A liquid injection apparatus for use with a compressor having a rotor shaft and a casing part is provided. The liquid injection apparatus includes at least one conduit and at least one nozzle coupled to the conduit(s). The liquid injection apparatus is panel-shaped and has a first panel segment, a second panel segment, and at least one of: a passage defined between the first panel segment and the second panel segment, the passage sized to receive at least one of the rotor shaft and the casing part; and a third panel segment positioned between the first panel segment and the second panel segment. The third panel segment is at least in part detachable from the first panel segment and/or the second panel segment for receiving at least one of the rotor shaft and the casing part between the first panel segment and the second panel segment.