Marathon Oil Corp. has installed new process-control equipment and systems at its Garyville, La., refinery.
Migration to the new control system required close cooperation with its primary automation contractor, Honeywell Process Solutions. The refinery staff collaborated with Honeywell's site support specialists to formulate and execute a plan for migration to the next-generation Experion Process Knowledge System without taking the refinery's process units off-line.
The project, described in this article, will provide a blueprint for future site migrations.
Marathon Oil has extensive refining, marketing, and transportation resources concentrated primarily in the US Midwest, upper Great Plains, Gulf Coast, and Southeast. Located to serve major markets, Marathon's operations include a seven-plant refining network with more than 1 million b/d of crude oil refining capacity.
The company's Louisiana refining division operation is located along the Mississippi River in southeastern Louisiana near Garyville (Fig. 1).
Migration requirements
At Garyville, a collection of complex refining operations converts 256,000 b/d crude oil into products such as gasoline and No. 1 and 2 fuel oils. Sulfur, asphalt, propane-propylene, isobutane, kerosene and coke are manufactured as secondary products.
As do other oil refining operations, Marathon requires automation solutions to increase the reliability, efficiency—and profitability—of its production assets. The refinery's legacy Honeywell TDC2000 distributed control system was originally installed in 1978.
As part of a plant expansion, the human-machine interface platform had been upgraded to the TotalPlant Solution platform with Global User Station capabilities. The aging data highway system no longer provided reliable day-to-day operation. Spare parts and support were also becoming scarce.
In addition, the legacy DCS did not provide the most current advanced control capabilities enabling the refinery to increase throughput, reduce costs and improve regulatory compliance, and answer customer demands for better product quality and faster delivery.
Marathon's initial attempt to migrate to Experion PKS for control of a crude unit was hampered by a lack of coordination among project participants, as well as insufficient computing capacity to handle demanding process-control functions. Through various trials, the refinery migrated its first TDC2000 Data Hiway to an Experion R200 system in 2004.
A subsequent migration project began in early 2007, when Marathon decided to convert a second Data Hiway to an Experion Version R301 system. This project encompassed a diesel hydrotreater, gas-oil hydrotreater and reformer, and a naphtha hydrotreater.
The work entailed moving about 1,400 control wire pairs to new marshalling panels, field termination assemblies, and process manager input/output modules, as well as migrating all advanced process-control functions to the new Experion platform.
For this migration, Marathon and Honeywell established a collaborative strategy based on common goal: To meet and exceed all end-user expectations and design requirements for implementation of a state-of-the-art automation architecture.
Keys
During normal operations, refineries are reluctant to schedule shutdowns for non-critical maintenance or replacement of field equipment. Therefore, control system migrations are typically executed via a "hot cutover," which involves moving one control loop at a time to the new system, while the unit operates in order to eliminate production losses.
A hot cutover also provides immediate feedback that the instrumentation is connected and working properly and is viewed as having overall lower risks to operations.
Marathon realized it would require help from the local Honeywell field office, in Baton Rouge, to perform the hot cutover to Experion. Key to the project was the ability to convert the legacy system to new technology one step at a time. Both existing and new equipment would have to operate simultaneously, without interrupting normal control functions or upsetting the process, until the cutover was complete. It was also essential that the cutover be transparent to unit operators.
From Marathon's perspective, project success hinged on close cooperation between all participants to formulate and execute a migration plan providing access to modern control technology without having to replace all of its legacy hardware and software assets. The project also required migration guidance to help the refinery develop a long-range automation plan to keep pace with future needs.
Marathon wanted project team members to work hand-in-hand to use the company's existing control system, with its large amount of proprietary programming, to maximize the daily production while minimizing production costs. Being able to migrate all Marathon's large investment in both hardware and software to a new Honeywell platform yields large cost savings. This included steps for migrating and supporting existing control system nodes, such as controllers, HMIs, and supervisory computing nodes.
Honeywell was designated as control system integrator for the migration project, overseeing design, procurement, installation, training, and support for the new automation solution. A software provider, ProSys, handled HMI graphics and advanced controls. Marathon's process-control group coordinated design review and testing, site preparations, field wiring preparation and termination, etc.
New technology
Marathon Oil relied on Honeywell's strategy of continual technology evolution to extend its existing automaton assets while upgrading legacy controls—the 30-years of hardware, field wiring, control programs, and engineering software and existing automation—to the latest Experion PKS technology. Built on a secure DCS architecture, Experion is an open system designed to improve plant operations, reduce incidents, improve decision-making, and enhance work flows.
Unlike traditional plant automation systems, Experion integrates the entire scope of production, equally addressing the needs of operations, maintenance, engineering, and business. It provides the operator with more than just the minimal knowledge he or she may need to make decisions to run the refinery, addressing alarm management, boundary management, and operations management to improve operational reliability.
Experion also allows operators to monitor the performance of critical plant processes and equipment and reduce process downtime and unplanned maintenance expenses.
Implementation of Experion provides a user friendly, Windows-based HMI delivering plant-wide process information such as pressures, temperatures, and flow information used to control the processes and improve monitoring of process history, trends, and averages. The system's graphical interface connects operators directly to the process and allows information to be easily accessed from anywhere in the plant. As a result, operators can react quickly and safely to changing situations.
Design, installation
Marathon's "design for performance" methodology was intended to ensure a proven, robust control system. Whether it was the I/O, controllers in the field, or the computer station operator interface, the project team evaluated each system component to determine its ability to perform under extreme conditions.
The detailed design process incorporated data flows for the entire control system, which included seven Honeywell redundant C300 controllers, one redundant C200 controller, two ACE nodes, OPC servers, process data historian interfaces, seven operator consoles, two engineering work stations, and redundant Experion system servers. The system configuration allowed new control hardware and cabinetry to be installed in the refinery's existing infrastructure.
As part of the design process, engineers looked at the maximum data-demand case that could be experienced during a process emergency, start-up, or shutdown. They also considered all aspects of the controller data load, including input/output processor (IOP) scan rates, control module execution, peer-to-peer subscription (PPS) rates, PPS for advanced application controller nodes, console station update rates, and subscribed data objects (SDOs) from controllers to operator stations. Their goal was to reduce unnecessary peer-to-peer communications among Experion C300 controllers, while ensuring a minimum of 50% free CPU under normal conditions.
Fig. 2 illustrates how the load on controllers was distributed so as to avoid the "focus effect," a situation in which all the data requesters ask for the same piece of information for a single data provider, causing the data provider to publish the same information to many different users. The system architecture allows efficient communication to operators and applications, as well as communications to and from controllers for process history, multi-variable control, alarm management, asset management systems, and other server applications.
In terms of HMI graphics performance, the project team defined reasonable limits for the number of parameters on each display, ensuring operators are not overwhelmed by the amount of data on their HMI panels. Parameters are updated no faster than necessary, and displays come up quickly and are uncluttered. Operators can also utilize standard shapes optimized for performance.
During electrical and instrumentation installation, new multi-conductor instrument wiring cables were run from the field junction box to the marshalling panel. The system was configured with field termination assemblies installed in separate cabinets, providing a standard 20% unassigned I/O spare capacity. Cables were prewired to the MP and FTAs, and terminations and tag labeling were reviewed during system analysis and testing.
For the control system conversion, all wire cutover was completed in the field at the junction box. Technicians reviewed each loop carefully to ensure that wires could be removed and moved while maintaining safe control of process operations.
Testing
Before shipping equipment to the refinery site and proceeding with the hot cutover, the project team tested the reliability and performance of the new plant automation technology to gain acceptance from operations personnel.
For example, the factory acceptance test involved 3 weeks of integrated testing at Honeywell's Baton Rouge facility. Project team members tested the configuration and redundancy of all hardware and reviewed configurations of all process points. They also verified graphic layouts, and all data and functionality of the objects on the graphics were accurate. This process provided an opportunity for operators to interact with the control system and provide specific feedback based on their experiences.
The project team also conducted tests simulating normal and abnormal load on the system in order to verify its performance under different operating scenarios. This included detailed trending to monitor system components throughout various levels of system loading. This simulates normal operating conditions and extreme abnormal operating conditions to ensure the system would perform under an extreme situation in which the data requests are at an extreme or abnormal level.
Results, future
Marathon's project team met its schedule for completing the 2007 control system migration, resulting in the hot cutover of 1,400 wire pairs during a 6-week period.
Phase I of the project, implemented in August 2007, provided operator stations with direct connections to the local control network for data and alarms. In addition, it provided servers with direct connection to the LCN for read/write to support history collection, advanced process control, data from third-party systems located in the field (Fig. 3).
Phase II, the addition of the new Experion hardware, was completed in November 2007. Cutover was accomplished ahead of schedule and with no disruptions to the process (Fig. 4).
The refinery hydrotreater units have now operated reliably on Experion technology for more than 2 years, including turnarounds, shutdowns, and start-ups (Fig. 5).
Operators now have a direct link to the process through a range of pre-configured standard and custom-built displays. They are better able to react to changing situations because operating, alarm, and system displays are dynamic and better represent the actual process infrastructure. The control system's familiar Windows environment further improves efficiency through ease of navigation among process displays and other applications.
In terms of performance, the open automation architecture allows multiple Experion systems, installed on different operating units, to communicate, exchange data, and work together seamlessly. Plant personnel can connect directly to information and control networks, providing full and immediate access to critical data across the enterprise.
Based upon the success of its control system migrations, Marathon is undertaking further modernization projects. Another Data Hiway migration was completed in late 2008, and an ongoing $3.2 billion expansion at the refinery will use Experion C300 controllers and C-Series I/O.
This expansion will increase plant capacity to 425,000 b/d, making it among the largest refineries in the US. Two additional Data Hiway migrations to Experion are planned for 2010 and 2011.
The authors
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