🔩 Metallic tubes of circular cross-section — flattening test between parallel platens to the distance H from the product standard (or close flattening), assessment of cracks visible to the naked eye; PN-EN ISO 8492

Materials and NDT PN-EN ISO 8492

Overview

WHAT THE STANDARD COVERS. ISO 8492:2013 (clause 1) specifies a method for determining the ability of metallic tubes of circular cross-section to undergo plastic deformation by flattening; the test can also be used to reveal defects in tubes. The standard covers tubes with an outside diameter of not more than 600 mm and a wall thickness of not more than 15 % of the outside diameter; a more precise range of diameters or thicknesses may be given in the product standard. Symbols (Table 1): a — wall thickness (in standards for steel tubes also T), b — inside width of the flattened test piece, D — outside diameter, H — distance between the platens measured under load, L — length of the test piece. The "Scope" field of the PKN card of PN-EN ISO 8492:2014-02 (English version, scope description in Polish): "This International Standard specifies a method for determining the ability of metallic tubes of circular cross-section to undergo plastic deformation during flattening. It can also be used to reveal defects in tubes. This International Standard applies to tubes with an outside diameter not greater than 600 mm and a wall thickness not greater than 15 % of the outside diameter" (our translation).

PRINCIPLE AND APPARATUS (clauses 3–4). The end of a tube or a test piece of specified length, cut perpendicular to the tube axis, is flattened until the distance between the platens, measured under load in the direction of flattening, reaches the value given in the product standard (Figure 1 a and b). In close flattening, the inside surfaces of the test piece shall be in contact over at least half of the inside width b of the flattened test piece (Figure 1 c). The machine shall flatten the test piece to the required distance H between two flat, parallel, rigid platens; the width of the platens exceeds the width of the flattened test piece, i.e. at least 1.6 D, and the length of the platens covers the whole length of the test piece.

TEST PIECE AND PROCEDURE (clauses 5–6). Length of the test piece: at least 10 mm and not more than 100 mm; the edges may be rounded with a file or chamfered (note: unrounded edges are acceptable if the result meets the requirements). For a test at the end of a full-length tube, the tube is cut perpendicular to its axis to a depth of at least 80 % of the outside diameter, at a distance from the end equal to the length of the test piece. The test is normally carried out at an ambient temperature of 10–35 °C, under controlled conditions at 23 °C ± 5 °C. The test piece is placed between the platens, the weld of welded tubes is positioned as required by the product standard, and it is flattened by moving the platens perpendicular to the tube axis; in case of dispute, the platen speed shall not exceed 25 mm/min. The result is assessed according to the product standard; if no requirements are given, the test piece passes the test when no cracks are visible without magnifying aids, and slight cracks at the edges are not a reason for rejection. A report is prepared when required by the product standard (clause 7).

EDITIONS. The third edition ISO 8492:2013 (ISO/TC 164/SC 2) replaced ISO 8492:1998 as a minor revision; EN ISO 8492:2013 was adopted without modification and replaced EN ISO 8492:2004 (conflicting national standards to be withdrawn by May 2014). In the iTeh catalogue (read on 27.10.2026) ISO 8492:2013 has the status "Published" and the stage "9060 – Close of review", and EN ISO 8492:2013 — "Published".

STATUS (PKN card as of 27.10.2026). The card of PN-EN ISO 8492:2014-02 (English version) has no withdrawal label: publication 24-02-2014, 14 pages, Metallurgy Sector, KT 123 Testing of Properties of Metals, "Adopts: EN ISO 8492:2013 [IDT], ISO 8492:2013 [IDT]", "Replaces: PN-EN ISO 8492:2005 - Polish version", ICS 77.040.10. PKN search, search term "ISO 8492" (27.10.2026): PN-EN ISO 8492:2005 (English and Polish versions) is withdrawn, and there is no Polish version of the 2014 edition in the results — the current standard is available only in English.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database refreshed from the production server on 27.10.2026 and current PCA documents downloaded on that day). Number 8492 appears in 7 records at 6 Polish laboratories: AB 001 (two entries), AB 024, AB 128, AB 193, AB 490, AB 1869. In all 6 current PCA documents the standard is in the same 7 rows; no entry is suspended. Forms: "PN-EN ISO 8492:2014-02" (AB 001, AB 193, AB 490, AB 1869), "PN-EN ISO 8492:2014" (AB 024), "PN-EN ISO 8492" (AB 128). AB 001 has five tube test standards at once in both entries: PN-EN ISO 8491 (bend), 8492 (flattening), 8493 (drift expanding), 8495 (ring expanding) and 8496 (ring tensile), with load ranges of 0.02 N–400 kN and 0.02 N–600 kN. The "Laboratories" tab ("PN-EN ISO 8492") shows 16 laboratories: these 6 Polish ones and 10 Czech ones (tab query on labcoda.pl, 27.10.2026).

WHAT THE LABORATORIES TEST (database copy and PCA documents). Tubes of metals and alloys (AB 001), metallic tubes of full circular cross-section (AB 128, "ability to undergo plastic deformation", flattening method), metallic tubes of circular cross-section (AB 490), tubes (AB 193 — with the scope copied from the standard: diameter up to 600 mm, thickness not more than 15 % of the outside diameter; AB 1869), tubes among metal products (AB 024).

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. First — H is the distance between the platens measured under load (Table 1, clause 3); a measurement after the force has been removed is not a measurement of H. Second — close flattening requires contact of the inside surfaces over at least half of the width b, not only at one point. Third — weld: welded tubes are positioned with the weld where the product standard requires (point 6.3); a different position tests a different part of the tube. Fourth — assessment: without requirements in the product standard, the criterion is no cracks visible to the naked eye, and slight cracks at the edges of the test piece do not count. Fifth — scope of the standard: tubes with a diameter above 600 mm or with a wall thicker than 15 % of the diameter lie outside it. Sixth — speed: in case of dispute at most 25 mm/min.

WHAT WE DO NOT GIVE. We read the text of ISO 8492:2013 up to the beginning of clause 7 (report — when required by the product standard); we do not give the list of report items. The values of H for specific tubes are given in product standards.

Method principle

The end of a tube or a length of 10–100 mm, cut perpendicular to the axis, is flattened between two flat, parallel, rigid platens with a width of at least 1.6 D, by a movement perpendicular to the tube axis, until the distance between the platens under load reaches the value H from the product standard; in close flattening the inside surfaces are in contact over at least half of the width b. Assessment: no cracks visible to the naked eye, unless otherwise specified in the product standard (ISO 8492:2013, clauses 3–6).

Applications

• Metallic tubes of circular cross-section, outside diameter ≤ 600 mm, wall thickness ≤ 15 % of the diameter (ISO 8492:2013, clause 1)
• Testing the ability to undergo plastic deformation and revealing defects of tubes, including welded ones (weld in the position from the product standard)
• In accreditation scopes: 6 Polish laboratories — tubes of metals and alloys, tubes of circular cross-section

Key parameters

Standard

Standard number

PN-EN ISO 8492:2014-02 (wersja angielska; wprowadza EN ISO 8492:2013 i ISO 8492:2013 [IDT])

Title (PL)

Metale — Rury — Próba spłaszczania

Title (EN)

Metallic materials — Tube — Flattening test

Step-by-step procedure

1. Test piece

   Length of 10–100 mm cut perpendicular to the axis or tube end cut to a depth ≥ 80 % D; the edges may be rounded or chamfered (clause 5).

2. Positioning

   Test piece between the platens; weld of a welded tube in the position from the product standard; temperature 10–35 °C or 23 °C ± 5 °C (points 6.1–6.3).

3. Flattening

   Movement of the platens perpendicular to the tube axis to the distance H under load (or to close flattening); in case of dispute ≤ 25 mm/min (points 6.4–6.5).

4. Assessment

   According to the product standard; without requirements — the test piece passes when there are no cracks visible to the naked eye; slight edge cracks do not disqualify (point 6.6).

5. Report

   When required by the product standard (clause 7). PN-EN ISO 8492:2014-02 — current (PKN card as of 27.10.2026; English version).

Required equipment and apparatus

Health and safety (OHS)

• TECHNICAL NOTE: the distance H is measured under load (Table 1)
• TECHNICAL NOTE: slight cracks at the edges of the test piece are not a reason for rejection (point 6.6)

Frequently asked questions