in Practice Automation Technology Reprint High Power Trunk concepts Breakthrough inFieldbus technology– July 7/2005

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Breakthrough in technology – High Power Trunk concepts

Do we see the breakthrough of fieldbus technology in process auto- mation? The fieldbus experience reports presented at the ‘Association of Users of Process Control Technology’ NAMUR general assembly in 2004 seem to confirm that.Topology concepts with high power in the field for all explosion hazardous areas, sophisticated protection and diagnostic functionalities of modern Fieldbus Installation Systems as well as easy-to-use planning tools form the basis for the positive ap- praisal of several major operational process production plants with continuous fieldbus instrumentation.These experiences confirm the expectations specified in 2002 by the FuRIOS study.

Introduction in the field, there are I/O inter- faces which convert the digital Nowadays, and signals of the control system FOUNDATION Fieldbus are fre- into conventional 4-20mA sig- quently discussed in the pro- nals.These may be I/O cards in cess automation industry.Whe- the control room or Remote ther at the NAMUR general as- I/O systems somewhere in the Fig. 1: Fieldbus segment, completely in explosion protection "Intrin- sembly in November 2004, in plant. In any case, there are sically Safe" the discussion forums at the analogue/digital conversions German Interkama fair in April during signal transmission, 2005 or in the many internatio- with all tolerances and risks of Fieldbusses for process au- defines some general conditi- nal brain trusts, plant instru- faults.The core of the current tomation and explosion ons for the structure of a field- mentation with digital commu- discussion is the term "conti- protection concepts bus network.Table 1 summari- nication seems to experience nuous" digital communication, zes the most decisive of these the breakthrough [1]. If approa- i.e. the direct data exchange In fact, the discussed fieldbus- conditions. Furthermore, there ching this topic as an outsider, between the process control ses are the PROFIBUS PA and are four cable types specified this great interest seems astoni- system and the chipset in the the , (table 2).Type A is used as refe- shing at the first sight.The con- field device, without interfaces which both are based on IEC rence cable and is especially re- trol of process plants by means and their tolerances. However, 61158-2 and allow the combi- commended for fieldbus instal- of computer and PLC is a long people want to keep the com- nation of supply current (direct lations.Type C and D should established technology. PROFI- fort of power supply and signal current) and digital signal (al- only be used for modifying BUS DP,HART or similar proto- transmission via the same two- ternating current) on the same existing plants and for heavily cols communicate without core cable, as known from con- two-wire cable.This standard reduced networks [2]. More- problems with the instruments ventional technology. Suddenly close to the processes. the choices are very limited. At least, this seems to be Many of the protocols used in the case. At a closer look, the automation technology, such decisive difference becomes as PROFIBUS DP, or In- apparent "in the last meters". In dustrial Ethernet, are not desig- most cases, at some point bet- ned for this purpose and requi- ween the digital controllers re additional power connecti- and the sensors and actuators ons.

Table 1: Basic fieldbus parameters according to IEC 61158-2 Parameters Specification according to IEC 61185-2 Data transmission rate 31.25 kbps Total length of all cables (cable type A) 1,900 m Max. spur length 120 m Max. number of nodes per segment 32 Signal coding Manchester II Min. operating voltage per device 9 V Min. current consumption per device 10 mA Fig. 2: Fieldbus segment according to the High Power Trunk concept Signal transmission ± 9 mA with fieldbus barriers 4

lows the use of up to eight field sembly in November 2002, devices per segment and consi- marked the turning point.This derably reduces the efforts for study was carried out by Aven- confirmation of intrinsic safety. tis Pharma Germany, now Sa- On the other hand, FISCO speci- nofi Aventis, and Infraserv fies certain cable parameter Höchst Technik with the sup- restrictions which lead to cable port of renowned manufactu- type A as the best choice for Ex rers of process automation ia IIC, increases the technical re- equipment.The basis was the quirements on the field devices newly developed fieldbus bar- and significantly reduces the rier technology, which separa- flexibility of the network. Espe- tes the two functions "fieldbus cially the reduction of the spur power supply" and "protection length to a maximum of 60m by intrinsic safety".This was and the entire cable length to preceded by the consideration 1,000m is quite a setback. For that interventions during live Zone 2, the "Fieldbus Non-In- operation are only necessary cendive Concept" FNICO was at the field devices and their Fig. 3: Fieldbus barriers in the Rubyred plant of Clariant developed and ultimately inclu- connecting leads (spurs), whe- ded in the new edition of IEC reas the passive wiring bet- 60079-27. It considers the lower ween the control room and over, the practical layout of a special precautions.The origi- safety requirements in Zone 2 the distributors in the field is fieldbus network depends on nal approach to fieldbus Ex i and thus allows a higher power subject to minimum stress on- the actual current consumption was a simple transfer of the supply. In all other aspects it ly and thus is hardly affected of the used field devices, the methodology used in conven- corresponds to FISCO with all by faults. Moreover, the com- desired reserves as well as the tional technology by introdu- obvious restrictions. Against munication in the segment ambient conditions. Since the cing special Fieldbus Power this background, it is compre- would be interrupted anyway specification in the standard re- Supplies which meet the requi- hensible that the acceptance of during works on a fieldbus fers to a temperature of 25°C, rements of intrinsic safety.This fieldbus technology in process trunk.Thus, it would hardly be the influences of deviating cli- subjects the complete fieldbus automation was rather restrai- possible to safely continue the matic conditions must be taken segment to the energy limitati- ned for many years. In particu- production process with se- into consideration.These consi- on, as shown in fig. 1.The ana- lar, since the investment costs veral instruments out of ope- derations show that the design logous adoption of the confir- did not bear comparison with ration.The result of these con- of a fieldbus network is a very mation of intrinsic safety, the the established conventional siderations is the use of two complex task, even in the safe so-called Entity concept, did technology due to the low different explosion protection area. Additionally, there are the not only cause a considerable number of fieldbus devices per methods, as shown in fig. 2. safety evaluations when loo- workload in terms of calculati- segment. The trunk between the safe king into explosion hazardous on and documentation, it also area and the fieldbus distribu- areas. For Zone 1, usually the led to the result that only 4-5 Breakthrough in connecti- tors close to the process is in- protection method "intrinsic instruments could be operated on technology – Fieldbus stalled using the explosion safety" Ex i is required because per segment. A different ap- Barriers protection method "increased it is the only method that al- proach, the "Fieldbus Intrinsi- safety" Ex e and thus allows a lows live maintenance and ser- cally Safe Concept" FISCO [3], The FuRIOS study [4], presen- significantly higher supply vice during operation without specified in IEC 60079-27, al- ted at the NAMUR general as- energy compared to Ex i as well as the use of cost-effecti- ve non-Ex power supplies. Fieldbus barriers such as the Breakthrough in Connection Technology: Fieldbus Barriers FieldConnex® FieldBarrier by Pepperl+Fuchs, which allow Profibus DP the intrinsically safe connecti- on of up to four field devices, Segment are used as distributors in Zo- Coupler ne 1. Devices according to En- Termination tity or FISCO can be combined at will since the confirmation of intrinsic safety is only requi- Fieldbus barrier Fieldbus barrier Fieldbus barrier red for the loop between the device and the output of the FieldBarrier. By daisy-chaining multiple fieldbus barriers it is possible now to connect the maximum number of 32 devi- ces as specified in the stan- dard, even in Zone 1 applicati- ons. Further advantages of the FieldBarrier include the indivi- Fig. 4: Conclusion of the fieldbus experience reports at the NAMUR general assembly 2004 dual short-circuit current limi- 5

Table 2: Cable types for fieldbus networks Type A Type B Type C Type D (reference) (*) (*) Cable description Twisted pair, One or more twisted Several twisted pairs, Several non-twisted shielded pairs, total shielding not shielded pairs, not shielded Nominal conductor cross-section 0.8 mm2 0.32 mm2 0.13 mm2 1.25 mm2 (AWG 18) (AWG 22) (AWG 26) (AWG 16) Max. DC loop resistance 44 Ohm/km 112 Ohm/km 264 Ohm/km 40 Ohm/km Characteristic impedance at 31.25 kHz 100 Ohm + 20 % 100 Ohm + 30 % ** ** Max. attenuation at 39 kHz 3 dB/km 5 dB/km 8 dB/km 8 dB/km Max. capacitive unbalance 2 nF/km 2 nF/km ** ** Group delay distortion (7.9 ... 39 kHz) 1.7 mysec/km ** ** ** Surface covered by shield 90% ** n.a. n.a. Recommended extend of network (incl. spur cables) 1,900 m 1,200 m 400 m 200 m All data based on an ambient temperature of 25°C (*) only to be used for retrofit applications and substantially reduced networks (**) not specified tation of each output, thus sented at the NAMUR general load sharing and automatic nitor the fieldbus installation protecting the trunk against assembly in November 2004, switchover in case of fault. and indicate error states via negative feedback of device ended with the conclusion Redundancy of the power LED, separate relay outputs as faults, as well as the option of shown in fig. 4: Breakthrough in sources:Two bulk power sup- well as a special diagnostic capacitive grounding (see [2] connection technology – field- plies can be connected in pa- bus. and [8]), which leads to signifi- bus barriers [7]. rallel by means of appropriate, The Power Hub is designed cant savings with regard to integrated decoupling diodes. to be used in High Power the earthing concept. Fieldbus power supplies Redundancy of the fieldbus Trunk concepts in safe and all Due to the high power sup- and safety communication:Two redun- explosion hazardous areas. A ply via the Ex e protected trunk, dant host interfaces can be choice of different mother- the fieldbus barrier concept is An essential component of any used per segment. Here a spe- boards and power modules al- often called "High Power Trunk fieldbus segment are the power cial short-circuit current limita- lows to meet any require- concept".The FuRIOS study was supplies, which carry out the tion of the host connections ment, from a simple segment based on a virtual fieldbus net- impedance matching for cou- protects the fieldbus segment without any special protection work according to this concept pling the DC supply current against negative feedbacks, needs up to four parallel seg- and compared it with a real with the AC amplitude of the too. ments with redundant host pharmaceutical chemical plant digital fieldbus communication. Protection against reso- connections, advanced diag- already in operation.The stu- In addition to a stable, error-free nances and crosstalk: For this nostic functionality and redun- dy’s target was to evaluate the signal transmission, a high ope- purpose, the innovative dant power modules with gal- cost/benefit aspects of the real rational safety is required be- "Crosstalk and Resonance vanic isolation. Fig. 5 shows the batch plant realized with Re- cause all field devices connec- Suppression Technology" Power Hub in its maximum mote I/O systems and to com- ted to the segment would fail CREST was developed, which configuration. Motherboards pare them to the plant planned simultaneously in case of a po- ensures a high stability of the with specific system connec- with fieldbus, under considera- wer supply failure. For this rea- fieldbus signal. tors or slots for linking devices tion of the complete life cycle. son, modern systems like the Monitoring and error mes- are available for many types of The theoretical results were ve- modular FieldConnex® Power sage: Diagnostic modules mo- control systems. ry promising. So Aventis deci- Hub offer a number of protecti- ded to realize the fieldbus solu- on mechanisms. tion: In May 2004 the new plant Passive impedance match- for producing the antibiotic Ke- ing: For current/signal cou- tek was commissioned, in pling, passive components are which 1,600 PROFIBUS PA devi- used.Their high efficiency of ces communicate fully digital up to 91% induces only mini- via 470 fieldbus barriers [5]. At mum thermal strains on the the same time, further plants environment and the modules based on the FuRIOS recom- themselves.The operational mendations were put into ope- safety is proven by high MTBF Fig. 5: Field- ration, such as at DSM, Novartis numbers. Connex® Po- and Clariant [6].The latter’s ex- Redundancy of the Power wer Hub for tensive use of the FieldBarrier is Modules:The power supplies’ Foundation documented in fig. 3. According- availability can be further incre- Fieldbus H1, ly, the experience reports on ased by means of an optional 4 segments in five fieldbus plants producing parallel configuration of the redundant at full speed, which were pre- electronic components with configuration 6

45mA. Field devices with a re- the High Power Trunk concept spective certification for Zone can be realized to the full ex- 2 or according to EEx i can be tent. connected.The safety parame- ters are calculated according Support tools for planning to the Entity concept. Due to a fieldbus network the individual consideration of each spur, this calculation is A support tool that was used in significantly simplified. For the designing several of the field- supply of the currently com- bus plants presented at the NA- mon intrinsically safe field de- MUR general assembly 2004 vices, the FieldConnex® Power was the fieldbus design soft- Hub system offers power mo- ware tool "Segment Checker". dules with a voltage limitation This planning tool allows a to max. 23V. By using power quick and easy layout of field- modules with a limitation to bus segments by simple "drag 17.5V, segments can be instal- and drop" from a device catalo- led according to the FNICO gue, which includes all modules concept as described above. necessary for fieldbus installati- However, there are currently on as well as a selection of field Fig. 6: High Power Trunk concept for Zone 2 only a few field devices certi- devices (fig. 7). Once the net- fied according to FNICO on work dimensions and environ- the market. Moreover, the pos- mental parameters have been High Power Trunk concepts used (see fig. 6). For the trunk sible maximum cable lengths entered, the energy calculation for Zone 2 the explosion protection and device numbers are redu- as well as the evaluation of method "non-sparking" Ex nA ced due to the voltage limita- fault conditions and system in- Due to the necessity to save applies and allows to lead tion. tegrity are performed automa- costs, the reduction of Zone 1 high currents into Zone 2.The In the future these voltage tically.The results are provided in favour of Zone 2 is increas- Segment Protectors are certi- limitations will be required less as a text file including a bill of ingly considered. Consequently fied according to EEx nA[L] often because more and more materials and form a good ba- it is reasonable to introduce and can be mounted in Zone field devices with certifications sis for plant detail planning. High Power Trunk concepts 2. Every output is energy limi- according to EEx nL with Ui > Segment Checker can be used that are adapted to the redu- ted according to EEx nL IIC, 32V become available.Thus, the flexibly as it is possible to add ced safety requirements of Zo- the output current is max. voltage limitation of the Seg- individual field devices as well ne 2 applications. 40mA, the output voltage ment Protector takes effect, the as to integrate additional field Instead of the fieldbus bar- max. 31V. In addition, each Power Hub’s standard high-po- device catalogues.This soft- rier, Segment Protectors of the output is individually short- wer modules can be used and ware tool is available for down- FieldConnex® system can be circuit current limited to ultimately the advantages of load at www.segmentche- cker.com.

Perspective The first practical experiences with extensive fieldbus appli- cations in large-scale industry projects are encouraging.The presentations at the NAMUR general assembly concluded with the statement that field- bus is the right path to the fu- ture. Nevertheless some re- quests were proposed to ma- nufacturers and fieldbus orga- nizations, which they are hap- py to take up. For example, the fieldbus barrier concept is now explicitly explained in the of- ficial Application Guide of the Fieldbus Foundation [8].The continuing development of the High Power Trunk con- cepts, especially for Zone 2, as well as advanced protection and diagnostic functionalities will contribute to the growing acceptance of fieldbus techno- Fig. 7: Fieldbus design tool "Segment Checker" logy. 7

Literature [5] Eckert, C.: The fieldbus is fin- Dipl.-Wirtsch.-Ing. Thomas Kasten is responsi- [1] Litz, L.: The breakthrough of ding its wings, in: MessTec & ble for the product group FieldConnex® in the Fieldbus in Process Automati- Automation 12/2004 Marketing Department of Pepperl+Fuchs on – do we see it now? [6] Eichhorn, T., Pelz, M.: Fit for the GmbH. Prior to that he held several positions in: FuRIOS 2 Compendium, future – fieldbus technology outside of Germany, covering technical marke- Pepperl+Fuchs GmbH, March at Clariant, in: CHEManager ting and service. He is a member of the Marke- 2005 07/05 ting Working Group of the PROFIBUS User Or- [2] PROFIBUS PA User and Instal- [7] Schwibach,M.,Meier-Künzig,T., ganisation and of the European Marketing lation Guideline, PROFIBUS Seintsch, S., Zobel, J.: Fieldbus Council of the Fieldbus Foundation. Nutzerorganisation e.V., 2003 Experience Reports, Presenta- Address: Pepperl+Fuchs GmbH, Division Pro- AG-140 Rev. 1.0, Foundation tion at the ‘Association of cess Automation, Königsberger Allee 87, 68307 Fieldbus Application Guide Users of Process Control Tech- Mannheim, Germany, Phone: +49 (0)621 776- 31.25 kbit/s Wiring and Instal- nology’ NAMUR general as- 1415, E-mail: [email protected], lation, Fieldbus Foundation, sembly Nov. 4th, 2004, publi- www.fieldconnex.info 1996 shed in: FuRIOS 2 Compendi- [3] Johannsmeyer, U.: Investigati- um, Pepperl+Fuchs GmbH, March 2005 Dipl. Ing. Bernd Schüssler is Business Develop- ons into the Intrinsic Safety of ment Manager for the product lines Remote fieldbus systems, PTB report [8] AG-163 Rev. 2.0, Foundation I/O, HART and Fieldbus at the North American W-53e, Pysikalisch-Technische Fieldbus Application Guide headquarters of Pepperl+Fuchs in Twinsburg, Bundesanstalt, Braunschweig 31.25 kbit/s Intrinsically Safe Ohio. Before, he held the position of Product 1994 Systems, Fieldbus Foundati- Manager for the product group Fieldbus com- [4] Tauchnitz, T., Schmieder, W., on, 2003 ponents at Pepperl+Fuchs, Inc. He is an active Seintsch, S.: FuRIOS: Fieldbus member of the North American Marketing and Remote I/O – a system Council of the Fieldbus Foundation. comparison, in: atp Automati- Address: Pepperl+Fuchs, Inc., 1600 Enterprise sierungstechnische Praxis 44 Thomas Kasten and Parkway, Twinsburg, OH 44087, USA, Phone: +1 (2002), Edition 12 Bernd Schüssler 330-486-0002, Fax: +1 330-425-4607, E-mail: [email protected] Comprehensive Interface Technology – including sensors for level measurement

Point-to-point – single standard Point-to-bus – conventional Installing – connecting – Practical sensors to measure signal lines transmit field signals point-to-point connections for protecting fieldbus systems with levels in liquids and solids. conventionally to the control the process and bus connec- Bus-to-Bus technology. Fully Sensors from Pepperl+Fuchs are system. tions for the control system. compatible components special- widely used in the Two systems are available for For applications in explosion ly developed for the demands of chemical and petro- conventional instrumentation. protection zone 2 the remote I/O process technology allow you to chemical industries, The K-System for mounting on RPI System is used, whilst for speedily plan and commission in bulk materials the support rail and the mother- direct installation in zone 1 your fieldbus system and to and waste water board solution with plug-in IS-RPI is the first choice – inclu- operate your plant safely and applications. Your modules on the system circuit sive of HART transfer. efficiently. FieldConnex®, the application can board. Configuration can be carried out fieldbus installation technology benefit from our using the FDT-compatible from Pepperl+Fuchs – for extensive product TM PACTware software with the PROFIBUS and Foundation range. appropriate DTMs. Fieldbus.

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Subject to reasonable modifications due to technical advances • Copyright PEPPERL+FUCHS • Printed in Germany • Part. No. 187 242 07/05 00