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MONDI RICHARDS BAY PULP MILL
Henk Coetzee*, Timo Kankkunen**, Jaakko Oksanen**, Markku Ylinen**
*Mondi South Africa, P.O. Box 1551, Richards Bay, 3900, RSA
** Metso Automation Inc., P.O.Box 237,Tampere, FIN-33101, FINLAND
KEYWORDS: Field bus, process automation, distributed control systems, field transmitter diagnostics, predictive maintenance
Mondi Business Paper South Africa's Richards Bay mill has recently commissioned a large, integrated process control network, on its new kraft fibre and recovery line. The large, demanding RB720 project utilized the latest in process automation and integrated fieldbus technology. Its success has been verified by a good process start-up. By rigorous type testing and pre-delivery factory checking, the Profibus DP/PA technology integrated with metsoDNA has been proven.
FieldCare maintenance diagnostics testing capability in metsoDNA is an integral part of the support engineering and installation work as well as being essential for maintenance. During commissioning of the new process FieldCare had played an important role in the on-line commissioning and verification of devices. Paybacktime for the online monitoring system has been short; the software has already paid for itself. Mondi believes that there are more benefits to unlock in the use of its predictive maintenance capabilities.
In March 2003, Mondi Business Paper South Africa, a member of the Anglo American plc group, announced its decision to embark upon a 25% increase in capacity of its Richards Bay kraft pulp mill in Northern KwaZulu-Natal, South Africa. The US$220 million expansion and modernization project, named RB720, would raise the pulp capacity to 720.000 adtp/a. The process changes included a new continuous digester to replace the old batch digester line, washing and screening equipment, a new bleach plant, evaporation plant, lime kiln and causticizing plant. The project was successfully completed on schedule and the new pulp production line started up in February 2005. During the construction and implementation of the new fibre and recovery lines, the old pulping and recovery process continued production.
In addition to the state of the art process equipment, Mondi decided to equip the mill with the most modern, flexible and serviceable process control network. The mill has used Valmet Automation (now Metso Automation) equipment since start-up in 1984. The original Damatic Classic systems had been updated to the status of the relatively new Damatic XDi , also from Metso Automation.
The new control network for the RB720 project would include a new metsoDNA control system for process and higher level controls, an integral Profibus field bus network for all process instrumentation, and FieldCare, an online diagnostic tool for field device configuration and predictive maintenance. This decision to implement the most modern process control, field instrumentation communication and diagnostic technologies was consistent with the mill's philosophy to make it one the most technologically advanced in the world.
2. MILL AUTOMATION SELECTION CRITERIA
The selection of both the DCS and field equipment technologies was aimed at the reduction of maintenance costs in the mill's life cycle. Maintenance cost reduction (cost/ton) would be achieved by changing the mills maintenance philosophy towards a proactive strategy. To be effective, a proactive maintenance philosophy requires more fault diagnostics information from all the equipment, especially from the field devices. Increased diagnostics information can be achieved from the intelligent field devices. Based on this diagnostic information, maintenance tasks can be allocated for the equipment which really needs maintenance. These maintenance tasks can therefore be scheduled for planned shut-downs. Predictive maintenance lowers maintenance costs and prevents unscheduled production stoppages.
Increased field device information needs more capacity in the DCS field interface. Technologies which fulfill these needs are HART technology and fieldbus technologies, e.g. PROFIBUS and Foundation Fieldbus. The fieldbus interfaces offer more information from the field devices as well as faster communication speed than HART technology. Fieldbus also offers a common interface to equipment other than field devices. For instance, motors and frequency converters as well as normal I/Os can be connected to the fieldbus. Mondi's aim was to have common uniform strategy in electrical and field equipment interfaces.
Fieldbus technologies offer some savings in wiring and cross connections costs, but especially savings in the commissioning phase. Field devices can be tested, commissioned and configured online through the network. There is no need to uninstall device and/or to walk to the distant device to check device parameters. All these things can be done through the DCS system online. Mondi also required integration of information in different levels. Diagnostic information is needed to be available seamlessly integrated in the process control system user interface. A typical integrated diagnostics display in shown in Figure 1.
Figure 1: Example of an integrated diagnostic display
For the RB720 project Mondi selected Metso Automation as a provider for the metsoDNA control system and intelligent valves. Endress+Hauser (E+H) supplied transmitters for the new line. Mondi was convinced that the co-operation between Metso Automation and E+H would bring the best results. The large field bus network connecting the control system to the intelligent field devices was also provided by Metso Automation.
For the field buses, Profibus technology was selected for the new line. Field bus technology had already become established in the existing mill through the use of Profibus DP for motor controls. In fact, Profibus DP had become the industry's de facto standard for motor controls. The mill was already using this solution and was confident it would work without problems.
Another version of the Profibus standard, Profibus PA (for process automation), is specifically designed for interface to process measurement instrument, valves and other process control actuation devices. The Profibus PA standard is not as well established in the pulp and paper industry as the Profibus DP standard. The capability of the DCS system to interface to both Profibus DP and Profibus PA field buses and the ability and experience of the supplier's engineers to implement them was therefore very important to ensure accurate, on time engineering and product delivery; therefore minimizing the project risk. Metso Automation demonstrated the capability in the metsoDNA system and the experience in implementing these bus interfaces. The interface capability and experience of the field instrumentation suppliers is also important for fast commissioning and the seamless functioning of the network.
3. MONDI BUSINESS PAPER RICHARDS BAY AUTOMATION
The Richards Bay mills new fibre line automation network was implemented within metsoDNA, Metso's dynamic network of applications. metsoDNA network advanced features were utilized , e.g. new generation metsoACN process controllers, integrated user interface and uniform engineering tools for all IO types. The new metsoACN (Application and Control Node) process controller offers high processing power for control applications as well as the possibility to connect several field bus types and gateways to it, all combined in one control node.
Profibus engineering is integrated seamlessly into the metsoDNA engineering system. Bus configuration can be done directly from the engineering environment without having to browse in other engineering tool environments. The user does engineering work in a common way regardless of the IO or field device type. Thus engineering with Profibus is not different compared to other application engineering. Maintenance of different IO types is much easier.
Intelligent field devices provide a lot of diagnostic information. Usually field devices offer two kinds of diagnostic information: "online" (cyclically retrieved) diagnostic information and "offline" (acyclically) retrieved information. "Online" information offers current status of the device, e.g. major status and fault bits. "Offline" information includes more detailed information about the device. This detailed information also includes historical information stored in the device itself. Note: "Online" and "offline" information can be retrieved through the system at any time. The terms just illustrate the way of using the information.
Figure 2: Overview process control picture of the Mondi Richards Bay pulp mill fibre line
It is very important that all diagnostic information is available in a user-friendly format to all the users. Online diagnostic information is integrated into the metsoDNA process control user interface so that all users, e.g. operators and maintenance people, can always check device status directly from the user interface without need to browse in files or other hierarchies. This helps to solve possible disturbance situations easily.
More detailed diagnostic information is available by using the FieldCare tool. FieldCare is integrated into the system for field device configuration and maintenance. It offers enhanced methods and displays for both device configuration as well as tools and alarm mechanisms for analytical purposes. FieldCare is an integrated part of the metsoDNA. Both field device configuration and diagnostic information goes smoothly through the system. No special gateway or multiplexer hardware or wiring is needed to make connection from the tool to the device.
FieldCare is based on the FDT (Field Device Tool) / DTM (Device Type Manager) concept. Intelligent field devices (transmitters and valves) are capable of interfacing onto a common network to provide a remote link for easy commissioning, device verification and performance diagnostics for predictive maintenance. Predictive maintenance programs, aided by this online diagnostic system, reduce the life cycle costs of field devices by avoiding unnecessary preventive repairs and by avoiding production losses due to unexpected failures . There are more than 700 devices linked to FieldCare. Neles valves integrated into this network are equipped with ND800 and ND9000 intelligent positioners.
With the intelligent field devices and desktop access the direct, hands-on service access to field transmitters and valve actuators is not so important any more as there is no need to check unproven or suspected problems. The problem can be directly identified at user terminals in the maintenance shop.
The selected metsoDNA system provides Profibus controls for motor and field devices for the new fibre line, the lime kiln, and the black liquor evaporators. There are 6 metsoACN process controllers in total. Altogether there are 1300 Profibus PA signals from over 700 instruments integrated into the system. There are 9 Profibus DP buses and about 40 Profibus PA buses. The Profibus devices are linked throughout the mill complex by redundant fibre optic cable loops. The control network at Richards Bay is shown in Figure 3.
Figure 3: Principle of Richards Bay pulp mill metsoDNA control network
4. ENGINEERING AND FACTORY CHECKOUT
The specification and pre-delivery engineering of the control network involved several suppliers and the project consultant, Jaakko Pöyry. To make the pre-delivery engineering as efficient and error-free as possible Metso Automation, Jaakko Pöyry and the major process equipment suppliers, Kvaerner and Andritz, had to be knowledgeable and experienced with Profibus technology.
The PROFIBUS DP and PA are established standards ensuring fast and error free installation in the mill. In all cases there is a possibility of a human error or misunderstanding. The importance of a 100% accurate factory checkout is underlined. To ensure uniform standards for this project and for the Richards Bay mill thereafter there was considerable effort by Mondi, Metso Automation and Jaakko Pöyry to establish best practices for engineering, documentation, loop drawings etc. All different Profibus field devices and automation applications to it were thoroughly type tested before starting the large-scale automation application engineering. At the same time, diagnostic windows to the new device types were generated. The process equipment suppliers also used the same standard solutions in their engineering. These type testing solutions were the base for the successful mill start-up.
In the lifecycle phase of the mill, similar automation applications will also help to maintain the automation equipment. There would be no special "handwriting" in the application even if the supplier is different. Type testing was done first together by Mondi, Metso and Jaakko Pöyry. All possible equipment that could be used during the project was tested, including connectors, cables, terminators etc. Based on the results and experiences of type testing the best practice document was provided by Jaakko Pöyry. After type testing, hardware and software were "frozen". None of the hardware types or software versions could be changed without proper testing.
The metsoDNA system was commissioned between April and November 2004. The on time process start-up was in February 2005, 24 months after the project initiation.
The large, demanding RB720 project utilized the latest in process automation and integrated fieldbus technology. Its success has been verified by a good process start-up. By rigorous type testing and pre-delivery factory checking the Profibus technology integrated with metsoDNA has been proven in a large project.
The engineering and maintenance teams at Richards Bay have been the main users of the FieldCare maintenance diagnostics testing capability in metsoDNA. They have found it easy to use. It is an integral part of the support engineering and installation work as well as being essential for maintenance During commissioning of the new process FieldCare played an important role in the on-line commissioning and verification of devices. Paybacktime for the online monitoring system has been short; the software has already paid for itself. Mondi believes that there are more benefits to unlock in the use of its predictive maintenance capabilities.
We wish to thank our colleagues at Mondi South Africa and Metso Automation who were instrumental implementing this successful technology application and process automation project.
PROFIBUS standard EN 50 170. , Technical Description, http://www.profibus.com/profibus.html