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Apache Corporation, one of the world’s top independent oil and gas exploration and development companies, needs to continually monitor and control oil export pumps located in the Forties oil field in the North Sea. Originally discovered by BP, the Forties oil field has been owned by Apache Corporation since 2003 and the company has modernised the facilities extensively. Apache intends to exploit the field - the eighth largest in the North Sea - to its full potential.

The Forties oil field has five production platforms called Alpha, Bravo, Charlie, Delta and Echo. Oil from four of them is pumped to Charlie, together with oil from other locations. Charlie platform has three powerful electric pumps controlled by Variable Speed Drives (VSDs) for oil export. Each pump is monitored by staff, to control oil production and flow, in the platform’s main control room.

Performance information about the pumps is sent across the serial interface to Perle’s IOLAN Terminal Servers (IOLAN SDS4) and via the Ethernet network to the main control room.

By presenting the VSD’s serial data across the network to the SCADA system, personnel on and offshore are able to monitor the output of the three pumps and control this according to demand.

The communications interface available at each VSDs was a Modicon Modbus communications adapter, with an RS485 serial data connection.

The design brief from Wood Group Engineering (North Sea) which provides engineering, design, procurement, construction and commissioning services to Apache’s Forties platforms, was to provide a Modbus communications gateway between the RS485 serial network of the VSDs and the SCADA Ethernet based network, and present data from the VSDs on their Ethernet based SCADA system.

To this end, Wood Group made use of the Perle IOLAN SDS4 which ship with the Modbus gateway feature. This allowed a server on the Ethernet network to obtain data from the serial network, using the Modbus Ethernet protocol, with the Perle IOLAN SDS Terminal Server acting as a Modbus RTU / Modbus Ethernet gateway.