Compressed Air System

Is an integrally geared centrifugal compressor right for you?

IGCCs can enable 8–20% better efficiency compared to conventional centrifugal compressors.

By Amin Almasi

In an integrally geared centrifugal compressor (IGCC), several pinion shafts are arranged around a large central bull gear. An impeller (usually a 3D semi-open one) can be mounted on each end of a pinion shaft. Currently, machines with up to 10 impellers (5 pinions) are available. The compressor shafts can run at high rotational speeds — up to 75,000 rpm. The bull gear generally is driven by an electric motor, which can be a conventional 1,500–1,800-rpm unit or a high-speed 3,000–3,600-rpm one.

In contrast to conventional centrifugal compressors in which all impellers run at the same speed, in IGCCs each pinion can run at a different speed. Thus, every impeller pair can operate at its optimum aerodynamics speed. This is an important advantage — particularly for gases with medium or high molecular weights — that results in higher efficiencies than those of conventional compressor designs.

To learn more about integrally geared centrifugal compressors, read “Investigate Integrally Geared Compressors” from Chemical Processing.

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