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Chapter 7

Drivers

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‡
†
Grant Musgrove*, Brian Bauer , Kenneth Hall , Martin Hinchliff , Cyrus
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¶
†
Meher-Homji , Rainer Kurz , Brian Pettinato , Dragan Ristanovic and
k
Matt Taher ¶
* †
Southwest Research Institute, San Antonio, TX, United States, Elliott Group, Jeannette, PA,
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‡
United States, Caterpiller Oil & Gas, Lafayette, IN, United States, Dresser-Rand, Painted Post,
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k
NY, United States, Bechtel, San Francisco, CA, United States, Solar Turbines, Inc., San Diego,
CA, United States
Introduction
Compressors are typically driven by an electric motor, gas turbine, gas engine,
steam turbine, or expander. In the most basic form, the selection of a driver may
be dependent on the operating profile needed for the compressor and the avail-
ability of a power source. For example, electricity may not be available in a
remote location, but steam from the process is available to drive a steam turbine.
Aside from operating loads and power source, other considerations of maintain-
ability, auxiliary systems, capital costs, and others are important factors in the
selection of a driver for compressor applications. This chapter provides a review
of the common drivers used for compressors in the oil and gas industry to pro-
vide background into important factors of their selection.

Gas Turbines
Overview of Gas Turbine Components

Any gas turbine consists of at least a compressor, a combustor, and a turbine.
The thermodynamic cycle is known as Brayton cycle (Fig. 7.1), which involves
the compression of a working fluid (such as air), the addition of fuel to in-
crease the temperature of the compressed fluid, and the expansion of the hot,
pressurized fluid through a turbine. Part of the work extracted by the turbine
is used to power the compressor.
The compressor, usually an axial type or a centrifugal type, compresses the
air to several times atmospheric pressure. In the combustor, fuel is injected into
the pressurized air from the compressor and burned, thus increasing the air tem-
perature. In the turbine section, energy is extracted from the hot pressurized gas,

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