This article gives a short introduction to the main European standards for railway wheel bearings – the EN (European Norm).
Railway operation is safety critical. Railway wheel bearings are one of the most critical machine elements for the safe and efficient operation of trains. A broken, overheated, or blocked wheel bearing can lead to stopping a train, high cost, and in the worst case accidents due to derailment or other critical events. Reasons for failures are many and for this reason, there are various approval processes used to control risk. All the manufacturers are, in general, are audited annually (both Original equipment manufacturers and Aftermarket users) by external auditors such as Lloyds, RITES, etc.
Main standards for Railway wheel bearings
There are two main standards existing for railway applications the EN (European) and the AAR (American Association of Railroads) standards. The European Committee for Standardization (CEN) is a distinct private international non-profit organization that develops EN standards for various industrial applications.
A standard is a technical document to be used by manufacturers, users, and third-party inspection agencies as a guideline or rule. So these standards are created by involvement and taking a consensus of various interested parties such as manufacturers, consumers, and regulators of a particular material, product, process, or service. There is no doubt that by following approved standard documents all the parties are benefited through enhanced safety, quality, reliability, and repeatability.
EN-standards
The EN standards for railways are a group of standards maintained by a committee under CEN called CEN/TC 256 “Railway applications” (TC = Technical Committee). In TC 256 there are many so-called Working Groups (WG) dealing with various aspects of Railway applications.
There are three main standards that regulate wheel bearings and they are reviewed by the Working Group 12 (WG12):
EN 12080 – Rolling bearings
EN 12081 – Grease lubrication
EN 12082 – Performance Testing
These standards define all types of traffic – both freight & passenger. They focus on how to assure quality and control risk. No specification of the interchangeability of products (in contrast to AAR) is given. There are other standards relating to axle boxes and sensors, cables, and connectors. They will not be addressed in this article for the sake of simplicity. Each WG can propose changes to the standards under its responsibility and submit proposals for changes or new standards to members of TC 256.
Main topics for EN 12080 –
Rolling bearings Main topics for EN 12080 – Railway applications – Axleboxes – Rolling bearings
Information and requirements to be agreed and documented
Quality systems
Manufacture
Steel manufacturing
Heat treatment
Traceability
Material properties
Steel for rings and rolling elements
Materials of other components (cages, spacers, seals, etc)
Geometry and dimensions Mechanical properties — inner ring expanding ability Soundness of rings and rolling elements (Non-destructive testing)
Case depth
Surface hardness
Marking Inspection
Quality records
Delivery & Packaging
Greasing
Main topics for EN 12081 –
Lubricating greases Main topics for EN 12081 – Railway applications – Axleboxes –
Lubricating greases
Bearing speed classes
Production
Manufacturing procedure
Traceability
Delivery
Packing
Marking
Storage
Approval tests
Main topics for EN 12082 –
Performance testing Main topics for EN 12082 – Railway applications – Axleboxes – Performance testing
Water tightness test
Rig performance test
General Execution
Carrying out the test
Acceptance criteria
Rig test report
Field test
General
Carrying out the test
Test parameters
Acceptance criteria Field test report