Question 1

What does CCC = A(B20/C16/D14/E10/F8/G6) mean?

Accepted Answer

It is a Component Cleanliness Code on an area basis: counts per 1,000 cm² of wetted surface. Each letter is a size class by particle length and each number is a contamination level that roughly doubles per step. Class B (5 to 15 µm) allows up to 1,000,000 particles, C up to 64,000 and D up to 16,000. E allows up to 1,000, F up to 250 and G (150 to 200 µm) up to 64. Classes H and above are not listed, so they carry no limit. B, C and D sit below the 50 µm floor of standard light-optical analysis, so a spec carrying them must say how they will be measured.

Question 2

Is a Component Cleanliness Code the same as an ISO 4406 cleanliness code?

Accepted Answer

No. An ISO 4406 code such as 18/16/13 describes particles per milliliter in a hydraulic fluid sample at 4, 6 and 14 µm(c). A CCC describes particles rinsed off a component, per 1,000 cm², per 100 cm³ or per part, in size classes from 5 µm to 3,000 µm and above. ISO 16232 excludes operating fluids, so an ISO 4406 code cannot stand in for a component cleanliness limit. If the fluid also needs a limit, state it separately.

Question 3

What does an ISO 16232 cleanliness report include?

Accepted Answer

The inspected object, the preparation steps, the extraction method and its parameters, the filtration and the analysis method, then the results. Results are the gravimetric residue in mg when a mass limit is specified, plus a size-class table with all particles, metallic-shiny particles and fibers in separate columns. The largest particle in each column is imaged, and the blank value is recorded. A Component Cleanliness Code is added when requested; coding is optional in both standards. A statement of conformity against the specification limits closes the report when asked for.

Question 4

How does the blank value limit the cleanliness spec I can write?

Accepted Answer

Both standards cap the blank value at 10 percent of the required cleanliness value in each size class, and it is never subtracted. A class limit of 8 particles leaves 0.8 particle for the blank. The blank then has to show no particle in that class at all before the result can be trusted. A gravimetric limit under 1 mg leaves a blank under 0.1 mg, which takes a high-resolution balance in a climate-controlled room to determine. Write limits the test can resolve, or pool enough parts per lot to raise the permitted amount. How the blank is measured is on the ISO 16232 and VDA 19.1 testing page.

Insights

How to Read a Component Cleanliness Code (CCC) and Write a Testable Spec

VDA 19.1 vs ISO 16232: What Is the Difference?

Gravimetric Cleanliness Test (Millipore) vs Particle Counting: What Each One Tells You