Failure Modes of steam Turbine

 

     The failure modes of steam turbines are classified into following main three categories:

1.         Steam Flow Path parts:   Control valves, Nozzles(HP), Blades (HP), Nozzles (LP), Blades (LP) .
2.         Rotating Parts: Blades (HP), Blades (LP), Rotor, Thrust collar and, Journal Shaft.
3.        Stationary Parts: Casing, Diaphragm, Seals, Thrust and Radial bearings.

       Basic root causes for each damage mode are listed in table below:

Components		Damage Mode	Root Causes
Flow Path Parts	Control Valves	Valve stem Bending Fatigue Failure	High Steam Velocity Fluid excitation
	Nozzles (HP)	Solid Particle erosion Fouling	Hard Foreign Materials inside of pipes
	Blades (HP)	Solid Particle erosion Fouling	Hard Foreign Materials inside of Pipes   Steam Impurity
	Nozzles(LP)	Fouling	Steam Impurity
	Blades(LP)	Drain attack Erosion Fouling	High moisture and High velocity Steam impurity
Rotating Parts	Blades (HP)	High Cycle Fatigue Failure Centrifugal Force Failure	Excessive Excitation Force Excessive Over speed
	Blades(LP)	High Cycle Fatigue Failure Centrifugal Force Failure	Improper water treatment Excessive Over speed
	Rotor	Rubbing and shaft Bow & High Vibration  Disk SCC	Improper start up Drain Intake, Steam Impurity
	Thrust Collar Journal shaft	Rubbing & Scratch or wear	Excessive Thrust Force Improper oil supply
	Bearings	Rubbing and melting	Excessive Thrust Force Improper oil supply
Stationary Parts	Casing	Creep Deformation/Creep Rupture, Erosion and Corrosion	Operation beyond operating widow, Excessive Drain, Galvanic corrosion
	Diaphragm	Diaphragm bending / Deformation , Erosion &Corrosion	Operation beyond operating widow, Excessive Drain, Galvanic corrosion
	Seals	Rubbing and Erosion	Improper startup Excessive Drain