Overview
ISO 6933:1986 - "Railway rolling stock material - Magnetic particle acceptance testing" specifies a standardized method and procedural framework for magnetoscopic (magnetic particle) inspection to detect surface discontinuities in railway components. Unless otherwise agreed, ISO 6933 is applied when magnetic particle tests are required for products such as axles and wheels supplied under ISO 1005 quality prescriptions. The standard covers equipment, magnetization methods, magnetic particle media, lighting, sensitivity adjustment, examination procedure, reporting and de‑magnetization.
Key topics and requirements
- Scope and purpose: Acceptance (reception) testing for detection of surface cracks and discontinuities on railway rolling stock parts (notably axles and monobloc wheels).
- Magnetization methods:
- Current through the part (electrodes) producing a magnetic field perpendicular to the electrode line.
- Flux methods using coils (cable around or through wheel bore) or yokes/culasses (electromagnets or permanent magnets).
- Current types: alternating, pulsed (including pulse trains), or direct current as appropriate to the chosen method.
- Particle application modes:
- Continuous method - apply magnetic suspension during peak magnetization.
- Residual method - apply after magnetization (only when DC, pulsed current or permanent magnets create residual magnetization).
- Magnetic particle media:
- Fluorescent magnetic liquids (for UV inspection) and non‑fluorescent suspensions (for machined surfaces).
- Carrier liquids may be water or petroleum‑based; additives (wetting agents, corrosion inhibitors) allowed as required.
- Liquids must be free of dust and kept at prescribed particle concentration; frequent concentration checks are recommended.
- Lighting and observation:
- Visible light inspection: normal lighting of at least 500 lux at the surface.
- Fluorescent particle inspection: ultraviolet illumination primarily between 330–390 nm with intensity ≥ 5 W/m² at 365 nm; ambient light reduced (around 10 lx) during UV inspection.
- Sensitivity and calibration:
- Sensitivity must be adjusted on a representative test piece of the same material and surface finish; field measurements shall be made with calibrated instruments and, in disputes, by a Hall‑effect meter.
- Reporting and acceptance:
- Test report must record equipment, magnetization method, current type, particle type/manufacturer, carrier liquid, particle application procedure, sensitivity setting, inspection conditions and any indications (size, location, quantity).
- Acceptance criteria are defined at contract/tender stage and depend on application, location, orientation and severity of discontinuities.
- De‑magnetization:
- If residual magnetism is excessive (e.g., on axles used with bearing boxes), de‑magnetization must be performed to agreed residual field limits.
Applications and users
ISO 6933 is used for acceptance testing and quality control during manufacture and maintenance of railway rolling stock components. Typical users:
- Rolling stock manufacturers and wheel/axle producers
- Railway procurement and quality assurance teams
- Inspection laboratories and NDT (non‑destructive testing) technicians
- Maintenance workshops and regulatory bodies
This standard ensures consistent, traceable magnetic particle inspections for detecting surface defects that could affect safety and service life.
Related standards
- ISO 1005 series (quality prescriptions for axles and wheels) - referenced for product application and acceptance conditions.
Keywords: ISO 6933, magnetic particle testing, magnetoscopic inspection, railway rolling stock, axles, wheels, fluorescent particles, UV inspection, degaussing, NDT acceptance testing.
