Patent ID: 7234324

Claim:
A method which may be used for controlling a compression line, wherein: a) said compression line comprises at least one cryogenic centrifugal compressor, wherein said line is able to initially compress a gas to a low temperature and a low pressure; and b) said method comprises controlling the speed of rotation of said centrifugal compressor, wherein said method further comprises: 1) selecting a predetermined curve, wherein: aa) said curve is in the form of a first parameter as a function of a second parameter; bb) said first parameter represents said speed of rotation of said centrifugal compressor; and cc) said second parameter represents the mass flow rate of said centrifugal compressor; 2) regulating the speed of rotation of the centrifugal compressor located furthest downstream on said compression line as a function of: aa) the inlet pressure of the cryogenic centrifugal compressor located furthest upstream on said compression line; and bb) a variable pressure setpoint; and 3) regulating said variable pressure setpoint as a function of the ratio of the instantaneous value of said first parameter for said downstream compressor to the theoretical value of said first parameter, as determined from said predetermined curve, for the instantaneous value of said second parameter.