What EN 10216-2 Covers
EN 10216 is the European standard that sets technical delivery conditions for seamless steel tubes used for pressure purposes. It is published in five parts, and EN 10216-2 is the part that applies to seamless tubes made from non-alloy and alloy steels with specified properties at elevated temperature. Tubes ordered to this part are intended for service inside the creep range of the selected grade, which makes the specification the normal choice for steam lines, hot water circuits and high-temperature process piping in power plants, refineries and chemical works.
Because EN 10216-2 is a harmonised standard under the Pressure Equipment Directive 2014/68/EU, a tube that conforms to it is presumed to satisfy the essential safety requirements of that directive. This is why European fabricators place the standard number, the part number and the steel grade directly on the purchase order instead of describing the material only by a yield strength figure. The same structure also makes the standard easy to audit: every part lists its own grades, chemical limits, mechanical values, delivery condition and inspection regime.
Steel Grades and Chemical Composition
Seven grades are specified in EN 10216-2. The three non-alloy grades P195GH, P235GH and P265GH carry the majority of general high-temperature piping work, while 16Mo3, 14MoV6-3, 13CrMo4-5 and 10CrMo9-10 add molybdenum and chromium for higher creep strength and better resistance to steam oxidation.
| Grade | C max, % | Si max, % | Mn, % | P max, % | S max, % | Cr, % | Mo, % |
|---|---|---|---|---|---|---|---|
| P195GH | 0.13 | 0.35 | 0.70 max | 0.025 | 0.020 | 0.30 max | 0.08 max |
| P235GH | 0.16 | 0.35 | 1.20 max | 0.025 | 0.020 | 0.30 max | 0.08 max |
| P265GH | 0.20 | 0.40 | 1.40 max | 0.025 | 0.020 | 0.30 max | 0.08 max |
| 16Mo3 | 0.12-0.20 | 0.35 max | 0.40-0.70 | 0.025 | 0.020 | 0.30 max | 0.25-0.35 |
| 14MoV6-3 | 0.10-0.15 | 0.15-0.35 | 0.40-0.70 | 0.025 | 0.020 | 0.30-0.60 | 0.50-0.70 |
| 13CrMo4-5 | 0.15 max | 0.50-1.00 | 0.30-0.60 | 0.025 | 0.020 | 1.00-1.50 | 0.45-0.65 |
| 10CrMo9-10 | 0.10-0.17 | 0.35 max | 0.40-0.70 | 0.025 | 0.020 | 0.70-1.15 | 0.40-0.60 |
Residual elements are capped as well: nickel, copper and molybdenum plus nickel and copper are limited so that an unintended alloying effect cannot push a tube outside the weldability and toughness envelope assumed by the standard. A minimum aluminium content applies to the fully killed non-alloy grades, which keeps the steel fine grained and protects low-temperature impact behaviour.
Room Temperature Mechanical Properties
Values below are taken from the room temperature tensile test requirements. Yield strength is quoted for wall thickness up to 16 mm, 16 to 40 mm and 40 to 60 mm, because heavier walls are tested on a specimen whose section reduces the apparent yield value.
| Grade | ReH min, t ≤ 16 mm, MPa | ReH min, 16 < t ≤ 40 mm, MPa | Tensile strength Rm, MPa | Elongation A min, % |
|---|---|---|---|---|
| P195GH | 195 | - | 320-440 | 27 |
| P235GH | 235 | 225 | 360-500 | 25 |
| P265GH | 265 | 255 | 410-570 | 23 |
| 16Mo3 | 280 | 270 | 450-600 | 22 |
| 14MoV6-3 | 320 | 320 | 460-610 | 20 |
| 13CrMo4-5 | 290 | 290 | 440-590 | 22 |
| 10CrMo9-10 | 280 | 280 | 480-630 | 22 |
Elevated temperature values for each grade and each product thickness are tabulated separately in the standard, and they are always lower than the room temperature figures shown here. Impact energy requirements of 40 J average apply to the alloy grades, measured on longitudinal specimens.
Dimensions and Tolerances
EN 10216-2 seamless tubes are produced over a wide size field, with outside diameters from 10.2 mm to 711 mm and wall thicknesses from 1.6 mm to 100 mm. The dimensional standard EN ISO 1127 and the EN ISO 4200 tables supply the preferred diameters and wall thickness series, and the tolerances below are applied to the delivered tube. Wall thickness tolerance is expressed as a percentage that depends on the ratio of wall thickness T to outside diameter D, so heavier walls in relation to diameter receive a wider percentage band than thin walls.
| Dimension | Tolerance |
|---|---|
| Outside diameter D | ±1% or ±0.5 mm, whichever is greater |
| Wall thickness, T/D ≤ 0.025 | ±12.5% or ±0.4 mm, whichever is greater |
| Wall thickness, 0.025 < T/D ≤ 0.05 | ±15% |
| Wall thickness, 0.05 < T/D ≤ 0.10 | ±12.5% |
| Wall thickness, T/D > 0.10 | ±10% |
| Inside diameter d | ±1% or ±2 mm, whichever is greater |
| Exact length L ≤ 6000 mm | 0 to +10 mm |
| Exact length 6000 < L ≤ 12000 mm | 0 to +15 mm |
For outside diameters of 355.6 mm and above, a local exceedance of the upper wall thickness limit by a further 5% of the nominal wall is permitted. This allowance exists because sizing and rounding of large diameter shells cannot hold a perfectly uniform wall around the full circumference, and the clause keeps such tubes acceptable provided the deviation stays local. Tighter values than the standard table can be agreed for a specific order, but they always raise cost and reduce mill yield.
Delivery Condition, Testing and Application
Heat treatment: tubes are delivered in +N (normalised), +NT (normalised and tempered), +Q (quenched), +QT (quenched and tempered) or +A (solution annealed) condition, chosen to suit the grade and the intended service temperature.
Hydrostatic test: mandatory, applied to every tube, with the test pressure derived from the outside diameter, wall thickness and grade of the tube.
Non-destructive testing: eddy current testing is normally specified; ultrasonic testing is added to detect longitudinal defects and magnetic flux leakage testing to detect transverse defects where higher integrity is required.
Process tests: flattening, flaring and bending tests are used to demonstrate ductility and end forming capability.
Typical end uses are superheater and reheater tubes, water wall tubes and main steam piping in boilers, heat exchanger and furnace tubes in petrochemical service, and high-temperature transfer lines in process plants. Compared with the welded equivalent covered by EN 10217, the seamless product removes the longitudinal weld as a potential weak point, and EN 10216-2 grades such as 13CrMo4-5 and P235GH sit broadly alongside the American grades ASTM A335 P12 and ASTM A106 Gr.B, although the two systems differ in testing and acceptance detail and should not be treated as interchangeable without review.
FAQ
Q: What is the difference between EN 10216-1 and EN 10216-2?
Part 1 covers non-alloy seamless tubes with specified room temperature properties, while Part 2 covers non-alloy and alloy tubes with specified properties at elevated temperature for service in the creep range.
Q: Which outside diameter range is available in EN 10216-2?
Seamless tubes are normally supplied from 10.2 mm up to 711 mm outside diameter, with wall thickness from 1.6 mm to 100 mm, subject to the capability of the individual mill.
Q: How is wall thickness tolerance determined?
It is selected from the T/D ratio bands in the standard table, ranging from ±12.5% or ±0.4 mm for thin walls up to ±10% for heavy walls where T/D exceeds 0.10.
Q: Is a hydrostatic test mandatory for every tube?
Yes. Each tube must pass a hydrostatic test before delivery unless a non-destructive test is agreed as an alternative under the conditions defined in the standard.
Q: Can EN 10216-2 tube be substituted directly for an ASTM A335 grade?
No. Grades such as 13CrMo4-5 are similar in composition to ASTM A335 P12, but chemical limits, tolerances and test requirements differ, so substitution requires engineering approval.
Q: What does the +N delivery condition mean?
+N indicates that the tube has been normalised, that is heated above the transformation range and air cooled, which refines the microstructure and gives a uniform ferrite-pearlite structure.