Repair Technologies Of Mechanical Drive Steam Turbines For Catastrophic Damage.

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Saga, Manabu; Iwasaki, Shugo; Tsurusaki, Yuzo; Hata, Satoshi
Texas A&M University. Turbomachinery Laboratories
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Mechanical drive steam turbines play an important role as core equipment in petrochemical plants, and these turbines are protected for safe operation by an antioverspeed trip device, as well as other monitoring and protection systems. However, in some cases a turbine will suffer severe mechanical damage due to improper operation or failure to activate the protection system as a result of human error. For urgent plant recovery and to minimize the duration of risky operation with no spare rotor, a damaged turbine has to be repaired in as short a time as possible. This paper introduces actual experiences in repairing and reviving catastrophically damaged turbine rotors through special welding procedures, based on element test to find the optimized welding condition, detailed strength calculations to confirm the integrity, and heat transfer analysis for proper heat treatment process conditions. These basic procedures are discussed to show useful data. The revived rotor of the extraction condensing turbine was placed back into the casing and operated. The turbine was uniquely modified in order to balance the required amount of power and minimize the repair time, to restart the plant as quickly as possible. The case study for this optimization is discussed by showing thermodynamic calculations, performance, and repair schedules. Root cause analysis for the process of the catastrophic failure is explained, for the integrated control system governing the control and operation positioner systems.