Development of a Complex Geometry Standard Fixture and Solvent Evaluation Method fo Assessing Replacement Solvents for AK-225G

Environmental regulatory requirements dictate the need for NASA Stennis, and NASA as a whole to identify new solvents that conform to changing environmental impact expectations while delivering appropriate contaminant removal capabilities.  The widely used AK-225G hydrochlorofluorocarbon (HCFC) will be banned for import or manufacture in the US beginning January 1, 2015.  NASA Stennis uses this solvent for cleaning propulsion testing components.  Many components, for example Bernoulli tubes used on pressure sensors, have complex geometries that must be efficiently and effectively cleaned by these solvents; however, visual inspection during and after cleaning is prohibitive owing to their complex geometric shape.  Testing the ability of a solvent to clean contaminated components, and then verifying contaminant removal from the insides of these complex geometries, is a critically important factor in selecting new cleaning solvents to replace AK-225G.

Overall, the project efforts succeeded in developing a complex geometry fixture and a test method that can be used to differentiate cleaning ability between different solvents for hydrocarbon residue.

The focus of this analysis was the development of a complex geometry test fixture and test method for determining solvent cleaning efficiency. AK-225 belongs to a class of chemicals called HCFC and is used for cleaning, drying and lubricant deposition applications. These compounds are regulated by the U.S Clean Air Act and can no longer be produced or imported into the United states.  Any alternative solvent must be able to dissolve the soil/contaminant on the part.

The determination of an environmentally safe but reliable quality cleaning solvent is critical to Stennis propulsion test operations.  A detailed methodology for determining the replacement solvent was devised and implemented during this project.   In reality, parts undergoing cleaning are not able to be inspected internally to determine a cleanliness level.  Therefore, a test rig that could be disassembled with complicated internal geometry was made using several computer aided design iterations. The test fixture disassembly allows for the inspection of the internals following the use of the cleaning solvent.  The contamination solution is made of various items that are used in the propulsion test environment.  Upon “dirtying” the test rig, a thorough post processing inspection exercise procedure was devised to be used when evaluating alternative solvents.