In the world of bulk material transportation, few innovations have matched the durability and efficiency of the nylon conveyor belt. Often referred to as NN belt (Nylon-Nylon), this synthetic fabric-reinforced belt has transformed industries ranging from coal mining to food processing.
Unlike cotton or polyester belts, nylon offers a unique combination of high tensile strength, exceptional flexibility, and superior impact resistance. But what exactly makes nylon the preferred choice for heavy-duty applications? This comprehensive guide covers everything you need to know about nylon conveyor belts: construction, properties, advantages, and selection criteria.
What is a Nylon Conveyor Belt?
A nylon conveyor belt is a type of fabric-reinforced rubber belt where the carcass (the reinforcing layer) is made entirely of nylon fabric. Nylon, or polyamide, is a synthetic polymer known for its high strength-to-weight ratio and excellent elastic recovery.
Key Construction Facts:
- Carcass Material: 100% Nylon (Polyamide) fabric
- Cover Material: Natural rubber, nitrile rubber, or PVC (depending on application)
- Layer Structure: Multiple plies of nylon fabric bonded with rubber skim coats
- Standard Widths: 300mm to 3000mm (12″ to 120″)
- Temperature Range: -20°C to +120°C (-4°F to +248°F)
How Nylon Conveyor Belts Are Constructed
Understanding the construction helps explain why NN belts outperform other types.
1. The Carcass (Reinforcement Layer)
The carcass consists of multiple plies (layers) of nylon fabric. Each ply is coated with a thin layer of rubber (skim coat) to bond the plies together and absorb shear stress.
2. The Cover Rubber
The top and bottom covers protect the carcass from:
- Abrasion (from sharp or heavy materials)
- Impact (from falling rocks or ores)
- Chemical attack (oils, acids, or alkalis)
- Heat (in foundries or cement plants)
3. The Edge Design
- Molded edges: Rubber covers the entire width, sealing the edges from moisture.
- Cut edges: The carcass is exposed at the sides, suitable for dry, non-abrasive materials.
NN vs. EP vs. Cotton: A Quick Comparison
| Property | Nylon (NN) Belt | Polyester (EP) Belt | Cotton Belt |
|---|---|---|---|
| Tensile Strength | Very High (200-400 N/mm/ply) | High (150-300 N/mm/ply) | Low (40-80 N/mm/ply) |
| Elongation at Break | 25-35% | 12-18% | 8-12% |
| Impact Resistance | Excellent | Good | Poor |
| Water Resistance | Good (absorbs some moisture) | Excellent (hydrolysis resistant) | Poor (rots) |
| Flexibility | Excellent (ideal for small pulleys) | Moderate | Good |
| Cost | Moderate | Moderate | Low |
Key takeaway: Choose NN belt when you need impact resistance and flexibility. Choose EP belt (polyester-nylon) when moisture and minimal elongation are critical.
Key Properties of Nylon Conveyor Belts
What makes nylon stand out from other synthetic fabrics?
1. High Tensile Strength
Nylon fibers have a tensile strength of 0.6-0.9 GPa (gigapascals). This allows NN belts to handle heavy loads without stretching permanently. Typical strength ratings range from 200 N/mm to 2500 N/mm per ply.
2. Excellent Impact Resistance
The elastic nature of nylon absorbs shock from falling materials. This makes NN belts ideal for:
- Loading zones under crushers
- Quarry conveyor lines
- Mining transfer points
3. Superior Flexibility (Low Minimum Pulley Diameter)
Nylon belts can bend around smaller pulleys than polyester belts. This allows for:
- Compact conveyor designs
- Lower building height requirements
- Reduced pulley diameters (saving cost)
4. High Elasticity and Recovery
Nylon can stretch significantly under load but returns to its original length when the load is removed. This “elastic memory” reduces belt sag between idlers and improves tracking.
5. Good Cavity Resistance
The synthetic nature of nylon resists rot, mildew, and insect damage—problems common with cotton belts in humid environments.
Major Applications of Nylon Conveyor Belts
Thanks to its toughness, the NN belt is found across heavy industries.
1. Mining Industry
- Coal handling: Transporting run-of-mine coal from face to processing plant
- Iron ore: Moving abrasive, heavy ores over long distances
- Quarries: Crushed stone, sand, and gravel conveyors
2. Steel and Cement Plants
- Sinter plants: Handling hot (but not molten) materials up to 120°C
- Clinker conveyors: Transporting cement clinker from kilns to mills
- Slag handling: Moving abrasive byproducts
3. Port and Harbor Terminals
- Ship loading/unloading: Grain, coal, and mineral terminals
- Stockyard conveyors: Reclaiming material from large piles
4. Agricultural Industry
- Grain elevators: Long-distance transport of corn, wheat, and soybeans
- Fertilizer plants: Handling chemical fertilizers (with proper cover compound)
5. Manufacturing and Logistics
- Assembly lines: Automotive and appliance manufacturing
- Baggage handling: Large airport systems
- Package sorting: E-commerce fulfillment centers
Advantages of Nylon Conveyor Belts
✅ High Strength-to-Weight Ratio
Nylon belts are lighter than steel cord belts but handle similar loads. This reduces drive motor requirements and energy consumption.
✅ Excellent Troughability
The flexibility of nylon allows the belt to form a deep “trough” between idlers, increasing material capacity without widening the belt.
✅ Good Resistance to Flex Fatigue
Nylon withstands millions of flex cycles over pulleys without cracking the carcass.
✅ Cost-Effective for Medium-to-Heavy Duty
For applications that don’t require steel cord strength, NN belts offer the best price-to-performance ratio.
✅ Easy Splicing
Nylon belts can be spliced using mechanical fasteners (rivets) or vulcanized splices (hot or cold). Vulcanized splices achieve 90-100% of belt strength.
Disadvantages and Limitations
❌ Water Absorption
Nylon absorbs moisture (up to 8% by weight). In very wet conditions, this can:
- Reduce tensile strength
- Cause belt elongation
- Lead to tracking issues
Solution: Use EP belts or waterproof nylon treatments for wet applications.
❌ Higher Initial Elongation (Stretch)
New NN belts require “take-up” adjustments during the first weeks of operation as the nylon settles. Without adequate take-up travel, the belt may slip on the drive pulley.
❌ Lower Modulus (Stretches More)
While elasticity is an advantage for impact absorption, it is a disadvantage for long, heavily loaded conveyors where minimal stretch is desired. EP belts are preferred for very long center distances.
How to Select the Right Nylon Conveyor Belt
Choosing the correct belt requires answering five questions:
1. What material is being conveyed?
- Abrasive materials (ore, stone): Thick rubber cover (4-6mm top, 2-3mm bottom)
- Sharp materials (scrap metal, glass): Cut-resistant rubber compound
- Oily materials: Oil-resistant NBR (nitrile) cover
2. What is the lump size and drop height?
- Large lumps (>200mm) or high drop heights require extra impact resistance (use 2-3 more plies than calculated).
3. What is the belt speed?
- Low speed (<1 m/s): Standard NN plies
- High speed (>3 m/s): Balanced fabric weave to prevent vibration
4. What is the pulley diameter?
- Minimum pulley diameter = Function of ply thickness. Check manufacturer’s chart.
5. What is the operating temperature?
- Below -20°C: Use cold-resistant cover compound
- Above 120°C: Use heat-resistant EPDM cover (nylon carcass may still be used)
Standard Specifications (Common Grades)
| Grade | Cover Material | Temperature Range | Typical Use |
|---|---|---|---|
| M24 | Natural rubber | -20°C to +80°C | General purpose, abrasion resistant |
| N17 | Nitrile (NBR) | -20°C to +100°C | Oil and grease resistance |
| HR120 | EPDM | -20°C to +120°C | Heat resistance (cement, sinter) |
| FRAS | Various | -20°C to +80°C | Fire resistant, anti-static (underground mining) |
Installation and Maintenance Tips
Do’s:
- ✅ Store belts upright on a dry, level surface away from sunlight.
- ✅ Use vulcanized splices for maximum strength on long conveyors.
- ✅ Check take-up travel weekly during the first month of operation.
- ✅ Keep pulleys clean to prevent belt misalignment.
Don’ts:
- ❌ Never expose nylon belts to ozone (near electric motors without covers).
- ❌ Avoid sharp folds or kinking during installation.
- ❌ Do not exceed the recommended minimum pulley diameter.
Nylon vs. Steel Cord vs. Solid Woven
| Feature | Nylon (NN) | Steel Cord | Solid Woven (PVG) |
|---|---|---|---|
| Tensile Strength (N/mm) | 200 – 2,500 | 500 – 7,500 | 500 – 2,000 |
| Elongation | 10-15% (operating) | 0.2-0.5% | 2-4% |
| Impact Resistance | Excellent | Poor (can rust) | Good |
| Weight | Moderate | Very Heavy | Light |
| Cost | Low-Moderate | High | Moderate |
| Best for | Medium-long conveyors | Very long, high tonnage | Underground mining |
Conclusion
The nylon conveyor belt (NN belt) remains a cornerstone of modern material handling. Its unique combination of high strength, excellent impact resistance, and superior flexibility makes it the go-to choice for industries ranging from mining and cement to agriculture and logistics.
While it has limitations—notably water absorption and higher initial stretch—these are well understood and manageable with proper design and maintenance.
Quick Selection Guide:
- Choose NN belt when: You need impact resistance, flexibility, and value for medium-to-heavy duty applications.
- Choose EP belt when: Moisture is present or minimal stretch is critical.
- Choose steel cord when: You need extremely high strength (over 3,000 N/mm) for very long single flights.
For most quarry, mining, and industrial applications, a well-specified nylon conveyor belt will deliver 5-10 years of reliable service with proper care.
French 
English