Application Engineering
Conveyor Belt Cover Grade Selection Guide: DIN 22102 & ISO 10247
Engineering guide to conveyor belt cover grade selection: DIN 22102 W/X/Y/Z, heat-resistant T1-T4, oil-resistant MOR/OR, and flame-resistant grades.
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- Application Engineering
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- conveyor beltcover gradeDIN 22102abrasionheat-resistantoil-resistantflame-resistant
- Keywords
- conveyor belt cover grade selection / DIN 22102 W X Y Z / heat-resistant conveyor belt T1 T2 T3 T4 / Nanjing Yuhang Rubber
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- Rubber FenderRubber TrackRubber SheetRubber HoseRubber ExtrusionCustom Rubber Parts
Industrial rubber product manufacturer covering rubber fenders, rubber tracks, rubber sheets, rubber hoses, extrusions, belts and custom molded rubber parts.
1. Why Cover Grade Selection Matters
The cover compound of a conveyor belt is the thin outer layer (typically 1.5–12 mm per side) that directly contacts the conveyed material. It constitutes only 20–30% of the belt's total mass but determines 80% of its service life. Selecting the wrong cover grade leads to:
- • Premature wear: Soft covers abraded by sharp aggregate
- • Thermal failure: Standard covers hardening and cracking under hot materials (cement clinker at 200°C)
- • Swelling failure: Oil-sensitive covers ballooning when conveying oil-contaminated scrap
- • Flame propagation: Non-flame-resistant covers in underground mines
The two principal international standards governing conveyor belt cover grades are:
- • DIN 22102 / ISO 10247 — general-purpose and abrasion-resistant covers (W, X, Y, Z)
- • ISO 4195 — heat-resistant covers (T1, T2, T3, T4)
- • ISO 22721 / EN 14973 — underground mine belts (fire safety)
2. Standard Cover Grades: DIN 22102 / ISO 10247
| Grade | Abrasion Limit (mm³) | Tensile Strength (MPa, min) | Elongation (%) | Base Polymer | Typical Applications |
|---|---|---|---|---|---|
| W | ≤90 | ≥18 | ≥400 | SBR or SBR/BR blend | Highly abrasive materials: granite, quartz, sinter, iron ore |
| X | ≤120 | ≥25 | ≥450 | NR or NR/SBR blend | General bulk: coal, sand, gravel, grain, wood chips |
| Y | ≤150 | ≥20 | ≥400 | NR or SBR | Moderately abrasive: cement, limestone, fertilizers |
| Z | ≤200 | ≥15 | ≥350 | NR or SBR (economy formulation) | Light-duty: packaged goods, agricultural products |
Key insight regarding abrasion testing: The DIN 53516 / ISO 4649 abrasion test uses a rotating drum method with a specified abrasive paper and 10 N load. The result (volume loss in mm³) is inversely proportional to wear resistance. Note that laboratory abrasion tests are indicative, not absolute predictors — the real-world wear mechanism (cutting, gouging, fatigue) may differ from the test's abrasive mechanism.
Cover Compound Recipes (Reference)
| Grade | Base Polymer | Carbon Black (phr) | Plasticizer (phr) | Antioxidant System |
|---|---|---|---|---|
| W | SBR 1500 + BR | 50–70 (N220/N330) | 5–10 (aromatic) | TMQ + 6PPD + wax |
| X | NR (RSS3) + SBR 1500 (70/30) | 40–55 (N330) | 3–8 (aromatic) | TMQ + 6PPD + wax |
| Y | NR (RSS3) | 35–45 (N330) | 5–8 (aromatic) | TMQ + 6PPD |
| Z | NR/SBR | 30–40 (N550) | 8–15 (aromatic) | TMQ |
3. Heat-Resistant Cover Grades: T1 to T4 (ISO 4195)
Heat-resistant belts convey materials at temperatures up to 400°C (material temperature, not belt temperature). The cover compound must resist thermal-oxidative aging.
| Grade | Max Continuous Material Temp (°C) | Max Peak Material Temp (°C) | Base Polymer | Key Features |
|---|---|---|---|---|
| T1 | 100 | 120 | NR/SBR with antioxidant package | Standard heat resistance; low cost |
| T2 | 125 | 150 | SBR with enhanced antioxidant | Improved aging vs T1 |
| T3 | 150 | 180 | EPDM (ethylene-propylene content 50–60%) | Excellent oxidation resistance, saturated backbone |
| T4 | 200 | 400 (peak) | EPDM or IIR (butyl) + heat stabilizers | Highest heat resistance; premium cost |
Engineering detail: The material temperature is not what the belt cover experiences. At a conveyed-material temperature of 200°C, the cover surface temperature stabilizes at approximately 120–140°C after the belt's return run (which acts as a cooling cycle). The belt carcass (the tension member) must be protected from heat — T3/T4 belts typically have a thicker top cover (8–12 mm) to act as a thermal barrier.
Heat aging test: ISO 4195 specifies accelerated aging at the grade's rated temperature for 168 h. The requirements:
| Grade | Aging Temp (°C) | Aging Time (h) | Tensile Retention (%, min) | Elongation Retention (%, min) |
|---|---|---|---|---|
| T1 | 100 | 168 | 70 | 65 |
| T2 | 125 | 168 | 70 | 65 |
| T3 | 150 | 168 | 60 | 55 |
| T4 | 175 | 168 | 50 | 45 |
4. Oil-Resistant Cover Grades
Oil-resistant belts are required when conveying materials contaminated with mineral oils, vegetable oils, or solvents — common in scrap metal recycling, biomass, and oil-sand mining.
| Grade | Oil Swell (%, max) | Base Polymer | Oil Type Resistance | Temp Range |
|---|---|---|---|---|
| MOR (Medium Oil Resistant) | 30–60% (ASTM #3 oil, 70h/100°C) | NBR (medium ACN, 28–33%) | Mineral oils, diesel, lubricating oils | -20 to +100°C |
| OR (Oil Resistant) | ≤10% (ASTM #3 oil, 70h/100°C) | NBR (high ACN, 38–42%) or CR | All mineral oils, aromatic-containing oils | -15 to +110°C (CR); -20 to +100°C (NBR) |
Polymer selection logic: NBR is the primary oil-resistant polymer for belts. The acrylonitrile (ACN) content determines the oil-swell balance: higher ACN = better oil resistance but poorer low-temperature flexibility. CR (Neoprene) is an alternative when both oil resistance AND flame resistance are required simultaneously.
5. Flame-Resistant Cover Grades (Underground Mining)
Conveyor belts in underground mines (coal, potash) must resist fire propagation. Three tiers of flame resistance exist:
| Standard | Test Method | Key Requirement | Application |
|---|---|---|---|
| ISO 340 | Single burner, 30 s flame exposure | Self-extinguishing within specified time; no glowing residues | Surface and above-ground (general flame-resistant) |
| EN 14973 C2 / ISO 22721 | Mid-scale gallery test; propane burner 50 kW, 15 min | Limited flame spread; limited afterflame time; temperature rise limits | Underground (EU, international) |
| MSHA 30 CFR Part 14 (USA) | Belt-flame test in full-scale gallery | Strict flame propagation limits | U.S. underground coal mines |
The flame-resistant cover compound typically uses CR (chloroprene) as the base polymer (chlorine content ~40% provides intrinsic flame retardance) plus antimony trioxide (Sb₂O₃) and aluminum trihydrate (ATH) as synergists.
| Flame-Resistant Compound | Base Polymer | LOI (%) | Passes |
|---|---|---|---|
| Standard FR | CR (chloroprene) | 32–38 | ISO 340 |
| Enhanced FR | CR/CSM blend | 38–45 | EN 14973 C2 |
| Premium FR | CR + Sb₂O₃ + ATH | >45 | MSHA 30 CFR Part 14 |
6. Cover Grade Selection Decision Tree
Use the following seven-factor framework to select the appropriate cover grade:
- Abrasiveness of conveyed material: Hard, sharp, angular (granite, sinter) → Grade W. Soft or rounded (grain, wood) → Grade X or Y.
- Material temperature: Ambient → standard W/X/Y/Z. >100°C → T1-T4 heat-resistant grades.
- Oil/grease contamination: Present → MOR or OR grade. Absent → standard grade.
- Flame risk: Underground mine or enclosed conveyor → ISO 340 / EN 14973 flame-resistant CR compound.
- Chemical exposure: Acidic or alkaline materials → check chemical resistance of the base polymer.
- Cut and gouge resistance: Large lump size, high drop height → use NR-based cover (tear-resistant), thicker cover layers.
- Economic life: Initial price + replacement downtime cost vs. premium cover grade cost. A Grade W cover may cost 20% more than Grade X but can deliver 60% longer service life in abrasive conditions.
7. Cover Thickness Selection
| Material Type | Recommended Top Cover (mm) | Recommended Bottom Cover (mm) |
|---|---|---|
| Fine, non-abrasive (grain, flour) | 1.5–3.0 | 1.5 |
| Granular, moderate abrasion (sand, gravel) | 3.0–6.0 | 1.5–3.0 |
| Lumpy, high abrasion (iron ore, granite) | 6.0–10.0 | 3.0–5.0 |
| Hot material (cement clinker, sinter) | 8.0–12.0 | 3.0–5.0 |
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Nanjing Yuhang Rubber Co., Ltd. manufactures the full range of DIN 22102 conveyor belts in grades W, X, Y, and Z, plus heat-resistant T1–T4, oil-resistant MOR/OR, and flame-resistant belts for underground mining. Our in-house testing laboratory verifies every production batch to ISO 4649 (abrasion), ISO 37 (tensile), and ISO 340 (flame) standards. Serving over 75 countries from our factory in Nanjing, China.
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FAQ
Can this article be used as the final selection basis?
It is intended for preliminary technical review. Final material or product selection should be confirmed with the actual medium, temperature, load, dimensions, drawings and sample testing when needed.
What information should be provided for an inquiry?
Please provide the application equipment, working medium, temperature range, dimensions, quantity, drawing or sample information so the technical discussion can be organized faster.