foundation fieldbus commissioning benefits

8/9/2019 FOUNDATION FIELDBUS Commissioning Benefits

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2 Freedom to Choose. Power to Integrate.2 Freedom to Choose. Power to Integrate.

Commissioning Benefits?

Since late 1990s, major end users like Shell, BP and Petronas

are standardizing their installations on Foundation Fieldbus.

First reports in 1997 by Dow Chemical1 indicated “74% reduction

in field wiring, a 93% reduction in required control room space,

and an 80% reduction in field-device commissioning time over

previous installations done with conventional input/output”.“Startup took only 15 man-hours instead of 200”2.

Too good to be true?

Why do end users report significant reductions in time?

– Let us find out.

Sources:1 Gregory K. McMillan, Douglas M. Considine ,“Process/industrial instruments and controls handbook”, McGraw Hill, 1999 2 InTech, June 1997, “Dow claims first fieldbus installation”, International Society of Automation (ISA), 1997




Contents

About project commissioning Comparing 4-20mA and Fieldbus infrastructure

Commissioning process

– 4-20mA

– Fieldbus

– Comparison Commissioning in practice

Conclusion




About Project Commissioning

Project commissioning is the process of assuring that allsystems and components of a building or industrial plant

are designed, installed, tested, operated, and maintained

according to the operational requirements of the owner or

final client.

A commissioning process may be applied not only to new

projects but also to existing units and systems subject to

expansion, renovation or revamping.

Source: Wikipedia




About Project Commissioning

Apply engineering techniques and procedures to check,inspect and test every operational component of the

project

– individual functions, such as instruments and

equipment

– complex amalgamations such as modules,subsystems and systems




Comparing 4-20mA and Fieldbus Infrastructure

One signal per I/O point Process value is coded in

4-20mA analog signal

Only little diagnostics

(LB/SC)

6

4-20mA

I/O

fieldbus

FF H1 T FF

PS

T

Parallel connection Cable carries power and

digital data

Plenty of information

Data integrity checks

Diagrams simplified


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Commissioning Process 4-20mA

4-20mA

Install the cables




4-20mA

Install the cables

Verify the cable installation

Test Report




4-20mA

Install the cables


Install the devices




4-20mA

Install the cables


Install the devices

Verify device installation




4-20mA

Install the cables


Install the devices


Install the DCS

Assigning the I/O

These two steps may also happen earlier or later in the commissioning process.

The actual work on the I/O is system-dependent. The required steps would be:

• Determine which I/O point of the system is connected to which field instrument• Assign/verify the tag (typically using walkie-talkie)

• Put it into the control application




4-20mA

Install the cables


Install the devices


Install the DCS

Assigning the I/O Calibrate the sensor

(sensor drift)

Thermocouple → mV

RTD → Ohm

Analog measurement

can drift and must be

calibrated from time

to time




4-20mA

Install the cables Verify the cable installation

Install the devices


Install the DCS


(sensor drift)

Ranging

Using HART (or sometimes DIP switches):

“4mA shall be 20 C, 20mA shall be 120 C”




4-20mA


Install the devices


Install the DCS


(sensor drift)

Ranging

Calibrate the 4-20mA

(current drift)

Analog output can driftand must be calibrated

from time to time

Simulate a

measurement

value using

HART

Measure

the output

current with a

precision tool




4-20mA


Install the devices


Install the DCS


(sensor drift)

Ranging


(current drift) System ranging (DCS)

DCS must know what 4mA means

and what 20mA means.

If your instrument is set to:

“4mA shall be 20 C, 20mA shall be

120 C”, your DCS must be set to

the same range.



Positioner

Ranging, 4-20mA

Transmitter

Range

40-200 °C

System

Range

0-200 °C

12 mAProcess

120 °C

Reading

100 °C

...alarms and trips

not working

Instrument range and DCS system range must match

Transmitter

CPU

AI

A/D

D/A4-20 mA

AO

D/A

A/D4-20 mA

Range #2Range #1

CPU

CTRL

CPU




4-20mA


Install the devices


Install the DCS


(sensor drift)

Ranging



System calibration 4-20mA

(current drift)

AI: Simulate a current

and check thereading on the DCS

AO: Set an output

value on the console

and verify the current



Commissioning Process Fieldbus

Fieldbus uses a bus structure, so a single trunk cable is run into

the field. This reduces the number of required terminations, and

hence reduces installation time and the number of potential

points of failures.

Fieldbus

Install the cables





Fieldbus uses digital communication and requires dedicated tools to

verify proper installation. These “Multimeters for fieldbus” are

operated similar to regular multimeters, so that no disadvantage

arises out of „being digital‟ (which someone may perceive as

complex).

Fieldbus

Install the cables


Install the devices






Fieldbus systems offer “commissioning wizards”, that enable fool-

proof and fast commissioning of FF instruments.

Fieldbus


Install the devices


Install the DCS

Assigning the I/O





Foundation Fieldbus devices are

recognized by three mechanisms:

• node address for communication

• device tag corresponding to the

project P&I diagram

• a unique identifier allowing thesystem to automatically resolve

any tag or address conflicts

Fieldbus


Install the devices


Install the DCS

Assigning the I/O

The system automatically assigns the address to all devices, avoiding human

errors such as address duplication associated with manually managed

protocols, and saving time.Therefore technicians work based on tag and need not be concerned with

address.

Thanks to the unique identifier, multiple devices can be connected and

commissioned at the same time. It is plug-'n'-play.





For instruments with analog sensors such as RTDs or

thermocouples, the measurement circuit may drift and may require

calibration. For other types like time-of-flight (e.g. radar level

sensor), they are considered “digital” and do not require calibration.

Fieldbus


Install the devices


Install the DCS


(sensor drift)





Transmission is digital. A conversion from one unit to another takes place inthe instrument function block:

Example: A temperature may transmit its reading in °C, °F, or Kelvin. It may

also scale a certain measurement range into a % value.

There is no conversion required by the DCS, as the readings are all

transmitted with the engineering unit included.

Fieldbus


Install the devices


Install the DCS


(sensor drift)

Ranging




Positioner

Ranging, 4-20mA

Transmitter

Range

40-200 °C

System

Range

0-200 °C

12 mAProcess

120 °C

Reading

100 °C

...alarms and trips

not working

Results:

Range mismatch

Range exceeded (more than100%, less than 0%)

Transmitter

CPU

AI

A/D

D/A4-20 mA

AO

D/A

A/D4-20 mA

Range #2Range #1

CPU

CTRL

CPU




PositionerTransmitter

Ranging, Fieldbus

FF FF

BUS

FF

CTRL

CPU

CPU

CPUDigital

Digital

Digital

Transmitter

Range

-200 to 850 °C

System

(No range)

120 °CProcess

120 °C

Reading

120 °C

Results:

Range mismatch impossible

Making full use of physical measurement range of transmitter





Digital signaling/communication is standardized and does not require any

kind of adjustment.

Fieldbus


Install the devices


Install the DCS


(sensor drift)

Ranging

Calibrate the comm‟s signal?





Not required and not reasonable, as the transmitter provides readings

inclusive engineering unit.

Fieldbus


Install the devices


Install the DCS


(sensor drift)

Ranging

Calibrate the comm‟s signal

System ranging (DCS)





Fieldbus


Install the devices


Install the DCS


(sensor drift)

Ranging


System ranging (DCS) System calibration comm‟s

signal

Digital signaling/communication is standardized and does not require any

kind of adjustment.




Commissioning Process Comparison

Fieldbus


Install the devices


Install the DCS


(sensor drift)

Ranging


System ranging (DCS) System calibration comm‟s

signal

4-20mA


Install the devices


Install the DCS


(sensor drift)

Ranging



System calibration 4-20mA

(current drift)




Commissioning in Practice

80 – 95% of problems are installation related

What are these problems?

How to avoid them?

How to find them if they occur? (Troubleshooting)



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Bad wiring technique

Welding, variable frequency drives (VFD), Motors,machinery:

Increase of HF noise

Increasing number of retransmissions

Can be a combination of both




Case study: faults in operationCable jacket stripped back

too far can causeinstrument malfunction:

– Water ingress

– Wires shorted to

housing

– Corrosion

– Tearing wires(increasing

resistance)

Increasing number of

retransmissions

Signal amplitude rises

Increase of FF noise Can be a combination of

above




Wires coming out of ferrules:

Spur:

Device drops off (may or may not return)


Trunk:

Devices drop off (may or may not return)

Signal amplitude sometimes ok,

sometimes high





Bend radius too tight, Upward facing gland risks water ingress

Two cables into one gland

prevents sealing of gland




Corroded terminals:


Increase of FF noise

Can be a combination of both




Commissioning 4-20mA

Always on the critical path (may bring signal down)

Manual, step-by-step procedure

Labor intensive

Requires

– Screw driver

– Check sheet – Pencil

– Multimeter

– Scope

Check one device at a time

Test Report




Portable Commissioning tools for fieldbus

Portable tools for commissioning, monitoring, and

troubleshooting. Different products on the market to suit

different needs.

Can connect to any spur or trunk

Menu guided user interface

Can store & upload data No paper needed

No manual recording

Check many devices at same time




Instrument Management Software

(including fieldbus diagnostics)

Fieldbus power

supply system

Host control system

Controller I/O

Portable Commissioning tools

Fieldbus

wiring components

Hand-held

Diagnostic Module




Fieldbus Diagnostic Modules

Integrated single tool for commissioning, monitoring, and

troubleshooting. Operated in the control room, usually

mounted on fieldbus power supply carrier.




Benefits of Fieldbus in Commissioning

Faster installation and checkout due to reduced wiring

and bus structure

Faster device troubleshooting due to dedicated portable

fieldbus multimeter

Faster device commissioning due to dedicated fieldbus

diagnostic modules Avoids ranging problems

Avoids double-addressing and addressing in general

Reduces number of tools required for testing

Eliminates troublesome calibration procedures

All this and more leads to

significant faster project commissioning.



Freedom to

Choose. Power to

Integrate.

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foundation fieldbus commissioning benefits

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