Mechanical drive gas turbines are available from a number of manufacturers. These gas turbines are grouped into "Industrial" and "aero-derivative" types. The industrial engines are heavy duty machines, with longer hours between overhauls but have lower efficiencies. The aero-derivative use aero engines for the gas generators and have higher thermal efficiencies. Commonly used mechanical drive gas turbines are available within a range of 3 to 30 MW. This range has been extended to 120 MW for LNG compressor drives by employing the larger "power generation" gas turbines. However, the number of engine models is still relatively small with engines available in discrete power sizes.

The selection of compressors when driven by gas turbines requires a very different approach. Since the maximum power of a gas turbine is fixed, compressor design flow capacity is determined by the available power and process requirements. Since gas turbines are the most expensive item, the compressor selection process revolves around determining the minimum number of gas turbines to meet the total plant flow capacity. The choice of engine is complicated by the need to install a spare compressor train to cover for planned and unplanned shut downs. This is an iterative process and requires many different process schemes before an optimum solution is finalised.