how to get value out of hart - fieldbus foundation · how to get value out of hart ... safe side of...

How to get value out of HART

Ensure HART is always connected

Topics Covered

Background

Training

Design

Procurement

Integration

Configuration

Factory Acceptance Test (FAT)

Installation

Commissioning

Change Work Practices

Network Maintenance

System Management

Design Procurement Integration Configuration FAT Installation Commissioning Operation

Background

Put HART to good use

Consumption Gap

Plants are built with intention to use HART

Plants struggle to utilize HART

HART only used for commissioning with the handheld

field communicator

o The control system uses only 4-20 mA signal

Only some plants use HART always connected

o Only some devices use HART always connected

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Digital HART is Not the Same as Analog 4-20 mA

HART does not get designed and procured correctly

Not installed and commissioned correctly

Not integrated and setup properly

Not maintained properly

People don’t get trained

Plant ends up using only handhelds or laptop with HART

modem, missing out on the smart always connected

capabilities

If you will only use a handheld you need not worry about

most of this…

HART Training

Competency is a critical success factor

HART Training Required

There are many misconceptions around HART

o The reason why in the end HART is underutilized

Use consultants, EPC contractors, and subcontractors

trained in HART

Train plant personnel on HART to ensure continuity

o If not HART will fall into disuse

Get trained on HART

250 ohm Filter

Line Conditioner Capacitance

600 ohm Master conflict

DD file Report by Exception

HART Design

Design for digital, not just analog

System HART Pass-Through

New systems

Make sure analog input and

analog output cards support

HART communication

Compliant with HCF_SPEC-

HART pass-through across the

higher level network

Existing control systems not

supporting HART

Install wireless adapters on

selected instruments

Plant-wide wireless gateway

infrastructure

HART Cable Selection

Individually shielded twisted pair cable o Single pair or multi-pair

Minimum conductor size: o 0.2 mm2 (#24 AWG) for cable runs less than 1.5km

o 0.5 mm2 (#20 AWG) for longer distances

Compliant to the HCF_SPEC-054 specification

Polyethylene (PE) insulation is preferred o Lower capacitance than PVC insulation

o More stable, will not increase as much over time

Low capacitance good-quality cable o Mutual capacitance of 60 nF/km is available

Additional cable requirements may apply depending on the hazardous area classification and local regulations etc.

Similar to FF and other digital

communication

###make sure every

slide has an image

Loop Resistance

HART loop resistance max 600 ohm

o Distance limitation on the wires

250 ohm resistor not required for valve positioner

Calculate the voltage drop to ensure I/O card voltage is

sufficient for all the loads in the loop:

o Transmitter, positioner, indicator, signal conditioner, wireless

adapter, filter, line conditioner, wire resistance

Each type of device and option is different

Replacement device may be different

Loop current may be as high as 23 mA

12 14 16 18 VDC

4-20 mA Operating Area

4-20 mA/HART

Operating Area

Loop Resistance Example

Max loop current is 23 mA

Device requires a minimum of 12 VDC at terminals

Voltage source from the AI card 15 VDC

o Internal 250 ohm shunt resistor

Maximum permitted loop resistance for the cable is (15-

12)/0.023 = 130 ohm

Loop Capacitance

Maximum device capacitance is 5 nF

Cable capacitance limits length

Determine max allowable cable length from the

65 microsecond chart

Use low capacitance cable (PE insulation) with

large conductor cross section

o A full 1.5 km is possible

o PE insulation cable with mutual capacitance

of 60 nF/km is available from many vendors

Additional cable requirements may apply

depending on the hazardous area classification

and local regulations etc.

HART Capacitance 65 us Chart 3.1.4

Loop Capacitance Example

Single device, 5 nF device capacitance, 250 ohm shunt

resistor

Cable Capacitance: 180 nF/km

Conductor Resistance: 49 ohm/km (22 AWG)

HART Safety Barriers

Intrinsic safety barriers have to be HART compatible

All intrinsic safety rules apply

Cabling Route Planning (Cable Trays)

4-20 mA/HART separate from power cables

4-20 mA/HART together with other signal wiring including

fieldbus and other data communication

Signal wiring cross power cables at a right angle

Same as FF and other digital

communication

>30 cm

Shield Connection

Shield must be maintained all the way from the field

device to the control system I/O card

Shield shall not be connected to the device housing

(HCF_SPEC-054 recommendation)

communication

Do not connect shield+ -

Enclosure Grounding

The device housing shall be connected to ground through

a large cross-section conductor

communication

Shield Grounding

The shield shall be grounded at the control system I/O

card (HCF_SPEC-054 recommendation)

communication

Junction Box

Control System Panel

Shield not connected at device

AI card

Transmitter

Filter

HART Communicator+R

HART Input Filters

If system has no low-pass filter in the AI card

Installed near control system AI card

Safe side of safety barrier

May not be suitable for surge controllers

3.1.10

HART Output Filters

If system has no filter in AO card

Installed near control system AO card

Safe side of safety barrier

Need sufficient AO card compliance voltage

Some 4-20 mA simulators (loop calibrators) also require a

HART output filter

AO card

Valve Positioner

Filter

HART Communicator

3.1.11

Solver

DO card

Partial

Stroke

Device

Communicator

ConditionerS

Solenoid

HART Line Conditioners

Used with Partial Stroke Test (PST) device on shutdown

Most logic solvers have no filter in the DO card

Similar to FF 3.1.12

HART Compliant Devices

Devices which have not

been registered may not be

fully compliant

Configuration, diagnostics,

auxiliary variables may not

work properly

Nuisance alarms

Specify “Device shall be

HART Registered”

communication

3.1.13

HART Loop Power Supply

Free from ripple and noise

o Less than 2.2 mV RMS

Old, faulty, or overloaded power supply may be a source

of noise

3.1.14

HART Master Conflict

Only two HART masters

Masters must be different class;

o One primary; control system, MUX, wireless adapter,

smart signal conditioner

o One secondary; handheld, laptop with HART modem,

wireless adapter, smart signal conditioner

If two or more masters of the same class are connected

the communication will fail

o Smart signal conditioner will set the analog output < 4

mA or > 20 mA tripping loop

HART Burst Communication

Do not use burst in devices connected to a control system

or multiplexer

o Mostly used for stand-alone smart signal conditioners

Cause diagnostics and auxiliary variable monitoring etc.

to slow down

o Nuisance alarms in the IDM software

Unpolled Address

Use a HART version 7 (HART7) host to ensure all

devices are detected

Version 5 of HART (HART5) only supports address up to

Older hosts do not support polling of addresses up to 63

o Will not detect newer devices such as wireless

adapters which use default addresses above 15

HART Command 48 (Diagnostics)

Used for the IDM software alarm management function to

filter the instrument diagnostic alarms from the devices

o Optional in HART5 devices

o Mandatory in HART7 devices

Specify devices shall support command 48

DD Files

DD files are not required to get a 4-20 mA signal

DD files are required for configuration and diagnostics

Without a DD file it is not possible to properly configure a

device to get a correct measurement

Warning: Not all devices come with a DD file

o Configured form a local display or by proprietary

software

o Setting up instrument diagnostic alarm management

filters becomes very challenging

Specify device shall come with DD file

Not all devices

come with DD files

communication

HART5 systems cannot support HART7 devices

o Only specify HART7 devices if the system is HART7

compatible

Some devices can be configured to operate as HART5 or

o Essentially two different devices so have two DD files

HART5 system do

not support HART7 devices

HART Polling

Set the polling time as short (fast) as possible

If the polling time is set longer than a minute;

o Intermittent problems may be missed

o Too short time left for operators to respond

Use polling for diagnostics of 4-20 mA devices

o Triggered burst mode and event notification (“report by

exception”) functions are intended for WirelessHART

Burst communication may interfere with diagnostics

polling

HART Procurement

Buy only tested and registered products

HART Procurement

A non-compliant component could jeopardize the ability to

utilize HART capabilities

o The analog 4-20 mA signal will work but the smart

features cannot be accessed and the benefits not

reaped

Verify products in bids are tested and registered

HART Integration

Load your DD

Load DD Files on Control System

Needed to configure diagnostics filtering to display as

human readable text

Some control system may also need an internal system

specific file for each device type

Load DD Files on IDM Software

Without DD file

o The device cannot be made to work correctly

o The 4-20 mA signal may not be correct

Need DD files to commission device

o Configure sensor type and many other settings

o Perform sensor trim and other functions

Some IDM software may also need an internal system

specific file

Load DD Files on Portable Tools

Without DD file

o The device cannot be made to work correctly

o The 4-20 mA signal may not be correct

Need DD files to commission device

o Configure sensor type and many other settings

o Perform sensor trim and other functions

DD File for Correct HART Version

The DD file for HART5 and HART7 version of device is

different

o Buy as HART5 or HART7

o Configure as HART5 or HART7

If the device is configured to operate as HART7 but the

HART5 DD has been loaded, the system cannot access

the device features

HART Configuration

Engineer to avoid alarm flooding

Avoid Alarm Flooding:

Instrument Diagnostic Alarm Management

If the instrument diagnostic alarm management system is

not configured there will be a flood of nuisance alarms

o System will not be used

ISA108 guidance to being developed

Interim guide:

o http://www.eddl.org/DeviceManagement/Pages/DeviceDiagnostic

s.aspx

Engineer and setup IDM software before start-up

Specify a control system which is able to categorize

instrument diagnostic alarms for command 48

Specify a control system which uses the DD file to display

the possible instrument diagnostic alarms from the device

as plain text

Instrument Diagnostics Alarm

Rationalization

Categorize severity of

diagnostics:

o NAMUR NE107

Identify criticality to the

process for each device tag

Configure system and devices

Same as FF and PROFI

• FAT to verify correct system configuration for alarm management and reports

• Tune device diagnostics to fit the application

• Rewrite maintenance procedures to include the IDM software

• Training

System shall display

diagnostics items as plain

Instrument Diagnostic Alarm Routing

Operator Instrument Tech • Failure • Function Check

• Failure • Maintenance Required • Out of Specification

Devices

Nuisance Alarms

Same as FF and PROFI

Valve Tight-Shutoff

If the valve tight-shutoff output current in the control

system is configured to 0 mA, HART communication

stops when valve is closed

o No power to smart valve positioner

o No power to wireless adapter

o Nuisance communication alarms

o No diagnostics

The valve tight-shutoff current setting in the control

system shall be somewhere in the range 3.6-3.8 mA

o Ensures the positioner still performs diagnostics and

devices plus accessories are able to communicate

HART Factory Acceptance Test (FAT)

Test to make sure instrument diagnostics alarm management will work as intended

Interoperability / Integration Test at FAT

Connect one of each type of device

Open each type of device in the IDM software

o Verifies the DD file has been loaded for each type and

version of the device

o Verifies the device displays correctly

Download a device configuration

o Verify the download is error free

communication

Instrument Diagnostic Alarm Routing Test at FAT

Simulate instrument diagnostic alarms of different severity

(Advisory, Maintenance, and Failure ) for each device

o Verify they are routed to the right person such as

operators or instrument technicians

HART Installation

Wiring

Poor Installation Jeopardize the Ability

to Utilize HART Capabilities

The HART signal is small, only 1 mA

Poor installation picks up noise

Communication stops updating in the system:

o Diagnostics

o PV, SV, TV, and QV

Nuisance communication alarms

Smart signal conditioner output < 4 or > 20 mA which may

cause a nuisance trip

communication

Don’t Ground Shield at Device

Do not connect the shield or drain wire to ground in the

device housing

Ground the shield only in a single point, at the power

supply

Only the signal wires are connected at the device

This is the recommendation in the HCF_SPEC-054

specification

o Some plants have other practice

8.1.1 Same as FF and

other digital communication

Insulate Shield at Device

Do not leave the shield or drain wire “flying” as it may

come in contact with the device housing

Cut the shield inside the device housing

Isolate the drain wire and shield using shrink tube or tape

to make sure it does not come in contact with grounded

metal parts

For armored cable, make sure shield drain wire is not

touching the cable armor

Maintain Shield Through Junction Boxes

The shield shall be continuous from system panel,

through junction box, up to the device

o But not connected to the device

Do not ground the shield in the junction box

Do not leave ‘flying’ shield or drain wire as it may touch

other wires or grounded metal parts

If two cables are joined, make sure the junction (splice)

also joins the shields of the two cables

Junction Box

Control System Panel

Shield not connected at device

Route Signal Cables In Separate Tray

From Power Cables

Do not lay communications signal cable in the same tray

as power cable

Route signal cable and power cable in separate trays

If signal cable and power cable is laid in the same tray,

maintain maximum possible separation, keeping power

cable and signal cables on separate sides of grounded

metal dividing wall

>30 cm

Observe Cable Minimum Bend Radius

Loop/bend cable too tight will damage the shield

o Reducing noise immunity

Cable minimum bend radius

o Cable type dependent

o For armored cable it can be space taking

Do not turn corners too tight in cable trays

o Use proper cable tray bend, cross, and tee pieces to allow cable

to round corners with wide radius

“Pig tails” must have a sufficiently large radius to not

damage the internal shield

Cable trunking / wire troughs / trays are usually too

narrow to permit looping of the cable

Ground Device Housing

Without a ground connection the device EMI/RFI

suppression will not work

Make sure the device housing is safety grounded to the

plant structural steel with a low impedance connection to

ensure personnel safety and EMI/RFI suppression

It is particularly important for those devices where surge

protection is used

Ground Junction Boxes

Make sure the junction box is safety grounded with a low

impedance connection

When using plastic junction boxes and metal cable

glands, these glands must be connected to the safety

ground bar inside the junction box, typically using a metal

plate inside junction box

Cable lug

Spring washerTooth washer

Don’t Coil Signal Cables And Power

Cables Together

Do not coil signal cables and power cables together

inside the device terminal compartment

o For example, in separately powered devices such as

Coriolis and magnetic flow meters, etc.

Cables shall be:

o Short

o Jacket on

o Shielded

o Separated

Signal AC Power

Don’t Damage Shield And Conductor Insulation

Cutting Cable Jacket

Do not damage shield and

conductor insulation

Do not use a knife

o It might damage the shield

and conductor insulation

Use a cable jacket/sheath

stripper

Cutting Cable Armor

Do not use a hacksaw

o It might damage the inner

jacket, shield, and

conductor insulation

For tube armor use a

pipe/tubing cutter

For SWA use a wire cutter to

cut strand by strand

split into two slides

Don’t Strip-Off More Than Necessary

Maintain shield and jacket as far as possible, close to the

connection terminals

Do not remove shield or jacket for cable running in

cabinet or junction box

o Bare shields (and drain wire) of different cables will

touch and may cause ground loops

Do not untwist the twisted pair

Ground Overall Shield For Multi-pair

The overall shield shall be grounded in the power supply-

Do not leave overall shield floating

Make sure overall shield does not touch any of the

individual pair shields

Overall

Shield

Control

System Panel

Ground The Cable Armor

Do not leave the cable armor floating

The metal cable gland must make contact with

the amour of the cable at the device and in the

junction box

If plastic cable glands are used at the junction

box, or the junction box is plastic, the cable

armor shall be grounded to safety ground bar

Ground the armor in multiple points:

o Before cable enters marshalling cabinet

o In cable tray

o And in the field junction box

Other Good Installation Practices

Do not pull cable with too much force

Make sure cable glands are tight

Seal unused conduit entries

Use correct size ferrule/fork and tool

Do not cram wires in device terminal compartment

Do not over/under-tighten terminal screws

Make sure covers are tight

Do not tighten cable-tie too much

Label wires

Observe polarity

8.1.13 Same as for any cables

HART Commissioning

Digital loop check

HART Communication Check at Loop

Check (Loop Test)

Also verify the HART communication

o Loop calibrator with HART communication capability

o Handheld field communicator

Communicate with the device to ensure communication is

error free

o Monitor the 4 dynamic variables (PV, SV, TV, and QV)

for some time

Confirms the design and installation is done correctly, so

digital communication will be reliable

communication

In addition to traditional 5-

point loop check

Digital Integration Verification at Loop

Open up each device in the IDM software

Confirms:

o Communication is enabled

o Communication is working from the system end

o The DD file matches the device type and version

Open the diagnostics page to see if any problem

o Incorrectly wired temperature sensor

o Valve supply air

o Flow meter auxiliary power

communication

what about reconciling device

configuration? Ranges, units…

Change Work Practices for HART

Getting into the habit of using the IDM software as part of the daily routine

Instrument Technician Culture Change

Review instrument diagnostic alarms

o Instrument technicians must review the instrument

diagnostic alarm summary and log every day

Spend time on devices which need attention

Check the software first

o When operations say a device is not working,

instrument technicians must check the software first,

before going to the field to take a look

Avoid unnecessary field visits

Rewriting Standard Operating Procedures (SOPs)

o Rewrite work procedures to include IDM software

Inspection, replacement, calibration and other tasks

10.1.1

10.1.2

10.1.3

split into 3 slides

HART Network Maintenance

Maintain installation in good condition to ensure the HART communication continues to work error free

Safety Instrumented Systems (SIS) Warning

If device diagnostics is used to claim safety credit, the

digital HART communication must maintained functional

Any communication issues must be resolved immediately

so the always connected diagnostics monitoring remains

functional

If the device is replaced;

o The new device must have the same or better

diagnostics

o Must be digitally integrated

Troubleshoot – Don’t Disable

If nuisance communication alarms appear personnel will

disable HART

o Only analog 4-20 mA remains

Troubleshooting should instead be done to bring HART

communication back alive

HART Issues Develop Over Time

Somebody ground cable shield

Inadvertent contact between shield and ground

High loop resistance due to corroded terminals

Added series devices like a wireless adapter

Device replaced with non-HART device

New source of noise

Moisture in device compartment or field junction box

Loose connections due to vibration

High capacitance in aging cable or stray capacitance

Device replaced with wrong HART protocol version

Replacement device not configured correctly

Additional master connected causing master conflict

Shield damaged

Shield continuity compromised

Housing ground disconnected

Field junction box ground corroded

communication

Monitor HART Network Health

Periodically check HART communication Packet Error

Rate (PER) to detect deteriorating communication before

alarms appear

o Built-in control system communication diagnostics

o External HART analyzer software with HART modem

communication

11.1.1

Maintain Installation Integrity

Technicians must be familiar with the additional

requirements of digital HART or mistakes will happen:

o Connecting shield to the ground screw on the device

o Contact between shield and device housing

o Device housing not grounded

Tighten covers and close doors to make sure and

terminals do not corrode

Make sure connections have not come loose due to

vibration, including ground connections

Look for shield damage and shield continuity

Check for noise

11.1.2

Management of Change

Replacement device must be:

o HART-enabled

o Correct HART protocol version

o Tested and registered

o Supports command 48

o Comes with a DD file

o Configured for communication and diagnostics

If a HART master is added make sure there is no master class conflict

If device is added in the loop make sure the voltage is sufficient

Make sure sources of noise are not introduced

Make sure new cable is laid in the correct trays

11.1.3

HART Troubleshooting

Troubleshooting digital HART is different from

troubleshooting analog 4-20 mA

It is not possible to troubleshoot HART with a multimeter

Troubleshooting guide for HART and other field

communication:

o http://www.eddl.org/SiteCollectionDocuments/TechPap

ers/ag_Field%20Communication%20Troubleshooting.

11.1.4

HART System Management

Keep system up to date with new device types and versions

Keep System Up to Date

Without the DD files the devices cannot be configured or

diagnosed

If the IDM software is not loaded with DD for new devices

and revisions it will fall into disuse

o Only analog 4-20 mA to control system remains

Load the DD files for new device types and versions on

the control system and IDM software

communication

12.1.1

DD File Management

DD files are easy to download from the Internet

It is a good idea to load any DD files available

o This way the system is ready for all kinds of devices

Some systems have DD wizard that automatically

distributes the DD to all workstations

Consider using DD update services which loads DD files

onto the system automatically as they become available

12.1.1.1

DTM Driver Software Management

Ensure DTM for the device is available for the particular Windows version used

Only install the DTMs you really need

o Avoid conflicts

o Reduce burden on the computers

Ensure instrument technicians can install DTM software for new device types and versions

Instrument technicians may need to be given ‘administrator’ level password

Install DTMs on all IDM workstations

Use only certified DTMs

Use only DTMs from the original device manufacturer

o Not third-party DTMs

DTM may require license to unlock device capabilities

Make sure all DTMs are available for the new Windows version before upgrading Windows

12.1.1.2

Make Sure DD Files are Available

A replacement device must be registered and must come

with DD files

Not all HART devices have DD files

o Make sure a device comes with DD files before

purchasing it

12.1.2

Conclusion

“Get Connected”

Many plants only use HART with handheld

Engineer correctly

o Design according to the rules

o Procure tested and registered

o Install and commission according to the rules

o Integrate and setup properly

o Maintain properly

o Train people

Get a field communications expert involved

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