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(Abstracts from "Bauteilreinigung") The classification of cleaning processes as subcategory of manufacturing processes can be done according to the draft German standard 8592. In this draft a hierarchical structure of the cleaning processes alongside the impact principle is proposed. Hierarchical levels are represented by a multi digit number. Initially "cleaning" is integrated into the structure of DIN 8580 as a subcategory of the manufacturing process "separating" receiving the order number 3.6. The next hierarchical level of the classification scheme states the physical impact principle of the cleaning processes. Whereby the blasting processes turn out to be problematic, as these processes combine the "mechanical" and the "jet" technique. Therefore the blasting processes were put into a special subgroup.

Draft DIN 8592 neither considers processes which combine several physical impact principles nor can newly developed special processes be integrated into the scheme. Also the proposed gradation is not detailed enough to clearly differentiate single processes from one another. E.g. diluting under 3641 covers the processes: steam degreasing, immersion cleaning, wiping, brushing, drum cleaning, spray cleaning, flooding, boiling and ultrasound supported solvent cleaning.

Standards providing clear guidance for the actual cleaning exist only for a limited number of processes. Only processes which have been applied for a long time have been standardized like: high pressure water blasting (DIN EN 1829), cleaning with alkaline agents (DIN 65079), solvent cleaning (DIN 65078, LN 29740), blasting (DIN 65468), electrolytic cleaning (DIN 65473) and flame blasting (DIN 32539). In recent years mainly in USA newly developed processes have not been introduced into European standards.

Degrees of cleanliness, which can be achieved by the single cleaning processes have only be standardized in very limited cases, e.g. photographic pattern for comparison of surface preparation degrees preceding coating in steel construction (DIN 55928, ISO 8501-8504) In addition some standards recommend different analytical methods, like e.g. the water break test, for the determination of a sufficient removal of fats. However these approaches cannot as such be applied to other cases.

As concerns the area of cleaning equipment mainly the safety aspects of this machinery shall be standardized without referring to utilization and application limits of the described equipment (pr EN 12921).

Summarizing it has to be noted, that the German and European standardization only give limited assistance when trying to select a specific cleaning process according to the actual workshop requirements.

Overview over the main standards regarding parts cleaning (2001):

Definition of degrees of cleanliness

A classification of the degree of soiling or cleanliness is not provided by the German or European standards. Only for surface preparation degrees for steel structures there is an existing standard (DIN 55928). But this definition cannot be applied in general to the cleaning of components. The US American standards give at least approaches to the definition of degrees of cleanliness and related cleaning methods.
The American ASTM (American Society for Testing and Materials) lays down compulsory test methods in many areas, which are meant to probe the fitness of a cleaning procedure for a given purpose. In most cases not the cleanliness of a component is tested but rather as to whether the subsequent process (e.g. coating, painting or gluing) can be successfully fulfilled. A quantitative cleanliness standard is applied at the US military: The American military standard MIL-STD 1246C contains an approach relating to the amount of soiling of a given type on a defined surface area or in a defined volume. The units depend on the type of dirts (e.g. number of particles, mass or covered area) and are given as follows:

MIL-STD-1246 LEVEL X Y, Z

X: Numerical particle cleanliness degree according to a table, gives the number of inorganic particles per surface unit
Y: Cleanliness description for NVR (non volatile residue) according to a table in mass per area unit, resp. mass per volume unit
Z: Alternative or additional degrees of cleanliness according to one or more elements of the following list in the given units
PAC: Covered area of component by dirt in percent
PC: Number of particles independed of the table for particle cleanliness
CVCM: Gathered volatile substances according to ASTM E595
VCM: Volatile substances, determined different from ASTM E595, with statement of test method
NTU: Nephelometric cloudiness, units as per table, for liquids
TML: Total loss of mass according to ASTM E595

The test methods for the determination of the degree of cleanliness are compulsory. This standard and the related degrees of cleanliness are based on very high requirements as they are needed for, among others, aeronautics. To apply these standards in ordinary manufacturing cannot be recommended because of the necessary expensive test methods.

Test- and analytical methods: