Leakage occurred on warm tubes of high pressure cylinder of a 600 MW unit turbine frequently.By pipeline stress analysis

the over large secondary stress on the pipe was considered as the major reason causing the pipe failure.The warm tube supports and hangers are mainly rigid and the design of the reducer at pipe connection is unreasonable

leading to overproof of secondary stress on the reducer connection joint.To avoid the stress concentration

the rigid supports and hangers should be better replaced by the resilient ones

and the reducer at the pipe connection joint should be designed in smooth transition.