A mechanical start system has been developed to start the Ship’s Service Gas Turbine Generators (SSGTG) on board U.S. naval destroyers. The current starting system uses either stored high pressure air or bleed air from another running turbine. The U.S. Navy has reviewed the high pressure air system and found it to be a costly system for both ship construction and maintenance. As a result, the Navy is requiring an alternative starting method that will replace high pressure air. It should be noted that any alternative that introduces compressed air to start the SSGTG depends on the start air regulating assembly and the pneumatic starter.
The Redundant Independent Mechanical Start System (RIMSS) consists of an Allison Model 250 turboshaft engine mounted above the SSGTG main reduction gearbox. The turboshaft power take off is connected to the pinion shaft of the reduction gearbox by means of a parallel shaft auxiliary transfer gearbox. The transfer gearbox connection to the reduction gearbox replaces the pneumatic starter adapter pad but provides a means to also connect the pneumatic starter. As a result, the pinion shaft can be driven either pneumatically by the air turbine or mechanically by the Model 250 engine. This provides an alternative starting mode which is totally independent of the present means of starting. This will increase the reliability and availability of the SSGTG since it can still be started even if the pressure regulator or the pneumatic starter is not functional. This system has undergone testing at the Naval Surface Warfare Center Carderock Division facility in Philadelphia.