Control system for compressors operating in parallel

Claim 2

Control apparatus for controlling the operation of a compressor station comprising at least two compressor plants connected to operate in parallel, said control apparatus comprising: means providing ''''raise'''' and ''''lower'''' signals responsive to the discharge pressure of said station being lower and higher respectively than a desired discharge pressure; means providing for the compressor plants a plurality of control signals responsive to differences between the actual and desired flow ratios between said compressor plants; control means for each of said compressor plants for controlling each of said compressor plants to raise of lower said discharge pressure of said station; means for supplying said ''''raise'''' and ''''lower'''' signals to said control means to raise or lower respectively said discharge pressure; and means responsive to said control signals for gating said supplying means on or off to permit supplying of or block delivery of said ''''raise'''' and ''''lower'''' signals to said control means.

Claim 3

Control apparatus for controlling the operation of a compressor station comprising at least two compressor plants connected to operate in parallel, said control apparatus comprising: means providing a first signal proportional to the gas discharge pressure of said station; means providing a second signal indicative of the desired gas discharge pressure of said station; means for comparing said first and second signals and providing ''''raise'''' and ''''lower'''' signals responsive to said first signal being less and greater respectively than said second signal; means providing third signals proportional to the actual flows of each said compressor plants; means providing fourth signals proportional to the desired flows of each of said compressor plants for a given compressor station flow; means for comparing said third and fourth signals for each compressor plant and providing for each compressor plant control signals responsive to differences between said third and fourth signals; speed control means for individually controlling the speeds of said compressor plants; means for supplying said ''''raise'''' and ''''lower'''' signals to said speed control means to vary the speeds of said compressor plants accordingly; and means for utilizing said control signals to permit supplying of or block delivery of said ''''raise'''' and ''''lower'''' signals to said speed control means.

Claim 4

Control apparatus for controlling the operation of a compressor station comprising at least two compressor plants connected to operate in parallel, said control apparatus comprising: means providing a first signal proportional to the gas discharge pressure of said station; means providing a second signal indicative of the desired gas discharge pressure of said station; means for comparing said first and second signals and providing ''''raise'''' and ''''lower'''' signals responsive to said first signal being less and greater respectively than said second signal; means providing third signals proportional to the actual flows of each said compressor plants; means providing fourth signals proportional to the desired flows of each of said compressor plants for a given compressor station flow; means for comparing said third and fourth signals for each compressor plant and providing for each compressor plant control signals responsive to differences between said third and fourth signals; speed control means for individually controlling the speeds of said compressor plants; means for supplying said ''''raise'''' and ''''lower'''' signals to said speed control means to vary the speeds of said compressor plants accordingly; and means for utilizing said control signals to permit supplying of or block delivery of said ''''raise'''' and ''''lower'''' signals to said speed control means.

Claim 5

Apparatus according to claim 2 wherein said means providing said fourth signals include means for varying the ratios of the station flow desired to be taken by said compressor plants.

Claim 6

Apparatus according to claim 2 wherein said means providing said fourth signals include an integrator having a plurality of input terminals and an output terminal, means connectinG a plurality of potentiometers equal in number to the number of said compressor plants in parallel with each other and to said output terminal, means for adding the signals derived across said potentiometers and providing a fifth signal equal to the negative of the sum of said third signals, and means for supplying said third signals and said fifth signal to said input terminals of said integrator, said fourth signals being derived across said potentiometers.

Claim 7

Apparatus according to claim 2 including means responsive to any one of said compressor plants reaching a low limit for blocking deliver of ''''lower'''' signals to said speed control means of such compressor plant.

Claim 8

Apparatus according to claim 2 including means responsive to any one of said compressor plants reaching a high limit for blocking delivery of ''''raise'''' signals to said speed control means of such compressor plant.

Claim 9

Apparatus according to claim 2 including means responsive to any one of said compressor plants reaching a low or high limit for blocking delivery of ''''lower'''' and ''''raise'''' signals respectively to said speed control means of such plant and for rendering said third and fourth signal for such plant ineffective.

Claim 10

Apparatus according to claim 2 wherein said comparing means are null detectors.

Claim 11

Apparatus according to claim 4 including means responsive to any one of said compressor plants reaching a low or high limit for blocking delivery of ''''lower'''' and ''''raise'''' signals respectively to said speed control means of such plant and for discontinuing the supply of said third signal of such plant to said integrator and for opening the circuit including said potentiometer that determines the flow ratio for such plant.