Making your Fieldbus Project as Painless as Possible
District heating company realizes advantages of reliable fieldbus control
solution
Having entered the digital era many years ago in nearly every aspect of our lives, it’s a wonderthat the process industries still struggle with the adoption of digital solutions. Whether users
install Modbus, HART, PROFIBUS, FOUNDATION™ Fieldbus or some other digital protocol, thecommon issue faced across all of them is underutilization of the digital information. These aresystems and devices with a lot of engineered smarts inside chattering away to anyone that will
listen, yet the process industries on the whole haven’t lent an ear. With the Industrial Internetof Things (IIoT) and Industrie 4.0 poised to be the process industry’s modern day renaissance,
digital integration of instrumentation into systems is a must. It is a profoundly different
approach meant to revolutionize how we think about our industry. People have begun
understanding that integrating information into systems doesn’t just save money; it saves
resources, it saves environments, it saves lives. There is no reason we should continuously send
humans into extremely hazardous locations to diagnose problems that can be done from thesafety of a keyboard.
How can the IIoT and Industrie 4.0 be successful without such utilization? Certainly there is no
shortage of benefits in digitally transforming our industry. In much the same way, engineersand end users alike must keep in mind that FOUNDATION Fieldbus is a digital technology and totruly realize the vast benefits, it must be integrated.
Certainly by now, the industry is aware of the upfront savings of FOUNDATION Fieldbus like
reduced hardware, reduced instrumentation, reduced wiring, more power, real‐time control
etc., but the real payback that separates an OK refinery from an industry leader is the one
taking advantage of the digital data. And if you are used to analog networks and do not havethe proper degree of training, it could be a painful “learning” experience. Fortunately,
however, FieldComm Group has developed many resources that can help first time users avoid
rookie mistakes. Here are some key pieces of information and advice you should know before
embarking on a fieldbus project.
Best Practices
Qualified Engineering Partner is Essential
We cannot emphasize enough, if you do not have an engineering partner that has had sometraining and knows how to implement a fieldbus network, your costs will go up. Many
engineering firms believe that there are no great differences between 4‐20 analog and fieldbus

1installations, but if you do not know what you are doing you can end up in the weeds pretty
quickly.
FieldComm Group offers certified training courses through our FOUNDATION Certified Training
Program (FCTP), with eight certified training institutions around the world. You can look at yourexisting engineering partner and see what kind of training staff engineers have. Even if they do
not have people that have taken a certified training course, they could still have successfulreference projects. FOUNDATION Fieldbus has almost 20,000 systems installed around the world,
and the pool of engineers with fieldbus experience is growing. Checking references, expertise,
and training does not take too much time and will provide a quick payoff.
Not surprisingly, engineering partners that do not have experience in fieldbus installations will
try to steer you away from the technology. Our advice is not to let engineering companies
dictate your automation strategy, but to form a coherent strategy beforehand and find apartner that can fulfill your requirements. There are plenty of engineering service providers on
the market today who will do a fine job. You may also want to consider retaining the servicesof a fieldbus consultant, who can provide years of experience and guidance on your project.
Project Requirements
Having a good understanding of project requirements is fundamental. The AG 181 System
Engineering Guide is a free resource that the FieldComm Group provides free of charge. It canbe downloaded at fieldcommgroup.org. AG 181 provides a lot of good guidance throughout
the project lifecycle, starting with project requirements. The guide points out five fundamental
differences between conventional projects and FOUNDATION Fieldbus projects. If you remember
these differences, you will be on your way to a successful project:With FOUNDATION Fieldbus, field devices and segments become an integral part of the
DCS. This requires an integrated configuration, data management, and systemarchitecture approach to field network design. You can no longer treat devices andprocess automation systems as separate islands of automation.



System integration aspects of FOUNDATION Fieldbus require some design activities to be
performed earlier and with greater detail in the project lifecycle.

You can achieve more advanced functions with FOUNDATION Fieldbus designs compared
to traditional technologies. These advanced functions offer considerable opportunities
for operating cost‐savings and improved commissioning and start‐up.



System, field device, and segment component testing capabilities are more advanced
than for simple analog connections.



Traditional lines of authority between crafts and legacy‐derived practices should be
reviewed to determine if they are a suitable “fit” for FOUNDATION Fieldbus. In otherwords, it will require a few different work processes than you have done before.

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Especially if you want to practice true predictive and proactive maintenance, which iswhere a lot of your operational cost savings will occur.
Use Registered Devices and Hosts
It may seem obvious, but it is always preferable to use a host system or device that has gone
through the FieldComm Group testing and registration process. The FOUNDATION Fieldbus“check mark” symbol is an obvious indicator that a product has been tested and registered, but
you should go beyond that to determine which version of the Interoperability Test Kit or Host
Profile Registration process the host or device conforms to. The FieldComm Group has greatly
strengthened its testing and registration requirements. Devices tested under the latest Version
6.0 of the Interoperability Test Kit (ITK) will provide more advanced diagnostic functionality,
including the NAMUR NE 107 recommendations for presenting diagnostic data. Our latest
iteration of host profile registration has made many previously optional requirements
mandatory, such as support of enhanced function blocks and DD V5.1 Device‐Level Access.
You Need a Good Plant Asset Management System
It does not matter which process fieldbus you
are installing. If you don’t have some kind ofplant asset management application (PAM)
to deal with all the new diagnostic data you
are going to get from your intelligent devices,
you will not realize the significant operationaland maintenance cost benefits that comewith the technology. A PAM system will help
you manage your data and will be a valuable
tool for maintenance personnel. Examples ofcurrent PAM systems include Emerson’s AMS
Suite, Honeywell Field Device
Screen Shot of a FOUNDATION Fieldbus PAM System
Manager, and Yokogawa PRM. The
PAM system is the core applicationthat will allow you to develop a predictive and proactive maintenance strategy. Remember
how we mentioned earlier that some aspects of the fieldbus project must be planned earlier inthe lifecycle? The plant asset management system is one of these items. You should start earlyin the front end engineering and design phase to determine how the PAM system will be used
and who will need to use it.
A Word about Work Processes
You should define any new or revised work processes that may be required because of the useof FOUNDATION Fieldbus. This is one of the most often overlooked aspects of a fieldbus project. If
you do not pay attention to proper work processes, the people that need the data from fieldbus
devices may not be able to get it, or you could remain stuck in traditional maintenanceprocesses that are transformed by fieldbus. Fieldbus is essentially a data pipeline, and users
must plan where that flood of data is going to go and how it will be transformed into useful3

information. In most cases today, this is a secondary consideration that is only addressed after
the system is up and running. Having a team in place consisting of personnel from all areas ofthe plant that are affected will expedite this process. What kinds of information are yourmaintenance personnel looking for? What about data storage and validation concerns forcompanies that must undergo regulatory compliance in industries such as pharmaceuticals andfood & beverage?
The information flow from the device level to the associated applications that need it must be
mapped out prior to startup to achieve maximum benefits. Intelligent field devices are reallydata servers, and much of the information in these data servers is not appropriate for thecontrol system operator. If you are dealing with a supplier that has an effective fieldbus
configuration tool integrated with a good Plant Asset Management (PAM) application, it should
be a minimal effort to get the right information to the right people at the right time.
Many end users may lack sufficient knowledge to implement these work processes. There iscurrently a new ISA standards effort underway to develop recommended work processes for
managing the data from your intelligent devices. The ISA 108 standard will define work
processes for different roles in the organization and provide best practices for the project
lifecycle.
System Capabilities
FOUNDATION Fieldbus and Redundancy
Today, FOUNDATION Fieldbus is used in critical applications and can support key functions fordemanding applications, including redundancy. FOUNDATION Fieldbus support redundancy on
many levels if that is one of your requirements. Redundant power supplies, redundant H1(device level) fieldbus interface cards, and redundant controllers are the most comment ways
to do this. With redundant H1 cards, it is possible to replace either H1 card under power withno impact on the H1 segments associated with the redundant cards. It is also possible toupgrade H1 card software/firmware without affecting communications on the related H1
segments.
FOUNDATION Fieldbus is comprised of the H1 network at the device level, and the HSE standard
Ethernet‐based network addresses high‐speed application and devices such as motor operated
valves (MOVs), drives, remote I/O. FOUNDATION HSE is based on unmodified IEEE 802.3 Ethernet
and, therefore, is compatible with standard Ethernet equipment. Unlike mere "ring topology,”
FOUNDATION HSE provides complete "DCS style" redundancy with redundant network switches,
redundant devices, and redundant communication ports for extremely high availability.
Integration of Wireless Devices and Remote I/O
The HSE network also provides integration with wireless networks such as ISA 100.11a andWirelessHART through FOUNDATION for Remote Operations Management (ROM). HSE can also
serve as a wireless or wired backhaul network for remote applications such as pipeline SCADA
and offshore platform automation. FOUNDATION for ROM provides for direct access to4

information and diagnostics in wireless and remote I/O devices. Conversely, FOUNDATION for
ROM can take the data from those devices and place into the FOUNDATION Fieldbus environment
for data management and quality.

FOUNDATION for ROM
FOUNDATION Fieldbus Function Blocks
One key thing to consider at the device level, aside from buying products that have been tested
and registered, is the support of advanced diagnostic functions and function blocks. The
support of function blocks is unique to FOUNDATION Fieldbus and is the enabler for control in thefield and many of the advanced diagnostic functions that we offer. Function blocks were reallythe first instances of object‐oriented programming, and enable FOUNDATION Fieldbus to take acomprehensive, object‐oriented approach to process control. FOUNDATION Fieldbus supports aseries of standard function blocks, as well as advanced function blocks and additional function
blocks such as flexible function blocks (FFBs). The ten standard Function Blocks are as follows:

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








AI ‐ Analog Input
AO ‐ Analog Output
B ‐ Bias
CS ‐ Control Selector
DI ‐ Discrete Input
DO ‐ Discrete Output
ML ‐ Manual Loader
PD ‐ Proportional/Derivative Control
PID ‐ Proportional/Integral/Derivative Control
RA – Ratio

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Advanced Function Blocks include:













Device Control
Set Point Ramp
Splitter
Input Selector
Signal Characterizer
Dead Time
CalculateLead/Lag
Arithmetic
Integrator
Timer
Analog Alarm

Additional Function Blocks:
Additional function blocks include Multiple Analog Input and Output and Multiple Discrete
Input and Output.
It can be seen from this list that not all function block types are suitable or available for all
instruments. It is, therefore, essential to make a considered choice when specifying thefunction blocks to be included in various field device types. Although it is appropriate to host
most of these blocks in controllers, their use infield devices on H1 networks/segments may
be limited (due to the availability of devices),to the following blocks: AI for transmitters, AO
and PID for valves, and DI/DO for discrete
devices. Additional function blocks are likely
to be added in the future, therefore, it is wise
to check function block availability with the
instrument manufacturer and ensure that the
Host system will allow the use of the desired
function blocks at the time of purchase, thus
ensuring that the features desired areavailable for use. It should be noted that there
is seldom a need to have all function blocks
available in all field devices. The user should
also verify that functionality in the Host andfield device is compatible, should it benecessary to revise the functionality location.
FOUNDATION Fieldbus Block6

User Application Blocks
Where function blocks allow the user to create control strategies, user application blocks allow
the user to configure devices and applications. The Resource Block (RB) describes
characteristics of the FOUNDATION device, such as the device name, manufacturer, and serial
number. The Transducer Block (TB) contains information such as calibration date and sensor
type. Field Devices require at least one Transducer Block to make the device useful. TBs
decouple FBs from the local Input/Output (I/O) functions required to read sensors andcommand output hardware (i.e., this is where parameterization, calibration and diagnostics forthe device are carried out).
Power Requirements
Power requirements for fieldbus are different from analog systems. FOUNDATION Fieldbus
devices may be powered either from the segment (bus), or locally powered, depending on thedevice design. Bus‐powered devices typically require 10‐30 mA of current at between 9 and 32
volts. Any network/segment designed to operate at less than 2 volts above the minimum
required voltage at any device or wiring component should normally carry a warning about
additional loads in the network documentation. Minimum network/segment voltage should
always be shown in the network documentation. The total current draw from all devices on the
network must not exceed the rating of the FOUNDATION Fieldbus power supply. The
network/segment design must take into account:






Total maximum device quiescent current draw
One spur short‐circuit fault (i.e., ~50 mA additional current draw)
15 ‐ 25% additional current load above the two (2) previous requirements (for inrush
current and expansion, etc.)
Current consumption of wiring components
Test equipment (typically 12 mA per device)

Cable
Just as we provide testing and registration services for field devices and host systems, there is awide range of registered FOUNDATION Fieldbus cable to choose from. In November 2007, theFieldbus Foundation (now FieldComm Group) released its H1 Cable Test Specification(Document FF‐844) for use by manufacturers developing cables for Foundation Fieldbus H1(31.25 kbit/s) installations. The specification test cases, based upon the IEC 61158‐2:2003
standard for Type A cable, include (but are not limited to) impedance, capacitive unbalance,
connector pin‐outs, and attenuation. Cable manufacturers submit their test reports to thefoundation, which provides official cable registration.
There are many choices today for registered cable, but there are also ways to test your installed
instrument cable to see if it would be compatible with a FOUNDATION Fieldbus installation.
Suppliers such as Relcom offer automated tools that can test your existing cable.

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Network Topology
Components offieldbus segments canbe connected together
in various topologies.
The topology selected
is often, though notalways driven by thephysical device
location in order toreduce installation
costs. Hence, control
narratives, plot plans
and risk management
considerations are
FOUNDATION Fieldbus Network Topologies
used in addition to P&IDs andinstrument indexes in the designof a fieldbus segment. FOUNDATION Fieldbus installation use the tree, spur or combination
topologies. Other topologies are not recommended.
Point‐to‐Point topology consists of a network having a maximum of only two devices. The
network could be entirely in the field (e.g., a transmitter and valve, with no connection beyond
the two) or it could be a field device connected to a Host system (doing control or monitoring).
This topology is illustrated below and should not be used. It is not an economical design except
as shown in the attached figure.
Tree topology consists of a single fieldbus segment connected to a common junction box toform a network. This topology can be used at the end of a home run cable, and is practical if thedevices on the same segment are well separated but in the general area of the junction box.
Spur topology consists of fieldbus devices connected to a multi‐drop bus segment through alength of cable called a spur. This technology is technically acceptable, but generally not a good
economical choice when there is a high density of devices.
Combinations of the above topologies must follow all the rules for maximum fieldbus
network/segment length, and include the length of spurs in the total length calculation. Thesetypes of topologies are preferred for designs using bricks with tray cable. Spurs are permitted toextend only from trunk lines and not from other spur lines.

8What is a Segment?

FOUNDATION Fieldbus Physical Layer Components
A FOUNDATION Fieldbus segment is a network or part of a network that serves as the primarycommunication highway for the connected fieldbus devices. It includes the fieldbus network
card interface, the power supply, and the power conditioner. The cable serves as the principal
link between the fieldbus network and fieldbus devices. It can be a part of the fieldbus network
wiring that is electrically independent from other parts and may or may not have an associatedpower supply (as in the use of repeaters).
Trunks, Spurs, and Terminators
Trunks, spurs, and terminators are all fundamental parts of a FOUNDATION Fieldbus installation.
A Trunk is the main communication highway acting as a source for other lines (spurs) from thecontrol room. Generally, the longest cable path between any two devices on a segment.
A Spur is a fieldbus branch line that connects to the segment. A spur does NOT haveterminators at either end of the spur cable. A Spur can vary in length from 1 m (3.28 ft.) to 120
m (394 ft.), depending on the number of devices on the Spur.
A Terminator is an impedance‐matching module used at each end of a segment. A Terminatoris required at each end of the longest cable path between any two devices on a segment toprevent distortion and signal errors. Only two terminators can be used on a single fieldbus
segment.
Segment Isolation
Segment isolation is a basic requirement for FOUNDATION Fieldbus design. Where devices are
installed in areas that are considered to be at a high risk of lightning strikes, segment
segregation shall be considered as an additional measure of protection. High‐risk applications
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include tank farms where transmitters are located on top of tanks, remote areas in open
spaces, devices requiring more than two wires (temperature), unprotected structures with little
or no surrounding steel, and transmitters that are located on the top of columns or in the open
on top of structures.
Number of Devices per Segment
Many end users are under the misconception that only a small number of devices can be placedon a fieldbus segment. As a rule of thumb, the AG 181 System Engineering guide recommends
the maximum number of devices on any segment (including future devices) should be no
greater than 12, but there are situations where more than 12 is possible. Students at some ofour training facilities routinely overload segments with as many as 16 devices and they continue
to function. Of course, we don’t recommend overloading your segments. The advice that AG‐
181 gives is that project staff shall set a design standard for the maximum number of devices
per segment for that project if less than 12. This design standard should be used as the basis forvoltage drop calculations and should include spare capacity for future expansion.
Further Reading
These are some of the key recommendations facts for designing and implementing a successful
fieldbus project, all of which can be seen in our AG‐181 System Engineering guide available forfree download from the Technical References section of this website.
FieldComm Group also offers a free automated segment design tool called DesignMate.
DesignMate automatically audits segment layouts for conformance with the FOUNDATION
physical layer specification, which is based on the international IEC 61158‐2 (Type 1) standard.
This assures end users their fieldbus infrastructure will work with desired parameters such as
cable length, number and type of installed devices, and selected power supplies. You candownload DesignMate from the Technical References section as well. Aside from our FCTP
certified training partners, FieldComm Group offers many free end user seminars around theworld year round. These seminars can provide even the experienced user with valuable tips
and information.

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