Which device is typically not used for starting a gas turbine?

In the context of gas turbine operation, the typical devices used for starting include pneumatic starters, electric motors, and small diesel engines. These devices are effective because they can provide the necessary initial rotational energy to bring the gas turbine up to speed before it can start combustion.

Small diesel engines are particularly useful because they can deliver a substantial amount of torque and can run independently of the turbine's fuel supply, making them reliable starters. Pneumatic starters are also commonly used due to their ability to rapidly deliver high-speed air pressure to spin the turbine. Electric motors can be employed as well, especially in situations where electrical power is readily available.

On the other hand, small gas engines are not typically utilized as starting mechanisms for gas turbines due to their operational characteristics and power output limitations. They are generally less efficient in providing the required starting torque and may not produce the necessary initial reversible speed compared to the other starter options. This makes them less favorable for reliably starting gas turbines, which require a significant amount of energy to overcome inertia and reach the necessary operational speeds.