ON-LINE LABORATORY GC’S REPLACE TRADITIONAL ANALYZERS UTILIZING DIGITAL COMMUNICATIONS AND THE OPC PROTOCOL. GAS GENERATOR HAS VIRTUALLY ELIMINATED COMPRESSED GAS CYLINDER USAGE

摘要

With the commercial offering of a new compact laboratory Gas Chromatograph (GC), it has now become feasible to install these robust Instruments into field applications. Utilizing CSA approved, Z-purged enclosures, eight (8) of these Instruments were installed in NOVA’s petrochemical production facility’s Analyzer Shelter situated inside the process battery limits. The OEM provided several customizations to their software responsible for the operation of the networked GC’s that made ‘repeat sequence’ and ‘multiple method’ functionality possible. With these enhancements online scheduled cleaning - ‘bakes’, of the Instruments’ heated zones became feasible. This feature, coupled with electronic pressure control (EPC) driving the split vent and injection system, has eliminated the need for back flush and heart cut valves. Utilizing hydrogen gas as the carrier, most GC runs are completed within a 5-minute, or less, cycle time. Communication to the DCS was accomplished utilizing a fibre optic network and Ethernet to the individual Instruments. Software employed included: OEM instrumentation software, a custom OPC interface from the instrument manufacturer and Matrikon’s OPC Client for ODBC. With the elimination of the traditional 4-20 ma communication, coupled with the Instruments’ auto-ranging Flame Ionization Detector (FID), these Instruments are now capable of accurate reporting through-out the FID’s entire dynamic linear range (107 ± 10%). Our trial installation testing demonstrated excellent accuracy from 5 - 200,000-ppm (20% w/w) with 60 - 80% w/w considered achievable.