Abstract: The invention concerns a compressor installation with a water-injected compressor element (1) having a water cycle (6) and a water supply device (15) for supplying water to the water cycle (6), containing a water supply line (16) with a controllable valve (18) and a reverse osmosis filter (17) therein. Onto the water cycle is connected a by-pass (21) in which are erected an ion exchanger (22) and a controllable valve (23). A valve (18) in the water supply line (16) is controlled by a device (20) for measuring the amount of water in the water cycle (6), and the valve (23) in the by-pass (21) is controlled by a device (24) for measuring the conductivity of the water.

Abstract: Connection piece for connecting a housing (4) of a drive unit (2) with a housing (5) of a compressor element (1). The connection piece is provided with ribs (12) over at least a part of its wall, the height of the ribs (12) being at least equal to one and a half times a thickness of the part of the wall upon which the rib is standing and the thickness of the ribs (12), half-way up the height, being equal to at least half of the thickness of the part of the wall. The ribs (12) form a pattern which divides the wall into adjacent wall segments (13) which have a first characteristic mode for bending that has a resonant frequency which excludes excitation by substantially all excitation frequencies up to and including a highest of the compressor element (1).