Crusher backing compound is a two-component, epoxy-based material poured into the gap between the manganese wear liners and the supporting body in cone and gyratory crushers. Aurox backing compound is CSP Mühendislik’s own two-component epoxy backing developed for this duty; CSP also supplies the well-known Nordbak (Loctite/Henkel) backing materials.
Although backing compound may look like a small item, it directly determines liner life, crusher reliability and how easy the next change will be. This guide explains what backing compound does, the correct application steps and the mistakes most often made in the field.
Why Is Backing Compound Needed?
Because of casting tolerances, irregular gaps remain between cast manganese liners and the crusher head or bowl. If the liner only makes contact at certain points, crushing forces concentrate at those points. The result:
- The liner flexes in unsupported areas and cracks,
- The liner loosens, knocks and hammers the seating surfaces,
- Permanent damage occurs on the head and bowl surfaces.
Backing compound fills these gaps completely so the liner is supported at every point, spreads impact and vibration over a wide area and allows the liner to reach its full life. Compared with traditional metal backings such as lead or zinc, epoxy backings need no melting equipment, are safer and are easier to remove.
Types of Backing Compound
- Aurox crusher liner backing compound (CSP Mühendislik): A two-component epoxy backing that provides high compressive strength and impact resistance to support wear parts in large gyratory crushers, cone crushers and grinding mills. Its viscosity allows easy mixing and pouring, and it is engineered to keep its performance in cold regions. See our Aurox backing compound guide for details.
- Standard backing (e.g. Nordbak Standard Backing): For general applications in cone and gyratory crushers.
- High-performance backing (e.g. Nordbak HP Crusher Backing / Loctite PC 9020): For heavy impact, large crushers and high-load applications. According to its technical data sheet, it is designed to work between about −30 °C and +105 °C in dry service.
- Pourable wear and wedge products: Special products such as eccentric liquid wedge, used to fill gaps in the eccentric and bushing areas. See Aurox eccentric liquid wedge and our eccentric liquid wedge application guide.
Which product to use should be decided according to the crusher manufacturer’s recommendation and the size of the crusher. Some modern cone crushers are designed with backing-free liners; no backing is used in these crushers.
How Much Material Is Needed?
The quantity required depends on the volume of the gap between liner and body, and crusher manufacturers and backing manufacturers publish tables by model. In practice:
- A safety margin should be added to the calculated quantity; if pouring stops halfway, the second mix is made when the first has started to cure, creating a layered, weak backing.
- In large crushers, several kits are prepared at the same time and poured without interruption.
For a step-by-step method to estimate the gap volume and the number of kits, see our crusher backing quantity calculation guide.
Step-by-Step Application
1. Surface preparation
- The surfaces of the head, bowl and liners that will contact the backing are completely cleaned of old backing, dust, oil and loose material.
- The liner is fully seated and secured according to the manufacturer’s instructions (lock nut, bolts). Backing compound does not “seat” the liner; it only fills the gaps.
- Gaps where the backing could leak out (the lower edge of the liner, bolt holes) are sealed with putty, foam or a suitable dam material. This dam directs the epoxy into the intended volume.
2. Temperature control
- The workability and curing of epoxy resin and hardener depend heavily on temperature. Follow the recommended application temperature range in the product data sheet.
- In cold weather, both the material and the crusher parts should be warmed beforehand; cold material thickens, cannot fill the gaps and takes longer to cure.
- In hot weather, the pot life shortens; the mix must be poured quickly.
For warming, enclosures, heaters and cure monitoring in winter, see our cold-weather backing application guide.
3. Mixing
- The whole of the resin and hardener is mixed in the proportions supplied in the pack; partial mixes are not made.
- Mixing is done with a low-speed mixer until a uniform colour is obtained, including the sides and bottom of the container. Under-mixed backing stays soft.
- Air should not be trapped during mixing.
4. Pouring
- The mix is poured immediately and without interruption. For example, the working life of Loctite PC 9020 at 25 °C is about 20 minutes; as the poured mass increases, curing speeds up because of the exothermic reaction.
- Pour slowly from a single point, so the material fills the gap from the bottom up and pushes air ahead of it.
- For mantle backing, the backing is poured through the pour holes at the feed opening; check that the backing level reaches the same height at every point.
5. Curing
- The crusher must not be put under load until the backing has completed its functional cure. For example, the functional cure time of PC 9020 at 25 °C is about 8 hours; at lower temperatures this time increases.
- To check the cure, the hardness of a small sample taken from the same mix can be used as a reference.
Common Mistakes
| Mistake | Consequence |
|---|---|
| Preparing too little material | An interrupted pour, layered and weak backing |
| Partial mixing or mixing in the wrong ratio | Backing that stays soft and does not cure |
| Pouring onto cold parts | Gaps not filled, longer cure |
| Pouring without a dam | Backing leaks out, volume left incomplete |
| Running before the cure is complete | Backing is crushed, the liner loosens and cracks |
| Dirty/oily surfaces | Porous backing that does not bond |
For root-cause analysis of symptoms such as loose liners, soft backing or cracked mantles, see our crusher backing problems and solutions guide.
Removing the Backing
At a liner change, the old backing comes out with the liner. Epoxy backings soften with heat; heating in accordance with the manufacturer’s instructions makes removal easier. The head and bowl surfaces must be completely cleaned of residue before the next pour. For all the replacement steps, see our mantle and concave replacement guide.
Safety
- Epoxy resins and hardeners can cause irritation and sensitisation on contact with skin and eyes; use gloves, goggles and suitable work clothing.
- Read the product’s safety data sheet (SDS) before application and follow the ventilation requirements.
- Temperature rises in large masses during curing; do not touch fresh backing.
Frequently Asked Questions
Does backing compound extend liner life?
Yes. Supporting the liner at every point reduces the risk of cracking and loosening, so the liner can be used up to its designed wear limit.
Can epoxy backing be used instead of zinc backing?
Most modern crusher manufacturers recommend epoxy backing. Even so, follow the backing type specified in your crusher’s manual.
What is the shelf life of backing compound?
Shelf life varies by product and is stated on the pack. The material should be stored in a cool, dry place and protected from freezing.
Epoxy Backing or Zinc Backing?
| Criterion | Epoxy backing (Nordbak, Aurox, etc.) | Zinc / metal backing |
|---|---|---|
| Application | Mix and pour at room temperature | Requires melting equipment and high temperatures |
| Safety | Chemical exposure precautions are sufficient | Molten metal, fumes and burn risk |
| Removal | Softens with heat, easy to remove | Difficult and time-consuming |
| Impact damping | Good | Hard, limited |
| Field of use | The great majority of modern cone and gyratory crushers | Some older designs and special applications |
Which backing to use must always be decided according to the crusher manufacturer’s instructions; in some designs specific backing types are mandatory.
Calculating the Quantity: A Practical Approach
- Find the backing volume for the crusher model and liner type in the manufacturer’s tables.
- Check the records for the quantity actually used at previous changes.
- Add a safety margin to the larger of the two.
- Round the total up to a whole number of kits (resin + hardener); do not split kits when mixing.
Unmixed kits left over can be stored under suitable conditions for the next change. Mixed material, however, must be used before it cures.
Checklist During Pouring
- Has it been confirmed that the liner is fully seated and the lock nut/bolts are at final torque?
- Have the dams and seals been made, and are any leak points left?
- Have material and part temperatures been measured?
- Are enough kits and mixers ready, and have tasks been assigned to the team?
- Have the pour points and air vents been identified?
- Has a reference sample been taken?
- Has the time when the cure will be complete been recorded?
Eccentric Liquid Wedge and Locking Products
Besides backing materials, there are two other product groups often used in crushers:
- Eccentric liquid wedge: Pourable materials used to fill gaps and secure parts in the eccentric and bushing area of cone crushers. Application must be carried out in the areas approved by the crusher manufacturer and in accordance with the instructions.
- Locking compounds: Prevent bolts and nuts loosening with vibration and protect connections against corrosion. They are widely used on crusher and screen connections.
For more information on these products, see our Aurox eccentric liquid wedge page, our zinc vs epoxy liquid wedge comparison and our Nordbak locking compound page.
An Example from the Field: Layered Backing
At a liner change on a large cone crusher, the backing quantity had been underestimated, and after the first mixes had been poured it took about an hour to prepare new kits. In the meantime the first backing had started to cure and a weak interface had formed between the two layers. When the next liner was removed, the backing was found to have separated at this interface and cracks had started in the upper area of the liner. At subsequent changes, the plant prepared enough material and enough people to pour the backing in one go; the problem did not recur.
More Questions
What happens if backing compound leaks onto the liner seating surface?
Backing residue on seating surfaces can prevent the liner seating fully. That is why the liner is first fully seated mechanically, and the backing is poured only into the gap behind it.
What temperature can cured backing withstand?
It varies by product; for example, the maximum dry-service operating temperature of PC 9020 is given in its technical data sheet as about 121 °C. Normal crusher operating temperatures are below this limit.
Is the same backing used in gyratory crushers?
Backing materials are used for both cone and gyratory crushers; however, in large gyratory crushers the backing volume and application procedure are different, and the manufacturer’s instructions should be followed.
Backing Materials from CSP Mühendislik
CSP Mühendislik supplies its own Aurox crusher liner backing compound and Aurox eccentric liquid wedge, together with Nordbak backing compound and Nordbak eccentric liquid wedge, as part of its crusher backing range from stock and provides application support. Contact us to determine the right product and quantity for your crusher.
