Overview
ISO 12669:2017 - "Hydraulic fluid power - Method for determining the required cleanliness level (RCL) of a system" provides a standardized, repeatable method to determine the required cleanliness level (RCL) for hydraulic and lubrication systems. The RCL identifies the most appropriate fluid cleanliness expressed in accordance with ISO 4406 (contamination coding). The standard covers both high- and low-pressure fluid power systems and supports consistent cleanliness targets for flushing, filtration and in-service monitoring. It does not cover soft deformable particles generated by thermal decomposition of fluids.
Key topics and requirements
- RCL selection method: Systematically evaluates six operational parameters, assigns weightings, sums them into a system weighting and uses a chart (grade line) to derive an ISO 4406 contamination code.
- Six parameters considered:
- Working pressure and duty cycle (severity and frequency of pressure changes)
- Component contaminant sensitivity (pump, valve, servo sensitivity)
- System life expectancy (hours)
- Total cost of component replacement
- Cost of downtime
- Risk (operational safety and criticality)
- Procedure highlights:
- Select the condition that best describes the system for each parameter and record the weighting.
- Sum weightings; if sum <10 use 10, if >32 use 32.
- Use the system weighting and the standard chart to determine the ISO 4406 RCL.
- Measurement guidance:
- RCL is intended to be achieved initially by flushing and maintained by filtration.
- The grade line is based on on-line contamination analysis; off-line sampling can introduce extraneous contamination and is unsuitable for cleanliness targets better than ISO 4406 Code 14/12/9.
- Scope limitations:
- Expressed in ISO 4406 coding (conversion to other coding systems possible).
- Excludes effects of soft deformable particles from thermal fluid breakdown.
Practical applications
- Establishing consistent cleanliness targets for new hydraulic system design, assembly, commissioning and maintenance.
- Defining filtration requirements and validating filter selection (used alongside ISO/TR 15640).
- Creating procurement and acceptance criteria for hydraulic components and systems.
- Informing contamination-control programs, predictive maintenance and reliability engineering.
Who should use this standard
- Hydraulic system designers and OEMs
- Maintenance engineers and asset managers
- Filtration and contamination-control specialists
- Reliability and condition-monitoring teams
Related standards
- ISO 4406 - Fluid power - Method for coding level of contamination by solid particles (primary contamination coding used by ISO 12669).
- ISO 5598 - Fluid power vocabulary (terms and definitions).
- ISO/TR 15640 - Used to assist in filter selection based on RCL.
Keywords: ISO 12669:2017, required cleanliness level, RCL, hydraulic fluid power, ISO 4406, contamination control, filtration, hydraulic systems, lubrication systems.