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Introduction

A company was experiencing a short service lifetime from the bearings used in the casting of gas turbine blades. NSK undertook an Application Review of the existing design which included an inspection of the failed bearings. An extremely caustic solution  combined with high loads and misalignment was causing lubrication and seizure problems. An alternative wheel design was proposed using a cylindrical roller bearing, with improvements in sealing and lubrication. This resulted in significantly improved performance and doubled lifetime.

Key Facts

  • Gas Turbine casting
  • Bearing replacement every 6 weeks
  • Caustic solution: 50% Sodium hydroxide at 180°C
  • NSK solution: Application design change of wheel used on carousel, with bearing substition to NSK sealed cylindrical roller bearing
  • Reduced downtime and maintenance
  • Doubled bearing life
  • Significant reduction in bearing and maintenance costs

Gas turbine blade casting Gas turbine blade casting
Sealed cylindrical roller bearing Sealed cylindrical roller bearing

Background Information

  • Sector: Steel and Metals
  • Country: UK
  • End-product: Gas Turbine Blade
  • Application: Gas turbine blade casting

  • Number of machines: 3
  • Approx. Lifetime: 6 weeks
  • Problem: Lubrication and seizure issues due to caustic solution ingress leading to a very short service life of the bearings used

Value Proposals

  • The customer was experiencing poor performance on bearings within a carousel application. A Failed Bearing Analysis erformed by NSK Engineers showed that this was caused by ingress of extremly agressive caustic solution, combined with high loads and misalignment

  • An Application Review highlighted inadequate sealing as the cause and NSK Engineers designed an alternative wheel design, incorporating improved sealing, easier assembly and an NSK sealed cylindrical roller bearing
  • A trial was conducted using the new design and the results were reviewed. The redesign was succesful with the remaining lines modified

Product Features

  • High load rating
  • Highly corrosion resistant phosphate coating
  • Contact seals prevent ingress of foreign particles or water
  • Increased radial and axial capability

  • Bearings pre-greased with Lithium grease
  • Re-lubrication holes for easy maintenance & grease replenishment
  • Snap ring (DIN 471) can be applied to the outer ring

Cost Saving Breakdown

Before Cost p.a. NSK Solution Cost p.a.
Cost of 1 set of assemblies
= € 4.462
€ 133.860 Cost of 1 set of assemblies
= €7.089
Cost of 1 bearing / seal kit
= €1.487
€ 39.111
Cost of labour to renew 1 set of assemblies =  € 297
€ 8.910 Cost of labour to renew 1 set of assemblies = € 297 € 3.564
Bearing life 6 weeks Bearing life 12 - 14 weeks
Total costs per year à 10 changes (x 3 rotators) = € 142.770 Total cost per year for 1 change (x 3 rotators) = € 42.675
Total Costs € 142.770 € 42.675

Reference: SS-E-2011

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