Axial thrust balancing system for a centrifugal compressor, having improved safety characteristics

1. Axial thrust balancing system for a centrifugal compressor, having improved safety characteristics, said centrifugal compressor comprising a rotor having impellers adjacent to each other and connected by a shaft, said rotor rotating in a stator, said centrifugal compressor including a balancing piston, a balancing line being provided between an intake of a first compression stage and an area downstream of the balancing piston, characterized in that said system comprises an intake mechanical gas seal around said shaft upstream of said first compression stage and an outlet mechanical gas seal downstream of said balancing piston, said balancing line being closable by means of blocking elements.

2. A balancing system according to claim 1 , wherein said mechanical gas seals are refilled with gas from a supply line.

3. A balancing system according to claim 1 , wherein said blocking elements comprise a shut-off valve.

4. A balancing system according to claim 1 , wherein said outlet mechanical gas seal is located at a delivery end of said compressor and has a function of balancing said axial thrust.

5. A balancing system according to claim 1 , wherein said outlet gas seal operates with a pressure on a primary ring equal to the delivery pressure of said compressor.

6. A balancing system according to claim 1 , wherein, in high-pressure applications of said centrifugal compressor, said outlet mechanical gas seal is refilled with a supply of gas at high pressure.

7. A balancing system according to claim 6 , wherein said supply line takes the gas from the delivery end of a diffuser of the final compression stage of said centrifugal compressor and, through pipes external to said centrifugal compressor, sends it to a high-pressure filter.

8. A balancing system according to claim 7 , wherein said gas, taken from said delivery end of said diffuser of said centrifugal compressor, is returned into said centrifugal compressor at the positions of end labyrinth seals of said centrifugal compressor, at the positions of primary rings of said mechanical gas seals.

9. A balancing system according to claim 1 , wherein uncertainties in the calculation of the pressures and in specification of the diameters of said mechanical gas seals can be compensated for by appropriate pressurization of primary ring of said outlet mechanical gas seal and/or that of said intake mechanical gas seal.

10. A balancing system according to claim 1 , wherein said balancing piston is keyed on said shaft of said centrifugal compressor, downstream of the final compression stage.