fieldbus operations benefits.pdf
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Fieldbus Operations BenefitsTRANSCRIPT
7/18/2019 Fieldbus Operations Benefits.pdf
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1 Freedom to Choose. Power to Integrate.1 Freedom to Choose. Power to Integrate.
Freedom to
Choose. Power to
Integrate.
Operation
Benefits
Andrew Sia,
Rockwell Automation
7/18/2019 Fieldbus Operations Benefits.pdf
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2 Freedom to Choose. Power to Integrate.2 Freedom to Choose. Power to Integrate.
Operation Benefits Topics
Why FF? Higher performance control
Early process warning from device alerts
Increased availability
High fidelity
7/18/2019 Fieldbus Operations Benefits.pdf
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3 Freedom to Choose. Power to Integrate.3 Freedom to Choose. Power to Integrate.
- Why Digital Fieldbus?
Operation & Maintenance – Better accuracy
• No precision lost in D/A & A/D
– High signal integrity• Distortions can be detected
– More powerful diagnostics• More current for devices
– Engineering unit• Measure to sensor limits
• No range mismatch
– Stave off obsolescence
• Firmware download
– Easier device troubleshooting• Remote Diagnostics
– Validity display and loop shuts
down
– Predictive maintenance• Diagnostics Alerts
– Fewer Connections
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4 Freedom to Choose. Power to Integrate.4 Freedom to Choose. Power to Integrate.
Easier:Fewer Connections Fewer signal wires to disconnect and connect
when replacing devices – Electric actuator (MOV)
• Open, stop, close, ESD, overload...
– Valve positioner
• Setpoint, feedback, limit switches... – On/Off actuator
• Setpoint, limit switches...
– Mass flow transmitter• Mass, volume, density, temperature...
Faster, fewer mistakes Conventional:
Multiple pairs
Per device
Bus:
Single pair
Many devices
Two wires,
non evenpolarity
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5 Freedom to Choose. Power to Integrate.5 Freedom to Choose. Power to Integrate.
Easier and Safer:High Signal Integrity
Digital signal does not get "limited" – If 18 mA becomes 16 mA you won't know• Increase in resistance due to terminal corrosion
– If 16 mA becomes 18 mA you won't know• Ground loop due to inadvertent ground connection
Digital signal distortion does not go undetected – It is not possible to tell difference between analog
signal noise and process fluctuations
Electrical noise or actual process? Any distortionof a digital
process
variable is
alerted
mA
t
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6 Freedom to Choose. Power to Integrate.6 Freedom to Choose. Power to Integrate.
6
0
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%
I n s
t r u m e n t a t i o n
V a l v e s
H e a t E x c h a n g e r s
V e s s e l s
P u m p s
C o m p r e s s o r s
D r i v e s
E l e c t r i c a l s
F u r n a
c e s / B o i l e r s
P i p i n g
P a i n t s / C o a t i n g s
M i x
e r s / A g i t a t o r s
I n s u l a t i o n
M a t e r i
a l s H a n d l i n g
T o o l s
O t h e r
Major Components of Maintenance Costs
Highest Maintenance Spend ing o n Field Devices
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63%“Unneeded” Trips To The Field- Avo ided Through Remo te Diagno st ics
35%
28%
20%
6% 6%4%
0%
10%
20%
30%
40%
50%
RoutineCheck
NoProblem
FailedInstrument
PluggedLines
ZeroOff
CalibrationShift
Source: Dow Chemical Company
Avoid “Unneeded” Trips To The Field
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Freedom to
Choose. Power to
Integrate.
High Performance
Digital Closed Loop Control
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Some “Digital Control Systems”Aren’t
If it’s not fieldbus, it’snot a digital control system
Hardwired Fieldbus
Process Discrete Process Discrete
Real-time
control
Analog
(4-20 mA)
Binary
(on/off)
Digital
(FF)
Digital
(FF)
Device
management
Digital
(HART and
proprietary)
None Digital
(FF)
Digital
(FF)
Digital Digital Digital Analog Analog
Digital Digital DigitalDigital Digital
Hardwired:
Fieldbus:
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End-to-End, Fieldbus Control is Faster
Analog Control – AI scan, controller, and
AO scan asynchronous• A 250 ms controller
cycle does not mean
250 ms control responseperiod
Fieldbus Control – AI scan, controller, and
AO scan asynchronous
AI
Controller Controller
AO AO AI PID AO
250 ms 250 ms 250 ms
> 2 x Controller Cycle Macro Cycle
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Freedom to
Choose. Power to
Integrate.
Early Warning
Act before process is affected
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Smart Diagnostics- Integrated Device Diagnostics
Normal operation... Device failure...
Faceplate...
Diagnostics
– No deviceconfiguration by
operator
Detailed
diagnostics in twoclicks
Help on the third
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On/Off Valves Fieldbus does discrete too
One pair of wires for multipleon/off valves
One pair of wires for solenoid
and limit switches
Diagnostics
HART not applicable
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Freedom to
Choose. Power to
Integrate.
Real-time Status
If its not the process, don’t trip
unnecessarily
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Digital All the Way- Digital Closed Loop Control
Speed
30 times faster than
hybrids of analog/digital
250 ms loops possible
Real-time value and
status
Status Propagation (CIF & CIC)
Validated information – Quality and limits
Windup protection
Bumpless transfer for valves
Fault-state for valves
etc.
Only fieldbus
eliminates the analog
signal
Validity:
Good/Bad/Uncertain
Initiate Fault-State
Command
Limited: High/LowBumpless Transfer
Windup Protection
Fault-state Status
Designed for
process control
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Process Variable Validity
Hardwired – Device drives current
<4 mA or >20 mA on
device failure• Looks like process
problem – PID counteracts thus
tripping the loop
– Operator cannot tell
the difference betweena process alarm and a
device alarm
Fieldbus – Device health indicated
by associated status
– Controller holds last
position on device
failure• Shutdown is optional
– Operator can easily
distinguish process
problem from a deviceproblem
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Valve and Positioner Actual position transmitter feedback
transmission on the same two wires – Further reduced wiring
– No AI card
– More than just value: status
Software limit switches
– No DI cards – No extra wiring
Easy to add feedback as an afterthought
Bumpless transfer on local hand operation – Smoother operation
Bumpless firmware download – Upgrade while process is running, without
replacing circuit board
Continuous, real-
time, actual
position feedback
for every control
valve
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Easy Operation- Status in Historian Status logged and shown next to value and color
codes trend
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Freedom to
Choose. Power to
Integrate.
Fidelity
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Digital Fidelity- Better AccuracyHardwired
Accuracy lost in signalconversations: – Digital to analog
– Analog to digital
Accuracy lost incurrent calibration
differences
Fieldbus
Measurements are notdistorted
Particularly important: – Tank gauging
– Batching
Transmitter
FF
BUS
FF
CTRL
CPU
CPU
Digital
Digital
Digital
AI
A/D
D/A4-20 mA
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21 Freedom to Choose. Power to Integrate.21 Freedom to Choose. Power to Integrate.
Easier and Safer:High Signal IntegrityHardwired
Analog gets distorted – Increased resistance
limits current
– Ground loop offsets
current ‘On-scale” distortion
cannot be detected
Fieldbus
Digital signal does notget "limited"
Any distortion of a
digital process
variable is alerted
AI
Marshalling
Field Junction Box
4-20 mA
Resistance = Voltage
Drop = Limited Current
Leakage = Ground Loop =More Current
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22 Freedom to Choose. Power to Integrate.22 Freedom to Choose. Power to Integrate.
Fieldbus Operational Benefits Summary
Higher performance control – Faster than analog
Early process warning from device alerts – Diagnostics in operator console
– Diagnostics from discrete devices
Increased availability – Real-time status
High fidelity – High accuracy
– No range mismatch
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2323
Freedom to
Choose. Power to
Integrate.
Thank you !