Overview
ISO/TR 6307:2023 clarifies how fluid electrical conductivity affects multipass filter testing, specifically for tests conducted to ISO 4548-12:2017. The technical report summarizes experimental work, laboratory surveys and oil analyses showing that changes in oil conductivity during a multipass test can materially change measured filter capacity and efficiency. Although focused on ISO 4548-12, the findings are relevant to other multipass test methods (for example ISO 16889 and ISO 19438).
Key topics and technical points
- Scope and objectives
- Examine how conductivity affects filter capacity test results under ISO 4548-12:2017 conditions.
- Compare findings to ISO 4548-12 operating parameters and uncertainties.
- Conductivity limits referenced
- ISO 4548-12 requires oil conductivity to be at least 1 000 pS/m, with a recommended 1 500 pS/m ± 500 pS/m.
- Observed effects
- Some labs reported final conductivity decreases during tests, which corresponded to increased measured filter capacity.
- The root cause of conductivity drop during testing was not determined.
- Experimental work
- Reference filter testing (spin-on filters) and flat-sheet media tests were performed; commercially available filters were also tested.
- Example test parameters in the report include terminal differential pressure 345 kPa, flow rates (e.g., 75 l/min for some reference tests), and ISO A3 test dust (ISO 12103-1:2016).
- Flat-sheet single-pass tests showed higher initial efficiency at higher conductivity (6 000 pS/m) leading to faster loading and lower apparent capacity versus lower conductivity (1 500 pS/m) - ~25% capacity difference in that study.
- Mitigation
- An active conductivity dosing system (small, continuous additions of a conductivity improver such as Stadis 450) maintained conductivity within about ±200 pS/m, improving consistency of multipass results.
Practical applications - who should use this standard and why
- Filter test laboratories - to understand and control conductivity-related variability in multi-pass filter capacity testing (ISO 4548-12, ISO 16889, ISO 19438).
- Filter and media manufacturers - to interpret test data accurately and to design robust internal QA test methods.
- Engine and lubrication system engineers - to translate laboratory multipass results into realistic service expectations.
- Standards committees and accreditation bodies - to evaluate test uncertainty and consider procedural controls for conductivity monitoring.
Related standards
Keywords: ISO/TR 6307:2023, conductivity, multi-pass testing, ISO 4548-12, filter capacity, filter testing, Stadis 450, ISO 16889, ISO 19438, lubricating oil filters.
