High-Abrasion VMQ and FKM Seals for Jaw, Cone, and Impact Crushers

Rock crushing is a violently abrasive process. Jaw crushers apply compressive force, cone and gyratory crushers utilize a gyrating mantle, and impact crushers accelerate rock into breaker plates or hammers. All generate vast amounts of dust and fine particulate matter that act as grinding paste on any exposed surface, including seals. Furthermore, these machines rely on complex lubrication systems (often grease or heavy gear oil) to protect bearings and gears, and seals must retain these lubricants while excluding contaminants.

Silicone Rubber (VMQ) offers a unique combination of properties: an extremely wide service temperature range (-60°C to +225°C), excellent flexibility at low temperatures, and good resistance to ozone and weathering. However, its tensile strength and abrasion resistance are inferior to many other elastomers. Therefore, VMQ is typically used in secondary sealing locations within crushers, such as electrical enclosure gaskets, sensor seals, or in areas with minimal direct abrasive contact but requiring thermal stability.

For primary sealing defense—such as on main shaft bearings, eccentric bushings, or hydraulic adjustment cylinders—Fluorocarbon (FKM) and Hydrogenated Nitrile (HNBR) are the frontline materials.

· FKM: Provides the best combination of high-temperature resistance and chemical/oil resistance. It's ideal for seals around the lubrication system and in areas exposed to heat from friction.

· HNBR: Created by hydrogenating NBR, it significantly improves heat resistance (up to 150°C), ozone resistance, and mechanical properties (tensile strength, abrasion resistance) over standard NBR. It offers excellent resistance to gear oils and greases. For many crusher applications, HNBR strikes an optimal balance between performance, durability, and cost, often outperforming FKM in pure abrasion scenarios.

The AS213 standard is frequently referenced for specific seal profiles used in heavy machinery like crushers, ensuring interchangeability. A critical maintenance practice is seal housing design: many modern crushers incorporate labyrinth seals or multiple lip seals in tandem with grease purge ports. The primary elastomeric seal (often HNBR) works in concert with these mechanical features. Grease is periodically injected to create positive pressure, forcing dust out rather than letting it in.

Case studies from copper mines in Indonesia and iron ore operations in India show that a proactive seal maintenance program, which includes:

1. Regular grease analysis to check for silica content (indicating seal failure).

2. Infrared thermography of bearing housings to detect overheating from failed seals.

3. Scheduled replacement of shaft seals during major liner changeouts.

   ...can extend crusher bearing life by 60-80%. In the USA, some aggregate plants have standardized on HNBR for all dynamic crusher seals and VMQ for static gaskets, simplifying inventory and improving repair reliability.