Overview - ISO/TR 10686:2013 (Hydraulic fluid power cleanliness)
ISO/TR 10686:2013 provides methods to relate and manage the cleanliness of a hydraulic system to the cleanliness of its constituent components and the hydraulic fluid. It explains how to estimate the final cleanliness of an assembled hydraulic system at release from manufacture, and how to derive component- and fluid-level requirements to achieve a specified Required Cleanliness Level (RCL) for the final system. The Technical Report applies to any particle size and can be adapted beyond hydraulic fluid power.
Key technical topics and requirements
- Cleanliness prediction approaches
- Bottom‑up (prediction): Estimate system cleanliness from the known cleanliness of each component and of the filling fluid. The final system contamination is treated as the sum of particles introduced by components and fluid.
- Top‑down (specification): Derive component and fluid cleanliness requirements from a target system cleanliness (RCL).
- Fundamental concepts
- Wetted volume (V) and wetted surface area (A) - geometry used to convert surface-based cleanliness specs into volume-based values and to compute contamination contribution.
- Volume-to-surface ratio (V/A) - used when specifications are expressed per unit area but predictions require per unit volume.
- Cleanliness arithmetic - for hollow components, predicted cleanliness of the filled item is the sum of particles in the component and in the filling fluid divided by the filled volume.
- Contaminant distribution assumptions
- Particles are considered either deposited on wetted surfaces or suspended in fluid; the TR treats deposited contaminants as if in suspension in the void volume for calculation purposes.
- Homogeneous distribution is assumed in the absence of filters during initial operation.
- Practical calculation aids
- Guidance on measuring or calculating wetted volumes/surface areas and on aggregating particle counts across assemblies.
- Informative annexes with geometrical determination, example calculations, and relationships between volume and surface cleanliness metrics.
Practical applications and typical users
Who benefits:
- Hydraulic system designers and OEMs specifying cleanliness limits
- Assembly and manufacturing engineers estimating final system cleanliness at release
- Quality, test and contamination-control engineers setting supplier and component cleanliness requirements
- Suppliers of hydraulic components and hydraulic fluids preparing acceptance criteria
Typical uses:
- Predicting as-built cleanliness after assembly and fill
- Allocating cleanliness budgets between components and fluid to meet an RCL
- Converting surface-cleaning specifications to volume-based contamination metrics for system-level assessment
Related standards
- ISO 5598 (Fluid power systems and components - Vocabulary)
- ISO 4406 (Hydraulic fluid - Contamination code for particle counts) - referenced for particle-size coding
ISO/TR 10686:2013 is a practical resource for contamination control and specification management in hydraulic fluid power systems, enabling traceable, quantitative cleanliness planning across design, supply and production.