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A quarrying company was experiencing bearing failures due to contamination on each side of the conveyor head pulley. This caused increased maintenance cost, reduced lifetime of the bearing and a downtime in production every 18 months. NSK analysed the bearing and recommended to use bearings in High Tough steel (HTF). After the bearings were put into service they lasted 6 years.

Key Facts

  • Conveyor Head Pulley
  • Highly abrasive conditions including water and grit
  • Failure of the bearing through contamination with consequental loss of production
  • NSK Solution: bearings in High Tough Quality (HTF)
  • Changing to bearings in HTF steel increased the life time circle to 6 years
  • Cost savings generated based on reduced maintenance and downtime cost

Quarry Conveyor Quarry Conveyor
Bearings in High-Tough Quality (HTF) Bearings in High-Tough Quality (HTF)

Background Information

  • Sector: Quarrying and Mining
  • Country: USA
  • End-product: Aggregates
  • Application: Conveyor Head Pulley

  • Number of machines: Conveyor handles 60 % of the plant production producing 7000 t per hour (84,000 t per 12 hrs shift)
  • Approx. Lifetime: 18 Months
  • Problem: Failure of bearing through contamination due to arduous conditions

Value Proposals

  • NSK performed a bearing analysis showing route cause as ingress of water and grit
  • Application assessment showed highly abrasive conditions
  • Technical support provided for improved bearing performance

  • NSK recommended to replace the bearings by products with HTF matieral
  • HTF Bearings were put into service and lasted 6 years instead of 18 months

Product Features

  • NSK High Tough Steel (HFT) bearings have been designed for outstanding toughness under harsh conditions
  • Longer service life and superior resistance against wear, seizure and heat
  • Resistance with contaminated lubrication
  • Innovative heat treatment technology

  • HTF material can be applied for cylindrical, tapered and spherical roller bearings
  • Up to 7 times service life with contaminated lubrication compared to conventional bearings
  • Up to 20 % improvement of seizure resistance

Cost Saving Breakdown

Cost p.a.
6 People, working 12 hours @ 32 € per hour € 2.304
7,000 tons per hour x 12 hour stoppage x 4 times x 13.5 € per ton € 4.536.000
Total Costs 4,538,304 euros

Reference: SS-E-0020

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