Fieldbus picks upmomentum
Successful fieldbus projects in the European Chemical Process Industry

For a long time, companies in the Chemical Process Industry (CPI)were reluctant to embark on new fieldbus projects. As recently as three years ago, users were complaining about a lack of devices that were suitable for field bus applications and no real interoperability. A joint effort by users and manufacturers has helped usher in a radical change in the world of automation.
Five years ago, when users had to choose between fieldbus technology and conventional 4 – 20 mA systems, they often decided to stick with proven technology. After all, an estimated 30 million devices worldwide use 4 – 20 mA signal transmission. HART offers a lot of options using simple technology. However, fieldbus systems offer more attractive alternatives.

Fieldbus technology requires migration to a new topology. Many users would have to abandon the traditional distinction between control cabinets (for control and interfaces) and field devices (sensors and meters). As a result, there has been significant reluctance on the part of users in the process industry to introduce fieldbus systems. Difficulties related to intrinsically safe systems also had to be overcome. However, due to the substantial economic benefits offered by fieldbus technology and following pioneering efforts by some companies, fieldbus systems are now being used to an increasing extent as communication solutions in the ChemicalProcess Industry (CPI). The results have been highly satisfactory. Successful projects such as the Ketek line at Sanofi-Aventis in Frankfurt/Germany, the Vitex line at DSM in Basel/Switzerland and the purple pigment line at Clariant site in Frankfurt clearly show that fieldbus technology is no longer at the pilot stage in the CPI. “We estimate that more than 500,000 FF devices have been installed and commissioned, and this does not even include systems that are at the FEED stage,” explained Rich Timoney, President and CEO of the Fieldbus Foundation. “FF technology can be found throughout the CPI worldwide.”
Significant potential
Several years ago, reducing installation cost was the main objective, but the focus has now changed. “In a study, Shell has estimated that the enhanced diagnostic capability of fieldbus technology can significantly reduce maintenance and repair costs at a typical petrochemical complex. For example, a one percent reduction in fixed maintenance costs would save the company around 4 million dollars”, explained Rich Timoney. “The savings are normally made through reduction in CAPEX (capital) and OPEX (operational) expenditure. Reduction in operational spending actually offers the greatest potential savings.” OPEX includes costs incurred as a result of unscheduled down time, and this can be reduced by conducting preventive maintenance. Improved system availability can be achieved by moving intelligence into the field devices. Peter Wenzel, Engineering Manager at the Profibus Users Organization (PNO), said that “fieldbus systems help drive down planning, engineering, installation and system operation costs.” He also emphasized the opportunities that the technology offers on complex systems. “Users want seamless production networking, particularly in hybrid applications in the pharmaceutical, chemical and cosmetics industries. The savings potential that can be achieved with a fieldbus solution grows as the size and scope of the application increases. Profibus is the only fieldbus technology which can deliver solutions that cover the entire range of production and process automation systems,” Wenzel said. Extensive fieldbus diagnostic capabilities offer significant potential. It is important not to overload the users with unnecessary information, which is difficult to interpret.
Broadening the base
German Namur recommendation NE 107 contains a requirement for clearly defined, standardized status messages: functional verification (invalid output signal caused by a fault in the field device or the device peripherals), maintenance required (valid output signal, but the wear out period has been exceeded), operation outside of specification (not within specified operating conditions) and failure of the measurement equipment (invalid output signal due to a fault in the field device or the device peripherals). PNO has implemented these guidelines. The classification can be used to provide detailed diagnostic information. When suitable functions are available on the control system or the plant asset management system, specific messages can be sent to various recipients (e.g. operators and maintenance personnel).
Conditions generally have continued to improve. The choice of fieldbus-enabled devices continues to expand, and the existing IEC 61158 standard has created a sound basis. Two factors have promoted the use of fieldbus technology in the European process industry. The Furios Study (field bus and remote I/O system comparison) conclusively demonstrated the superiority of fieldbus systems compared to Remote I/O. The fieldbus barrier has enabled users to take full advantage of fieldbus technology in explosion hazard zones. “Explosion protection based on intrinsic safety imposes power restrictions on existing fieldbus designs such as Entity and FISCO. As a result, the number of devices which could be operated on a fieldbus segment was considerably lower compared to a safe zone, where the only limitation is the threshold defined in IEC 61158-2,” explained Thomas Kasten, Product Marketing Manager at Pepperl + Fuchs in Mannheim/Germany. There were also other limitations including a reduction in maximum cable lengths. “Now that we have the fieldbus barrier, we can supply more power and increase both the maximum number of devices and the network size to the limits defined in the standard, even in Ex zones. State-of-the-art fieldbus barriers also provide protection functions such as individual short-circuit protection on each output, so that communications by other fieldbus nodes are not affected if a fault occurs.” This helps meet customer demands for high availability and operational reliability.
Past experience has shown that constructive collaboration promotes the use of fieldbus technology. The integration of protocols from other manufacturers is now an important issue which is being addressed. The joint EDDL project, for example, was initiated by four user organizations and well-known control system manufacturers. EDDL, which is defined in international standard IEC 61804-2, is a method which can be used to integrate field devices into automation systems. 1,000 field devices made by more than 100 manufacturers are now described with EDDL, and more than 15 million EDDL-based FF, Hart and Profibus field devices are installed worldwide. A joint team was founded at this year’s Hannover Fair to continue the development of EDDL technology. This activity will include generation of a test specification, the development of a test procedure for compliance testing and the incorporation of all of the enhancements into the IEC standards.
Working together
Several Ethernet-based communications systems with real time extensions have become established in the industrial sector during the last five years or so. Wenzel from PNOoutlined the future direction as follows: “We initially concentrated on production automation and motion control applications, which are key markets. We have now initiated activities which are focused on preparing Profinet for use in process automation applications based on a suitable migration strategy.” However, Ethernet-based process automation systems are unlikely to be used in the field anytime soon.
For one thing, there is currently no Ethernet solution for intrinsically safe zones. Ethernet-based systems essentially come from Europe or the US. Asian manufacturers will basically have the choice of either Ethernet IP or Profinet if they want to provide solutions for complex applications. A PNO working group has defined a solution for integrating Interbus into Profinet I/O, so that the installed base of Profibus and other fieldbus systems can be easily integrated with Profinet on system expansion projects. About a year ago, Interbus expressed a preference for Profinet as the Ethernet protocol. One reason for this is the hope that there will be an Ethernet standard one day, which is supported by as many manufacturers and components as possible. Work is currently under way to integrate other fieldbus systems into Profinet I/O using a uniform schema. The primary focus is one DeviceNet, CC-Link, CANopen and Foundation Fieldbus.
There are some regional differences in the acceptance level and the field of application. “We have seen strong growth in fieldbus technology in countries where the economy is growing at a significant rate,” reported Timoney. “There are enormous projects out there involving thousands of devices. In markets that are experiencing low growth rates where economic conditions are more difficult, investment in plants and equipment has come to a virtual standstill expect for purchases of essential spare parts. Once investment picks up in these markets again, Foundation Fieldbus technology will make an important contribution to increased productivity and competitiveness,” he added.
Regional differences
With more than 20 million installed nodes, Profibus and Interbus account for 75 percent of the entire fieldbus market. PNO is currently ramping up its activity in North America, China and Southeast Asia. “Elaborate road shows are being staged in Southeast Asia and China in response to dynamic market conditions in the region.
Some of the stops along the way were in Singapore, Kuala Lumpur, Jakarta, Manila, Bangkok and number of industrial centers in China,” explained Wenzel. “The response to the presentations was excellent. Many very knowledgeable persons attended the presentations, and these individuals would like to make greater use of Profibus and Profinet.” Fieldbus is already commonly used in various countries. According to Kasten from Pepperl+Fuchs, “there is a whole series of systems, particularly in the Asian region, which have been using the Pepperl+Fuchs FieldBarrier for more than a year now. This includes Shanghai Coking in China, Plaju Refinery in Indonesia, the Shell E11 and F13 oil platforms in Malaysia and Thai Acrylic Fibre in Thailand.
The use of intrinsic safety to provide explosion protection is not very common in North America, but there are some plants that use FieldBarrier, for example Boehringer Chemicals in Virginia and BIOX in Ontario, Canada. Class I, Div. 2 applications are far more common in the US. This roughly corresponds to our Ex 2 zone. A Pepperl+Fuchs Segment Protector provides the same advantages as a Fieldbus barrier in Zone 1, except that has been adapted to reflect the different safety aspects of Zone 2.”
Despite some very promising installations, you get the impression that the work is only beginning. Investment security is still the crucial criterion for users. Integration into higher-level networks (NE 105) will also be an important factor in the future.
The work is only beginning
Before they start using a fieldbus system, every user should be fully aware that this transition involves a change in planning and maintenance know-how.
Some of the main aspects to consider include the location and functionality of the field devices, and this is determined by the bus topology. The experience gained by other users or service companies can be quite helpful. German R&M Industrieservice Höchst GmbH (formerly the InfraServ Höchst test lab) installed a test segment in the lab, which contained various fieldbus devices for the Ketek project. The installation strategy and the training of the installation team were also developed.
“We need to increase user confidence in fieldbus technology and its advantages, particularly asset management, preventive maintenance and system life cycle costs,” emphasized Kasten. “This is why we support studies such as FuRIOS and make an active contribution to the Profibus user organization and the Fieldbus Foundation. When FuRIOS was presented at the Namur annual meeting in 2002, the team mentioned some things that manufacturers would like to see, and these issues now have been addressed. The modular FieldConnex Power Hub, which was introduced in 2004, offers a whole series of redundancy, isolation and diagnostic features which are designed to maximize fieldbus availability. Fieldbus Process Interfaces, which provide efficient integration of conventional signals, is another area that is being addressed. Back in 2002, the FuRIOS team realized that fieldbus systems would not be cost-effective without a valve interface box, and development work has been ongoing. We now have the FieldConnex Temperature Multi-Input and the Fieldbus Pneumatic Interface, and the work is by no means finished. Both fieldbus organizations are working on basic approaches to integration of safety-related signals, and this is yet another area that offers a lot of potential.”
“The PROFIsafe for PA amendment, which was recently approved, provides the basis for optimal use of PROFIsafe in process automation applications. The rules reflect the requirements contained in Namur recommendation NE 97 and in IEC 61508,” explained Wenzel. This ensures that the best version of a product can be offered to suit a particular application. PNO is also currently developing diagnostic strategies which offer better PAM (Plant Asset Management) support.
Timoney summarized the main areas of interest at the Fieldbus Foundation as follows: “During the past year and a half, the Fieldbus Foundation has concentrated on technology improvements such as graphic visualization to simplify operation of complex field devices. We are also working with the OPC Foundation to create a robust interface between field devices and OPC architecture using EDDL. The interface would allow us to provide complete, consistent data to OPC clients including alarm management programs and HMI and asset management programs without the need for customer-specific software. The Fieldbus Foundation is also working on user-focused applications. We are currently developing a specification for FF architecture on safety systems. We are expecting to receive german TÜV approval at the end of the year.” The development goals have now been identified, and both the organization and the manufacturers are working diligently to ensure that fieldbus becomes a recognized standard in this country as well.