EN 10357 standard | DIN 11850

EN 10357 | DIN 11850 - is a European standard defining the dimensions, tolerances and manufacturing conditions for stainless steel pipes and fittings used in the chemical, food and pharmaceutical industries. The standard covers both welded and seamless pipes and fittings intended for welding into pipe systems. The standard ensures that the pipes are resistant to corrosion and can operate in environments where hygiene and resistance to various substances are critical.

Main specifications

The main specifications of EN 10357 are:

Material: includes different types of stainless steel tubes, the type of steel depends on the application and environment.
Size and shape: defines various sizes and shapes including round, square, rectangular and oval with specified dimensions and tolerances.
Welding: contains welding process specifications including weld type, quality and testing.
Surface condition: determines the condition of the outer surface of the pipe without requirements for the roughness of the inner surface.
Testing and checking: describes procedures for testing mechanical properties, corrosion resistance and dimensional accuracy.
Marking and packaging: contains recommendations for the correct identification and protection of pipes during transportation.

EN 10357 replaces DIN 11850 as the standard for stainless steel pipes. This change introduces more detailed specifications, welding standards and testing procedures.

Material

According to EN 10357, the materials used for manufacturing must be:

Austenitic stainless steel: Austenitic stainless steel that contains at least 16% chromium and 6% nickel, giving it excellent corrosion resistance. It is also non-magnetic and has good formability and weldability. It is often used in food processing equipment, kitchenware, and piping. AISI 304 and AISI 316 stainless steel are commonly used types of austenitic stainless steel.
Austenitic-ferritic (duplex) stainless steel: duplex stainless steel contains approximately equal amounts of austenite and ferrite, giving it a balance of properties. It has good resistance to stress corrosion cracking, higher strength than austenitic stainless steels, and is weldable. Duplex stainless steels are used in the chemical industry, seawater desalination plants, and heat exchangers.
Ferritic stainless steel: this type contains high levels of chromium but little or no nickel. It has less corrosion resistance than austenitic stainless steel, but still better than regular steel. It is magnetic, has good formability and weldability. Ferritic stainless steel is often used in the automotive industry, architecture, and industrial equipment.

Requirements for the manufacturing process

According to EN 10357, pipes must be manufactured as follows:

The pipes must be made from cold-rolled plate, sheet or strip (stainless steel is shaped at a temperature below its recrystallization point, which provides increased strength and a smooth surface). They must be longitudinally fusion welded, i.e. the welding must run the length of the pipe.
Pipes without bright annealing or heat treatment must be pickled and passivated inside and outside. Pickling and passivating remove impurities and oxidation from the metal surface, increasing its resistance to corrosion.
The weld seam must be precisely adjusted to align it with the pipe wall and then smoothed. There should be no overlap between the weld metal and the base metal.
Ra (roughness value) should be measured along.
For tubes manufactured using the BC and BD processes, the inspection certificate must state whether the tube has been illuminated, annealed, heat treated, pickled and passivated.
The ends of the tubes must be smooth and free of burrs.

Manufacturing process and surface characteristics
Manufacturing process	Heat treatment	Surface characteristics and roughness			Symbol
Manufacturing process	Heat treatment	Inner surface	Internal weld	Outer surface and welding zone	Symbol
Made from cold rolled material	Not subject to heat treatment	Ra < 0.8 µm etched and passivated	Ra < 1.6 µm etched and passivated	Etched and passivated	CC
Made from cold rolled material	Not subject to heat treatment	Ra < 0.8 µm etched and passivated	Ra < 1.6 µm etched and passivated	Ra < 1 micron	CD
Made from cold rolled material	Heat treated	Ra < 0.8 µm etched and passivated or bright annealed	Ra < 1.6 µm etched and passivated or bright annealed	Etched and passivated or bright annealed	BC
Made from cold rolled material	Heat treated	Ra < 0.8 µm etched and passivated or bright annealed	Ra < 1.6 µm etched and passivated or bright annealed	Ra < 1 µm	BD

Ra - roughness value. This is the average distance between the peaks and valleys of a surface, which allows us to determine the overall smoothness or roughness of a surface.

Testing and inspection documents

Stainless steel pipes manufactured in accordance with EN 10357 shall be tested for compliance with the following requirements:

Testing shall be carried out for austenitic and austenitic-ferritic materials in accordance with EN 10217-7 using test categories TC1 or TC2. TC1 involves non-destructive testing and TC2 involves destructive testing of pipes.
Ferritic materials shall be tested in accordance with EN 10028-7. Tubes with an outside diameter greater than 219.1 mm shall be subjected to a transverse weld tensile test. The tensile strength shall correspond to the requirements of the base material.
Intergranular corrosion tests should be carried out according to EN 10217-7 for austenitic and austenitic-ferritic grades. For ferritic grades, the test procedure must be agreed upon.
Roughness shall be measured inside the tube, at a minimum distance of 5 mm from the end, in accordance with ISO 4288. These measurements shall be made in at least one test run for every 20 tubes in each production batch and the results shall be documented.
Measurements should be taken on both the weld bead and the base material and an inspection certificate should confirm that these measurements comply with the standards.

According to EN 10357, pipes must be manufactured and tested as follows:

In case of pipes manufactured by CD and BD methods (see table above ⇑), additional measurements of external roughness should be taken at a distance of at least 100 mm from the end of the pipe. The frequency of these measurements should match the frequency of internal.
The relevant inspection documents must be issued in accordance with EN 10204.

Marking

Each pipe must be clearly and permanently marked with the following details:

Manufacturer's name or trade mark
EN 10357 TC1 or TC2 to designate test category 1 or 2 respectively in accordance with EN 10217-7
Conventional designation of the production process (according to the table) ⇑)
The grade of steel used
Stainless steel tube dimensions
The heat number that identifies the batch of stainless steel from which the pipe is made
For TC2 pipes, an identification number (e.g. order or item number) according to EN 10217-7 that links the product or delivery unit to the associated document
Mark of the inspection representative
If there is a need for other markings or additional markings, this must be agreed upon when ordering.

Packaging and transportation

Pipes must be supplied dry. Those manufactured using the CD or BD process and ground (to smooth the surface) must be protected by polyethylene sleeves unless otherwise specified at the time of order. Packaging and shipping details must be agreed upon when placing the order.

Necessary information

At the time of ordering, the supplier must provide the following information:

Quantity (weight, length and quantity)
Reference to standard EN 10357
Designation of manufacturing process and surface characteristics
Outside diameter and wall thickness
Length of a single unit and its tolerance
Designation of steel grade according to EN 10217-7, excluding ferritic grades
The designation of steel grade according to EN 10028-7 is only intended for ferritic grades
Manufactured and tested according to EN 10217-7 TC1 / TC2

EN 10357 measurements

EN 10357 - is a European standard that came into force at the beginning of 2014. This standard defines the dimensions, tolerances, materials, surface characteristics and marking of welded stainless steel pipes. This standard applies to pipes for the food and chemical industries and is valid for all countries of the European Union.

With the introduction of EN 10357, the old standards were adopted for all series. As a result, there is now one standard with four dimensions:

Old/new standards
Standard	Old standard
EN 10357 Serie A	DIN 11850 Serie 2
EN 10357 Serie B	DIN 11850 Serie 1
EN 10357 Serie C	ISO 2037
EN 10357 Serie D	BS-4825-1, Nederlandse Zuivel, SMS 3008, 3A

Dimensions and tolerances for round cross-section pipe (mm)

Series A: dimensions and tolerances (mm)
Series A
Outside diameter of the pipe	13,0	19,0	23,0	29,0	35,0	41,0	53,0	70,0	85,0	104,0	129,0	154,0	204,0
Outside diameter tolerances	±0,10	±0,10	±0,12	±0,15	±0,18	±0,21	±0,27	±0,35	±0,43	±0,78	±0,97	±1,16	±1,53
Inner diameter (theoretical)	10	16	20	26	32	38	50	66	81	100	125	150	200
Wall thickness	1,5	1,5	1,5	1,5	1,5	1,5	1,5	2,0	2,0	2,0	2,0	2,0	2,0
Wall thickness tolerances	±0,15	±0,15	±0,15	±0,15	±0,15	±0,15	±0,15	±0,20	±0,20	±0,20	±0,20	±0,20	±0,20

Series B: dimensions and tolerances (mm)
Series B
Outside diameter of the pipe	12,0	18,0	22,0	28,0	34,0	40,0	52,0
Outside diameter tolerances	±0,10	±0,10	±0,12	±0,15	±0,18	±0,21	±0,27
Inner diameter (theoretical)	10	16	20	26	32	38	50
Wall thickness	1,0	1,0	1,0	1,0	1,0	1,0	1,0
Wall thickness tolerances	±0,10	±0,10	±0,10	±0,10	±0,10	±0,10	±0,10

Series C: dimensions and tolerances (mm)
Series C
Outside diameter of the pipe	17,2	21,3	26,9	33,7	42,4	48,3	60,3	76,1	88,9	114,3
Outside diameter tolerances	±0,10	±0,11	±0,14	±0,17	±0,21	±0,24	±0,30	±0,38	±0,44	±0,86
Inner diameter (theoretical)	14,0	18,1	23,7	29,7	38,4	44,3	56,3	72,1	84,9	110,3
Wall thickness	1,6	1,6	1,6	2,0	2,0	2,0	2,0	2,0	2,0	2,0
Wall thickness tolerances	±0,15	±0,15	±0,15	±0,20	±0,20	±0,20	±0,20	±0,20	±0,20	±0,20

Series D: dimensions and tolerances (mm)
Series D
Outside diameter of the pipe	25,0	25,4	32,0	38,0	38,1	38,1	50,8	50,8	51,0	63,5	63,5	76,1	76,1	76,1	101,6
Outside diameter tolerances	±0,13	±0,13	±0,16	±0,19	±0,19	±0,19	±0,25	±0,25	±0,25	±0,32	±0,32	±0,38	±0,38	±0,38	±0,76
Inner diameter (theoretical)	22,6	22,2	29,6	35,6	35,1	34,9	47,8	47,6	48,6	60,5	60,3	73,1	72,9	72,1	97,6
Wall thickness	1,2	1,6	1,2	1,2	1,5	1,6	1,5	1,5	1,2	1,5	1,6	1,5	1,6	2,0	2,0
Wall thickness tolerances	±0,12	±0,16	±0,12	±0,12	±0,15	±0,16	±0,15	±0,16	±0,12	±0,15	±0,16	±0,15	±0,16	±0,20	±0,20