Processing made easy
ABB has used Foundation Fieldbus as the basis for a distributed control application

A control system extension at the Heglig oilfield in Africa required state-of-the-art data gathering using several different bus protocols, plus close integration with an existing system. Distributed technology from ABB provided a solution as the following article describes.

Today’s distributed control applications are based on communications, and the performance of controllers and devices is now defined to a great extent by their network capability. But since no single communication protocol is accepted and available to every system everywhere in the world, both hardware and software products need to support a variety technologies.
An example of the effective integration of several protocols—Foundation Fieldbus, Profibus and Hart—is a distributed control system supplied by ABB in the Heglig oil and gas production area in
Africa. Here, an expansion of an oil processing unit was successfully equipped with ABB’s automation technology based on the Industrial IT AC 800F controller, and seamlessly connected to the field’s existing automation infrastructure.
The Greater Nile Petroleum Operating Company (GNPOC) is a joint operating company responsible for petroleum exploration and production in the concession area located in the oil-rich Muglad Basin in Africa. For the expansion of its crude oil processing plant for the Heglig fields, GNPOC wanted the latest technology so as to be able to gain all the advantages offered by intelligent field devices. Since the company was already a satisfied user of ABB automation technology, Industrial IT was the obvious choice for the new plant. GNPOC was also keen to save installation costs by using ABB’s MultiBarrier technology, which reduces cabling costs by up to 30 percent by allowing four field devices to be connected to a single intrinsically-safe (IS) barrier unit.

The best of both worlds
The new automation equipment was delivered through a partnership between GNPOC (the end user), CPECC (China Petroleum Engineering and Construction Corporation), VECO (Engineers) and ABB. The scope of supply included both instrumentation and control equipment, allowing Foundation Fieldbus and Hart instruments to serve as information sources for the system’s advanced asset management functions. Remote I/O devices were connected to the controllers using high-speed Profibus DP links.
GNPOC did not want to upgrade an existing installation running a previous version of ABB’s proven Industrial IT Freelance control system. As a result, the new control system was required to work alongside the existing one, as well as interfacing with a Telvent Scada system and an emergency shutdown system (ESD) delivered by Hima. Flexibility and openness were therefore key requirements for the new control solution.
The equipment finally chosen includes ABB Control IT AC 800F controllers in a redundant configuration, state-of-the-art Foundation Fieldbus technology using the LD 800HSE linking device, S800 distributed I/O and a full Fisco-based Atex field installation. Profibus communication was the first choice in connecting the I/O system.
To link the two control systems, the existing Freelance system offers a powerful data exchange mechanism based on function blocks that are independent of the system version. Easy engineering with the Control Builder tool achieves synchronization of better than one minute between the two systems.
Integration as key
“The ABB solution takes advantage of the advanced information features enabled by the intelligent field devices, connected through various communication protocols,” says Paul Rix, who from his base in Abu Dhabi (UAE) is ABB’s ATPA Manager for Projects and Engineering in the Middle East and Africa region. “With this solution and the asset management features enabled through the FDT interface we expect significant improvements while operating and maintaining the entire installation.”
The intelligent field devices which act as the information sources for the new installation are distributed in a heterogeneous control topology: control functions run on fieldbus links with function blocks executed in the field devices. The scenario uses Foundation Fieldbus (high-speed Ethernet (HSE) and H1) for regulatory control, in conjunction with a redundant controller pair. Another two controllers, using Profibus as their communication vehicle, interface with discrete I/O and Hart-capable instruments.
The existing Freelance control system integrates all the different communication protocols and delivers the measured values to management stations. The latter include engineering and operator workstations running asset management software and connected using a Fast Ethernet backbone.
The system variables and tag values from the different process segments, such as the Profibus and Foundation Fieldbus segments, are shared across the system by the controllers and the operator stations. This means that there is no consistency problem in tag names across the system, so engineering, commissioning and plant operation become child’s play. The engineering tool also offers a choice of five IEC61131–3 standard programming languages, and enables application design and programming for Foundation Fieldbus links (function block application diagram and Foundation Fieldbus scheduling). This easy engineering saves a lot of configuration time during the engineering phase. Even more importantly, it simplifies commissioning of a system running several Fieldbus technologies.
The application requires some of the instruments to be installed behind IS barriers for operation in hazardous areas. However, the relatively low output power available from the segment coupler in Profibus or power conditioner in Foundation Fieldbus systems limits the number of EEx(i) Fieldbus devices.
Networking in segments
To overcome this limitation, GNPOC used ABB’s unique MultiBarrier technology. MultiBarrier is a four-fold Fieldbus distributor for both hazardous and non-hazardous areas. By creating an EEx(e) H1 trunk environment with EEx(i) protection for each H1 spur line, it increases the number of devices per bus and so offers the ultimate in installation flexibility whilst reducing the cost of supplying power and wiring by approximately 30 percent. The segments are powered by ABB’s NPC 100 power conditioning units, which “mix” the H1 segment outputs of the redundant HSE-H1 coupling devices and redundant power supplies—all in a single ultra-high-availability device with an MTBF of 500 years. LD 800HSE linking devices serve as gateways between the field devices on FF-H1 links and the HSE subnet. These devices allow data to be republished from an H1 link to the HSE subnet as well as from one H1 link to another. This enables cyclic communication between field devices on different H1 links and devices on the HSE subnet, so that control loops can be closed on the Fieldbus links themselves. The gateway also allows client/server access to function blocks on H1 devices via HSE. For each H1 link it manages the live list of connected H1 devices and grants access to them.
The new system has brought a sustainable competitive advantage to GNPOC by combining the best of modern real-time plant information handling with seamless integration into the existing control system at Heglig. ABB’s Industrial IT AC 800F technology provides state-of-the-art control solutions in a form that is flexible and upgradeable for the
future.