EN 10357 Stainless Steel Sanitary Tubing

EN 10357 is a harmonized European standard that defines the technical delivery conditions for stainless steel tubes specifically intended for use in equipment for the food, chemical, and pharmaceutical industries. Its full title is “EN 10357: Flanged and butt-welded tube fittings and assemblies of austenitic and austenitic-ferritic stainless steel – General Technical Delivery Conditions.” This standard effectively consolidates and supersedes various national standards, including Germany’s influential DIN 11850, providing a unified specification for the European market and for global suppliers targeting it.

Crucially, EN 10357 mandates that the internal surface of the tube is suitable for sanitary applications. While it may not prescribe a single numerical roughness value, it requires a smooth, polished finish that is clean and free from scale, contaminants, and imperfections that could impede cleaning or foster bacterial growth. In practice, this aligns with industry expectations for a mechanically or electropolished bore. The standard also sets forth rigorous testing and inspection requirements. Tubes must undergo non-destructive testing, such as eddy current testing, to verify their integrity, and they must be supplied with specific documentation, including a mandatory 3.1 certificate of conformity, which provides full traceability of the material’s properties and origin. For engineers and fabricators building process systems for the European market, specifying tubing to EN 10357 is a fundamental step in ensuring regulatory compliance, hygienic performance, and reliable interoperability within a sanitary processing line.

Dimension of EN 10357 Sanitary Tubing

The wall thickness is relatively thin, making it suitable for low-pressure or normal-temperature applications (such as low-pressure conveying in the food and pharmaceutical industries).

Typical applications: Non-corrosive media or low-pressure scenarios

Nominal Diameter	Tube OD	Tolerances, OD	Wall Thickness	Telerances, WT	Telerances, Length	Weight
	mm	mm	mm		mm	Kg/m
DN10	12	±0.12	1.0	±10%	＋3.0	0.27
DN15	18	±0.12	1.0	±10%	＋3.0	0.42
DN20	22	±0.12	1.0	±10%	＋3.0	0.51
DN25	28	±0.12	1.0	±10%	＋3.0	0.66
DN32	34	±0.12	1.0	±10%	＋3.0	0.82
DN40	40	±0.12	1.0	±10%	＋3.0	0.97
DN50	52	±0.2	1.0	±10%	＋3.0	1.27

Medium wall thickness, combining strength and lightweight, suitable for medium pressure or general industrial applications.

Typical applications: Chemical industry, water treatment and other conventional working conditions.

Nominal Diameter	Tube OD	Tolerances, OD	Wall Thickness	Tolerances, WT	Tolerances, Length	Length
	mm	mm	mm		mm	(m)
DN10	13	±0.3	1.5	±10%	＋3.00	0.43
DN15	19	±0.3	1.5	±10%	＋3.00	0.66
DN20	23	±0.3	1.5	±10%	＋3.00	0.81
DN25	29	±0.3	1.5	±10%	＋3.00	1.03
DN32	35	±0.3	1.5	±10%	＋3.00	1.26
DN40	41	±0.3	1.5	±10%	＋3.00	1.50
DN50	53	±0.3	1.5	±10%	＋3.00	1.944
DN65	70	±0.3	2.0	±10%	＋3.00	3.43
DN80	85	±0.3	2.0	±10%	＋3.00	4.16
DN100	104	±0.3	2.0	±10%	＋3.00	5.03
DN125	129	±0.4	2.0	±10%	＋10.00	6.36
DN150	154	±0.4	2.0	±10%	＋10.00	7.612
DN200	204	±0.4	2.0	±10%	＋10.00	10.116
DN250	254	±0.4	2.0	±10%	＋20.00	12.555
DN300	304	±0.4	2.0	±10%	＋20.00	15.045

The wall thickness is relatively thick, with a higher pressure-bearing capacity, making it suitable for high-pressure, high-temperature or highly corrosive media.

Typical applications: High-pressure steam, strong acids, strong alkalis and other harsh environments.

Nominal Diameter	Tube OD	Tolerances, OD	Wall Thickness	Tolerances, WT	Tolerances, Length	Weight
	mm	mm	mm		mm	Kg/m
10	14	±0.3	2.0	±10%	+3.00	0.60
15	20	±0.3	2.0	±10%	+3.00	0.90
20	24	±0.3	2.0	±10%	+3.00	1.10
25	30	±0.3	2.0	±10%	+3.00	1.40
32	36	±0.3	2.0	±10%	+3.00	1.70
40	42	±0.3	2.0	±10%	+3.00	2.00
50	54	±0.3	2.0	±10%	+3.00	2.60

Finish Specifications

The standard mandates that the interior surface must be smooth, non-toxic, non-absorbent, and corrosion-resistant. This is primarily achieved through a mechanical polishing and electropolishing process. The result is an ultra-smooth finish that minimizes the ability for microbes and product particles to adhere, and it allows for effective cleaning and sterilization.

The most common and accepted finish is defined by a maximum Ra (Roughness Average) value. A typical Ra specification for ASTM A270 tubing is ≤ 0.38 µm (15 microinches) or better, often referred to as a “sanitary finish” or “micro-finish.” Some applications, like high-purity pharmaceutical or biotech processes, may require an even smoother finish of ≤ 0.25 µm (10 microinches).

This smooth surface is created by first mechanically abrading the tube with progressively finer abrasives to remove imperfections and weld beads. This is often followed by electropolishing, an electrochemical process that removes a thin layer of surface material. Electropolishing further smooths the surface, removes embedded contaminants, and enhances the natural passive oxide layer, which significantly improves corrosion resistance.

The primary purpose of this meticulously controlled surface is to prevent contamination, facilitate easy and effective cleaning-in-place (CIP) and sterilization-in-place (SIP) procedures, and provide superior corrosion resistance against aggressive cleaning chemicals and process fluids.

Process	RA Micro Inch	RA Micron	ISO Designation
150 grit	30-35	0.75-0.875	N6
150 grit + Electropolish	12-20	0.3-.05
180 grit	20-25	0.5-.0625
180 grit + Electropolish	10-16	0.25-0.4
240 grit	15-20	0.375-0.5	N5
240 grit + Electropolish	8-12	0.2-0.3
320 grit	8-12	0.2-0.3	N4
320 grit + Electropolish	6-12	0.15-0.3

Chemical Composition of Stainless Steel Tubing

TUBE GRADES	UNS	Cr	Ni	Mo	C	P	S	Mn	Si
TP304	S30400	18.0-20.0	8.0-11.0	–	0.08	0.045	0.03	2	1
TP304L	S30403	18.0-20.0	8.0-13.0	–	0.035	0.045	0.03	2	1
TP316	S3160	16.0-18.0	11.0-14.0	2.0-3.0	0.08	0.045	0.03	2	1
TP316L	S31603	16.0-18.0	10.0-14.0	2.0-3.0	0.035	0.045	0.03	2	1

Tensile Properties of Stainless Steel Tubing

Material	Heat Treatment	Yield Strength Ksi (MPa), Min.	Tensile Strength Ksi (MPa), Min.	Temperure Min. ℉(℃)	Elongation %, Min
ASME SA270 304	Solution	30(205)	75(515)	1900 (1040)	35
ASME SA270 304L	Solution	25(170)	70(485)	1900 (1040)	35
ASME SA270 316	Solution	30(205)	75(515)	1900(1040)	35
ASME SA270 316L	Solution	25(170)	70(485)	1900(1040)	35

Sanitary Fittings in Process Piping (Food, Pharma, Dairy, etc.)

In industrial contexts, Sanitary Fittings (or Hygienic Fittings) refer to the specialized components used to connect pipes in systems where purity and cleanliness are critical. They are designed to prevent bacterial growth, allow for complete cleaning, and ensure product integrity.

Key Idea: These are the connectors and pipes themselves, used to build a system for processing sensitive products.

Key Characteristics:
Smooth, Polished Surfaces: Internally, they have a very smooth finish (often measured in Ra micro-inches) to prevent bacteria from clinging and to allow for easy cleaning.
No Crevices or Dead Spaces: They are designed to be flush with the pipe, creating a seamless flow path so that product or cleaning fluids don’t get trapped.
Easy to Disassemble and Clean (CIP/SIP): They are designed for frequent cleaning, often using methods like Clean-in-Place (CIP) or Sterilize-in-Place (SIP).
Material: Almost exclusively made from 304 or 316L Stainless Steel for its corrosion resistance and non-reactivity.

Common Types of Sanitary Fittings:
Clamp Fittings (Tri-Clamp): The most common type, using a three-piece clamp to seal a gasket between two ferrules.

Butt Weld Fittings: Permanently welded to create a perfectly smooth, crevice-free joint. Used where disassembly isn’t needed.
Bevel Seat Fittings: An older style, similar to clamp fittings but with a different gasket and connection system.
DIN/SMS Fittings: Standards more common in Europe, using a threaded nut to compress a gasket.

Common Components:
Elbows (90°, 45°)
Tees
Reducers
Caps
Ferrule (the stub end that gets connected)

EN 10357 EN 10357 EN 10357

EN 10357 EN 10357 EN 10357 EN 10357