Condition Monitoring, Troubleshooting and Reliability in Rotating Machinery

14Gas Turbine Drivers: What Users Need to Know

By Robert X. Perez

Overview

Mechanical-drive gas turbines are used primarily to provide rotational power to a fluid mover, such as a centrifugal pump or a centrifugal gas compressor. The majority of gas turbine-powered mechanical drive machines are used in the oil and gas industry for pumping, injection, re-injection, and compression applications (see Figure 14.1) and for the transfer of oil or gas through pipelines. Most of these gas turbines utilize natural gas as their primary fuel.

Industrial gas turbines can either be used solely as mechanical drives or can be used in association with a recovery steam generator. Mechanical drives differ from electrical power generating sets in that they are often smaller and feature a dual shaft design as opposed to a single shaft. Their rated power range varies from 1 megawatt (1341 hp) up to 50 megawatts (67051 hp) [1]. In drive applications, gas turbine engines can be connected directly or through a gearbox when driving pumps or compressors.

Single Shaft versus Two Shaft Gas Turbines

Industrial gas turbines are available in two main varieties: single shaft and double shaft designs.

• Single shaft turbines, as their name implies, have a single shaft running through the entire turbine. Therefore, the gas turbine compressor, turbine, and the output drive shaft all turn at the same speed.
• In two shaft gas turbine applications, the gas generator, i.e., gas producer, and the power turbine turn ...