This SAE Aerospace Information Report (AIR) provides technical information to assist the development of specific cleaning methods for filter elements. Consideration is limited to filter elements which are designated as "cleanable" (not "disposable"), but which cannot be cleaned by simple and obvious procedures. Cleaning methods developed according to this report should be evaluated by the methods of ARP725.

Satisfactory cleaning methods can be developed for most "cleanable" filter elements. Technical or economic feasibility of the cleaning method may be limited, however, by incompatibility of filter-element construction materials, by mechanical weakness or lack of corrosion resistance to withstand repeated or continued cleaning, or by the presence of unusually tenacious contamination. These factors must be considered when selecting approaches to the development of specific methods.

Purpose:

The purpose of this report is to provide economical and technically sound methods for cleaning and testing filters. These methods are intended to provide a uniform basis for the development of detailed procedures by the prospective users.

Economic Purpose: The primary reason for cleaning filters is to eliminate the cost of replacement. Additional considerations include the reduction of logistic problems in stocking new replacement filters and the conservation of strategic materials and skills in the event of a national emergency. Considering all of these factors, the total cost of cleaning must be less than the total cost of replacement for a given situation. While process economy is desirable for its own sake, economic evaluation and decision for a particular case can be undertaken by the user alone.

Technical Purpose: Applicable cleaning processes are mainly determined by the geometry and materials of construction used in the filter. Additionally, final cleanliness requirements and the characteristics of contamination plugging the filter must be considered. Cleaning processes should be selected which will be effective on most "cleanable" filters under usual circumstances. Test methods must detect inadequately cleaned or damaged filters.