ISO 16232 and VDA 19.1 Cleanliness Testing

The seven steps below are the same for every part. Your specification sets the parameters, the reference unit and the limits inside them.

1. Extraction method selection

Both documents describe five liquid extraction methods (pressure rinsing, internal rinsing, ultrasonic bath, agitation and dissolving) and air extraction. Our laboratory runs the first four liquid methods. Pressure rinsing covers exterior and accessible surfaces. Internal rinsing flushes wetted internal passages. Ultrasonic bath suits small parts and complex surfaces. Agitation suits parts that can be filled and shaken. The part and the specification decide; if your specification fixes the method and start parameters, we run those. Extractions take place in our PALL PCC61 and Gläser ACM18 ISO Class 5 extraction cabinets.

2. Blank value

We first run the procedure without the part. The blank value captures particles from the test liquid, cabinet, glassware and environment, and the standards cap it at 10 percent of the required cleanliness value. It is recorded in the report and is not subtracted from the result.

3. Declining test

A new component or component family is qualified by repeating the extraction, up to six times, on the same part. The criterion is met at the first step whose yield is 10 percent or less of everything collected up to and including that step. The routine procedure is built from the steps it took to get there, which shows the procedure is removing the contamination present rather than a fraction of it. If six steps do not reach the criterion, the parameters are intensified and the test repeated.

4. Filtration and membrane drying

We draw the extraction liquid through an analysis filter chosen for particle retention, chemical resistance to the test liquid and optical contrast. The filter then dries in our CleanTec membrane drying system or Quincy Lab 30GC gravity convection oven. When gravimetry is specified, we condition the filter to constant weight before and after filtration.

5. Gravimetric residue

The residue mass is the difference between the two conditioned filter weights. We measure it on an Ohaus analytical balance with 0.01 mg readability and normalize it per 1,000 cm² of wetted surface or per 100 cm³ of wetted volume. Mass says nothing about particle size or count, so a specification that must control large or hard particles also needs a size distribution.

6. Automated particle counting and sizing on the Jomesa HFD

The Jomesa High Focal Depth microscope scans the whole filter, detects each particle and measures its length (maximum Feret diameter) and width. Particles are counted into the size classes shared by both standards, class B (5 to 15 microns) through class N (3,000 microns and above). That is the 5 to 3,000+ micron range. Two polarization images separate metallic-shiny from non-metallic particles. Fibers are typified by shape: stretched length more than 20 times the maximum inner circle diameter, that diameter 50 microns or less, and not metallic shiny. VDA 19.1 has the longest or widest particle in each category recorded as an image.

7. Reporting

The standards require the inspection report to document the extraction method and parameters, the filtration and analysis conditions, and the results. For cleanliness testing to either document, the results are the size-class table with all particles, metallic-shiny particles and fibers, plus the gravimetric residue when specified. They are laid out in the same units as your limits. Counts are normalized to your reference unit: A (per 1,000 cm² of wetted surface), V (per 100 cm³ of wetted volume) or N (per component). A Component Cleanliness Code can be added. Example: A(B-E17/F-G14/H-I4/J-K2/L-N00). Particles that need a material identification are relocated from the HFD to the Jomesa PSE for SEM-EDS elemental analysis.