ISO 14085-6:2015 PDF

Overview

ISO 14085-6:2015 - Aerospace series - Hydraulic filter elements - Test methods - Part 6: Initial cleanliness level - defines a reference method for measuring the initial cleanliness of new hydraulic filter elements intended for aircraft hydraulic systems. The standard establishes a repeatable extraction and analysis procedure to quantify built-in particulate contamination after production, before shipment or installation, enabling comparison between filter elements and verification against specified cleanliness requirements.

Key topics and requirements

• Purpose: Determine the initial cleanliness level of new filter elements so they do not degrade hydraulic system fluid cleanliness.
• Test principle: Install the element in a pre‑cleaned test housing, fill ~2/3 with a specified test liquid, agitate to extract built‑in contaminants, collect the extraction liquid and analyse the entire volume.
• Extraction sequence: Multiple extractions (C1, C2, C3, …) are performed until the latest extraction Cn ≤ 0.1 × ∑(C1…Cn) or a maximum of six extractions; if not met, extraction parameters must be revised and retested.
• Contaminant analysis methods (Annex A):
  • Gravimetric analysis - mass of contaminants via membrane filtration and weighing (ISO 4405 referenced).
  • Particle size - microscopy or image analysis to size individual particles (ISO 4407 referenced).
  • Particle size distribution - particle counting methods to quantify size classes.
• Reporting unit: Contaminant amount expressed per 100 cm of wetted volume of the housing/element assembly.
• Quality controls: Clean test liquid (compatible with filter materials and system fluid), pre‑cleaned housing and containers (ISO 3722), and blank checks (housing blank must be