Technical Cleanliness to ISO 16232 - how to verify?

What does technical cleanliness to VDA 19 mean?

Technical cleanliness assesses particulate contamination that adheres to functionally relevant components and can cause damage in operation. Testing follows VDA 19.1 (inspection) and the technically identical international standard ISO 16232, complemented by VDA 19.2 for cleanliness in the assembly environment.

Hard particles such as metal chips, burrs or mineral residues are especially critical. In hydraulics, injection technology or electronics, particles as small as 50 µm can block valves, damage seals or cause short circuits.

• VDA 19.1 / ISO 16232: residual dirt analysis on the component.
• VDA 19.2: cleanliness of the manufacturing and assembly environment.
• Goal: reproducible, comparable results across the supply chain.

How does residual dirt analysis work?

The analysis splits into three steps: extraction, filtration and evaluation. First the particles are released from the component with a test fluid, then captured on an analysis filter, and finally weighed or measured under a microscope.

Extraction efficiency must be validated with a decay curve: extraction is repeated until one stage yields less than 10 percent of the dirt collected before. Only then is the component considered largely free of residual particles.

Gravimetry or particle counting - what to measure?

The two evaluations complement each other. Gravimetry gives the total dirt mass in milligrams per component or normalised per 1000 cm² of surface. Particle counting under a light microscope records number and size and assigns them to size classes.

• Gravimetry: simple figure for total load, ideal for series monitoring.
• Optical particle counting: size distribution by size classes B to N (5 µm to over 1000 µm).
• Metallographic analysis: separates shiny metallic from non-metallic particles.
• Largest single particle: often decisive for functional damage.

How do you set sensible limit values?

Limit values derive from the component function, not from the standard. What matters is the smallest safety- or function-critical clearance - for example the guide clearance of a valve or the electrode spacing on a circuit board.

A four-step approach works well in practice: determine the critical size, measure a reference series, capture the statistical spread, and set the limit with a safety margin above the real process level. This keeps the value achievable yet protective.

Frequently asked questions