Understanding IEST-STD CC -1246D LEVEL 100 Classifications

IEST 1246D Is a process specification that establishes a surface cleanliness requirement for The cleaning and cleanroom packaging of products, after fabrication and before assembly.

Requirements

All parts, components, assemblies, systems or related equipment requiring cleaning must be cleaned to the specified cleanliness level and inspected in accordance with this specification. Assemblies and systems may require disassembly to permit cleaning. Remove any part or component that might degrade during cleaning before cleaning and clean them as separate items. Only trained and certified personnel should perform cleaning and disassembly operations on precision cleaned parts.

Cleaning

All surfaces of your product must be pre-cleaned to remove dirt, grit, scale, corrosion, grease, oil and other foreign matter, prior to any final precision cleaning process. Metallic parts should be surface treated (cleaned, passivated, pickled and/or coated) as necessary to prevent any latent corrosion and contamination. Assembled items that do not lend themselves to this type of treatment should be treated prior to assembly. Surface treated areas that have been degraded during subsequent fabrication and assembly should be reprocessed to restore the original protective finish.

General Requirements

Your engineering department should select a cleanliness level from the two available options. The following two categories of cleanliness levels are for use in providing a uniform and cost-effective contamination control option to cover a wide range of cleanliness needs:

Precision cleanliness.

Precision cleanliness levels may be described as quantitative. This includes particulate counts, with or without nonvolatile residue (NVR), or other suitable film/non-particulate limits. These levels are usually specified for internal surfaces of fluid systems.

Visible cleanliness.

Visible cleanliness levels may be described as qualitative. The verification and/or inspection of these levels is done visually. However, these levels are considered to be adequate, since the application of these levels must be viewed with respect to hardware design and operation. These levels represent a cost-effective alternative to precision cleanliness levels, and offer greater flexibility for the appropriate design or engineering group. Visible cleanliness levels may be used as either interim or final cleanliness levels.

Guidelines for Selection and Use of Visible Cleanliness Levels

As a point of reference, the human unaided eye (corrective lenses are acceptable) can detect particles as small as 40 to 50 microns under ideal conditions.

Visually Clean + Ultra Violet Light

This level provides a surface condition free of all visible contamination (particulate and non-particulate) augmented by UV (UV light of 3,200 to 3,800 angstroms wavelength) inspection. UV inspection will detect some, but not all, hydrocarbon film matter. This level is usually specified for hardware that cannot tolerate buildup of hydrocarbons between uses or operations.

The VC + UV level requires:

Mandatory cleaning

Heat-sealed double bagging for preservation

Visually Clean

This level provides a surface condition similar to VC + UV except that UV inspection is not a requirement. This level is usually designated for:

Hardware that requires removal of surface particulate and non-particulate contamination for operation or use; or

Hardware for which re-cleaning would be difficult and/or time-consuming, therefore making continuous packaging protection desirable. This level requires mandatory cleaning and pro¬tection by heat-sealed bagging.

Generally Clean

This level is similar to VC but differs in the following significant areas:

Cleaning is only required if the item does not pass inspection. If the item has ever been inspected; i.e., is acceptable "as is," it does not need to be cleaned.

Inspection is not as rigorous as VC in that clumps or agglomerations of contamination are removed instead of individual particles.

Heat-sealed bagging protection is not required; but normal protection is required for handling, shipping, and storage.

The GC level should therefore be specified for hardware that is not sensitive to contamination and is easily and quickly cleaned or re-cleaned.

Packaging Techniques and Materials Of Cleaned Parts

Package items to be cleaned to a precision cleanliness level should use the double-bagging technique. Double bagging of precision-cleaned parts is required to provide redundancy, if one bag is damaged. Double bagging also enables removal of the outer bag before placement of the parts in the clean room, spacecraft, or test chamber, to maintain area cleanliness requirements. Materials used for the outer bag may differ from those used for the inner bag in order to obtain overall slough resistance and moisture barrier qualities. Referring to IEST-STD 1246 will provide a ready reference to acceptable bagging techniques, and materials, for component cleanliness requirements. The use of two different bagging materials is quite common where strength or puncture resistance is a requirement. Nylon inner bags ( strength and puncture resistance) combined with polyethylene outer bags, cleaned to the required level offer both the cleanliness and the puncture resistance required for some fabricated parts.