tailieunhanh - Volume 17 - Nondestructive Evaluation and Quality Control Part 3

Tham khảo tài liệu 'volume 17 - nondestructive evaluation and quality control part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Dry-developer powder form A is applied after the workpiece has been dried and can be applied in a variety of ways. The most common is dusting or spraying. Electrostatic spray application is also very effective. In some cases application by immersing the workpiece into the dry powder developer is permissible. For simple applications especially when only a portion of the surface of a large part is being inspected applying with a soft brush is often adequate. Excess developer can be removed from the workpiece by a gentle air blast 140 kPa or 20 psi maximum or by shaking or gentle tapping. Whichever means of application is chosen it is important that the workpiece be completely and evenly covered by a fine film of developer. Water-soluble developer form B is applied just after the final wash and immediately prior to drying by dip flow-on or spray techniques. No agitation of the developer bath is required. Removal of the developer coating from the surface of the workpiece is required and easily accomplished because the dried developer coating is water soluble and therefore completely removable by a water rinse. Water-suspendible developer form C is applied just after the final wash and immediately before drying. Dip flow-on and spray are common methods of application. Care must be taken to agitate the developer thoroughly so that all particles are in suspension otherwise control of the concentration of the applied coating is impossible. Removal of the water-suspendible developer can best be achieved by water spray rinsing. If allowed to remain indefinitely on the workpiece the developer can become difficult to remove. Solvent-suspendible nonaqueous developer form D is always applied after drying by spraying either with aerosol containers or by conventional or electrostatic methods. Proper spraying produces a thin uniform layer that is very sensitive in producing either fluorescent or red visible indications. The volatility of the solvent makes it impractical to use in .