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Fieldbus
Fieldbus
Accessing all Areas
1
Fieldbus
Scope of presentation
Safe Area Applications
Non-Arcing Systems
Zone 2
Non-Incendive Systems
Zone 2
FNICO
Intrinsic Safety Systems
FISCO
2
Zone 2,1,0
Fieldbus
Generalised Fieldbus connection
Non-hazardous area
Hub
T
T
Fieldbus
Host
18-30 volt
Power
General fieldbus application in safe area
3
terminated at both ends of bus
Fieldbus
Generalised Fieldbus connection
Non-hazardous area
Hub
T
T
Fieldbus
Host
18-30 volt
Power
Need for hazardous area protection
suitable certified interface applied
Non-hazardous area
Hazardous area
T
4
T
T
T
Fieldbus
Host
Fieldbus
MTL5995 Power Supply
For general purpose applications in
31.25 kbit/s fieldbus systems
terminate at both ends of fieldbus
switched internal terminator option
Isolated power conditioning
19V, 350mA output
Suitable for Safe Area &
Hazardous Area applications
Certified for installation in Zone 2
hazardous areas
Needs suitable certified interface
eg, MTL791, for intrinsically safe
field connection
5
ATEX II 3 G
EEx n A IIC T4
Fieldbus
Redundant Fieldbus Power System
Backplane connects to :
bus terminator
input power supplies
host system
fieldbus trunk
alarm circuitry
Load sharing by redundant
supplies
Up to 8 units may be
daisy-chained
with common alarm
carrier jumper supplied
version without segment
terminator available
6
Fieldbus
Redundant Fieldbus Power System
Fieldbus
Host
Power Conditioning
high impedance to fieldbus network
Redundant DC Power Inputs
Power Isolation to fieldbus
250 V ac galvanic isolation
Redundant Output Power
25 Volt, 350mA output per module
LED indicates bus is powered
Hot-swappable
modules & / or input supply can be
replaced without affecting fieldbus
operation
T
System
Alarm
Supply
‘A’
Supply
‘B’
18-30 volt
Power
Alarm Circuitry
input power or unit failure
galvanic isolation from other
functions
Certification
FM Class 1 Div2
ATEX II 3 G EEx nA IIC T4
7
Zone 2 Mounting
Fieldbus
Fieldbus
Redundant Fieldbus Power System
Common connections
within addressing
limitations
Fieldbus
Host
System
Alarm
Fieldbus
Host
T
T
Fieldbus
Fieldbus
Supply
‘A’
Supply
‘B’
18-30 volt
Power
8
Fieldbus
Redundant Fieldbus Power System
Note :
the fieldbus connection is
certified as non-arcing
EEx nA IIC T4
It is NOT a FISCO / FNICO
field connection
an added interface would be
necessary to achieve this end
9
Fieldbus
MTL5053 Isolator / Power Supply
The MTL5053 extends 31.25kbit/s fieldbus networks into hazardous areas
Provides power to the highway & for communication to field devices
Separate power may be required for safe-area field devices
Supply voltage 20 to 35Vdc
Isolation : 250V ac between
safe area fieldbus circuits
hazardous area fieldbus circuits
power supply
Provides 18.4 volts at max 80 mA
Safety description 22V, 102, 216mA
Isolator transparent to fieldbus, hence
31.25kbit/s fieldbus
termination at isolator is not a pre-requisite
Switchable safe area terminator
Hazardous area
Safe area
MTL5053
Ex II (1) GD
[EEx ia] IIC
10
T
T
Fieldbus
Some definitions
Safe area
Zone 2
Division 2
Safe Area
system
NA
system
NI
system
Non-Arcing Systems
Non-Incendive Systems
12
Zone 1
Zone 0
Division 1
Fieldbus
The principle of
live working
Limit the energy
in the circuit
Ethylene group
Propane group
Current
Methane group
Hydrogen group
Power = volts x amps
Resistive Curves
13
Voltage
Fieldbus
Safety Factor
Unity : Zone 2
1.5 : Intrinsic Safety
Fault-tolerant
components not
required for Zone 2
Hydrogen group
Current
230 mA
Apply a
Safety Factor
14
Resistive Curves
24 Volts
Voltage
Fieldbus
Types of circuit in Zone 2
NON-INCENDIVE
CIRCUITS :
NON-ARCING
CIRCUITS :
Energy-limited
• Unity Safety Factor
• Low energy
circuits
• Systems concept
• Live-workable
• High energy & mains
circuits
• No systems concept
• Not live-workable
User must
NOT permit arcing
15
Fieldbus
Complete hazardous area capability
Safe area
Unclassified location
Safe Area
system
NA
system
NI
system
IS
system
Zone 0
system
16
Zone 2
Division 2
Zone 1
Zone 0
Division 1
Fieldbus
Safe Area or Non Arcing Installation
Installation in => IP54
Live working NOT permitted
in a hazardous area
Max output :
32 V
1.5 A
‘nA’
All trunks & spurs
EEx nA IIC T4
Vmax 32 V
Imax 1.5 A
MTL5995
FPS-I
‘nA’
System Certification :
Ex nA IIC T4
Class 1, Div 2, Groups A,B,C,D, T4
Terminator : FBT-1
17
Vmax 32 V
FF-816 specification :
32 V
1.5 A
Fieldbus
Non Incendive / ‘Spurguard’ legs
Installation in => IP54
Live working NOT permitted
on ‘nA’ trunk
‘nA’
‘nL’
Max output :
32 V
1.5 A
Main trunks :
EEx nAL IIC T4
Vmax 32 V
Spurguard legs :
Imax 1.5 A
EEx nL IIC T4
MTL5995
Vmax 32 V
‘nA’
FPS-I
Imax 60 mA
‘nL’
Live working safe on ‘NI’ spurs
System Certification :
Ex nA [nL] IIC T4
Class 1, Div 2, Groups A,B,C,D, T4
Terminator :
18
Vmax 32 V
FF-816 specification :
32 V
1.5 A
Fieldbus
Non Incendive System
Installation in => IP54
Live working permitted
throughout
‘nL’
MTL9111
Max output :
14 V
233 mA
‘nL’
All trunks & spurs
EEx nL IIC T4
Vmax 14 V
Imax 233 mA
‘nL’
MTL9112
‘nL’
System Certification :
Ex nL IIC T4
Class 1, Div 2, Groups A,B,C,D, T4
Terminator :
19
Vmax 32 V
option for IIB
with appropriate
safety parameters
Fieldbus
Non Incendive >> ‘Spurguard’ legs
Installation in => IP54
Live working permitted
throughout
‘nL’
‘nL’
MTL9111
Max output :
14 V
All trunks & spurs
233 mA
EEx nL IIC T4
Vmax 14 V
Spurguard legs
Imax 233 mA
EEx nL IIC T4
Vmax 14 V
‘nL’
Imax 60 mA
MTL9112
‘nL’
System Certification :
Ex nL IIC T4
Class 1, Div 2, Groups A,B,C,D, T4
Terminator :
20
Vmax 32 V
option for IIB
with appropriate
safety parameters
Fieldbus
Intrinsically Safe (Non-FISCO) Installation
Installation in => IP54
Live working permitted throughout
‘IS’
‘IS’
MTL5053
Available output :
‘IS’
18.4 V
into Zone 0
80 mA
Safety parameters :
22 V
216 mA
‘IS’
System Certification :
Ex ia IIC T4
Class 1, Div 1, Groups A,B,C,D, T4
Terminator :
21
FF-816 specification :
Vmax 24 V
24 V
Imax 250 mA
250 mA
FISCO
22
Fieldbus
Fieldbus
Intrinsically Safe (FISCO) Installation
Installation in => IP54
Live working permitted throughout
‘IS’
MTL9121 IS : IIC
‘IS’
14.0 V
180 mA
MTL9122 IS : IIB
14.8 V
Megablock rating :
380 mA
Vmax 14.8 V
‘IS’
Imax 380 mA
‘IS’
System Certification :
Ex ib IIC T4
Class 1, Div 1, Groups A,B,C,D, T4
Use in appropriate gas group
Terminator :
Vmax 24 V
23
Imax 250 mA
Limited to Zone 2 & 1
All devices to be approved
for FISCO
Fieldbus
Network
Calculations
24
Fieldbus
Multiple power supply configuration
Sufficient current capacity ?
T
T
25
Host
T
T
Fieldbus
Basic configuration
Host
L
N
E
9121 & 9122
T
24V
supply
Host trunk
2- 3+
4- 5 S 6+
T
T
7+ 8 S 9 -
Safe Area
Zone 1 / Div1
Hazardous Area
6 devices (120 mA) in IIC
13 devices (260 mA) in IIB
if 20 mA consumption each
device
T
26
Fieldbus
Power
& data
Host
L
N
E
T
24V
supply
2- 3+
4-
6+
T
T
7+ 8 S 9 -
Safe Area
Zone 1 / Div1
Hazardous Area
The Fieldbus
The 24 volt
power supply is
converted to an
intrinsically safe
supply to feed
the IS trunk
27
T
signal, which is
superimposed on the
IS voltage, is fed via
the interface device
to & from the field
devices
Fieldbus
Mains or 24-volt
power supply
8913
8914
Power
Units
Zone2 / Div2
Host
Power consumption
9121 : 190mA
9122 : 300mA
Mains
5991
Power
Unit
8914 : 10 A
5991 : 2 A
T
Mains
28
Safe
Area
T
T
T
Fieldbus
Design Parameters
System design determined from :
power supply output voltage
power supply available current
knowledge of current consumption of each field device
survey shows a range of 10 to 28 mA
20 mA is assumed
application of Ohm’s Law to the cable network
assessment for adequate voltage at each field device
Line resistance of 50 /km is assumed
within the FISCO range of 15 to 150 /km
Model
Apparatus
Number
Class
9121-IS
9122-IS
29
IIC
IIB
Useable
Output
V
mA
12
120
12.8
260
Parameter
Value
Loop resistance
15 ohm to 150 ohm / km
Loop inductance
0.4 mH to
1 mH / km
Capacitance
80 nF
to 200 nF / km
Spurs are in addition to permitted maximum cable length
FISCO cable parameters
Fieldbus
Model
9121-IS : IIC
5 connected
field devices
at end of
trunk
Eg :
I = 100 mA
600 metres
30
= 3 volts
30m spur
= 1.5
carrying 20 mA
volt drop
= 30 mV
31
Hydrogen
Gas Group
Typical IIC calculation
600 metre
IS trunk
Useable
Output
V
mA
12
120
12 volts
600 metre
IS trunk
3 volts
100 mA
If current
drawn < 20 mA
then
instrument
population can
be increased
9 volts
NODE
T
each
instrument
draws 20 mA
Fieldbus
Typical IIC calculation
I = 80 mA
12.5
= 1.0 volt
I = 40 mA
12.5
= 0.50 volts
32
Model
9121-IS : IIC
5 distributed
field devices
I = 100 mA
12.5
= 1.25 volts
750 metre
IS trunk
Hydrogen
Gas Group
12 volts
Useable
Output
V
mA
12
120
each
instrument
draws 20 mA
250 metres
10.75 V
250 metres
9.75 V
250 metres
9.25 V
T
Fieldbus
Typical IIB calculation
12 connected
field devices
at end of
trunk
I = 240 mA
= 3.8 volts drop
316
thru 316 metres
of 15.8
316 metre
max
IS trunk
33
Ethylene
Gas Group
Model
9122-IS : IIB
12.8 volts
Useable
Output
V
mA
12.8
260
metres
3.8 volts
240 mA
Trunk length will
increase if device
population is reduced
9 volts
NODE
T
12
instruments
each
drawing
20 mA
Fieldbus
Power Supply as a IIB Repeater
Safe Area
Zone 2 / Div 2
Zone 1 / Div 1
316 metres
24
volts
Power &
Ex protection
only
Power,
Repeater &
Ex protection
1.8 kms
12 instruments
316 metres
Power drawn
in either direction
Cable protection
required
34
24
volts
A similar scenario exists for a IIC repeater
Fieldbus
Power Supply as a Repeater
Safe Area
Zone 2 / Div 2
Host probably has no Ex protection in powering the 912x device :
Cable is a non-arcing circuit due to incendive level of energy
Cable protection required - hazardous area wiring may not
be disconnected to reveal floating wires
Repeater terminals carry limited energy; hence circuit is
non-incendive and power plug may be removed
912x device may power host equipment (max 30 mA) and power
plug may be removed
Power,
Repeater &
Ex protection
1.8 kms
Power drawn
in either direction
35
Zone 1 / Div 1
Fieldbus
ATEX Certification
The ‘CE’ Mark
Confirms compliance with all
relevant Community directives
Conformite European
ex
38
The ‘Explosive
Atmosphere’ Mark
Confirms compliance with
ATEX
or previous
Flammable Atmosphere Directive
Fieldbus
Equipment Marking - 9121 Power Supply
CENELEC / IEC
[E Ex ib] IIC T4 -40 OC < Tamb < +70 OC
Referenced to ambient
of -20 to +40 OC unless
indicated as above
Temperature Class (Group II)
Apparatus Group (Hydrogen)
Type of protection code
Explosion protection symbol
Conformity with European Standard
39
T1 : 450 OC
T2 : 300 OC
T3 : 200 OC
T4 : 135 OC
T5 : 100 OC
T6 : 85 OC
Fieldbus
Equipment Marking - 9121 Power Supply
CENELEC / IEC
[E Ex ib] IIC T4 -40 OC < Tamb < +70 OC
[ ] indicates the apparatus is safe area
mounted ‘associated apparatus’ suitable
for connection to Ex ib equipment
Referenced to ambient
of -20 to +40 OC unless
indicated as above
Temperature Class (Group II)
Apparatus Group (Hydrogen)
Type of protection code
Explosion protection symbol
Conformity with European Standard
40
T1 : 450 OC
T2 : 300 OC
T3 : 200 OC
T4 : 135 OC
T5 : 100 OC
T6 : 85 OC
Fieldbus
Equipment Marking - 9121 Power Supply
ATEX
II (2) GD
0600
G : Gas, vapour, mist
D : Dust
Type of explosive atmosphere
(Group II)
Equipment Category
Equipment Group
M1 : energised
M2 : de-energised
1 : Zone 0, 20
2 : Zone 1, 21
3 : Zone 2, 22
I : Mining
II : Non-Mining
EU Explosive Atmosphere Symbol
Ref to Notified Body responsible for testing
41
CE mark
Fieldbus
9121 - BASEEFA Certification
0600
II (2) GD
ATEX
[E Ex ib] IIC T4 -40 OC < Tamb < +70 OC
CENELEC / IEC
BAS 02 ATEX 7276
EC-type examination
certificate
ATEX Category 2 certification
42
Additional information on product :
Safety parameters, where applicable
Year of manufacture & Serial No.
Name & address of manufacturer
Manufacturers type identification
Fieldbus
9121 - MTL Declaration of Conformity
II 3 GD
ATEX
E Ex nA IIC T4 -40 OC < Tamb < +70 OC
CENELEC / IEC
MTL 02 ATEX 9121X
MTL Declaration of
Conformity
ATEX Category 3 certification justifying
mounting the 9121 power supply in Zone 2
43
9121X refers to special conditions of use :
> power supply is installed in an appropriate enclosure
> it must be protected from large supply transients
Fieldbus
9122 - BASEEFA Certification
0600
II (2) GD
ATEX
[E Ex ib] IIB T4 -40 OC < Tamb < +70 OC
CENELEC / IEC
BAS 02 ATEX 7277
EC-type examination
certificate
ATEX Category 2 certification
44
Fieldbus
9122 - MTL Declaration of Conformity
II 3 GD
ATEX
E Ex nA IIB T4 -40 OC < Tamb < +70 OC
CENELEC / IEC
MTL 02 ATEX 9122X
MTL Declaration of
Conformity
ATEX Category 3 certification justifying
mounting the 9122 power supply in Zone 2
45
Fieldbus
Fieldbus Intrinsically Safe Concept
(FISCO)
Adopting FISCO raises the issue :
Can Entity certified fieldbus equipment (non-FISCO) be
incorporated into a FISCO network ?
YES
47
9321-SC 9323-SC
Fieldbus
I.S. Entity Spur Connections
(non-FISCO devices)
9121-IS : IIC
9321-SC
Entity spur
connector
output safety
parameters :
14 V; 180 mA; 2.52 W
deliver 12.0 V; 110 mA
EEx ib IIC T4
II 2 (2) G
Live working
throughout
9321-SC
Zone 1
Entity IS certified
device
48
Entity device to FF-816 has
an input safety description of
24 V; 250 mA; 1.2 watts
HUB
T
FISCO
devices
Fieldbus
Fieldbus Intrinsically Safe Concept
(FISCO)
The use of active current limitation restricts the categorisation
to ‘EEx ib’, ie, connection to Zone 1 only
Can a fieldbus device be installed in a Zone 0 by adding further
protection to achieve ‘ia’ status ?
YES
9322-SC
50
Fieldbus
Networking into Zone 0
9322-SC
Zone 0 spur
connector
Useable
with either
9121-IS : IIC
9122-IS : IIB
II 2 (1) G EEx ib IIC T4
II (1) G EEx [ia] IIC
9322-SC
Zone 1
ia : Zone 0
energy limit
NODE
Zone
0
51
T
FISCO
devices
Fieldbus
Wiring
Components
52
Fieldbus
Wiring Components - Megablock Series
Megablocks :
DIN-rail mounting Fieldbus network
hubs
connect multiple field devices to trunk
network
minimise hand wiring
network integrity maintained during
connection / disconnection of
individual devices
LED indicates minimum 9 volts
present at hub
Megablocks available in
2, 4 & 8-way (10-way) versions
Megablock terminator available
Terminator
Short-circuit protection option using SpurGuard
53
Fieldbus
Megablock Series
Trunk /
Home run
Field
device
connection
Power LED >= 9V
Optional
SpurGuard
short circuit protection
- visual indication of fault
Trunk /
Home run
Securable, pluggable
connectors
54
8-way
Megablock
Fieldbus
Megablock Series
Choice of junction box
Use site standard
suitable for
environment
trunk
4 + 8 drop = 12 drop
Easy to retrofit
Junction box for
specific application
standard
instrument cable
spur
55
terminator
Fieldbus
Relcom SpurGuards™
System reliability and availability may be affected
by the shorting of the fieldbus highway,
by the failure of any individual fieldbus device,
thus interrupting data communication across the entire bus segment
could occur during installation or routine instrument maintenance
A SpurGuard™ is a current-limiting device that provides short circuit
protection to the fieldbus segment
By attaching a SpurGuard™ at each point where a field device is attached
to the segment home run cable, isolation of the network from
individual device failures is achieved
SpurGuards™ are available with any Megablock
a red LED indicates when a SpurGuard™ is
providing overcurrent protection
Because a SpurGuard™ leg draws power from the
56
segment when in short circuit mode, their
short circuit current consumption must be
taken into account during segment design
The SpurGuard™ short-circuit current is nominally
60 mA
Trunk to Spur max. voltage drop = 0.4 volts
57
Fieldbus
Fieldbus
Lightning Strikes
Handling
the
effect
58
Fieldbus
Lightning Strikes
There is no remedy for direct lightning strikes
the energies involved are too high
but measures can be taken to minimize the effects of near-lightning
strikes on Fieldbus networks
Lightning is a short burst of very intense voltage and current.
Even when a direct lightning strike is shunted to ground by a
lightning rod, it induces high voltages and currents in metal
components nearby
eg, the conductors & shield of Fieldbus cable
The purpose of lightning surge protection
59
in Fieldbus wiring is to minimize
the induced voltages & currents
and hence to minimise damage
to Fieldbus equipment
a lightning strike might produce
100,000 Amps in a lightning rod
induced currents in nearby grounded
metal objects may be several
thousand Amps
induced current in the shield of a
fieldbus cable might be several
hundred Amps
I PK
(100 kA)
90%
50%
10%
8µs
20µs
t
Fieldbus
Principles & Practicalities
Flash-over
100kA
Local Ground
Strike
Flash-over
Fieldbus
High local
potential on
building earth
system
60
Induced Voltage V = L
x I/ t
Local ‘ground’
High potential across
insulation on field
instrument
Fieldbus
Transient Surge Suppression
The shield of the Fieldbus cable is grounded
but according to the installation standard, in only one place
Single-point grounding eliminates current loops in the shield
reduces induced noise in the signal concerned
is a pre-requisite for an intrinsically safe circuit
the shield is normally grounded at the control room
Any lightning strike in the field could produce a large current in the shield
that needs to travel to the control room to pass to ground
in a long network a large shield voltage could occur
by capacitive coupling a large voltage might appear on the internal
twisted pair
A surge may be minimized by using a Transient Surge Suppressor
Centralised control
equipment
Shield
Transient Surge
Suppressor
61
Fieldbus
Differential Voltage Suppression
The next consideration is to minimize the voltage that might be
induced in the twisted-pair inside the shield
Due to the capacitance between the shield & each of the wires in
the twisted pair,
a voltage change on the shield will induce a voltage on the
wires
Using twisted-pair cable, the shield-to-wire capacitances for the
two wires are nearly equal
hence the voltage induced in each of the wires in the twisted
pair will be identical
(Common Mode Voltage effect)
The Fieldbus standard requires that the common mode
immunity of Fieldbus devices should be of a high order,
eg, Surge Protection Devices :
FP32 = 225 volts DC trigger point
TP32 = 120 volts DC trigger point
62
Fieldbus
Protection Devices
The FP32 surge protection device prevents surges & transient
overvoltages conducted along the Trunk or Spurs of fieldbus
systems from damaging the associated electronics
may be used at any point on a Trunk to safely divert any surges
to ground
The TP32 is the protection equivalent installed at an instrument
Fully automatic in operation, the devices react instantly to make sure
that equipment is never exposed to damaging surges between
lines or between lines & earth
Reacting instantaneously to surges they then reset automatically
FP32
63
TP32
Fieldbus
Surge Protection Device
Line
inductors
Circuit fuses
Signal
lines
Protected
equipment
Gas
discharge
tube
Circuit
earth
Solid-state
limiters
I PK
(100 kA)
90%
The multi-stage elements of the FP32 / TP32
use a combination of solid state electronics
and a gas filled discharge tube (GDT) to
64
50%
10%
t
provide surge protection up to 20kA
20µs
Fieldbus
Power problems due to transient spikes
Surge < 10%
Sag < 10%
Transient 85% to 90%
65
Outage < 1%
Fieldbus
Generalised Fieldbus connection
Power
conditioner
Hub
T
Terminator
T
Trunk
Power
supply
Power
distribution
panel
Incoming
AC supply
66
Fieldbus
Host System protection
Power
conditioner
Hub
FP32
T
Terminator
T
Trunk
Power
supply
MA 4000
Power
distribution
panel
Incoming
AC supply
67
Fieldbus
Field Device Protection - ‘compact’
Hub
FP32
Trunk
T
Terminator
Spurs
< 50m horizontal
< 10m vertical
All spurs less than :
50m horizontal or
10m vertical
Surge invasion from host
end of trunk
all devices are protected by
one surge protection device
in trunk
68
Fieldbus
Field Device Protection - ‘widespread’
Hub
FP32
Trunk
T
Terminator
Spurs
> 50m horizontal
> 10m vertical
Spurs greater than :
50m horizontal or
10m vertical
surge invasion from Host
69
end of trunk
surge protection installed to
each device
70
Fieldbus