system engineering guidelines ff

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Compliments of:The Fieldbus Foundation

© 2003-2004 Fieldbus Foundation


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FOUNDATION ™ FieldbusSystem Engineering Guidelines

(AG-181) Revision 2.0

This preface, as well as all footnotes and annexes, is included for information purposes and isnot part of AG-181.

This document has been prepared under the direction of the End User Advisory Council(EUAC) of the Fieldbus Foundation. To be of real value, it should not be static but should besubject to periodic review. Toward this end, the foundation welcomes all comments andcriticisms and asks that they be addressed to:

ChairmanEnd User Advisory Council

Fieldbus Foundation9005 Mountain Ridge DriveBowie Building - Suite 190

Austin , Texas 78759-5316 USATel: 512.794.8890Fax 512.794.8893

E-mail: [email protected] our Worldwide Web Site:

www.fieldbus.org

This document in its present revision and at time of publication recognizes that High SpeedEthernet (HSE) products are available from the Fieldbus Foundation and its members. Thenext revision of this document will incorporate guidelines for the installation andimplementation of HSE.

The use of specific Vendor/Manufacturers in this document does not entail implicitendorsement of the product over other similar products by the authors or the FieldbusFoundation. Individuals using this document are encouraged to seek out equivalent functionequipment from other sources of which the authors may be unaware. To assist in our efforts tomake this document as relevant as possible, should such equipment be known to a user of this

document please forward that information to the address given above.

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It is the policy of Fieldbus Foundation to encourage and welcome the participation of allconcerned individuals and interests in the development of F OUNDATION™ fieldbus standards,recommended practices, and technical reports. Participation in the Fieldbus Foundationstandards-making process by an individual in no way constitutes endorsement by the employerof that individual, of the Fieldbus Foundation, or of any of the standards, recommendedpractices, and technical reports that the Fieldbus Foundation develops.

The Fieldbus Foundation would like to thank the End User Advisory Council and the membersof the End User Councils who have committed so much time and effort to the preparation ofthis guide.

In particular the Foundation wishes to acknowledge the following individuals without whosededication this guide would not have been possible:

Ian Verhappen (Editor) ICE-Pros, Inc. Chairman, EUAC, CanadaChris Baltus DSM EUAC, EuropeJohn Bazley Beca Simons EUC, Australia

Ambrose Hargan CSBP EUC, AustraliaHenry Marks Marks & Associates EUC, USANorihko EGI IT Engineering (Retired) EUC, JapanNola Ogar BP Group EUC, USADeon Rae Chevron Texaco EUC, USAJim Russel Keyfleet Pty Ltd EUAC, AustraliaHerman Storey Shell Global Solutions EUAC, USARon Szanyi ExxonMobil Director, Fieldbus Foundation

Al Chan Canadian NaturalResources Ltd

EUC, Canada

Jim SpragueRalph A. Hartman II

Saudi Aramco EUC, Saudi Arabia

Rev. No. Date Descr ipt ion By0 October 2003 Original Release IV

1.0 December 2003 Editorial Revisions IV2.0 August 2004 Editorial Revisions IV

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Revision Memo

REVISION 1.0 – DECEMBER 2003

Addition of Saudi Aramco contributors to prefaceRenumber 1.3.3 to 1.3.2Renumber 4.4.3 to 4.4.2Reference in Section 8.6.2 changed from 6.5.2 to 6.7.2

REVISION 2.0 – AUGUST 2004

Add abbreviation MOV – Motor Operated Valve to abbreviations list.Section 2.2.9 Addition of reference to AG-163Section 2.3.5 Correct IAONA URL from http://www.iaona-eu-com to www.iaona.orgSection 5.2.7 Statement of power conditioner isolation.Section 6.3.5 Change to 8/20uS, not 8/20SSection 6.5 & 6.6 RewrittenSection 6.7 Addition of Section on FNICO. Renumber balance of Section 6. Section 7.3.3 Correction SM Timer default settings were 2440000 (76.25 seconds) changed to

1440000 (45 seconds)Table title changes “Network/Segment Checkout Form” and “Fieldbus Cable Checkout Form”Update noise levels to


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CautionThe use of this guide may involve hazardous materials, operations or equipment. The guidecannot anticipate all possible applications or address all possible safety issues associated withuse in hazardous conditions. The user of this guide must exercise sound professional

judgment concerning its use and applicability under the user’s particular circumstances andaccording to their established corporate policies and procedures. The user must also considerthe applicability of any governmental regulatory limitations and established safety and healthpractices before implementing this standard.

Disclaimer of Warranties

This document is informative only and is provided on an “as is” basis only. The document maybe subject to future additions, modifications or corrections without notice. The FieldbusFoundation disclaims all warranties of any kind, express or implied, including any warranty ofmerchantability or fitness for a particular purpose, for this document. IN NO EVENT WILL THEFIELDBUS FOUNDATION BE RESPONSIBLE FOR ANY LOSS OR DAMAGE ARISING OUTOF OR RESULTING FROM ANY DEFECT, ERROR OR OMISSION IN THIS DOCUMENT ORFROM ANYONE’S USE OR RELIANCE ON THIS DOCUMENT.

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How To Use This Document

This document reflects standard industry practices for the application F OUNDATION fieldbus H1projects at time of publication. As this is a “living document” it will be maintained and updatedperiodically to reflect changes in the technology including the adoption and application of HighSpeed Ethernet (HSE).

The authors recognize that each facility planning to or installing a F OUNDATION fieldbus projectmay not wish to adhere to all the recommendations as reflected in this guideline. Towards thatend, the Council recommends that rather than change this document, which has several cross-references, that the user instead prepares a forward clearly identifying those sections to bemodified or applied in a different way. An example of this follows:

“XYZ Company applies Section 6.3.3 to provide additional grounding protection for fielddevices."

Recommended changes additions or suggestions should be forwarded via email to:[email protected]

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1.0 Introduction ...........................................................................................................11.1 Contents ...........................................................................................................1

1.2 Purpose ............................................................................................................21.3 Scope................................................................................................................2

2.0 References ............................................................................................................3

3.0 Definitions .............................................................................................................4 Abbreviations ..........................................................................................................13

4.0 Field Device Requirements ..................................................................................154.1 Support for F OUNDATION fieldbus Functionality..................................................154.2 Device Diagnostics ...........................................................................................174.3 Field Device Power ...........................................................................................184.4 Service Conditions ............................................................................................194.5 Logical Field Devices ........................................................................................194.6 Factory Configuration........................................................................................20

5.0 Ancill ary Device Requirements ...........................................................................215.1 Bulk Power Supplies .........................................................................................215.2 F OUNDATION fieldbus Power Supply/Conditioner (FFPS)...................................215.3 F OUNDATION fieldbus Terminators .....................................................................225.4 F OUNDATION fieldbus Repeaters........................................................................22

5.5 F OUNDATION fieldbus Wire .................................................................................235.6 F OUNDATION fieldbus Junction Boxes ................................................................23

6.0 Fieldbus Network/Segment Design Guidelines ..................................................256.1 F OUNDATION fieldbus Network/Segment Topology ............................................256.2 F OUNDATION fieldbus Wiring ..............................................................................276.3 F OUNDATION fieldbus Power, Grounding & Lightning Protection........................296.4 F OUNDATION fieldbus Segment Risk Management ............................................326.5 Intrinsically Safe (IS) Installations .....................................................................356.6 Fieldbus Intrinsically Safe Concept (FISCO) Installations.................................356.7 Fieldbus Non-Incendive Concept (FNICO) Installations ……............................386.8 F OUNDATION fieldbus Loading and Calculations ................................................386.9 F OUNDATION fieldbus Network/Segment Naming Convention............................40

7.0 Host System Requirements .................................................................................417.1 Use of Standard Products.................................................................................417.2 Spare Capacity and Expansion.........................................................................417.3 Interoperability ..................................................................................................41

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7.4 Host Interoperability Support Test (HIST) Description ......................................427.5 Support for F OUNDATION fieldbus Functionality..................................................43

7.6 Configuration Tool.............................................................................................457.7 Redundancy & Robustness ..............................................................................467.8 Troubleshooting, Maintenance and Diagnostics ...............................................477.9 Advanced Diagnostics and Computer Based Maintenance ..............................487.10 Evaluation Guidelines .....................................................................................49

8.0 Software Configuration Guidelines .....................................................................508.1 Control System Graphics ..................................................................................508.2 Node Addressing and Naming Conventions .....................................................508.3 Control Functionality Location ...........................................................................538.4 Configuration Options and Defaults ..................................................................548.5 Alarms and Alerts..............................................................................................548.6 Network Communications and Scheduling .......................................................568.7 Data Import and Export.....................................................................................618.8 Operator Display ...............................................................................................618.9 Software Revision .............................................................................................628.10 System Management ......................................................................................628.11 Control and Data Handling..............................................................................628.12 System Configuration Tools............................................................................66

8.13 Displays ..........................................................................................................68

9.0 Documentation Requirements .............................................................................709.1 Drawings ...........................................................................................................719.2 Control Narrative...............................................................................................739.3 Instrument Index/Database...............................................................................739.4 Instrument Datasheets ......................................................................................739.5 Material Requisitions.........................................................................................739.6 Manufacturer Documentation............................................................................739.7 Maintenance Manuals .......................................................................................74

10.0 Factory Acceptance Testing Requirements .......................................................7710.1 Introduction .....................................................................................................7710.2 Factory Staging...............................................................................................7710.3 Assumptions ...................................................................................................7710.4 Factory Acceptance Test (FAT) Requirements...............................................7810.5 FAT Procedure................................................................................................79

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11.0 Site Installation Guidelines ..................................................................................8111.1 Introduction .....................................................................................................81

11.2 Network Installations.......................................................................................8111.3 Cable Test Procedure .....................................................................................8111.4 Network/Segment Checkout Procedure..........................................................8311.5 Loop Checkout/Site Integration Tests .............................................................8911.6 Hot Cutover.....................................................................................................8911.7 Bench Simulation Testing ...............................................................................9211.8 System Development Room ...........................................................................9211.9 MCC Testing ...................................................................................................9211.10 Provision of Spares.......................................................................................93

11.11 Removal of Redundant Equipment ...............................................................9311.12 Maintenance Practices..................................................................................93

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1.1 CONTENTSThe F OUNDATION fieldbus EngineeringGuideline is separated into sections. Thefollowing is an explanation of the intent ofeach chapter:

Section 01 – Introduct ion and ScopeThe purpose and scope of the F OUNDATION fieldbus Engineering Guidelines.

Section 02 – ReferencesReferences used to compile F OUNDATION fieldbus Engineering Guidelines.

Section 03 – Defini tionsTerms used specifically with F OUNDATION fieldbus technology.

Section 04 – Field Device RequirementsFunctional requirements of the field deviceswhen used to implement F OUNDATION fieldbus technology.

Section 05 – Ancillary DeviceRequirementsFunctional requirements of the ancillarycomponents such as bulk power suppliesand power conditioners for use withFOUNDATION fieldbus technologyimplementation.

Section 06 – Network/Segment DesignGuidelinesInformation, explanations & guidelines foruse when designing F OUNDATION fieldbusnetworks/segments.

Section 07 – Host System RequirementsFunctional requirements of the host systemwhen used to implement F OUNDATION fieldbus technology.

Section 08 – Software ConfigurationGuidelinesInformation, explanations and guidelines foruse when configuring control system soft-ware for use in a strategy that incorporatesFOUNDATION fieldbus. Items covered includecontrol module configuration, function blockimplementation, condition-based monitoringsoftware configuration, and alarmmanagement and configuration.

Section 09 – DocumentationRequirementsRequired documentation for use whendesigning and maintaining F OUNDATIONfieldbus technology. Documentation suchas control philosophy, P&IDs & instrumentlocation drawings is covered in this chapter.

Section 10 – Factory Acceptance Test(FAT) RequirementsTasks and functions required to FAT acontrol system utilizing F OUNDATION fieldbustechnology.

Section 11 – Site InstallationRequirementsInformation and procedures for use wheninstalling fieldbus networks. This sectionalso specifies the procedures required tocheck out a F OUNDATION fieldbus system, aswell as identifying required tools for use ininstalling and maintaining F OUNDATION fieldbus equipment.

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1.2 PURPOSEThe F OUNDATION fieldbus SystemEngineering Guideline is intended tocompliment the principal’s existing series ofinstrument specifications. It details howfieldbus devices are specified, installed,configured, commissioned, and maintaineddifferently than conventional analog or"smart" instruments.

Since this guideline covers several different"topics" it has been separated into anumber of individual parts, one for each ofthe components of its "life cycle."

This Engineering Guideline addresses theimplementation of F OUNDATION fieldbusonly. Other fieldbus technologies exist thatmay be integrated to the basic processcontrol system, if the engineering designrequires. F OUNDATION fieldbus is primarilyused to replace the traditional analoginput/output signal types. F OUNDATION fieldbus technology is charted by theFieldbus Foundation.

This guideline deliberately uses the termsfieldbus and Fieldbus. Lower case fieldbusrefers to the generic use of the term and isapplicable to all fieldbuses defined in theIEC documentation. Upper case Fieldbusrefers specifically to F OUNDATION fieldbus.

1.3 SCOPEDefinition of the design, specification,installation, configuration, commissioningand maintenance for a F OUNDATION fieldbus-based control systems.

This guideline will only discuss the voltagemode (parallel coupling) mediumattachment unit, as defined in ISA 50.02,operating at a signal speed of 31.25 kilobitsper second (i.e., H1). This revision of thespecification does not cover the High

Speed Ethernet (HSE) version ofFOUNDATION fieldbus.

FOUNDATION fieldbus systems includeinstruments and hosts that cover allapplications and aspects of instrumentationand control. Therefore, it is intended that allFOUNDATION instrumentation and controlsystem standards apply to F OUNDATION fieldbus systems, except as noted herein.Note, however, that only those standardscalled out by name within this document arespecifically referenced.

Subject to the disclaimer at the front of thisdocument, this Engineering Guideline is foruse by users, contractors and controlsystem vendors.

1.3.1 GeneralFieldbus is an all digital, two-way multi-dropcommunications link among intelligentsmart field devices and automationsystems. F OUNDATION Fieldbus is the Local

Area Network (LAN) for instruments used in

process automation with built-in capabilityto distribute the control application acrossthe network.

1.3.2 Project Consideration As with any new project it is critical that theright skill sets be brought forth for theproject. The same is true for a Fieldbusproject. Experience has shown that trainingof all members of the project team,engineers, maintenance personnel, andoperations staff is critical to the projectsuccess. This training should be provided atthe ‘front end’ of the project to minimizerework as this information is gained through‘experience.’

Bringing in the right consultants at key junctures in the project to review and adviseon the next steps is also often a prudentinvestment.



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2.0 Other References

2.1 F OUNDATION Fieldbus Specifications2.1.1 FF-569 Host Interoperability Support Test2.2 Industry Codes and Standards2.2.1 IEC 61158-1: Introductory Guide2.2.2 IEC 61158-2: Physical Layer Specification and Service Definition2.2.3 IEC 61158-3: Data Link Layer (DLL) Service Definition2.2.4 IEC 61158-4: Data Link Layer (DLL) Protocol Specification2.2.5 IEC 61158-5: Application Layer Service Specification2.2.6 IEC 61158-6: Application Layer Protocol Specification2.2.7 IEC 61158-7: System Management2.2.8 IEC 61158-8: Conformance Testing2.2.9 AG-163: Foundation Fieldbus Application Guide 31.25 kbit/s Intrinsically Safe Systems

Note that the parts dealing with the DDL and the Application Layer contain parallel sections foreight different protocols, including F OUNDATION fieldbus.

De facto standards are available from the Fieldbus Foundation that will comply with and becompatible with the IEC 61158 suite of standards.

2.3 Other References

2.3.1 Fieldbus Technical Overview Understanding Fieldbus Technology – Fisher Rosemount2.3.2 Yokogawa TI 38K02A01-01E Fieldbus Book – A Tutorial2.3.3 F OUNDATION Fieldbus Wiring Design & Installation Guidelines

Author – Relcom, Inc.ISBN – Download @ http://www.relcominc.com/download/fbguide.pdf

2.3.4 Fieldbuses for Process Control: Engineering, Operation and Maintenance Author – Jonas Berge

ISBN – 1-55617-760-7 (note – ISA publication) Also available in Chinese2.3.5 Industrial Ethernet Planning and Installation Guide

Sponsoring Organization: IAONA e.VDownload @ http://www.iaona.org

2.3.6 F OUNDATION Fieldbus: A Pocket Guide Authors – Ian Verhappen, Augusto PereiraISBN – 1-55617-775-5 (note – ISA publication) Also available in Portuguese



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3.0 Defini tions

3.1 General Defin itionsThe definitions below shall be included ifthe words defined are used in the Code ofPractice.

The Contractor is the party that carries outall or part of the design, engineering,procurement, construction, commissioningor management of a project, or operation ormaintenance of a facility.

The Principal may undertake all or part ofthe duties of the Contractor.

The Manufacturer/Supplier is the party thatmanufactures or supplies equipment andservices to perform the duties specified bythe Contractor.

The Principal is the party that initiates theproject and ultimately pays for its designand construction. The Principal willgenerally specify the technical

requirements. The Principal may alsoinclude an agent or consultant authorized toact for, and on behalf of, the Principal.

The words shall/must/will indicate amandatory requirement.

The word should indicates an acceptablecourse of action or feature based on pastproject implementations.

The words may/can indicate oneacceptable course of action.

3.2 F OUNDATION fieldbus DefinitionsThe following represent definitions of termscommonly encountered in the use andapplication of Fieldbus technology. Acomprehensive list of definitions related toFOUNDATION fieldbus can be found on the

Fieldbus Foundation web site athttp://www.fieldbus.org/.

A

Acyclic PeriodThat portion of the communication cycletime, during which information other thanPublish/Subscribe data is transmitted.Typical information transmitted during thistime includes Alarms/Events, Maintenance/Diagnostic information, Programinvocations, Permissives/Interlocks, Displayinformation, Trend Information andConfiguration.

Appl ication Layer A layer in the communication stackcontaining the object dictionary.

Automation System A process automation, control, anddiagnostic system that is composed ofdistinct modules. These modules may bephysically and functionally distributed over

the plant area. The automation systemcontains all the modules and associatedsoftware required to accomplish theregulatory control and monitoring of aprocess plant. This definition of automationsystem excludes field instruments, remoteterminal units, auxiliary systems andmanagement information systems.

Auto SenseCapability by the system to automatically

detect and recognize any hardware uponaddition to or removal from the systemwithout any user intervention.

Auxi li ary System A control and/or monitoring system that isstand-alone, performs a specialized task,and communicates with the automationsystem.



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Commentary:Network Management (NM) permitsFOUNDATION Network Manager (NMgr)entities to conduct management operationsover the network using Network Management

Agents (NMAs). Each NMA is responsiblefor managing the communications within adevice. The NMgr and NMA communicatethrough use of the FMS and VirtualCommunications Relationship (VCR).

FISCOFieldbus Intrinsic Safe COncept. Allowsmore power to an IS segment for approvedFISCO devices, allowing for more devicesper IS segment.

Commentary:FISCO eliminates the requirement ofcalculating entity parameters of capacitanceand inductance when designing networks.

Flexible Function Block (FFB) A Flexible Function Block (FFB) is similar toa Standard FB, except that an application-

specific algorithm created by a program-ming tool determines the function of theblock, the order and definition of the blockparameters, and the time required toexecute the block. Flexible Function Blocks(FFBs) are typically used for control ofdiscrete processes and for hybrid (batch)processes. A Programmable LogicController (PLC) can be modeled as aFlexible Function Block device.

FNICOFieldbus Non-Incendive COncept. Allowsmore power to a Fieldbus segment in aZone 2 Area thus allowing for more devicesper segment.

G

GatewayTranslates another protocol to Fieldbus, forexample HART to Fieldbus or Modbus toFieldbus.

H

H1H1 is a term used to describe a fieldbusnetwork operating at 31.25 kbit/second.

H1 Field Device An H1 Field Device is a fieldbus deviceconnected directly to an H1 fieldbus.Typical H1 Field Devices are valves andtransmitters.

H1 Repeater An H1 Repeater is an active, bus-poweredor non-bus-powered device used to extendthe range over which signals can becorrectly transmitted and received for a

given medium. A maximum of fourRepeaters and/or active Couplers can beused between any two devices on an H1fieldbus network. Repeaters connectsegments together to form larger networks.

High Speed Ethernet (HSE)High Speed Ethernet (HSE) is the FieldbusFoundation's backbone network runningEthernet and IP.

HISTHost Interoperability Support Testperformed by the foundation to test hostconformance to the FF specifications.

HSE Field Device An HSE Field Device is a fieldbus deviceconnected directly to a High SpeedEthernet (HSE) fieldbus. Typical HSE FieldDevices are HSE Linking Devices, HSE



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Field Devices running Function Blocks(FBs), and Host Computers.

HSE Linking Device An HSE Linking Device is a device usedto interconnect H1 fieldbus networks/segments to High Speed Ethernet (HSE)to create a larger system.

HSE Switch An HSE Switch is standard Ethernetequipment used to interconnect multipleHigh Speed Ethernet (HSE) devices suchas HSE Linking Devices and HSE Field

Devices to form a larger HSE network.

I

Input/Output (I/O) Subsystem Interface An Input/Output (I/O) Subsystem Interfaceis a device used to connect other types ofcommunications protocols to a fieldbussegment or segments. Refer also toGateway.

InterchangeabilityInterchangeability is the capability tosubstitute a device from one manufacturerwith that of another manufacturer on afieldbus network without loss of functionalityor degree of integration.

InstantiableThe ability, for function block, to createmultiple tagged function blocks of differenttypes from a library as required byapplication. Quantity per device restrictedby device memory and other resources

InteroperabilityInteroperability is the capability for a devicefrom one manufacturer to interact with thatof another manufacturer on a fieldbusnetwork without loss of functionality.

ISIntrinsic Safety

ITKInteroperability Test Kit used by thefoundation to tick mark devices andconfirms compliance with the relevantFOUNDATION fieldbus standards. This is apass/fail test. Only devices passing the fullsuite of tests receive the FF "tick mark."

J

Junct ion Box / Quick Connection Station A junction box station allows for quickinstallation of four to eight field instrumentsvia Terminal connectors.

K

L

Link A Link is the logical medium by which H1Fieldbus devices are interconnected. It iscomposed of one or more physicalsegments interconnected by bus,Repeaters or Couplers. All of the deviceson a link share a common schedule, whichis administered by that link's current LAS. Itis the data link layer name for a network.

Link Active Scheduler (LAS) A Link Active Scheduler (LAS) is a

deterministic, centralized bus scheduler thatmaintains a list of transmission times for alldata buffers in all devices that need to becyclically transmitted. Only one Link Master(LM) device on an H1 fieldbus Link can befunctioning as that link's LAS.



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Link Master (LM) A Link Master (LM) is any device containingLink Active Scheduler (LAS) functionalitythat can control communications on an H1fieldbus Link. There must be at least oneLM on an H1 Link; one of those LM deviceswill be elected to serve as LAS.

Link Objects A Link Object contains information to linkFunction Block (FB) Input/Output (I/O)parameters in the same device andbetween different devices. The Link Objectlinks directly to a Virtual CommunicationsRelationship (VCR).

M

MAC Address A unique hardware address given to eachEthernet interface chip.

MethodsMethods are an optional (but highlydesirable) addition to Device Descriptions(DDs). Methods are used to define/automate procedures (such as calibration)for operation of field devices.

ModeControl block operational condition, such asmanual, automatic, or cascade.

N

Network A network as applied in this document, isthe termination of one or more fieldbussegments into an interface card of the hostsystem.

Commentary:In this document, as has become industrypractice, the term segment is used to

represent a cable and devices installedbetween a pair of terminators.

Network Management (NM)Network Management (NM) permitsFOUNDATION fieldbus Network Manager(NMgr) entities to conduct managementoperations over the network by usingNetwork Management Agents (NMAs).Each Network Management Agent (NMA) isresponsible for managing the communica-tions within a device. The NMgr and NMAcommunicate through use of the FieldbusMessaging Specification (FMS) and VirtualCommunications Relationship (VCR).

Noise AV Average noise in the network during thesilence period between frames.

O

Object Dictionary An Object Dictionary (OD) contains all

Function Block (FB), Resource Block (RB)and Transducer Block (TB) parametersused in a device. Through these para-meters, the blocks may be accessed overthe fieldbus network.

OPC (Object Linking and Embedding forProcess Control)Software application which allows bi-directional data flow between two separateapplications. These applications may berunning on the same or on separateservers.

Operator Console A console used by an operator to performthe functions required to monitor andcontrol his assigned units.



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P

Physical LayerThe Physical Layer receives messagesfrom the Communications Stack andconverts the messages into physical signalson the fieldbus transmission medium, andvice-versa.

Q

Quiescent CurrentThe device power consumption, the currentdrawn while the device is not transmitting.Shall be as low as possible to enable manydevices and long wires, particularly inintrinsic safety.

R

Redundant Configuration A system/subsystem configuration thatprovides automatic switchover, in the event

of a failure, without loss of a systemfunction.

Regulatory Contro lThe functions of process measurement,control algorithm execution, and finalcontrol device manipulation that provideclosed loop control of a plant process.

Resource Block (RB) A Resource Block (RB) describescharacteristics of the fieldbus device suchas the device name, manufacturer andserial number. There is only one ResourceBlock (RB) in a device.

S

SchedulesSchedules define when Function Blocks(FBs) execute and when data and status ispublished on the bus.

Segment A Segment is a section of an H1 fieldbusthat is terminated in its characteristicimpedance. Segments can be linked byRepeaters to form a longer H1 fieldbus.Each Segment can include up to 32 H1devices.

Commentary:In this document, as has become industrypractice, the term segment is used torepresent a cable and devices installedbetween a pair of terminators. The Fieldbusspecifications use the term network todescribe the system of devices though thisdocument uses the terms interchangeably.

See ANSI/ISA–50.02, Part 2 (IEC 61158-2):

SEGMENT = The section of a fieldbus thatis terminated in its characteristicimpedance. Segments are linked byrepeaters to form a complete fieldbus.Several communication elements may beconnected to the trunk at one point using amulti-port coupler. An active coupler maybe used to extend a spur to a length thatrequires termination to avoid reflections anddistortions. Active repeaters may be used toextend the length of the trunk beyond that

of a single segment as permitted by thenetwork configuration rules. A fully loaded(maximum number of connected devices)31,25 kbit/s voltage-mode fieldbus segmentshall have a total cable length, includingspurs, between any two devices, of up to1,900 m. There shall not be a nonredundantsegment between two redundant segments.



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Self-DiagnosticThe capability of an electronic device tomonitor its own status and indicate faultsthat occur within the device.

Splice A Splice is an H1 Spur measuring less than1 m (3.28 ft.) in length.

Spur A Spur is an H1 branch line connecting tothe Trunk that is a final circuit. A Spur canvary in length from 1 m (3.28 ft.) to 120 m(394 ft.).

Standard Function Block (FB)Standard Function Blocks (FBs) are builtinto fieldbus devices as needed to achievethe desired control functionality. Automationfunctions provided by Standard FBs include

Analog Input (AI), Analog Output (AO) andProportional/Integral/Derivative (PID)control. The Fieldbus Foundation hasreleased specifications for 21 types ofStandard FBs. There can be many types of

FBs in a device. The order and definition ofStandard FB parameters are fixed anddefined by the specifications.

Rate/Stale CountThis is a number corresponding to theallowable missed communications before adevice will shed mode. This is basically aWatchdog Timer.

System Management (SM)System Management (SM) synchronizesexecution of Function Blocks (FBs) and thecommunication of Function Block (FB)parameters on the fieldbus, and handlespublication of the time of day to all devices,automatic assignment of device addresses,and searching for parameter names or"tags" on the fieldbus.

T

Tag A collection of attributes that specify eithera control loop or a process variable, or ameasured input, or a calculated value, orsome combination of these, and allassociated control and output algorithms.Each tag is unique.

Tag IdThe unique alphanumeric code assigned toinputs, outputs, equipment items, andcontrol blocks. The tag ID might include theplant area identifier.

TerminatorImpedance-matching module used at ornear each end of a transmission line thathas the same characteristic impedance ofthe line. Terminators are used to minimizesignal distortion, which can cause dataerrors by converting between currentvariations and voltage variations. H1terminators also have another even moreimportant function. It converts the currentsignal transmitted by one device to avoltage signal that can be received by alldevices on the network.

TopologyShape and design of the fieldbus network(for example, tree branch, daisy chain,point-to-point, bus with spurs, etc.).

Transducer Block (TB)

A Transducer Block (TB) decouplesFunction Blocks (FBs) from the localInput/Output (I/O) functions required to readsensors and command output hardware.Transducer Blocks (TBs) containinformation such as calibration date andsensor type. There is usually one TBchannel for each input or output of aFunction Block (FB).



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Abbreviations Descript ion

ITK Interoperability Test Kit

LAS Link Active Schedule

LM Link Master

MAI Multi Analog Input

MAO Multi Analog Output

ML Manual Loader

MOV Motor Operated Valve

MV Manipulated Variable (controller output)

NM Network ManagementOD Object Dictionary

OPEX Operational Expenditure

PCS Process Control System

PAS Process Automation System

P/S Publish/Subscribe

PD Proportional/Derivative Control

P&ID Process & Instrumentation Diagram

PID Proportional/Integral/Derivative Control

PTB Physikalisch-Technische Bundesanstalt

PV Process Variable

PLC Programmable Logic Controller

RA Ratio

RB Resource Block

SIL Safety Integrity Level

SM System ManagementSP Set Point

SS Safety Systems

TB Transducer Block

TCoO Total Cost of Ownership

TPE ThermoPlastic Elastomer

VCR Virtual Communication Resource



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4.1 Support for F OUNDATION fieldbusFunctionality

All Fieldbus instruments should supportMethods to allow automation of onlineprocedures (such as calibration) from theHost.

4.1.1 Fieldbus Registration All devices must, as a minimum, satisfy therequirements of the fieldbus registrationlaboratory. In the case of the FieldbusFoundation, this is the FF “check mark”logo and listing on the approved devices listmaintained on their web site(http://www.fieldbus.org/ ). This verifiesinteroperability of devices as indicated inthe following example:

Example 4.1 F OUNDATION fieldbus Check Mark Logo

4.1.2 Fieldbus Function BlocksThe following function blocks are defined bythe Fieldbus Foundation. Not all of thesefunction blocks are available for use in allfield devices, and some are not availableand/or do not yet have interoperability tests.

Standard Function Blocks:FF-891: Function Blocks – Part 2 definesthese. The ten standard Function Blocksare as follows:

AI - Analog Input AO - Analog OutputB - BiasCS - Control Selector

DI - Discrete InputDO - Discrete Output

ML - Manual LoaderPD - Proportional/Derivative ControlPID - Proportional/Integral/Derivative ControlRA - Ratio

Advanced Funct ion Blocks: Advanced Function Blocks are defined inFF-892: Function Blocks – Part 3 are asfollows:

• Pulse Input

• Complex AO• Complex DO• Step Output PID• Device Control• Setpoint Ramp• Splitter• Input Selector• Signal Characterizer• Dead Time• Calculate• Lead/Lag• Arithmetic• Integrator• Timer• Analog Alarm• Discrete Alarm• Analog Human Interface• Discrete Human Interface

Addi tional Function Blocks:Function Blocks are defined in FF-892:Function Blocks – Part 4 are as follows:

• Multiple Analog Input• Multiple Analog Output• Multiple Digital Input• Multiple Digital Output


http://www.fieldbus.org/http://www.fieldbus.org/


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Flexible Function Blocks are defined inFF-892: Function Blocks – Part 5 asfollows:

• Flexible Function Block (IEC 1131Logic)

Commentary:It can be seen from the list that FunctionBlock types are not suitable or available forall instruments. It is therefore essential tomake a considered choice when specifyingthe Function Blocks to be included invarious field device types. Although it isappropriate to host most of these blocks incontrollers, field devices on H1 networks/segments due to the availability of devices,may be limited to the following blocks: AI fortransmitters, AO and PID for Valves, andDI/DO for discrete devices. See Section 8.3and Section 8.6 for further guidance on useof field device function blocks. FurtherFunction Blocks are likely to be added inthe future, it is therefore wise to checkFunction Block availability with theinstrument manufacturer at the time ofpurchase, thus ensuring that the featuresdesired are available for use.

Function Block Testing:The Fieldbus Foundation tests of FunctionBlocks only confirm that they are presentand how their external interface behaves,not how well they work internally. Eachmanufacturer can configure the internaloperations of Function Blocks as they wishand will in fact do so since this will providethem a competitive advantage. It is thusworthwhile to check which manufacturergives the best result in regards tomacrocycle efficiency and the needs of yourprocess.

Example:Each manufacturer can implement the PIDalgorithm with unique equations while stillproviding control in a PID block.

4.1.3 User Application BlocksFunction Blocks handle the control strategy.The Function Block diagram is a graphicalprogramming language for building controlstrategies.

There are two kinds of blocks that are foundin FOUNDATION fieldbus devices: Deviceapplication blocks, where the execution ofthese blocks uses predefined schedulingspecified by the device manufacturers andare used to configure devices, these arethe:

• Resource Block• Transducer Block• Function Blocks (FBs) whose

schedule and usage is completelyuser-configurable.

4.1.4 Resource BlockThe Resource Block (RB) describescharacteristics of the fieldbus device suchas the device name, manufacturer, andserial number. The following should beconsidered for design purposes:

• The user cannot make modifications.• User can change parameters.• There is only one RB in a device.• The RB is the only obligatory block in

FF devices.• The RB contains ID information and

general information related to thewhole resource or state of theresource (no real details about devicefunctionality).



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• Consider this: contains overall healthand operational status, contains writeprotection and enabling of simulationetc.

4.1.5 Transducer BlocksThe Transducer Block (TB) containsinformation such as calibration date andsensor type.

TBs decouple FBs from the local Input/Output (I/O) functions required to readsensors and command output hardware.I.e. this is where parameterization,

calibration and diagnostics for the deviceare done.

There is typically one TB channel for eachinput or output channel of a device (thismay differ for some devices).

4.1.6 Function BlocksFunction Blocks (FBs) should be used inuser-defined function block applications toprovide various functions required in a

control system (for example, input, output,signal selection, and other control actions).I.e. function blocks are the control strategy.The Fieldbus Foundation has definedseveral device profiles outlining the "root"requirement for several device types. Thisincludes pressure, temperature, valves andsome others. It is a good idea to usedevices that conform to thesespecifications.

FBs are built into fieldbus devices, asneeded, to achieve the desired controlfunctionality. Section 4.1.2 provides a list ofstandard, advanced, and multiple I/O FBs.

Commentary:The Fieldbus Foundation has defineddozens of standard function blocks.

Additional function blocks may be definedand implemented by each manufacturer to

accommodate individual control strategiesand signal processing needs.

Each manufacturer configures the internaloperations of FBs as they wish looking forcompetitive advantage. FF organizationtests only confirm that FBs are present andhow their external interface behaves, nothow well they work internally. It may be agood idea to as far as possible only usestandard blocks in the control strategy.Because enhanced blocks (standard blockswith additional parameters) haveextensions that are unique to eachmanufacturer, it becomes much moredifficult to replace a device that usesenhanced blocks. Devices with"instantiable" blocks have the advantagethat they typically support both the standardblock (e.g. PID) plus enhanced blocks (e.g.enhanced PID with some additionalfeatures). This way it becomes easy tochose standard blocks whenever sufficient,and enhanced blocks only when reallyrequired. Thus instantiable blocks make

interchangeability much easier.

4.2 Device DiagnosticsThe diagnostics shall be able to provide keyinformation on the ability of the device tomeasure or control the process, includingbut not limited to basic device failurediagnostics and advanced diagnostics. Thetypes of diagnostics required are explainedin the following sections.

Basic Diagnostics:Basic diagnostics are the device failurediagnostics that shall be viewable from anyprocess control host. They help determinecommon problems with the device,communication path, and host. Diagnosticsthat indicate a device failure shall force theaffected loop into MAN (Manual) forTransmitters and IMAN the PID block in theoutput device, typically a valve.



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Advanced Diagnost ics: Advanced diagnostics include full devicediagnostics so that the device health can bedetermined without removing it from theprocess. Advanced diagnostics come in twoforms, online and off-line.

Online:Online diagnostics perform their functionwhile the device is performing its normalfunction, and provide the capability toalert operations in real time if a problemneeds attention. This function providesone of the primary benefits of F OUNDATION fieldbus and should be supported by allfield devices as rapidly as possible.

Offline:Offline tests provide limited benefits andmay not justify their cost.

FF devices should be capable of supportingincremental device description (DD) forextra functionality and/or software revisionsin device memory.

Capabilities include the followingdiagnostics and should provide keyinformation on the impact that an outputdevice has on the process, including but notlimited to:

• Position accuracy• Operating resolution• Total valve travel• Packing friction and hysteresis• Static and sliding friction• Dead band

The following types of diagnostics shouldbe provided:

Public Diagnostics:Output device diagnostics that are viewablefrom any process control host. They help

determine common problems with valve,actuator, and host.

Advanced Diagnostics:Full output device diagnostics thatdetermine output device health withoutremoving it from the line. Advanceddiagnostics come in two forms – dynamicscan and step scan. Dynamic scan (onlineor offline method): cycles output device,and in one test collects all parameters fordrive signal, dynamic error band, outputsignal, and output device signature. Stepscan (online or offline method): test movesoutput device in unique patterns, which helpexamine device’s action in specific areas oftravel. This action shall be passwordprotected and require approval of a processoperator before implementation.

Process Diagnostics:Test that is run as the process is running.This test moves output device within arange until the process exceeds itsconfigured maximum deviation. It allows

maintenance personnel to compare hostaction, actuator action, output deviceaction, and process action.Process diagnostics helps determines thefollowing:

• Is the output device sticking? Howmuch? Where?

• Is the output device controlling theprocess for small variations?

• Is the output device properly sized?

4.3 Field Device PowerFieldbus devices may be powered eitherfrom the segment (bus), or locally powered,depending on the device design. If at allpossible field devices should be buspowered.



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Commentary:Bus-powered devices typically require 10-30 mA of current at between 9 and 32 volts.

Devices should strive for minimum powerconsumption, without negatively impactingdesired functionality.

4.3.1 PolarityFieldbus device’s communication signalshall be polarity insensitive.

Commentary:Some older FF devices were polarity

sensitive and if installed incorrectly couldcause network problems.

4.3.2 2-WireField devices shall be loop powered fromthe host control system. Fieldbus devicesshall work with voltages of 9–32 VDC.

Commentary:The 9 VDC specified is a minimum: it ishighly desirable that a margin of at least 1 V

(i.e. a minimum of 10 VDC) be maintainedat the field end of the bus. Some devices donot conform to FF standards and require 11volts to operate. Any segment designed tooperate below 15 V normally should carry awarning about additional loads in thesegment documentation. Minimum segmentvoltage should always be shown in thenetwork/segment documentation.

4.3.3 4-WireExternally powered devices (e.g. 4-wiredevices) with F OUNDATION fieldbus shouldhave isolation between external power andFieldbus signal inputs.

4.3.4 Short-circuit ProtectionDevices should work with 60 mA currentlimiting short-circuit protection though a limitof 40 mA is preferred.

Commentary:For practical purposes this means alldevices shall draw no more than 50 mAsince approximately 10 mA is needed toactivate the short-circuit protection circuitry.

4.4 Service ConditionsSpecific Fieldbus conditions should notrelax any device requirements specified inother corporate specifications related tosensor or component selection.

4.4.1 GeneralThe equipment shall be designed to

withstand vibration forces of up to 1.0 gover the range of 5 to 100 Hz, and for a5 msec duration a vibration force of 4.0 gover the same range. Networks, Data, I/Ohighways are required to have an approvedtype of electrical isolation at the point ofconnection to the Host System hardware,Fieldbus junction box, and the fieldinstrument.

4.4.2 Electrical Certi fication (Hazardous

Area Class if ication) All devices shall be certified by a nationally-recognized testing laboratory, and labeledfor Area classification (Zone or Division)where they will be installed.

4.5 Logical Field Devices A Fieldbus device is divided into two ormore Logical Field Devices, each of whichis called a Virtual Field Device (VFD).These Logical Field Devices are:

• The Management VFD containing thedevice’s physical and resource data.Resource data includes the VirtualCommunication Resources (VCRs).

• One of more Function Block Application Processes (FBAP VFD).

Each device has a set number of VCRs asdoes each host system and each publish/



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subscribe relationship link to another deviceor the host consumes one VCR. It istherefore important to be aware of the VCRavailability in a device. Refer to Section8.6.6 for more information on VCRs.

4.6 Factory ConfigurationInternal software of fieldbus instrumentsshould be configured by the manufacturer,including at least the following information:

• Serial number• Tag name• Process use description



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5.1 Bulk Power Suppli es

5.1.1 The 24 VDC bulk power suppliesshall be redundant.

Commentary:FFPS requires an input voltage of 20–35VDC. Unless an appropriate DC bus existsin the plant, the BPS provides the powerconversion from 240/120 VAC to 24 VDC.

Bus Power after conditioning is oftenapproximately 19 VDC.

5.1.2 Two separate, independent, powercircuits should source power the BulkSupply. The Bulk Supply can be fed fromUPS power or the bulk supply can includebattery backup.

5.1.3 Overcurrent protection shall beprovided for each feed supplying power toFF power conditioners.

5.1.4 The negative leg of the Bulk Supplyshall be grounded.

5.1.5 The Bulk Supply may be eitherdedicated solely to the fieldbus network orshared between the fieldbus network andconventional I/O.

5.1.6 If the site has an existing powersupply for conventional 4-20 mAinstrumentation, this power supply may beused to supply the FFPSs. The availablespare capacity of the power supplies shallbe verified to meet the FFPS demands. TheEnd User representative shall approve, inwriting, the use of the existing powersupply.

5.2 F OUNDATION fieldbus Power Supply/Conditioner (FFPS)

5.2.1 One (1) Fieldbus Power Supply/Conditioner is required for eachfieldbus network/segment.

Commentary:If an ordinary power supply were to be usedto power the Fieldbus, the power supplywould absorb signals on the cable becauseit would try to maintain a constant voltagelevel. For this reason, an ordinary powersupply has to be conditioned for Fieldbus.Putting an inductor between the powersupply and the Fieldbus wiring is a way toisolate the Fieldbus signal from the lowimpedance of the bulk supply. The inductorlets the DC power on the wiring butprevents signals from going into the powersupply.

In practice, a real inductor is not used.Inductors cause undesirable ringing onFieldbus segments. The electronic circuitprovides isolation of the Fieldbus circuitsfrom ground, current limiting to the segmentif the cable is shorted, and a high

impedance for the Fieldbus signals.

5.2.2 Fieldbus Power Supplies/Conditioners should be redundant, loadsharing, and output current limited.

5.2.3 FF Power Conditioners shouldprovide impedance matching required forFF signals.

5.2.4 Fieldbus Power Supplies/Conditioners should be poweredfrom the primary and secondary(redundant) bulk power supplies. Thesemay be linked primary-to-primary andsecondary-to-secondary if desired.

5.2.5 FF Power Conditioners units may beconnected together with common BulkPower Supply feeds, and common alarms.No more than eight (8) FF Power

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The host system and network schedule limitwill likely be exceeded before the physicalmaximum number of devices is reached.

5.4.4 When Fieldbus Repeaters are usedthe Principal engineer is to be informed andit is to be clearly marked on the associatednetwork drawing.

Typical uses:If a segment (network) needs to extendfurther than the 1900 meter lengthconstraint, then a repeater may beconsidered. The repeated segment design

must be reviewed and approved in writingfrom the Principal.

The most common use of repeaters is notto get longer distance, but to join ISsegments together. Because an entitybarrier only supports 3-4 devices, manybarriers are needed on a network to getloading of 16 devices per network .

Commentary:

In the cases where it is economically justified, a repeater may be considered toextend the total segment length. This wouldtypically be in cases where the H1 interfacecard cannot be located relatively close tothe process (e.g. flare systems).

Repeaters clean up the signal, by boostingit, re-timing it, and thereby improving thereliability of the communications. A repeatercan be used in cases with wire less than1900 m to improve network robustness.

5.5 F OUNDATION fieldbus WireFF wire is discussed in Section 6.2. Referalso to Section 6.3.7.

5.6 F OUNDATION fieldbus Junction BoxesIt is recommended that all trunk and spurconnections in the field junction boxes,including pass-through trunk pairs without

spurs, be terminated on ‘wiring blocks’specifically made for F OUNDATION fieldbusnetworks. An alternate connection may beprovided by weatherproof molded “bricks”that can be used without a junction box withfactory molded plug connectors.

Commentary:Fieldbus supports the use of traditionalterminal blocks though the User must beaware that the wiring of all devices to thenetwork is done via parallel connections.

The wiring block/Junction Box or Brick

should meet the following requirements:• Two (2) dedicated connections for the

Fieldbus homerun/trunk cable.• Integral short-circuit protector for spur

connections, maximum current to spuris limited by the area classification andcurrent available to the network. Spurcircuits shall have a non-incendiverating.

Commentary:The short-circuit protector can beconnected to the terminating block at thehomerun or main network cable.

• Pluggable (removable) ‘trunk’ and‘spur’ connectors.

• An indicator for each spur connectionindicating when a spur is shorted andis in overcurrent mode.

• Indication when bus power isavailable.

• Electrical regulatory (e.g. CSA or FM)approved for Ex n; Class I, Division 2,Groups B, C, D or Zone 2, IIA, IIB, IIC.

• Wire capacity: 12-24 AWG.• Temperature range: -45° to +70° C.• DIN rail mounting (terminal blocks).



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• Available in four (4) spur, six (6) spurand eight (8) spur configurations.

Exception:Inactive spare Fieldbus trunk pairs may beterminated on conventional terminal blocks,per End User standards.

Commentary:Wiring Blocks with integral short-circuitprotectors will prevent a fault (short-circuit)in the device or spur cable run frombringing the entire FF segment down.Typically an additional 10 mA load is addedwhen this spur is short-circuited.

The system design should be well under-

stood before the network and individualsegment design is started. The P&ID’s,Instrument Location drawings and PlotPlans are needed to effectively designfieldbus segments.

Commentary:Prior to defining Fieldbus segments, theprocess control strategy should becomplete, the P&IDs available, andinstruments selected with locations

determined. This is a necessary conditionto allow for the design of control in the field,which requires all devices for the loop to bepart of the same network/segment.



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6.1 F OUNDATION fieldbusNetwork/Segment TopologyThe fieldbus installation shall use the Tree,Spur or Combination topology. Do not usethe daisy chain topology.

Commentary:Components of fieldbus segments can beconnected together in various topologies.The topology selected is usually, though notalways 1 driven by the physical devicelocation in order to reduce installation costs.Hence, control narratives and plot plans areused in addition to P&IDs and instrumentindexes in the design of a fieldbus segment.

Spur connections shall be connected tocurrent-limiting connections to the bus toprovide short-circuit protection, and toprovide the ability to work on field deviceswithout a hot work permit. This currentlimiting connection should provide a non-incendive or intrinsically safe connection tothe field device.

Commentary:The drops and current limiting can beprovided by terminal blocks in junctionboxes or by bricks that are field-mounted.

The connection from the marshallingcabinet/host to the first junction box in thefield for the topologies shown in 6.1.2,6.1.3, and 6.1.4 are often provided by amulti-pair, individually shielded cable of thesame type (ITC) and wire gauge used forthe individual network and spur wires.

6.1.1 Point-to-Point TopologyThis topology consists of a network havingonly two devices. The network could beentirely in the field (e.g. a transmitter and

1 The desire to implement control in the field will drivethe need to connect all the devices for the affectedloop to reside on the same segment.

valve, with no connection beyond the two)or it could be a field device connected to ahost system (doing control or monitoring).This topology is illustrated below andshould not be used . It is not an economicdesign except as listed below.

Figure 6.1 Example of Point-to-Point Topology

Commentary:Until such time as the F OUNDATION fieldbusfor Safety specification is complete, this isthe only way in which a user may wish toself-certify and apply Fieldbus technology ina safety application.

6.1.2 Tree Topology (Chicken Foot)

This topology consists of a single fieldbussegment connected to a common junctionbox to form a network. This topology can beused at the end of a home run cable. It ispractical if the devices on the samesegment are well separated but in thegeneral area of the junction box. Whenusing this topology, the maximum spurlengths must be considered. Maximum spurlengths are discussed in 6.2.4. Thistopology is illustrated below in figure 6.2.

Figure 6.2 Example of Tree (Chickens Foot) Topology



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This is the preferred topology to be used forreuse of existing wiring, as it is most similarto the conventional installation and willtherefore provide the optimal use of existinginfrastructure.

Tree branch topology should be used forthe following situations:

• Retrofit installations• High density of fieldbus devices in a

particular area• High Speed Ethernet (HSE) is being

used

This topology also allows maximumflexibility when configuring and assigningdevices to networks/segments.

6.1.3 Spur TopologyThis topology consists of fieldbus devicesthat are connected to a multi-drop bussegment through a length of cable called aspur. This technology is technicallyacceptable but not generally a good

economic choice.

Figure 6.3 Example of Spur Topology

Bus with spur topology should be used innew installations that have a low density ofdevices in an area. Spurs shall beconnected to current-limiting connections(30 mA, or as appropriate for the device ona particular spur) to the bus as this providesShort-circuit protection.

6.1.4 Combination Topology:Combinations of the above topologies mustfollow all the rules for maximum fieldbusnetwork/segment length, and include the

length of spurs in the total lengthcalculation. These types of topologies arepreferred for designs using bricks with traycable. Spurs are permitted to extend onlyfrom trunk lines and not from other spurlines.

Figure 6.4 Example of Combination Topology

6.1.5 Daisy Chain TopologyThis topology consists of a network/segment that is routed from device todevice, and is connected at the terminals ofthe fieldbus device. This topology isillustrated below in figure 6.5 . This topologyshould not be used , as it is unacceptablefor maintenance purposes.

Commentary:The daisy chain topology is not usedbecause devices cannot be added orremoved from a network/segment duringoperation without disrupting service to otherdevices. Similarly, failure of one device willimpact all other devices “downstream” ofthe failed field device.

Figure 6.5 Example of Daisy Chain Topology



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6.2 F OUNDATION fieldbus Wiring

6.2.1 Cable TypesFor new installations or to get maximumperformance for a F OUNDATION fieldbusNetwork, individually shielded twisted-pairoverall screened cable designed especiallyfor FOUNDATION fieldbus may be used.However, specially designed FF cable doesnot always provide significant benefits overstandard tray cable that is available at amore attractive price.

Commentary:

Twisted pair wire is used rather than a pairof parallel wires to reduce external noisefrom getting onto the wires. A shield overthe twisted pairs further reduces noisesusceptibility.

Wire Size 18 GA (0.8 mm 2)Shield 90% coverage

Attenuation 3 db/km at 39 kHzMaximumCapacitance 150 pF/mCharacteristicImpedance

100 Ohms +/- 20%at 31.25 kHz

Table 6.1 Typical FF cable characteristics perIEC Physical Layer Standard

Type Meters/Feet ImpedanceOhms

Resistivity Attenuation(db/km)

Description

A 1900 / 6270 100 22 3 Individual shielded pairs

B 1200 / 3960 100 56 5 Multiple pairs with overallshield

C 400 /1320 Unknown 132 8 Multiple pairs with no shield

D 200 / 660 Unknown 20 8 Multiconductor, no pairing

Table 6.2 Fieldbus Cable Specifications

If the project is not using one of the cabletypes specified above, the cable should be

tested before it is installed with inducedFieldbus signals at the anticipatedmaximum length plus 25%. Tests shallinclude signal captures at the Power Supplyoutlet, as well as at the remote end of thecable.Cables for FF installations shall be labeledType ITC (16 Gauge) and shall be installedin tray or conduit. All cables shall be single

or multiple twisted pair with an individualshield for each pair. Multi-pair cables shallhave an additional overall shield.

Fieldbus cable is to be unique in color andcan be easily distinguished fromconventional 4–20 mA cable.



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Commentary:Facilities will continue to have 4–20 mAsignals for some time as fieldbustechnology develops, hence the advantageof having the cable differentiated. Thisdifferentiation can be at the cable ends onlythrough the use of lugs or colored heatshrink markers.

Fieldbus signals and 4-20 mA signals maybe run together in multiconductor cablesprovided each wire pair is individuallyshielded. This may be convenient when itis necessary to install a conventionalinstrument in the field until such time as aFieldbus version of the device becomesavailable. Once the Fieldbus device isavailable it is possible to swing the deviceover to the Fieldbus Network in the FieldJunction box.

Cables shall have thermoplastic elastomer(TPE) flame-retardant insulation andcomply with color conventions andpolarities of existing facility. Cable should

be as follows:• Suitable for the electrical area

classification• Suitable for outdoor use in cable trays

Cable jacket shall be flame-retardant poly-vinyl chloride (PVC).

6.2.2 Distance Constr aintsThe maximum allowed length of a fieldbussegment is 1900 meters (6232 ft.) exceptwhere repeaters are installed. This totalsegment length is computed by adding thelength of the main trunk line and all thespurs that extend from it.

Total Segment Length = Trunk + All Spurs

Commentary:The maximum length given is specified inthe ISA 50.02 Fieldbus standard. From fieldexperience these lengths have been foundto be conservative. As stated in thisspecification, the length of a segment islimited by voltage drop and signal quality(i.e. attenuation and distortion). As the EndUser gains field experience these lengthlimits may be revised to reflect real worldexperience. See 6.7.4 for furtherinformation on signal attenuation limits tosegment length.

6.2.3 Homerun Cable (Trunk)Either prefabricated molded cables orindustry standard 16 AWG multi-pair,individually shielded cable for analogsignals shall be used for all trunk wiring.Cable routing should conform to siteEngineering Specifications. Runs parallel tohigh power cables should be minimized,and adequate spacing and shielding shouldbe employed.

Ten percent (10%) spare pairs should beprovided for all muiltipair Fieldbus segmenttrunk cables, with a minimum of one sparepair. This requirement includes spares ontrunk cable runs between marshalling racksand junction boxes, and between junctionboxes.

Commentary:The decision to use multi-pair or single pairtrunk cabling depends on the number of

networks/segments installed in the fieldarea. Typically, the trunk cable will be amulti-pair cable if more than onenetwork/segment is required in the area orthe network/segment in the area would beloaded to maximum. Facilities may havetheir own rules relative to spare capacityrequirements upon completion of a project.This is suggested as a guideline in caseswhere a standard has not been established.



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6.2.3.1 When installing F OUNDATION fieldbus in a Brownfield Facility, the existinghomerun cables shall be tested forsuitability for reuse. This test can be doneusing the Relcom FBT-3 and FBT-5 cabletesting tools.

Commentary : At present these are the only known simplehandheld test products available for thisservice.

6.2.4 Spurs A spur can vary in length from 1 meter to

200 meters (656 ft.). A spur that is less than1 meter is considered a splice.

Commentary: A spur that is less than two hundred (200)meters is negligible as a transmission lineand can accurately be modeled as anequivalent capacitor. Note: quarter-wavelength at H1 frequencies is in excessof 2 kilometers. The spur length allowancesgiven in this document are considerably

more generous than allowed by the FFwiring guide provided by Relcom; however,these allowances are based ontransmission line theory, lab tests, and fieldinstallation experience. Strictly following theoriginal ISA 50 wiring guide can placeunnecessary and costly restrictions on FFfield wiring.

Only one (1) F OUNDATION fieldbus deviceshall be connected to each spur.

Commentary :Since a short-circuit protection wiring blockis being used, the segment design is limitedto one (1) device per spur.

The maximum spur length shall be 200meters (656 ft.). The spur length is thelength of the cable from the wiring block tothe FF device.

Commentary: A spur is a drop-off of the main trunk line.The trunk is considered to be the maincable run and will contain segmentterminators at each end.

While un-terminated spur lengths up to 200meters are allowed, any spur over 100meters (328 ft.) requires Principal approval.The intent of the selected multi-drop buswiring method is to eliminate the need forlong spur lengths and to keep spurs underthe recommended length of 30 meters(98 ft.) or less. Longer spurs may beneeded to keep the bus out of high-riskareas.

6.3 F OUNDATION fieldbus Power,Grounding & Lightning Protection

6.3.1 PowerFieldbus devices may be powered eitherfrom the segment (bus), or locally powered,depending on the device design.

Commentary:Bus-powered devices typically require 10-30 mA of current at between 9 and 32 volts.

Any network/segment designed to operatebelow 15V normally should carry a warningabout additional loads in the networkdocumentation. Minimum network/segmentvoltage should always be shown in thenetwork documentation.

The total current draw from all devices onthe network must not exceed the rating ofthe F OUNDATION fieldbus Power Supply.The network/segment design must take intoaccount:

• Total device quiescent current draw• One spur short-circuit fault (i.e. ~10

mA additional current draw)• 25% additional current load above the

two (2) previous requirements



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Instrument signal conductors shall not beused as an earth/ground. If an instrumentsafety earth/ground is required, it shall bemade through a separate conductor. Theconductor may be in the same cable as theinstrument signal conductors and shield,but shall be located outside the shieldwithin this cable.

Fieldbus devices should not connect eitherconductor of the twisted pair to earth/ground at any point in the network.

Commentary:

The earthing/grounding of either fieldbusconductor would be expected to cause alldevices on that bus network/segment tolose communications for the period that theconductor is earthed/grounded.

6.3.4 ShieldingThe instrument shield shall be terminated atthe host (power conditioner) end of thenetwork in the marshalling cabinet and shallnot be connected to ground at any other

place. If a multiple home run cable goes toa field junction box, do not attach the cableshield wires from different networkstogether. This creates ground loops andnoise onto the network.

6.3.5 Lightning/Surge ProtectionWhere surge protection is deemednecessary (e.g. areas of high lightningincidence, or where large inductive loadsare started and stopped), surge protectionshould be provided. This surge suppressionshall consist of low-capacitance siliconavalanche diodes or spark gaps, wired forboth normal- and common-mode protection,connected to the electrical safety groundgrid. Typical installations will be on fielddevices installed in tank farms or on top ofdistillation columns.

It is vitally important that the surgesuppression device does not measurablyattenuate the Fieldbus signal.

Commentary :The expected surge values on signalconductors within shields, provided that thegrounding practice for shields is followed,should be low. A surge rating of 1 kA for an8/20 µ S wave shape should be adequate.

Avalanche diodes generally fail to short-circuit. Where this is a concern, the surgesuppression devices may be connected via

a series fuse.

6.3.6 Terminators All terminators located in the field shall beinstalled in a junction box. Terminatorsshould not be installed in the Fieldbusdevices.

Commentary: A cable signal encountering a discontinuity,such as a wire open or short, produces a

reflection. The reflection is a form of noisethat distorts the original signal. Aterminator, consisting of a capacitor inseries with a resistor, is used at the ends ofa Fieldbus cable, to prevent a reflection.

6.3.7 Repeaters

Commentary :Repeaters replace one of the field devicesin the physical device count, allowing theaddition of the equivalent of an entire newsegment. By adding a repeater, a newsegment is created. Repeaters can be usedto split a network into smaller segments.

If a repeater is added to the network, a newsegment is connected, and the followingshould apply:



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The newly created segment should haveterminators at both ends. Repeatersshould be considered as a field device inthe physical device count. The number ofdevices on the network may be increasedto the maximum determined by the fieldbus type.

Note: The host system and networkschedule limit will likely be exceeded longbefore the physical maximum number ofdevices is reached.

Using barriers with built-in repeaters one

gets four (4) devices per barrier and therepeater function permits four (4)hazardous area segments to be joined toform a network of sixteen (16) devicesgoing to the host.

Actual number of devices may vary,depending on fieldbus type, type of powersupply, and power consumption of the fielddevice itself.

Power supplies shall comply withIEC 61158-2 criteria and performancerequirements, with preferentialconsideration given to the low-powersignaling option.

Power conditioners should be redundantunits that provide flawless transfer from oneunit to the other. Primary and secondarysources shall be physically separated, notsharing a common backplane or AC source.Power supply may be connected anywhereon a bus network/ segment.

In practice, power supply will probably bean integral element of the host controlsystem’s manufacturer.

6.4 F OUNDATION fieldbus Segment RiskManagementEach end user facility shall identify anddocument a risk assessment philosophy(method) by which Fieldbus devices areassigned to network/segments.

Existing plant risk area or card loadingmethods in place may be used. Thephilosophy shall consider network/segmentsegregation, multiple segments per H1 port,etc. The risk assessment ranking should beclearly shown on the network/segmentdrawings. Topology design should minimizesingle points of failure.

The following valve criticality rating andnetwork/segment loading method should beused. The valve and associated measure-ment criticality shall be defined for prudentloading of Fieldbus segments. The followingratings should be assigned to each valveand segment.

Commentary:

The design restrictions are intended tominimize the effect of human error andinteroperability problems from affectingplant reliability. The intent of Level 1 and 2designs is to keep the number and varietyof devices on a network small so that aminimum of interaction is required with thesegment. Less is better; however, a unitwith large numbers of dependent servicevalves may decide to increase themaximum number of valves to three (3) for

Level 1 and 2.Instruments that are part of a commonreliability concept should not be on thesame network (share the same host I/Ocontroller) and if possible backplane tominimize the number of possible commonmode failure points.



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6.4.1 Multi -variable DevicesMulti-input and multi-variable transmittersusing F OUNDATION fieldbus Analog Input(AI) function block(s) may be used forcontrol and monitoring. A multi-variabletransmitter input should be used in onecontrol loop only. All other variables fromthe transmitter can be used for monitor-onlyapplications.

Multi-input transmitters using F OUNDATION

fieldbus Multiple Analog Input (MAI)function block(s) shall be used for monitoronly applications.

6.4.2 Discrete DevicesDiscrete FF devices (using DI/DO functionblocks) may be used on the same network/segment as regulatory control andmonitoring devices.

6.4.3 Level 1 Valves and Networks

Risk Management Selections

Redundant Controller RequiredRedundant H1 Interface RequiredRedundant Power Supplies RequiredDC Power Supply Battery Capacity Required - 30 minutes minimumRedundant Power Conditioners RequiredField Backup LAS RequiredControl in Valve Positioner Preferred for simple loopsControl in Transmitter Only for Cascade PrimaryControl in Host Required for Complex LoopsValve / Segment Criticality Ranking Required

Maximum Devices per Segment 12 (default unless otherwise noted insection 6.4 or 6.7)

Maximum Valves per Segment 4 (default unless otherwise noted insection 6.4 or 6.7)Repeaters Requires Project Lead Engineer approval

Table 6.2 Network/Segment Risk Management Selections

Failure of a Level 1 valve will result in atotal system trip, causing a shutdown of theentire unit, or other unavoidable losses inexcess of $10M. Normal Valve failuremode is to be used for this classification.

Design Requirements:Level 1 valves and their associatedmeasurement device (transmitter) shouldreside on H1 networks that are only used

for Level 1 control. The segment may haveone (1) Level 1 Valve and associatedTransmitter when services are independent,or two (2) Level 1 Valves and associatedTransmitters when services are dependent.Dependent means that either of the two (2)valves will shut down the same piece ofequipment (example pass flows on a firedheater).



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To aid in assurance of interoperability,consideration may be given to having theLevel 1 field devices in the loop supplied bya single vendor. Host interface cards andfield devices for all Level 1 loops shall beindependently tested for interoperability.The devices and interface cards shall bekept at compatible revision levels for thelifetime of the network. Upgrades should bedone during plant turnarounds if necessary.

The network/segment drawing should showthe criticality rating and shall prominentlydisplay that no additional devices shall beloaded on this network/segment.

6.4.4 Level 2 Valves and NetworksFailure of a level 2 valve will result in a totalsystem trip, causing a shutdown of theentire unit, or other unavoidable losses inexcess of $100K. However, the Level 2valve’s process dynamics allow time forquick recovery from the failure, either byquickly fixing a fault or by taking manualcontrol. The material and energy capacity of

associated vessels, geographic location,and elevation/accessibility of such valvesshould be considered. The difference inLevel 1 and 2 valves are dependent onoperations ability to respond to a singlefailure.

Commentary:For example, a level control valve on avessel with less than three minutes ofholdup time, on the edge of the physical

plant, might become a level 1 valvebecause of its limited accessibility, if loss oflevel or high-high level would result in atotal unit shutdown.

Design Requirements:Level 2 valves and their associatedmeasurement device (transmitter) shouldreside on H1 networks/segments that areonly used for control. The segment may

have one Level 2 valve and associatedtransmitter when services are independent,or two Level 2 valves or a Level 2 and aLevel 3 valve and associated transmitterswhen services are dependent. Dependentmeans that either of the two valves will shutdown the same piece of equipment(example pass flows on a fired heater).

To aid in assurance of interoperability,consideration may be given to having theLevel 2 field devices in the loop supplied bya single vendor. Host interface cards andfield devices for all Level 2 loops shall beindependently tested for interoperability.The devices and interface cards shall bekept at compatible revision levels for thelifetime of the network. Upgrades should bedone during plant turnarounds if necessary.

The network/segment drawing should showthe criticality rating and shall prominentlydisplay that no additional devices shall beloaded on this network/segment.

6.4.5 Level 3 Valves and SegmentsFailure of this valve will not result in anyshort-term risk of total unit shutdown ormajor operating losses. Level 3 valves cango to their fail position without requiringimmediate operator action.

Design Requirements :Level 3 valves can reside on cards ornetworks/segments with up to three otherlevel 3 valves, or on a segment with a level2 valve (see Section 6.7.2 for otherlimitations on the number of valves on asegment). Networks containing Level 3control contain products from multiple(approved) vendors including measurementonly devices.

The devices and interface cards shall bekept at compatible revision levels for thelifetime of the network. Upgrades may be



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done online. The network/segment drawingshall show the criticality rating.

6.4.6 Level 4 Segments – No ControlLevel 4 devices are measurement onlydevices that shall not be used for controland may be configured in a way that couldinterrupt control on a network/segment.This class includes MAI, MAO, MDI, andMDO block communication devices.

Design Restrictions :Level 4 devices can reside on segmentswith up to the maximum number of devices

based on network design bandwidth andphysical limitations. The devices andinterface cards shall be kept at compatiblerevision levels for the lifetime of thenetwork. Upgrades may be done online.The network/ segment drawing shouldshow the criticality rating.

6.4.7 Network/Segment Shorting A shorted network/segment or powersupply failure shall send valves to their

designated failure position, regardless ofthe device hosting the PID algorithm.

6.4.8 Transmit ter AssignmentNormal practice shall be to include thetransmitter with the primary processvariable on the same segment with itsassociated valve.

Commentary:This is a necessary condition to allow forfield-based control.

6.4.9 Multiple Process VariablesMultiple measurements used to provide acalculated differential shall be assigned to acommon segment with the differentialcalculation performed in one of thetransmitters as they typically have a lower‘load’ than an output device.

Commentary:This restriction does not apply for systemssupporting bridge capability between H1networks.

6.5 Intrinsically Safe (IS) InstallationsIn general the design of IS Fieldbusinstallations must follow the sameguidelines as imposed by the technology fornon-IS installations. The major differencesare the power constraints imposed by theneed to remain Intrinsically Safe and therequirement to use suitably certified powersupplies, field instruments and wiringcomponents.For IS applications, cable should:

• Comply with IS inductance andcapacitance limitations, as specified inthe approvals documentation. ForFISCO installations, additionalrequirements apply to the resistancecharacteristics of the cable.

• Be identified as carrying intrinsicallysafe circuits. This may be by meansof marking or the use of a coloredsheath.

Commentary:Typically, IS wiring has a light blueinsulation or shield.

6.6 Fieldbu

system engineering guidelines ff

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