Conoco makes a quantum leap with PLCs

Modbus Plus is proving its worth on an offshore gas gathering station, providing the high speed link between Modicon Quantum PLCs and a Honeywell SCADA system quantum PLCs from modicon, a brand of Schneider Electric, are playing a central role in the £9 million upgrade project recently implemented at the Lincolnshire Offshore Gas Gathering Station (LOGGS) of major international petrochemical company, Conoco.

The highly successful project was a joint operation also involving main subcontractor Brown & Root and systems integrator Excel Industrial Systems.

The LOGGS field comprises a main platform complex, five central bridge-linked platforms, eleven satellite gas-producing platforms, and five subsea developments feeding into the main complex. Production processing is performed in the central complex before gas is piped onshore.

Each satellite platform is provided with a hot-standby Quantum PLC with dual-cabling remote I/O for field device control and interfacing. Most of the remaining new PLC systems on the main complex, which is a normally manned installation, use a single-channel processor and single I/O configuration. A Modbus Plus network, incorporating both fibre and copper, with network repeater modules, is implemented for the five central bridge-linked platforms.

Quantum PLCs from the Modicon brand of Schneider Electric were chosen because of their ability to communicate with the Honeywell SCAN3000 SCADA system, using high-speed peer-to-peer Modbus Plus networking capabilities which incorporate dual-cable redundancy.

Proven reliability

Other important factors in the choice of Quantum PLCs were the proven reliability of the previous-generation Modicon 984A, B-80 series and 800 series I/O systems already in place on Conoco's LOGGS, and the new IEC61131 CONCEPT programming facilities, which made it easy to port application programs from existing redundant hardware systems to the new PLCs.

Design, programming and installation of the Quantum systems were carried out by Excel Industrial Systems, which was also responsible for configuring the bridge multiplexers and modems used to provide dual serial communication links with the unmanned satellite platforms. Additionally, Excel handled the configuration of hot-standby PLCs and provided training to complement the courses offered by Schneider Electric.

"The way this project was set up, with a fully integrated team, has significantly cut both time scales and costs, compared with traditional methods of project management," says Andy Hedron, Conoco's Project Manager

• Schneider Electric
  Email c146@industrialnetworking.co.uk