Test arrangement for a centrifugal compressor stage

A method for obtaining non-extrapolated empirical data associated with performance characteristics of a compressor at head values lower than head value losses associated with a test loop connected to the compressor, the method comprising:

• connecting an auxiliary compressor to a main compressor in a test loop such that a process fluid output from the auxiliary compressor is connected to a process fluid input of the main compressor and a process fluid output from the main compressor is connected to a process fluid input of the auxiliary compressor;
• installing a control valve in the test loop between the auxiliary compressor and the main compressor;
• installing one or more process fluid coolers and one or more orifices in the test loop between the auxiliary compressor and the main compressor;
• installing a first plurality of sensors in the test loop adjacent to the process fluid input of the main compressor;
• installing a second plurality of sensors in the test loop adjacent to the process fluid output of the main compressor;
• and
• collecting data from the first plurality of sensors and the second plurality of sensors while operating the test loop at conditions such that the main compressor head is lower than head value losses associated with the test loop.