gaskets.
| Parameter | DIN 11850 | EN 10357 | Key difference |
|---|---|---|---|
| Scope | Hygienic stainless steel tubing | Hygienic stainless steel tubing | EN 10357 supersedes DIN 11850 |
| Series | A, B | A, B, C | EN 10357 adds Series C |
| Dimensional basis | Metric | Metric | Largely identical |
| Material specification | DIN 11850 | EN 10357 / EN 10088 | EN 10357 references EN 10088 |
| Surface finish | Basic requirements | Detailed Ra values | EN 10357 more specific |
| Current status | Withdrawn | Active | Current European standard |
EN 10357 provides a unified European framework, consolidating dimensional standards for hygienic tubing while adding stricter specifications for surface roughness.
The three tube series: A, B, and C
Under EN 10357, tubing is categorised into three series. Choosing the correct series is critical because a mismatch in wall thickness can create internal ledges at joints, compromising the hygienic, crevice-free interiors required for CIP (clean-in-place) systems.
| Series | Standard Reference | Wall Thickness | Typical Application |
|---|---|---|---|
| Series A | DIN 11850 Series A / EN 10357 Series A | Light wall | Dairy and food processing |
| Series B | DIN 11850 Series B / EN 10357 Series B | Medium wall | Pharmaceutical and biotechnology |
| Series C | EN 10357 Series C | Heavy wall | High pressure hygienic applications |
For most standard duties, products in the Hygienic range are suitable. However, duties with extra high demands on hygiene and cleanability, such as those in the pharmaceutical industry, often turn to the UltraPure range. These components are manufactured under extra strict quality control methods, where after cold forming, the tube product is resized to ensure ovality falls within prescribed tolerances.
Dimensional data: Series A, B, and tolerances
The following tables provide the metric dimensions for Series A and Series B tubing. These dimensions are the foundation for selecting compatible bends, tees, and reducers.
| Table 2 — Series A Tubing Dimensions | ||||
|---|---|---|---|---|
| Nominal Size DN | Outside Diameter mm | Wall Thickness mm | Internal Diameter mm | Mass per Metre kg per m |
| 10 | 13 | 1 | 11 | 0.29 |
| 15 | 18 | 1 | 16 | 0.41 |
| 20 | 23 | 1.5 | 20 | 0.67 |
| 25 | 29 | 1.5 | 26 | 0.87 |
| 32 | 35 | 1.5 | 32 | 1.06 |
| 40 | 41 | 1.5 | 38 | 1.25 |
| 50 | 53 | 1.5 | 50 | 1.63 |
| 65 | 70 | 2 | 66 | 2.6 |
| 80 | 85 | 2 | 81 | 3.18 |
| 100 | 104 | 2 | 100 | 5.01 |
| Table 3 — Series B Tubing Dimensions | ||||
|---|---|---|---|---|
| Nominal Size DN | Outside Diameter mm | Wall Thickness mm | Internal Diameter mm | Mass per Metre kg per m |
| 10 | 13 | 1.5 | 10 | 0.42 |
| 15 | 18 | 1.5 | 15 | 0.6 |
| 20 | 23 | 1.5 | 20 | 0.77 |
| 25 | 29 | 1.5 | 26 | 0.97 |
| 32 | 35 | 1.5 | 32 | 1.16 |
| 40 | 41 | 1.5 | 38 | 1.35 |
| 50 | 53 | 1.5 | 50 | 1.73 |
| 65 | 70 | 2 | 66 | 2.6 |
| 80 | 85 | 2 | 81 | 3.18 |
| 100 | 104 | 2 | 100 | 5.01 |
| Table 4 — Dimensional Tolerances | ||||
|---|---|---|---|---|
| Parameter | Tolerance Class | Tolerance Value | Applicable Standard | Notes |
| Outside diameter | Normal | ±0.5 mm | DIN 11850 / EN 10357 | |
| Outside diameter | Precision | ±0.2 mm | EN 10357 | For high purity applications |
| Wall thickness | All | ±10% | DIN 11850 / EN 10357 | |
| Straightness | All | 1 mm per m | EN 10357 | |
| Length | All | 0 / +10 mm | EN 10357 | Random length |
| Length | All | ±1 mm | EN 10357 | Fixed length |
Maintaining wall thickness integrity is vital, which is why fabrication grade minimum wall tubing is used for all cold-formed tubular products.
Choosing the right series
- Identify if the application is standard food/dairy (Series A) or higher pressure/pharma (Series B/C).
- Verify nominal size (DN) against the required outside diameter to prevent connection mismatches.
- Check if the system will use orbital welding; if so, ensure the tube ends provide a machined square-cut finish.
- Consult material test reports (MTRs) for traceability, especially when using 316L stainless steel.
Approved material grades and corrosion resistance
The chemical composition of the steel is vital for both weldability and corrosion resistance. In the hygienic range, wetted steel parts are primarily available in 304, 304L, 316, and 316L. We choose 1.4404 (316L) as our standard for high-performance applications because it matches the corrosive demands of modern processes effectively.
| Table 5 — Approved Materials | ||||
|---|---|---|---|---|
| Material Grade | European Designation | Composition | Typical Application | Corrosion Resistance |
| 304 | 1.4301 | X5CrNi18-10 | General food and beverage | Good |
| 304L | 1.4307 | X2CrNi18-9 | Dairy, beverage | Improved (low carbon) |
| 316 | 1.4401 | X5CrNiMo17-12-2 | Pharma, biotech | Very good |
| 316L | 1.4404 | X2CrNiMo17-12-2 | Pharma, high purity | Excellent (low carbon) |
| 316L | 1.4435 | X2CrNiMo18-14-3 | High purity, aggressive media | Superior |
For Tri-Clover UltraPure ASME BPE weld ends, the sulphur content is strictly controlled between 0.005% and 0.017% to ensure accurate and consistent orbital weld results. This metallurgical precision allows the product to arrive to the job site in a clean orbital weld condition, ready for installation in pharmaceutical or biotechnology environments.
Surface finish requirements under EN 10357
Surface texture is a key differentiator in hygienic design. Our philosophy is to provide a uniform surface finish that meets or exceeds standard requirements such as EHEDG and 3A. Mechanical polishing is achieved by using a progressive series of abrasives, from low to high grit, allowing for economical cleaning.
- H3 designation
| Table 6 — Surface Finish Requirements | ||||
|---|---|---|---|---|
| Surface Location | Finish Type | Ra Maximum µm | Method | Applicable Standard |
| Internal | Mechanically polished | 0.8 | Polishing | EN 10357 |
| Electropolished | 0.6 | Electropolishing | EN 10357 | |
| External | Mechanically polished | 1.6 | Polishing | EN 10357 |
| External | Unpolished | 3.2 | As manufactured | EN 10357 |
| Sealing surface | Fine polished | 0.8 | Polishing | DIN 11866 / EN 10357 |
Electropolishing promotes a chromium-enriched surface layer that maximizes corrosion resistance while minimizing bacterial build-up on surface cavities. All fittings, whether mechanically or electro polished, are put through a 100% visual inspection, and surface finish is verified with a calibrated profilometer to ensure the maximum Roughness average (Ra) is never exceeded.
Electropolishing maximizes corrosion resistance and minimizes bacterial build-up, making it ideal for duties with extra high demands on hygiene.
Where DIN 11850 and EN 10357 tubing is used
These standards serve as the backbone for fluid handling in several key industries. In food and dairy processing, secure, self-aligning joints and smooth interiors are essential for C.I.P. compliance with 3A standards. Typical components include Tri-Clamp connections, which are the industry standard for simplifying design and installation.
In the biotechnology and pharmaceutical sectors, the focus shifts to the UltraPure range. These items are individually capped and bagged to preserve their clean orbital weld condition. Whether used for WFI (Water for Injection) or active ingredient transport, the combination of ASME BPE compliance and traceable heat numbers ensures process validation is straightforward.
How to specify hygienic tubing correctly
When specifying tubing for a new project, we recommend following a clear checklist to ensure component compatibility. At Alfa Laval, all products are labelled with a bar code, product information, and manufacturing date to provide optimum identification.
- Define the range: Determine if you need the Hygienic range (standard duties) or UltraPure range (high cleanliness).
- Select material: Choose between 304 or 316L based on chemical composition requirements.
- Specify finish: State the required Ra value (e.g., < 0.8 µm) and whether electropolishing is required.
- Connection type: Choose between orbitally weldable Tri-Weld ends or self-aligning Tri-Clamp connectors.
- Seal selection: Pick appropriate gasket materials such as EPDM, NBR, or PTFE based on the product and process temperature.
| Table 7 — DIN 11850 vs EN 10357 Comparison | |||
|---|---|---|---|
| Parameter | DIN 11850 | EN 10357 | Key Difference |
| Scope | Hygienic stainless steel tubing | Hygienic stainless steel tubing | EN 10357 supersedes DIN 11850 |
| Series | A, B | A, B, C | EN 10357 adds Series C |
| Dimensional basis | Metric | Metric | Largely identical |
| Material specification | DIN 11850 | EN 10357 / EN 10088 | EN 10357 references EN 10088 |
| Surface finish | Basic requirements | Detailed Ra values | EN 10357 more specific |
| Current status | Withdrawn | Active | Current active standard |
How Euroflow can help
Navigating the transition from legacy DIN references to modern EN standards requires technical expertise. Our team supports engineers and procurement specialists in selecting the exact tube series and surface specifications needed for compliant operation. Whether you are designing a high-pressure pharmaceutical line or a dairy process, we provide the technical guidance to ensure your system components match perfectly, from seal rings to orbital weld fittings.
