Collect robust data from the plant-floor in real time
Medical Manufacturing Corp. (MMC, Erie, PA) is a contract sterilization firm, where pallets of pre-packaged medical devices are put into temperature-controlled vessels, in which multiple 50-torr vacuum cycles are coordinated with injections of steam, ethelyne oxide (EtO), and N2 to complete sterilization.
Medical Manufacturing Corp. (MMC, Erie, PA) is a contract sterilization firm, where pallets of pre-packaged medical devices are put into temperature-controlled vessels, in which multiple 50-torr vacuum cycles are coordinated with injections of steam, ethelyne oxide (EtO), and N 2 to complete sterilization.
Use of a managed Ethernet switch in this star layout provides adequate bandwidth for intermittent file/print functions with out interruption on the constant data stream among the operator interface, PLC, and enterprise data server.
Accurate data recording of each sterilization cycle is critical for customer reporting and to meet U.S. Food and Drug Administration requirements. However, MMC's existing control system required periodic operator intervention; was not CFR 21 Part 11 compliant; and did not have real-time backup. To perform the upgrade it needed, MCC called in Optimation Technology Inc. (Rush, NY), a system integrator.
MMC's former system used a Microsoft Excel spreadsheet to record data and produce reports. Excel 4 macros automatically recorded five-minute characterized averages from the PLC. Each record contained a time stamp, a high/low value, the mean average, and a standard deviation for each variable per sample period. These Excel macros automatically printed reports and trend charts at the completion of each cycle. Once the report was printed, an Excel macro wrote to the PLC to permit the end of cycle, and allowed the operator to open the vessel door.
While the Excel spreadsheets provided reliable data in a form that was easy to understand and analyze, Optimation was asked to upgrade the data-acquisition system to meet additional requirements and solve operational problems. Optimation provided a Microsoft SQL Server database with a Wonderware (Lake Forest, CA) InSQL data acquisition front end and Excel reports to replace the older spreadsheet-only system. Besides recording the five-minute characterized averages from the PLC, the new SQL system saves 200 process values at five-second intervals. An Excel VisualBasic for Applications (VBA) program queries multiple tables in the database using ADO and SQLOLE to produce an Excel spreadsheet with raw data, reports, analysis tabs, trend charts, and regulatory calculations.
In addition, MCC's new data acquisition system, implemented by Optimation, met the following objectives:
Accommodate system growth. As a job shop, MMC sterilization cycles change to meet customer needs. Excel macros in the old system grew too large and sometimes required operator intervention to complete automated functions. The new VisualBasic 6 modules are compiled so they run faster and are much more powerful, giving MMC the flexibility to expand or revise the system as needed.
Provide hardware redundancy. The old system used manual tape backups to maintain a copy of the data and reports. In the event of a hard disk failure, data could be lost, resulting in severe commercial penalties. The new system uses a RAID 5 disk array. If a hard disk fails, it is swapped with a replacement disk and the RAID controller automatically reformats and re-stripes the volume without any data loss or production downtime. Data are automatically backed monthly to a CD.
Include an audit trail. FDA's CFR 21 Part 11 guideline requires that electronic records be protected from tampering, with restricted access and audit trails of any manual changes. Optimation's solution allows only administrator access to raw data, and records all external update transactions as an audit trail, detailing who, what, when, etc.
Provide enterprise data integration. The data server, I/O server and operator interface workstation clocks are periodically synchronized by the server to make sure alarm and data time stamps agree. The PLC, data server, operator interface, and several printers are attached to an Ethernet switch to allow for enterprise access to the data acquisition system. Over 250 million records are maintained on line in real time for enterprise access.
Retain ease of data access. A new Excel cycle spreadsheet is generated automatically at cycle end and at an operator's request directly from secured data in the SQL Server. The Excel spreadsheet approach provides data to the end-user in a common office tool and in an easy-to-understand format with familiar data analysis.
MMC's redesigned control system from Optimation provided the functionality that the firm's sterilization process needed. It has functioned well for more than a year, and continues to provide MMC with flexible functionality as well as regulatory compliance.
Bill Carson, staff engineer, Optimation Technology Inc. (Rush, NY)
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