A screw compressor includes a screw rotor having a plurality of helical grooves, a first rotor configured to mesh with the helical grooves of the screw rotor, a second rotor configured to mesh with the helical grooves of the screw rotor, and a casing having a partition wall rotatably retaining the screw rotor and covering an outer peripheral surface of the screw rotor. The partition wall includes first and second envelope portions to form first and second compression chambers. The first compression chamber compresses a fluid introduced into the casing with a suction pressure to an intermediate pressure higher than the suction pressure. The second compression chamber compresses the fluid with the intermediate pressure to a discharge pressure higher than the intermediate pressure.

An element for compression of a gas to be compressed having a low temperature of 40 C. or lower, which element (1) is provided with a housing (2) containing at least one rotor (3) which is mounted rotatably with its shaft (5) with respect to the housing (2) and with an inlet (6) for the gas to be compressed and an outlet (7) for compressed gas, characterized in that the element (1) is provided with a heating means for an end (9a) of the shaft (5) of the rotor (3) located closest to the inlet (6).

The present invention concerns a volumetric compressor (1) that can be used, preferably, for producing equipment and/or a plant for the suction of material in liquid, solid, powder or slurry form. The compressor according to the invention comprises a body (2) defining an operative chamber (5), a suction section (51) and a discharge section (52) of an operating fluid. The compressor further comprises at least two lobe rotors (8A. 8B), the lobes (81A. 81B) of which are housed inside said operative chamber (5), cach rotor (8A. 8B) rotating around a corresponding longitudinal rotation axis (101A. 101B). The compressor comprises a first header (6) and a second header (6) which delimit on opposite sides the operative chamber (5): cach header comprises a bank (61, 61) connected to the body (2) and configured to support the rotors (8A, 8B) and a cover (62, 62) connected to the bank (61, 61) so as to define an inner volume (65, 65) comprised between the cover (62, 62) and the bank (61, 61) and designed to house, in use, a lubricating bath. According to the invention the compressor comprises a generator unit for generating a forced flow of cooling gas and, for at least one of the headers (6, 6), the bank (61, 61) defines a cooling chamber (70, 70) physically separated from the operative chamber (5) and from the inner volume of lubricant. Said chamber (70, 70) comprises an inlet (71, 71) and an outlet (72, 72) for a cooling gas, where said inlet communicates with the generator unit of the forced flow of said cooling gas.

A device for painting a compressor or vacuum pump housing including a first semi-cylindrical structure adjoined to a second semi-cylindrical structure, a dispersing head including a rotating part having a bell shaped structure and a stationary part; a paint reservoir connected to the stationary part through a conduit; a supporting structure including fixing means. The device further includes a controller for controlling a rotational speed of the rotating part. The controller is provided with means for controlling a rotational direction of the rotating part in a clockwise direction for painting the first semi-cylindrical structure of the compressor or vacuum pump housing and for changing the rotational direction to a counterclockwise direction for painting the second semi-cylindrical structure of the compressor or vacuum pump housing.