A casing for a turbine, comprising: a stationary component defining at least a portion of a working fluid path for directing a working fluid across a blade stage including a plurality of blades operatively coupled to a rotor; a fluid injection nozzle in the stationary component configured to impact a pressurized damping fluid on a surface of at least one of the plurality of blades of the blade stage in opposition with a vibratory movement thereof to cause damping of vibration of the at least one of the plurality of blades during operation of the turbine; a valve for selectively admitting the pressurized damping fluid to the fluid injection nozzle from a source of pressurized damping fluid; and a control system for controlling the valve, wherein the control system is configured to open the valve to operate the fluid injection nozzle in response to an operational parameter of the turbine; wherein the fluid injection nozzle includes a plurality of fluid injection nozzles circumferentially spaced in the stationary component, each fluid injection nozzle including a respective valve for selectively admitting the pressurized damping fluid to the fluid injection nozzle from the source of pressurized damping fluid under control of the control system; characterized in that, the casing further comprises a sensor system operatively associated with the plurality of blades for determining an amplitude of vibration of the at least one of the plurality of blades; and wherein the control system is configured to open at least one respective valve to operate at least one respective fluid injection nozzle in response to the amplitude of vibration of the at least one of the plurality of blades exceeding a threshold during operation of the turbine. a stationary component defining at least a portion of a working fluid path for directing a working fluid across a blade stage including a plurality of blades operatively coupled to a rotor; a fluid injection nozzle in the stationary component configured to impact a pressurized damping fluid on a surface of at least one of the plurality of blades of the blade stage in opposition with a vibratory movement thereof to cause damping of vibration of the at least one of the plurality of blades during operation of the turbine; a valve for selectively admitting the pressurized damping fluid to the fluid injection nozzle from a source of pressurized damping fluid; and a control system for controlling the valve, wherein the control system is configured to open the valve to operate the fluid injection nozzle in response to an operational parameter of the turbine; wherein the fluid injection nozzle includes a plurality of fluid injection nozzles circumferentially spaced in the stationary component, each fluid injection nozzle including a respective valve for selectively admitting the pressurized damping fluid to the fluid injection nozzle from the source of pressurized damping fluid under control of the control system; characterized in that, the casing further comprises a sensor system operatively associated with the plurality of blades for determining an amplitude of vibration of the at least one of the plurality of blades; and wherein the control system is configured to open at least one respective valve to operate at least one respective fluid injection nozzle in response to the amplitude of vibration of the at least one of the plurality of blades exceeding a threshold during operation of the turbine.