Overview - ISO 20238:2018 (Conveyor belts - Drum friction testing)
ISO 20238:2018 specifies a standardized laboratory method to evaluate a conveyor belt’s propensity to generate heat, glow or flame when held stationary under tension in contact with a rotating steel drum. The test simulates a stalled belt in service and records visual indications of ignition or glowing and the maximum drum surface temperature. The standard defines apparatus, test-piece size, tensioning regimes, drum speed and measurement methods for both still-air and moving-air conditions.
Key topics and technical requirements
- Test principle: A belt sample is wrapped around a rotating steel drum to simulate a stalled contact; the belt is held under specified tension until breakage, ignition or a defined time limit. Presence/absence of flame or glow is noted and drum temperature recorded.
- Apparatus:
- Steel drum: nominal external diameter (210 ± 1) mm, surface roughness Ra ≤ 1.6 µm, rotated at (200 ± 5) r/min.
- Thermocouple: mineral‑insulated sheath, tip ≤ 0.5 mm below drum surface (EN 60584-1 referenced).
- Tensioning system: capable of incremental loads as specified.
- Air supply for moving-air tests: velocity (2.0 ± 0.1) m/s at 200 mm from drum.
- Arc of contact: Two options - standard 180° or reduced 135° (reduced arc uses higher initial load and is considered equivalent when 180° cannot be achieved).
- Test methods:
- Method A (still air) options: fixed end-load (e.g., 343 N or 686 N) and increasing end-load sequences (progressive increases up to specified maximums and durations).
- Method B (moving air) parallels still-air variants with airflow applied.
- Measurements and observations: maximum drum surface temperature, visual detection of flame or glow during/after test (examined in subdued light if unbroken).
- Limitations: Conveyor belts with steel reinforcement may not meet some setup requirements; premature termination procedures (Clause 7.3) are provided.
Applications - who uses ISO 20238 and why
- Belt manufacturers: to characterize materials for fire-risk and thermal degradation under stall conditions and to support product specifications.
- Mine, quarry and bulk-handling operators: to assess belt selection and residual risk from stalled drives in conveyors where frictional heating could start fires.
- Safety engineers and specifiers: to compare belt constructions, define acceptance criteria and inform risk assessments, emergency planning and procurement.
- Test laboratories: to provide repeatable, comparable data for compliance, R&D and supplier verification.
Related standards
- ISO 7590 - steel cord conveyor belts (thickness measurements)
- ISO 9329-1 / ISO 9330-1 - tube material for drum shell
- ISO 65 - steel tube sizing (perforated pipe)
- EN 60584-1 - thermocouple specifications
Keywords: ISO 20238:2018, drum friction testing, conveyor belts, belt stall, frictional heating, ignition testing, drum temperature, arc of contact, still air test, moving air test.