| 摘要 |
<p>A control system, particularly adaptable to multiple-pump operations in process units, is disclosed. A measured variable, such as pressure, is sensed by a master controller. The master controller, in turn, sends a signal to the driver of the individual pumps or in other ways regulates the output of the two pumps. The master controller is configured to send different signals simultaneously to the two pumps in response to a change in the measured variable. The result is that the response time of one of the pumps is faster than the other. Thus, minor deviations from the desired setpoint of the measured variable are primarily responded to by the pump configured to react faster. Dramatic upsets, resulting in a significant deviation from the desired setpoint for the measured variable, allow one pump to react fast and change its capacity dramatically to bring the measured variable back to the desired setpoint, while the other pump responds more slowly and thus maintains a reasonable forward fluid flowrate all the time to prevent a process unit shutdown. On sensing a loss of the fast-responding pump the master controller automatically speeds up the response time of the slowly responding pump so that its capacity can be varied reasonably fast enough to maintain the measured variable at the target condition. By use of differing response times on the pumps, the tendency of the pumps to fight each other when operated by steam turbines, for example, is eliminated. Additionally, the pumps with the control system can quickly respond to large process upsets without triggering shutdown conditions of both pumps which would otherwise cause a processing unit shutdown.</p> |
