Abstract: A process control system which is controlling a continuous process produces an output product having a first grade. The process control system performs quality checks at predetermined times on the output product for verifying predetermined parameters of the output product of the first grade are within predetermined limits. A method for dynamically monitoring the continuous process (without shutting down the process) when the grade of the output product is changed to a second grade having second predetermined limits, comprises the steps of initiating new setpoints for the continuous process to produce an output product having the second grade. The predetermined parameters of the output product is verified by the process control system to be within second predetermined limits of the second grade. When the predetermined parameters of the output product fall outside the second predetermined limits, an alarm is indicated, and the output product divert to a bypass path.

Abstract: A process control system has a network which includes a plurality of modules, each module performing a predetermined function. The modules include at least one history module, and at least one application module, the modules being linked via a medium such that each module can communicate with every other module of the network. The network interfaces with a control subsystem which interfaces with control elements of a plant process, the control elements having associated therewith process data. The process data includes data values and event data; the total data includes process data, data calculated from the process data, off-line data, and external data, the total data being stored in a storage device of the history module. A method for maintaining the total data comprises the steps of queuing messages requesting selected portions of the total data to be stored in said storage device.