One of the most critical mistakes at a mantle or concave change is starting the pour with too little backing compound. If the pour stops halfway, the first mix starts to cure before the second is ready, producing a layered, weak and porous backing. Ordering far too much, on the other hand, creates stock costs and shelf-life problems. In this guide we explain step by step how to calculate the quantity of crusher backing compound and how to verify it on site.
For the role of backing compound and application steps, see our crusher backing compound guide, and for CSP’s own backing product our Aurox backing compound guide.
Factors That Determine the Quantity
- Crusher model and size: Head and bowl diameter, liner height and geometry.
- Liner type: Crushing chamber profile (fine, medium, coarse) and liner thickness change the volume of the liner–body gap.
- Liner manufacturer: The back-face geometry of aftermarket liners can differ from the OEM’s, changing the gap volume.
- Condition of supporting surfaces: Worn or damaged head and bowl surfaces increase the gap volume.
- Dams and losses: Material left in containers, leakage and material remaining in pour holes.
Method 1: Manufacturer Tables and Past Records
Crusher and backing manufacturers publish approximate backing quantities for common crusher models. The most reliable source, however, is your own plant’s past records: if the number of kits used, the liner brand and the profile are recorded at every change, the requirement for the next change is easy to determine.
Method 2: Calculating the Gap Volume
If there are no tables or records, the gap volume can be estimated:
- Determine the gap geometry: After the liner is seated, measure the average thickness of the gap between liner and supporting surface at different points (e.g. several points around the circumference at the top, middle and bottom).
- Average diameter and height: Measure the average diameter (D) of the area the backing will fill and the backing height (H).
- Approximate volume: For a thin cylindrical/conical shell, the volume is approximately V ≈ π × D × H × t (t: average gap thickness). If all dimensions are in the same unit (e.g. dm), the volume comes out in litres (dm³).
- Convert to weight: Multiply the volume by the mixed density given in the product’s data sheet to find the weight required.
- Number of kits: Divide the weight required by the net weight of one kit and round up.
- Safety margin: Add a margin to the calculated quantity for measurement uncertainty, leakage and container losses, and keep at least one spare kit ready.
Worked Example (To Illustrate the Method)
Suppose that behind a concave the average backing diameter is 12 dm, the backing height is 6 dm and the average gap thickness is 0.15 dm (15 mm):
V ≈ 3.14 × 12 × 6 × 0.15 ≈ 34 litres
This volume is converted to kilograms by multiplying by the mixed density in the product data sheet, then divided by the kit weight to find the number of kits; a safety margin is then added. The dimensions in this example are only to illustrate the method; actual values must be measured for your crusher and liners.
Method 3: Measuring on the First Change
When switching to a new liner brand or profile, measure the gap thicknesses carefully at the first change and record the number of kits used. This first application becomes the reference for later changes.
Pour Plan: When to Mix the Kits?
- On large crushers it is not possible to fill the whole gap within the pot life of a single kit; kits are mixed by a team simultaneously or at short intervals to achieve an uninterrupted pour.
- The mixing team, pour points and kit sequence should be planned before the pour.
- In hot weather the pot life shortens, so more mixing equipment and people may be needed; in cold weather, a warming plan is required (cold-weather backing application).
Suggested Record Form
| Field | Record |
|---|---|
| Crusher model and serial no | — |
| Liner brand, profile and part no | Mantle / concave separately |
| Measured average gap thicknesses | Top / middle / bottom |
| Calculated volume and number of kits | Litres, quantity |
| Actual number of kits used | Quantity, surplus/shortfall |
| Ambient and part temperature | °C |
| Product and batch number | e.g. Aurox, Nordbak |
| Cure time and time returned to service | Hours |
Common Mistakes
- Assuming the quantity used last time applies unchanged to a different liner brand.
- Not allowing a safety margin or keeping a spare kit.
- Ignoring container losses and leakage.
- Sending kits to site without checking expiry dates.
Frequently Asked Questions
How many kits of backing does a cone crusher need?
It depends on the crusher model, liner profile and gap volume. Send us your model and serial number and we will calculate it together.
Can leftover material be used at the next change?
Unopened kits can be used if they are within their shelf life and have been stored correctly. Mixed material cannot be stored.
Is there an easier way to measure the volume?
Past records and manufacturer tables are the most practical method. Measuring carefully and keeping records at the first application with a new liner geometry makes later changes easier.
CSP Mühendislik Support
CSP Mühendislik helps determine the backing quantity needed for your crusher model and liner type and supplies Aurox backing compound and Nordbak backing compound kits from stock. See our crusher backing page for all backing products and our cone crusher spare parts page for mantles and concaves.
