What happens when a centrifugal compressor equipped with anti-surge valve is run on lighter gas than design?
(Design MW of gas= 22, Actual MW of gas=13)?
To get the same discharge pressure, the compressor will have to go higher up on the head - flow curve with a lighter gas.
How does your ASV work, on discharge pressure only, or on simple differential pressure( discharge - suction), or on mol wt / density compensated flow control?