Examination of gas turbine CDP Seal teeth with varying types of FPI indications

The CDP (compressor discharge pressure) seal is positioned in the compressor discharge cavity, the area where high-pressure air exits the final stages of the high-pressure compressor and flows into the combustor and adjacent cavities. Its function is to maintain the proper pressure level for the combustor supply air. The CDP seal is manufactured from wrought nickel-based alloy, operates near 1100 F, and the teeth have a metallic bond coat, and ceramic top coat During a shop visit, many of these CDP seal teeth were found to have rejectable FPI indications on the tooth faces classified as ruler-like linear indications, V-shaped, and dot-like. The presentation will describe the features observed, depth, and mechanism.