Patent ID: 7096669

Claim:
A method for providing limit control, not antisurge control, of a compression process comprising at least one turbocompressor having a limit variable, L, values of said limit variable being divided into a first region wherein closed loop limit control is used and a second region in which open loop limit control is used, the method comprising the steps of: (a) determining the value of the limit variable, L, based on parameters associated with the compression process; (b) calculating a value of a first temporal derivative, dL/dt, of the limit variable, L; (c) providing closed loop limit control when the value of the limit variable, L, is in the first region; (d) calculating an open loop limit control set point based on the value of the first temporal derivative, dL/dt; and (e) providing open loop limit control when the value of the limit variable, L, is in the second region.