🔩 Metallic tubes of circular cross-section — drift-expanding test of the tube end with a conical mandrel (angle 30°, 45° or 60°) to the outside diameter Du or the diameter increase from the product standard; PN-EN ISO 8493

Materials and NDT PN-EN ISO 8493

Overview

WHAT THE STANDARD COVERS. ISO 8493:1998 (clause 1) specifies a method for determining the ability of metallic tubes of circular cross-section to undergo plastic deformation by expanding with a mandrel. It is intended for tubes with an outside diameter of not more than 150 mm (100 mm for light metals) and a wall thickness of not more than 10 mm, although the range of diameters or thicknesses may be specified more precisely by the product standard. Symbols (Table 1): a — wall thickness (in standards for steel tubes also T), D — original outside diameter, Du — largest outside diameter after the test, L — length of the test piece before the test, β — angle of the conical mandrel. The "Scope" field of the PKN card of PN-EN ISO 8493:2005 (Polish version): "A method is given for determining the ability of metallic tubes of circular cross-section to undergo plastic deformation during expanding with a mandrel. It applies to tubes with an outside diameter not exceeding 150 mm (100 mm for light metals) and a wall thickness not greater than 10 mm" (our translation).

PRINCIPLE, APPARATUS, TEST PIECE (clauses 3–5). The end of a test piece cut from the tube is expanded with a conical mandrel until the largest outside diameter of the expanded tube reaches the value from the product standard. Apparatus: a press with adjustable speed or a universal testing machine and a conical mandrel with the angle from the product standard, of polished material of sufficient hardness; the recommended angles are 30°, 45° and 60°. The length of the test piece depends on the angle: for an angle up to and including 30° L ≈ 2 D, for an angle greater than 30° L ≈ 1.5 D; the test piece may be shorter if a cylindrical part with a length of at least 0.5 D remains after expanding. Both ends of the test piece lie in a plane perpendicular to the tube axis, the edge of the tested end may be rounded with a file or chamfered (unrounded edges are acceptable if the result meets the requirements), and in welded tubes the internal weld bead may be removed.

PROCEDURE (clauses 6–7). The test is normally carried out at an ambient temperature of 10–35 °C, under controlled conditions at 23 °C ± 5 °C. The mandrel is forced into the test piece without shock until the required outside diameter is obtained, with the mandrel axis coinciding with the tube axis. The largest outside diameter Du or the diameter increase as a percentage of the original diameter D is given in the product standard (which may also give the angle β). For longitudinally welded tubes the mandrel may have a groove for the internal weld bead. The mandrel may be lubricated; it shall not rotate relative to the test piece. In case of dispute, the forcing speed shall not exceed 50 mm/min. The result is assessed according to the product standard; without requirements, the test piece passes when no cracks are visible without magnifying aids, and slight cracks at the edges are not a reason for rejection. Report (when required by the product standard): reference to ISO 8493, identification and dimensions of the test piece, Du or diameter increase in per cent, mandrel angle, result.

EDITIONS. The second edition ISO 8493:1998 (ISO/TC 164/SC 2) replaced ISO 8493:1986 as a technical revision. In the iTeh catalogue (read on 27.10.2026) ISO 8493:1998 has the status "Published" and the stage "9060 – Close of review", and EN ISO 8493:2004 — "Published" (stage "9093 – Decision to confirm").

STATUS (PKN card as of 27.10.2026). The card of PN-EN ISO 8493:2005 (Polish version) has no withdrawal label: publication 16-12-2005, 7 pages, Metallurgy Sector, KT 123 Testing of Properties of Metals, "Adopts: EN ISO 8493:2004 [IDT], ISO 8493:1998 [IDT]", "Replaces: PN-EN ISO 8493:2005 - English version", ICS 77.040.10. PKN search, search term "ISO 8493" (27.10.2026): the English version PN-EN ISO 8493:2005 is withdrawn and replaced by the Polish version.

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 8493 appears in 6 records at 5 Polish laboratories: AB 001 (two entries together with four other tube test standards: PN-EN ISO 8491, 8492, 8495 and 8496), AB 024, AB 128, AB 193, AB 490. In all 5 current PCA documents the standard is in the same 6 rows; no entry is suspended. Forms: "PN-EN ISO 8493:2005" (AB 001, AB 024, AB 193, AB 490) and "PN-EN ISO 8493" (AB 128). The "Laboratories" tab ("PN-EN ISO 8493") shows 13 laboratories: these 5 Polish ones and 8 Czech ones (tab query on labcoda.pl, 27.10.2026). The same laboratories have in their scopes the flattening test according to PN-EN ISO 8492 (separate entry of this database).

WHAT THE LABORATORIES TEST (database copy and PCA documents). Tubes of metals and alloys (AB 001, load ranges 0.02 N–400 kN and 0.02 N–600 kN), tubes with a diameter below 100 mm among metal products (AB 024), metallic tubes of full circular cross-section (AB 128, expanding method), tubes of circular cross-section (AB 490), tubes — with the scope copied from the standard: outside diameter up to 150 mm (100 mm for light metals), wall up to 10 mm (AB 193, "expanding with a mandrel").

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. First — the mandrel angle and the length of the test piece are linked: for an angle up to 30° L ≈ 2 D, for a larger one L ≈ 1.5 D, and a shorter test piece is acceptable only if a cylindrical part with a length of at least 0.5 D remains after expanding (point 5.1). Second — the mandrel shall not rotate relative to the test piece, and its axis must coincide with the tube axis. Third — criterion: Du (absolute diameter) or the increase as a percentage of D — the report gives what the product standard requires, together with the mandrel angle. Fourth — welded tubes: the internal weld bead may be removed (point 5.3) or, for longitudinally welded tubes, a grooved mandrel may be used (point 6.2) — the report should say what was done. Fifth — scope of the standard: tubes over 150 mm (over 100 mm of light metals) and with a wall over 10 mm lie outside the scope, unless otherwise specified in the product standard. Sixth — in case of dispute the forcing speed is at most 50 mm/min.

WHAT WE DO NOT GIVE. We read the full text of ISO 8493:1998 (3 pages). The values of Du, the diameter increase and the mandrel angle for specific tubes are given in product standards.

Method principle

A polished conical mandrel with the angle from the product standard (recommended 30°, 45°, 60°) is forced without shock, coaxially and without rotation, into the end of a tube length with L ≈ 2 D (mandrel angle up to 30°) or L ≈ 1.5 D (larger angle), until the largest outside diameter of the expanded part reaches Du or the percentage increase of D from the product standard. Assessment: no cracks visible to the naked eye, unless otherwise specified in the product standard (ISO 8493:1998, clauses 3–6).

Applications

• Metallic tubes of circular cross-section, outside diameter ≤ 150 mm (≤ 100 mm for light metals), wall ≤ 10 mm (ISO 8493:1998, clause 1)
• Testing the ability to undergo plastic deformation during expanding, also of longitudinally welded tubes (mandrel with a groove for the bead)
• In accreditation scopes: 5 Polish laboratories — tubes of metals and alloys, tubes of circular cross-section

Key parameters

Standard

Standard number

PN-EN ISO 8493:2005 (wersja polska; wprowadza EN ISO 8493:2004 i ISO 8493:1998 [IDT])

Title (PL)

Metale — Rury — Próba roztłaczania

Title (EN)

Metallic materials — Tube — Drift-expanding test

Step-by-step procedure

1. Test piece

   Length L ≈ 2 D (angle ≤ 30°) or ≈ 1.5 D (angle > 30°), ends perpendicular to the axis; the edge may be rounded or chamfered; the internal weld bead may be removed (clause 5).

2. Conditions

   Temperature 10–35 °C or 23 °C ± 5 °C; mandrel with the angle from the product standard, possibly lubricated (points 6.1, 6.3).

3. Expanding

   Forcing in the mandrel without shock, coaxially and without rotation relative to the test piece, to Du or the diameter increase from the product standard; in case of dispute ≤ 50 mm/min (points 6.2–6.4).

4. Assessment

   According to the product standard; without requirements — no cracks visible to the naked eye, slight edge cracks do not disqualify (point 6.5).

5. Report

   ISO 8493, identification and dimensions of the test piece, Du or increase in %, mandrel angle, result (clause 7). PN-EN ISO 8493:2005 — current (PKN card as of 27.10.2026).

Required equipment and apparatus

Health and safety (OHS)

• TECHNICAL NOTE: the mandrel shall not rotate relative to the test piece, and its axis must coincide with the tube axis (points 6.2–6.3)
• TECHNICAL NOTE: after expanding, a cylindrical part of the test piece with a length of at least 0.5 D must remain (point 5.1)

Frequently asked questions