Integrally geared compressor having a combination of centrifugal and positive displacement compression stages

1. A method comprising:

combining at least one centrifugal compression stage and at least one positive displacement compression stage in an integrally geared compressor;

compressing a gas with the integrally geared compressor based on a temperature of gas to be compressed;

switching from a first type of compression carried out at the at least one centrifugal compression stage and a second type of compression carried out at the at least one positive displacement stage as the gas goes from cryogenic to non-cryogenic.

2. The method of claim 1 , wherein the integrally geared compressor includes a drive gear, the drive gear including a drive shaft coupled to a drive unit, a first pinion meshed with the drive gear on a first side of the drive gear, the first pinion including a first pinion shaft, a second pinion meshed with the drive gear on a second side of the drive gear, the second pinion including a second pinion shaft, and a third pinion meshed with the drive gear on a different plane than the first pinion and the second pinion, the third pinion include a third pinion shaft.

3. The method of claim 1 , wherein the positive displacement compression stage is arranged after a third compression stage of the integrally geared compressor.

4. The method of claim 1 , wherein the at least one centrifugal compression stage is arranged at a supply side of the integrally geared compressor and the at least one positive displacement compression stage is arranged at a delivery side of the integrally geared compressor.

5. A method comprising:

mounting a centrifugal compression stage to a first end of a pinion shaft, the pinion shaft being part of a gear system enclosed by a housing of a compressor; and

mounting a positive displacement compression stage to an opposing second end of the pinion shaft so that a single pinion shaft includes two different types of compression stages within the housing of the compressor;

wherein the centrifugal compression stage is located closer to a delivery side of the compressor than the positive displacement compression stage as a function of a temperature or volume of gas to be compressed;

wherein a screw gearing is attached to the second end of the pinion shaft and located between the positive displacement compression stage and the pinion shaft, the screw gearing being separate from the gear system, and allowing for a speed adjustment of the positive displacement compression stage with respect to the centrifugal compression stage.

6. The method of claim 5 , further comprising:

mounting an additional centrifugal compression stage to a first end of an additional pinion shaft, the additional pinion shaft being a part of the gear system enclosed by the housing; and

mounting an additional positive displacement compression stage to an opposing second end of the additional pinion shaft so that another single pinion shaft includes two different types of compression stages.

7. The method of claim 6 , wherein the pinion shaft includes a pinion engaged with a drive gear at first side of the drive gear along a same horizontal plane, the drive gear being a part of the gear system and located within the housing of the compressor.

8. The method of claim 7 , wherein the additional the pinion shaft includes a pinion engaged with the drive gear at second side of the drive gear opposite to the first side and along the same horizontal plane.

9. The method of claim 5 , wherein the compressor is an integrally geared compressor.

10. The method of claim 5 , wherein the gear system further comprises a drive shaft operably connected to the drive gear.

11. The method of claim 5 , wherein the centrifugal compression stage includes an impeller.

12. The method of claim 5 , wherein the positive displacement compression stage includes a rotary screw compressor.

13. The method of claim 5 , wherein the positive displacement compression stage is directly mounted.

14. The method of claim 5 , wherein the positive displacement compression stage is indirectly mounted.

15. A method comprising:

drawing in a gas from a supply side of an integrally geared compressor;

compressing the gas at a first compression stage with a first centrifugal compressor, the gas being cryogenic and low pressure at the first compression stage;

directing the compressed gas to a second compression stage;

further compressing the compressed gas at the second compression stage with a second centrifugal compressor;

directing the compressed gas from the second stage to a third compression stage; and

further compressing the compressed gas at the third compression stage with a positive displacement compressor, the compressed gas at the third compression stage being non-cryogenic and high pressure, wherein the third compression stage is proximate a delivery side of the integrally geared compressor;

wherein the method allows for different types of compression based on a temperature or a volume of gas to be compressed by the compressor.

16. The method of claim 15 , further comprising:

directing the compressed gas from the third compression stage to a fourth compression stage; and

further compressing the compressed gas at the fourth compression stage with another positive displacement compressor, the fourth compression stage being located closer to the delivery side of the integrally geared compressor than the third compression stage.

17. The method of claim 16 , wherein the integrally geared compressor is enclosed by a housing, for use with liquefied natural gas applications.

18. The method of claim 16 , wherein the first compression stage is connected to the second compression stage by piping and the second compression stage is connected to the third compression stage by piping, further wherein compressed gas flows through the piping to reach a next compression stage.

19. The method of claim 17 , wherein the integrally geared compressor includes a drive gear, the drive gear including a drive shaft coupled to a drive unit, a first pinion meshed with the drive gear on a first side of the drive gear, the first pinion including a first pinion shaft, a second pinion meshed with the drive gear on a second side of the drive gear, the second pinion including a second pinion shaft, and a third pinion meshed with the drive gear on a different plane than the first pinion and the second pinion, the third pinion include a third pinion shaft.