🔥 Flammability of conveyor belts on a laboratory scale — 200 × 25 mm test piece above a 1000 °C propane burner flame for 45 s, afterflame and afterglow time after removal of the burner and re-ignition in a 1,5 m/s air current; PN-EN ISO 340

Materials and NDT PN-EN ISO 340

Overview

WHAT THE STANDARD COVERS. ISO 340:2022 (clause 1) specifies a method for assessing, on a small scale, the reaction of a conveyor belt to an ignition flame source; it applies to conveyor belts with a textile carcass and to steel cord conveyor belts. Caution at the beginning of the standard: the method is not designed to assess the fire hazard of any given product; the results may help in the assessment of ignition hazard but should not be used in isolation as evidence that a product or material is safe. Normative references: ISO 8056-1 (thermocouple extension cables), ISO 9162 (liquefied petroleum gases — specifications), EN 12882 (general purpose conveyor belts — electrical and flammability safety requirements) and EN 14973 (belts for underground installations — electrical and flammability safety requirements). Terms (clause 3, after ISO 13943:2017): afterflame after removal of the ignition source and its time, afterglow after removal of the ignition source and cessation of flaming and its time.

REQUIREMENTS (clause 4). Afterflame after removal of the burner (4.1): the sum of the flame periods for each series of six tests shall be less than 45 s and no individual value shall be greater than 15 s. No reappearance of flame after applying the air current (4.2). Regional requirements (4.3): in the countries of the European Single Market, the requirements of 4.1 and 4.2 are replaced by the requirements of the applicable class of EN 12882 (general purpose belts) and EN 14973 (belts for underground installations).

TEST PIECES (point 5.3). Test pieces are taken at least 50 mm from the edges of the belt. Belts with a textile carcass, tested with and without covers: 12 test pieces (200 ± 5) mm × (25 ± 1) mm — three longitudinal and three transverse with covers and three longitudinal and three transverse with covers removed. Covers are removed by stripping, cutting or buffing — when buffing, care must be taken not to overheat the test piece or damage the carcass threads; they are removed on both sides, typically until the top of the fabric knuckles exposing only skim material is visible over most of the area; the knuckles must not be damaged or frayed. Where the product specification requires testing only with covers intact — six tests (three longitudinal, three transverse); belts designed without covers — six test pieces without removal of material. Steel cord belts: six longitudinal test pieces 200 ± 5 mm long and as close as possible to 25 mm wide (depending on the cord diameter and pitch), at least 20 mm, with at least two cords, cut on the centreline between adjacent cords; where the specification requires testing without covers — covers are removed on both sides so that the cords are visible.

APPARATUS AND TEST LOCATION (points 5.4–5.6). Bunsen-type gas burner with a tube of inside diameter (10 ± 0,5) mm; commercial propane according to ISO 9162; timing devices readable to 0,2 s or less; length measuring devices graduated in millimetres; test piece holder — a rectangular frame at least 520 mm high, with sides at least 75 mm apart, holding the test piece vertically at least 20 mm from the frame (of material resistant to corrosive combustion products); calibrated NiCr/NiAl thermocouple according to ISO 8056-1 or equivalent; a means of applying a current of air with normal oxygen content, relative humidity not greater than 80 % and temperature not exceeding 30 °C, at a velocity of (1,5 ± 0,1) m/s at the lower tip of the test piece. Test location: air movement at the start of the test less than 0,2 m/s, not influenced by mechanical devices during the test, sufficient volume of air so that the oxygen concentration does not drop; in an open-fronted cabinet the test piece at least 300 mm from any wall. Samples are stored flat and dry for at least 24 h before testing. Where LPG cylinders are stored in a cooler place, the gas must reach the required temperature before flow measurement — e.g. through a metal tube immersed in water at 25 °C (point 5.1.2).

PROCEDURE (point 5.7). Test atmosphere: from 10 °C to 30 °C, relative humidity from 15 % to 80 %. The test piece is mounted in the holder vertically. The burner flame is adjusted to a total height of 150–180 mm, with an inner cone of about 50 mm; the thermocouple in the hottest part of the flame (just above the inner cone) shall read 1000 °C ± 20 °C — the flame is adjusted if necessary. The burner is positioned at 45°, immediately under the central vertical axis of the test piece, with the top of the tube 50 mm below the bottom edge of the test piece. After 45 s the burner is removed without extinguishing it (sheltered from air currents if further tests follow) and the afterflame and afterglow times of the test piece are recorded. Immediately after the flame disappears, the air current at the set velocity is turned on for 1 min, measuring the afterglow time and checking whether the test piece re-ignites; the re-flame time is added to the flame time of the previous step and not included in the afterglow time.

RESULTS (point 5.8). For each test piece — whether and for how long it flamed after removal of the burner and whether and for how long it re-flamed in the air current; the maximum of the individual values; with no flame — “No flame”, with no re-ignition — “No re-flame”; the total afterflame time of each test piece (including re-ignition) and the afterglow time of each test piece; the sum of afterflame and afterglow for each set of 6 test pieces.

EDITION. The fifth edition ISO 340:2022 (2022-05; ISO/TC 41/SC 3 in collaboration with CEN/TC 188 under the Vienna Agreement) cancelled and replaced the fourth edition ISO 340:2013. Changes according to the foreword: updated references, a new terminological entry, regional requirements in clause 4, clause 5 supplemented with illustrations, clarifications and tolerances.

STATUS (PKN card as of 06.11.2026). The card of PN-EN ISO 340:2022-12 (English version) has no withdrawal label: published 06-12-2022, 20 pages, Chemistry Sector, KT 186 Rubber and Rubber Products, “Adopts: EN ISO 340:2022 [IDT], ISO 340:2022 [IDT]”, “Replaces: PN-EN ISO 340:2013-07 - English version”, ICS 13.220.40, 53.040.20; the card has no “Directive” or “Mandate” fields. The “Scope” field (in Polish): “This document specifies a method for assessing, on a small scale, the reaction of a conveyor belt to a fire source. The standard applies to belts with a textile core and to belts with steel cords.” The PN-EN ISO 340:2013-07 edition, cited next to 2022-12 at AB 005, has therefore been replaced by PN-EN ISO 340:2022-12 (we know this from the “Replaces” field of the 2022 card; we did not read the card of the 2013 edition).

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database of 02.11.2026; “Laboratories” tab on labcoda.pl, 06.11.2026). The number ISO 340 appears in 9 records at 6 Polish laboratories: AB 005 (two), AB 169, AB 665 (two), AB 710, AB 1340, AB 1552 (two). Forms: “PN-EN ISO 340:2022-12” alone (5 records; at AB 1340 “pkt.5.7 z wyłączeniem pkt.5.7.5 i pkt.5.7.6” — point 5.7 excluding points 5.7.5 and 5.7.6, at AB 169 “p. 5.3.2”), at AB 005 jointly “PN-EN ISO 340:2013-07 PN-EN ISO 340:2022-12” (two records, in one together with PN-93/C-05013 p. 2.1 and PN-98/C-05019 p. 3.1), and “PN-EN ISO 340” without year (AB 665, two records). We count the forms “ISO 340” not followed by a digit, full stop or hyphen (e.g. ISO 3405 is not counted). Outside Poland there are 2 Czech records (1004 — “ČSN EN ISO 340”; 1025 — procedure PP-03.04.02 based on ČSN EN ISO 340, CSA M422:23 and AS 1334.10). The “Laboratories” tab (“PN-EN ISO 340”, matching by family and number) shows 8 laboratories: these 6 Polish and 2 Czech ones, with the same number of items as the copy (query of the tab on labcoda.pl, 06.11.2026). We did not compare the current PCA scope documents of these laboratories with the copy.

WHAT THE LABORATORIES TEST (database copy, complete items). Conveyor belts: with a textile core — flammability, parameters “occurrence of ignition and its duration” and “occurrence of re-ignition and its duration” (AB 169, p. 5.3.2); flammability by the flame method — ignition and glowing and re-ignition and re-glowing with their duration (AB 710); burning time, flame method (AB 1552, together with PN-93-C-05013); belts and glued belt joints — burning and glowing time, flame method (AB 005 — together with PN-93/C-05013 and PN-98/C-05019; AB 665). Non-metallic materials and plastics: burning time by the flame method with a flame application time of 10 s “in accordance with PN-EN ISO/IEC 80079-38:2017-02 p. 6.2” (AB 005, AB 1552; AB 665 — with PN-EN ISO/IEC 80079-38); plastics and other non-metallic materials — “flammability – exposure time 10 s”, point 5.7 excluding points 5.7.5 and 5.7.6 (AB 1340). No item gives a measuring range.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. Sampling: a test piece closer than 50 mm to the belt edge or with a carcass damaged when removing the covers (overheating during buffing, frayed knuckles) is not a test piece according to point 5.3, although it can be tested in the same way; the number of test pieces depends on what the product specification requires — 12 for a textile belt tested with and without covers, 6 in other cases. Measurement: the flame must be checked with the thermocouple (1000 ± 20 °C) at a height of 150–180 mm, and at the start of the test the air movement must be less than 0,2 m/s, without influence of mechanical devices during the test — a result obtained under other conditions is not a result according to point 5.5. The flame application time is part of the method: the items for non-metallic materials use 10 s according to PN-EN ISO/IEC 80079-38 (and AB 1340 excludes points 5.7.5 and 5.7.6, i.e. 45 s and the air current), so the result of such a test is not a belt result according to ISO 340 and must not be compared with the criteria of 4.1–4.2. Calculation: the sum of afterflame times is calculated for a series of six tests — the re-flame time in the air current is added to the afterflame time, not to the afterglow; both components are measurements of this method (timer readable to 0,2 s). Assessment: in the European Union the criterion is a class of EN 12882 or EN 14973, not the values of 45 s and 15 s of 4.1 — a result “meets ISO 340” without the class of the product standard does not say whether the belt is fit for use. AB 005 cites both editions (2013-07 and 2022-12) — the report must state which was used, because the 2022 edition added tolerances and regional requirements.

WHAT WE DO NOT GIVE. The fragment of ISO 340:2022 we read (iTeh sample) ends at point 5.8.7; we do not give the content of the test report (clause 6) or the bibliography, and we did not read Figures 1 and 2 (burner and holder) with dimensions. We did not read the text of PN-EN ISO/IEC 80079-38 (point 6.2 — we know the 10 s only from the scope items), EN 12882 or EN 14973 — we do not give their classes or criteria. We do not give the differences between the 2013 and 2022 editions beyond the list in the foreword. The status of ISO 340:2022 at the publisher (ISO) could not be read — the ISO page was not accessible from our machine. We did not check references to the standard in legislation.

Method principle

A 200 mm × 25 mm belt test piece suspended vertically is heated for 45 s by the flame of a propane burner positioned at 45°, 50 mm below the bottom edge (flame 150–180 mm, 1000 ± 20 °C at the hottest point); after removal of the burner the afterflame and afterglow times are measured, and then an air current of 1,5 m/s is directed at the test piece for 1 min to check re-ignition; the result of a series of six tests is compared with the requirement of 4.1–4.2 or, in the European market, with the class of EN 12882 or EN 14973 (ISO 340:2022, clauses 4–5).

Applications

• Conveyor belts with a textile carcass and with steel cords — with and without covers (ISO 340:2022, clause 1, point 5.3)
• Assessment of conformity with the flammability class according to EN 12882 (general purpose belts) and EN 14973 (underground installations) — in the European Single Market (point 4.3)
• Glued belt joints (in accreditation scopes)
• In accreditation scopes also non-metallic materials and plastics — with a flame application time of 10 s according to PN-EN ISO/IEC 80079-38 (a different time than 45 s in ISO 340)
• In accreditation scopes: 6 Polish laboratories

Key parameters

Standard

Standard number

PN-EN ISO 340:2022-12 (English version; adopts EN ISO 340:2022 and ISO 340:2022 [IDT])

Title (PL)

Taśmy przenośnikowe — Charakterystyka palności w skali laboratoryjnej — Wymagania i metoda badania

Title (EN)

Conveyor belts — Laboratory scale flammability characteristics — Requirements and test method

Step-by-step procedure

1. Test pieces

   Cutting ≥ 50 mm from the edge; textile belt: 3 longitudinal and 3 transverse with and without covers (12) or 6 if the specification so requires; steel cord belt: 6 longitudinal with at least two cords; storage ≥ 24 h flat and dry (points 5.3, 5.6).

2. Flame adjustment

   Flame 150–180 mm with a cone of about 50 mm; thermocouple just above the cone — 1000 ± 20 °C; room 10–30 °C, humidity 15–80 %, air movement < 0,2 m/s (points 5.5, 5.7.1–5.7.3).

3. Flame application

   Test piece vertical in the holder; burner at 45°, under the central axis, top of the tube 50 mm below the bottom edge; after 45 s removal of the burner without extinguishing; recording of the afterflame and afterglow times (points 5.7.2, 5.7.4–5.7.5).

4. Air current

   Immediately after the flame disappears — 1 min of air current (1,5 ± 0,1) m/s; measurement of afterglow and any re-flame; re-flame is added to the afterflame time (point 5.7.6).

5. Result

   For each test piece the afterflame time (including re-flame), afterglow time, “No flame” / “No re-flame”; the maximum value; the sum of afterflame and afterglow for the series of 6 test pieces; assessment against 4.1–4.2 or the class of EN 12882 / EN 14973 (points 4, 5.8). PN-EN ISO 340:2022-12 — current (PKN card as of 06.11.2026; English version).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Burning of polymers releases smoke and toxic gases — the test station must have effective smoke extraction (point 5.1.1)
• Liquefied petroleum gas — local regulations on storage of cylinders and disposal of used containers (point 5.1.2)
• TECHNICAL NOTE: the method does not assess the fire hazard of a product — the result cannot be used in isolation as evidence of safety (caution of the standard)
• TECHNICAL NOTE: a test with a 10 s flame (items with PN-EN ISO/IEC 80079-38) is a different test from 45 s according to ISO 340

Frequently asked questions