Method of Applying Spray Solvent

T.O. 33B-1-1 2-28 NOTE With the elimination of the use of 1,1,1 trichloroethane (methyl chloroform), the solvent remover in portable penetrant kits is most likely to be Class 2 (non- halogenated). Most Class 2 solvent removers are hydrocarbon solvents such as aliphatic naphtha. While they are excellent solvents, because of their high boiling point (in excess of 300F) such Class 2 solvent removers will not rapidly evaporate at room temperature. Consequently, when used as a precleaner, care must be taken to assure there is no residual solvent remover on the part surface prior to the application of penetrant. This can be accomplished by thoroughly drying the surface with a cloth or rag or, alternatively, using a more volatile solvent such as isopropyl alcohol to remove the less volatile solvent remover. Portable penetrant kits contain aerosol spray cans of penetrant, developer and solvent remover. The solvent remover is used in three ways: it serves as a precleaner before penetrant application; it removes the last of the excess penetrant after completion of the penetrant dwell; and serves as a postcleaner to remove residual penetrant materials when the inspection has been completed. This section deals with using the solvent as a precleaner. 2.3.7.2 Method of Applying Spray Solvent. The method of applying spray solvent remover as a precleaner is different than when it is used to remove penetrant following penetrant dwell. When used as a precleaner, the solvent remover may be sprayed directly on the test surface. Spraying the solvent directly on the surface is not permitted when removing excess surface penetrant during a penetrant inspection process. As a precleaner, a liberal amount of solvent should be applied and the excess solvent and contaminants wiped from the test surface with a dry, lint free cloth or paper towels. The spray and wiping operation should be repeated until a clean surface is obtained. Following the, application of spray solvent, a dwell period must be allowed to permit evaporation of any residual solvent before applying penetrant. 2.3.7.3 Hazards Of Aerosol Cans. Aerosol cans are a convenient method of packaging a wide variety of materials. Their wide use, both in industry and the home, has lead to complacency and mishandling which can be hazardous. Some of the hazards in the use of aerosol cans are discussed below: a. The containers are gas pressure vessels. When heated the gas pressure increases. At temperatures above 120°F (49°C) the container may burst. b. Any combustible material, regardless of flash point, can ignite with explosive force when it is finely divided and dispersed in air. c. Penetrant materials (penetrant, cleaner/remover and developer) may contain petroleum distillates and aliphatic (kerosene, mineral spirits, etc.) or aromatic (benzene type hydrocarbon) solvents. These chemicals must be carefully used in the aerosol form to avoid health hazards. 2.3.8 Postcleaning After Penetrant Inspection. 2.3.8.1 Effects Of Inspection Residues on Subsequent Service. Penetrant inspection residues can have several adverse effects on subsequent processing and service. Developer and penetrant residues, if not removed, have detrimental effects on the application of surface finishes such a painting, plating and anodizing. Penetrant residues in flaws or discontinuities can seriously affect weld quality if not removed prior to repair welding. Parts that will contact liquid oxygen must be given special attention. Traces of oil can cause an explosion when contacted by liquid oxygen. Developer residues can interfere with the functioning of the part if they involve a moving or wear surface. In addition, developer materials can absorb and retain moisture resulting in corrosion of the part.