As the various work orders are processed within the plant, production scheduling personnel are able to query the database to ascertain their current state of completion. MMI screens are able to present the status of the coils that were assigned to a particular work order. Completed sessions and the current working session for all coils within a work order can be displayed. This allows critical customer orders to be monitored and rescheduled in the event that they run the risk of failing to be completed in the required time.
Data collection and communications protocols
During the many process steps through which each coil must pass, relevant data at these steps are gathered and stored in the Oracle database within the MSC system. Process controllers at each unit are responsible for gathering any cyclic data for each coil on a continuous basis. The operator NT station at each process step communicates any singular data for each coil via an MMI entry screen. For example, at the vertical annealing furnace, data entered by the operator on his input screen contain the following information: coil ID, work order, session, start time-stop time, alloy, coil weight on and coil weight off.
In addition, cyclic data that are gathered during coil processing are comprised of items such as furnace speed, furnace zone temperatures, control zone set-point temperatures, cooling fan speeds, cooling gas gate positions and strip zone tensions.
The cyclic data at each process are gathered at varying rates depending on the granularity desired. At the vertical annealing furnace, these values are gathered every two minutes (contrasted with the value of two seconds at the rolling mill). Cyclic data are collected continuously by the process controller (i.e. PLC) and transmitted to the MSC system. These data are then stored in a shared memory segment in a circular list fashion. At any time, there exists a list of cyclic values for the past six hours. When the coil enters the process, the operator uses the workstation to enter the singular data on an MMI screen. Subsequently this information is transmitted by depressing a ''start'' push button on the screen. This establishes the appropriate table entries for the coil in the database. Once the coil has been declared as started by the operator at the workstation, the cyclic data are then periodically copied into the Oracle database. After the coil has totally traversed the process, the operator utilizes the workstation to assert that the coil is complete. This is accomplished once again by using the MMI screen at the workstation. Any final singular data are added and the "stop" push button is depressed. At that time, the final data items are received and cyclic data transfer into the database is terminated. This procedure is repeated in a similar fashion at each processing step, with the exception of the rolling mill. The rolling mill system contains a tracking system that initiates data transfer automatically and is described under rolling mill automation.
Communication from the rolling mill system and all of the other processing steps utilizes only two protocols to send data to the MSC system. All communications between servers and workstations or operator displays utilize the TCP/IP protocol. Employing layer 4 in the open systems interconnect (OSI) model allows the TCP/IP protocol suite to operate with high reliability and at speeds more than sufficient for the data transfer rates encountered in these processes. A simplified network diagram can be seen in Fig. 5, showing the protocols used between the various nodes. Access to the Oracle database from all the workstations and other servers employs SQLnet® server or client application software.
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