ISO 4407:2025 PDF

Overview

ISO 4407:2025 - Hydraulic fluid power - Fluid contamination - Determination of particulate contamination by the counting method using an optical microscope - defines uniform, non‑subjective methods for measuring particulate contamination in hydraulic and power-system fluids by capturing particles on a filter membrane and counting them with an optical microscope. The standard covers both automated counting (image analysis software) and manual counting, and emphasizes analysing the entire effective filtration area (EFA) where feasible to ensure consistent classification results.

Key topics and requirements

• Scope: Applicable to fluids that can be vacuumed through an appropriately pore-sized filter membrane.
• Counting methods:
  • Automated counting (Annex A): image capture, thresholding, automated sizing and counting using image analysis software.
  • Manual counting (Annex B): microscopy‑based visual sizing and statistical counting by a trained operator.
• Sample preparation & filtration: Requirements for sample handling, vacuum filtration, and membrane preparation to avoid contamination (blank analysis).
• Microscope & calibration: Calibration procedures for microscopes and validation of the automated system; resolution and accuracy depend on optical system and software.
• Effective filtration area (EFA) and measured filtration area (MFA): Determination and reporting rules to ensure representative counts.
• Particle sizing: Particle size defined by maximum Feret diameter; definitions for fibres and other terms provided.
• Verification & reporting: Validation of results, threshold settings, and example report formats (Annexes A–E).
• Safety & compatibility: Guidance on solvents, mountants and handling; users must observe safety and regulatory limits.

Practical applications and users

ISO 4407:2025 is used to:

• Monitor and control fluid contamination in hydraulic systems, lubrication systems and power‑transfer fluids.
• Support condition monitoring, maintenance planning and root‑cause analysis by quantifying particulate levels.
• Verify cleanliness of fluids from suppliers and after filtration, repairs or component assembly.

Primary users:

• Contamination control laboratories and test houses
• Hydraulic system designers and maintenance engineers
• Quality assurance teams in manufacturing and OEMs
• Fluid suppliers and filtration system vendors

Related standards

• ISO 5598 - Fluid power systems and components - Vocabulary (terms used)
• ISO 3722 - Hydraulic fluid power - Fluid sample containers - Cleaning methods
• ISO 4406 - Particle contamination classification (used as reference for classification accuracy)

Keywords: ISO 4407:2025, hydraulic fluid power, fluid contamination, particulate contamination, optical microscope, automated counting, image analysis software, manual counting, filter membrane, effective filtration area (EFA).