Inlet and outlet nozzles are available in a variety of configurations, depending on the manufacturer. They are normally flanged. (Typical arrangements are shown later in this section.) API 617 covers requirements for flange type, and ratings of main and auxiliary connections.
The increased use of fabricated cases has provided additional flexibility in nozzle orientation.
If the installation permits, the following should be considered:
1. Horizontally-split units with process connections in the lower half (downconnected) allow removal of the top half, and internals including rotor, without disturbing the process piping.
2. If overhead process piping is required, the use of vertically-split barrel compressor casings still allow removal of the inner casing and access to the internals without removing process piping. Fabricated casing design makes the vertically-split unit a cost-effective alternative for larger medium pressure applications.