What Cover Grades Mean
Conveyor belt cover grades define the physical properties of the rubber compound used on the belt's carrying surface and bottom cover. The grade tells you how the rubber performs under abrasion, tensile stress, and elongation — and therefore how long the cover will last in a given application.
The two most common grades in global mining and industrial use are M (formerly called X or W in some standards) and N (sometimes called Y). Within these, specific grades like M24 and N17 define the exact performance thresholds.
The Numbers Explained
The numbers refer to abrasion loss measured by the DIN 53516 (ISO 4649) rotating drum abrasion test:
- M24 — Maximum abrasion loss of 90mm³ (some standards allow up to 120mm³ for this grade; check the specific standard your application references)
- N17 — Maximum abrasion loss of 150mm³
Lower abrasion loss = harder, more wear-resistant cover = longer life in abrasive conditions.
In addition to abrasion loss, cover grades specify: - Minimum tensile strength (force needed to tear the rubber) - Minimum elongation at break (how much it stretches before tearing)
| Property | M24 Grade | N17 Grade |
|---|---|---|
| Max abrasion loss (DIN 53516) | 90mm³ | 150mm³ |
| Min tensile strength | 24 MPa | 17 MPa |
| Min elongation at break | 450% | 400% |
| Relative wear resistance | Higher | Lower |
| Cost | Slightly higher | Lower |
| Typical hardness | 60–70 Shore A | 55–65 Shore A |
M24 — The General Mining Standard
M24 (sometimes labeled as "Grade M" or "Grade X" in older standards) is the baseline cover grade for mining and heavy industrial applications worldwide. It offers good abrasion resistance suited to ore conveying, quarry applications, coal mining, and most bulk material handling.
Typical M24 applications: - Iron ore, copper ore, gold ore conveying - Coal mining — both open-cut and underground - Limestone quarry conveyors - Cement plant raw material handling - Aggregate production - Port bulk material handling
If you're not sure which grade to specify for a mining application, M24 is the standard starting point. Most conveyor belt specifications for mining default to M24 unless there's a specific reason to go higher or lower.
N17 — Light Duty and Non-Abrasive Applications
N17 is a softer, less abrasion-resistant grade suitable for lighter duty and less abrasive applications. Its lower tensile strength and higher abrasion loss make it unsuitable for hard rock mining, but its lower cost is justified where abrasion is not the primary concern.
Typical N17 applications: - Packing and dispatch conveyors at cement plants (finished cement is not abrasive) - Grain, fertilizer, and agricultural product handling - Light industrial conveying - Bagging lines - Product conveying where the material is not abrasive but the belt needs rubber protection from belt structure contact
Not suitable for: Any application with abrasive ore, rock, or aggregate. N17 will wear rapidly in mining applications that call for M24.
Beyond M24 — When Standard Isn't Enough
Some applications are too abrasive even for M24:
DIN W (Super Abrasion Resistant): Abrasion loss ≤50mm³. For highly abrasive materials — taconite, corundum, certain iron ores with high silica content, abrasive aggregate. More expensive but significantly longer life in the right application.
DIN Z (Extra Super Abrasion Resistant): Abrasion loss ≤40mm³. For the most abrasive conditions — quartz-rich ores, very hard aggregate. Premium cost but necessary for some applications.
If your current M24 belts are wearing out in less than 12 months, it may be worth evaluating a higher abrasion resistance grade rather than simply replacing like-for-like.
How to Choose
The material being conveyed drives the choice:
| Material Type | Recommended Cover Grade |
|---|---|
| Hard rock ore (iron ore, copper, granite) | M24 minimum; consider W grade if wearing fast |
| Coal | M24 for mining; N17 acceptable for light coal handling |
| Limestone (quarry) | M24 |
| Cement (finished product) | N17 acceptable |
| Grain, fertilizer | N17 |
| Aggregate (sand, gravel) | M24 |
| Abrasive quartz-rich ore | DIN W or Z |
| Wet slurry | M24 with consideration of PU cover for sliding abrasion |
Frequently Asked Questions
My conveyor handles both abrasive ore and clean product depending on the shift. Which grade? Specify for the most abrasive condition. Using N17 because it's sometimes carrying clean product and then running abrasive ore will wear the cover rapidly in ore cycles.
Does cover grade affect carcass selection? Not directly. Cover grade and carcass (EP vs steel cord, tension rating) are specified independently. You can have M24 cover on any EP or steel cord construction.
Is there a visual way to tell M24 from N17? Not reliably by looking. The difference is in the compound formulation and is measured by laboratory test. On any belt we supply, the cover grade is marked on the belt edge.
We're paying for M24 but the belt wears out in 6 months. Is something wrong? Possibly. Either the belt is not genuinely M24 grade (test data should confirm), or the application is more abrasive than M24 is suited for. Share your material characteristics and wear rate with us and we can advise.
Contact Elephant Rubber
We supply M24, N17, W, and Z grade covers on EP and steel cord belts. If you're not sure which grade is right for your material, contact us with your ore type and current belt wear rate.