Page 147 - Compression Machinery for Oil and Gas

P. 147

Chapter 4

Integrally Geared Compressors

†
†
Aoron Rimpel*, Karl Wygant , Rob Pelton , Christian Wacker ‡
and Kolja Metz ‡
* †
Southwest Research Institute, San Antonio, TX, United States, Hanwha Power Systems Americas
‡
Inc., Houston, TX, United States, MAN Energy Solutions, Berlin, Germany

Introduction
Integrally geared compressors (IGCs) have been in use worldwide since before
the 1950s. Early applications were primarily in plant air service, but IGCs have
been used increasingly in the process industry since the 1980s [1, 2]. The term
“integrally geared” refers to the fact that IGCs enable the rotational speed
change from the input device (motor, etc.) to the driven component (compressor
impeller) within the frame of the machine—that is, rather than with a separate
gearbox unit and high-speed shaft coupling required by other compressor archi-
tectures. This typically allows an IGC to have a smaller footprint than other
compressor types. In general, integrally geared (IG) architecture can be used
for any type of turbomachine—including centrifugal compressors, axial compres-
sors, expanders, etc.—but most applications involve centrifugal compressors.
An IGC comprises a bull gear shaft and one or more pinion shafts, with
impellers attached to each end of the pinion shafts—see Fig. 4.1. IGCs with
up to 5 pinions and 10 compressor stages are not uncommon. Typically, the bull
gear shaft is driven by an electric motor at a fixed speed, although different
drivers and variable speed operation are possible. For motor-driven IGCs,
the bull gear typically runs at 1500–3600rpm, allowing a standard, low-cost
driver to be used. The bull gear then drives the individual pinions at higher rel-
ative speeds, depending on their respective gear ratios, which may be over
50,000rpm in the latter stages of compression. It may also be possible to have
more than one bull gear meshed with one another, each driving separate pinions.
The basic configuration of the IGC rotating assembly is depicted in Fig. 4.1 and
shows the bull gear shaft driving two separate pinion shafts and a total of four
impellers. The bull gear is shown with a dedicated thrust bearing on one side of
the gear, and each of the pinions utilize thrust collars. Other bearing configu-
rations are possible and are discussed further within the topics of bearings
and thrust management later.

142 143 144 145 146 147 148 149 150 151 152