Abstract: The high disc temperature(DCT) of M701F3 gas turbine which is caused by the wear and tear on the downstream side of seal ring housing threatens the security and economical efficiency of the unit operation. In this paper, the necessity and scheme for the technical retrofit are expounded with detailed key processing and constructing techniques. The technical difficulties encountered such as the accuracy of machine tools, and the innovation of computer numerical control, lathe and cutting tools, as well as drill stems and heads, are solved with the manufacturing technique and standards improved. In addition, the modifications of the seal ring housings from the second to fourth stages turn out to be a big breakthrough in local manufacturing techniques, which will have very promising prospects to popularize.

Key words: gas turbine, DCT, seal ring housing, downstream side, modification, localization