Sistemas electricos Categoria 3

1. COMMAND SYSTEMS PARTIES
RELATED TO SAFETY
- CATEGORY 3-
-
EN 954-1
Celso Eduardo Forner – CSP
Machine Guarding Specialist
Foto: Otto Görnemann / SICK AG © 2005

2. Safety interlocking Category # 3
 Why Category # 3?
- Our Goal is Zero Amputees
-A method for achieving this goal is to provide higher
levels of protection to machine operators and
maintenance personnel.
-The safety interlocking Category # 3 is an essential part
of any plan to increase the level of protection, especially
for machines classified as being “Risk A. “
- Note: If there is a possibility of death or direct contact
with the risk category # 3 may not be enough.

3.  Keys (End-of-course or devices operated by cams)
The contacts are welded
The springs are broken and not conducive to a safe state
The cables come loose or shorted
Negative performance
 Relays (Power or out put devices)
The contacts are welded
The springs are broken
The cables come loose, fall short or are mixed up
No status change
Positively guided contacts are not
 PLC - can be programmed incorrectly
DISPOSITIVOS QUE PUEDEN FALLAR:

4. SEVERITY of injury
S1 –Minor injury (usually reversible)
S2 –Serious injury (not reversible)
FRECUENCY or EXPOSURE TIME to risk
F1 –Rare to uncommon
F2 –Frequent to continuous
POSSIBITY of avoiding the accident
P1 –Possible under certain circumstances
P2 –Rarely possible
RISK ASSESSMENT:
 Risk Estimate:

5. B 1 2 3 4
S1
S2
F1
F2
P1
P2
P1
P2
Recommended
Oversized
Possible. You may need additional measures
RISK ASSESSMENT - EN 954-1:
 Selection Guide by Category:

6. B 1 2 3 4
S1
S2
F1
F2
P1
P2
P1
P2
Starting point
RISK ASSESSMENT - EN 954-1:
 Selection Guide by Category:

7. B 1 2 3 4
S1
S2
F1
F2
P1
P2
P1
P2
RISK ASSESSMENT - EN 954-1:
 Selection Guide by Category:

8. B 1 2 3 4
S1
S2
F1
F2
P1
P2
P1
P2
RISK ASSESSMENT - EN 954-1:
 Selection Guide by Category:

9. B 1 2 3 4
S1
S2
F1
F2
P1
P2
P1
P2
RISK ASSESSMENT - EN 954-1:
 Selection Guide by Category:

10.  Security-Related Parts of Control Systems
Categories B and 1 have a lower integrity that
categories 2, 3 and 4
IT IS IMPORTANT TO KNOW THAT THESE CATEGORIES
ARE NO LEVELS OF RISK AND ARE NOT TO BE USED IN
A PARTICULAR HIERARCHY
The requirements of category B and 1 apply to other
categories as well as peripherals such as control
systems and security keys involucres
SAFETY CATEGORY - EN 954-1:

11.  Security Category B
The devices involved must resist the expected operating (load,
number of operations), the influence of material processing
(detergents, washing machines) and external environmental
influences (vibrations, disturbances in energy).
A simple fault can lead to loss of safety function
The control system related to security must, at minimum,
be designed and have been selected according to the latest
technological innovations
The category B has no special security measures, in addition to
those, but forms the basis for other categories
SAFETY CATEGORY - EN 954-1:

12.  Security Category 1
Using well-proven devices, namely, (a) components
widely used in the past with success in similar
applications, (b) manufactured and tested principles
proven to be adequate and reliable security features
A simple fault can lead to loss of safety function
Additional measures to ground equipment, oversizing the
device, avoid short with increased insulation, ensure the
opening of the circuit to remove power on failure
All applicable requirements of Category B
SAFETY CATEGORY - EN 954-1:

13. LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX
TO PLC OR ANNUNCIATOR LIGHTS
EMERGENCY STOPS CATEGORY 1 SCHEM-7.DWG 10/3/98
CIRCUIT BKR
CORD
PULL STOP
EMERGENCY EMERGENCY
PULL STOP
CORD 33CR2
G
SAFETY
RESET
33CR2
POSITIVE
GUIDED
RELAY
TO MACHINE MOTION
INTERLOCKING AS REQUIRED
33CR2
INTERLOCKING AS REQUIRED
TO MACHINE MOTION
33CR2
APPROVED DEVICES
MINIMUM ACCEPTABLE
(IF NOT REQUIRED TO BE CAT. 3)
CATEGORY #1 ACCORDING – EN 954-1:
Emergency Stop
Category 1
Just 1
Relay
Isolation
Stop Button
Emergency
Single Channel
Contact
Relay

14. LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX
INTERLOCKING AS REQUIRED
TO MACHINE MOTION
TO PLC OR ANNUNCIATOR LIGHTS
TO MACHINE MOTION
INTERLOCKING AS REQUIRED
GUARD DOOR SWITCHES CATEGORY 1 SCHEM-6.DWG 10/3/98
GUARD
DOOR
GUARD
DOOR
GUARD
DOOR
GUARD
DOOR
GUARD
DOOR
GUARD
DOOR
GUARD
DOOR
GUARD
DOOR
33CR2 33CR2
CIRCUIT BKR
33CR2
GUIDED
RELAY
POSITIVE
APPROVED DEVICES
Category
protections. 1
Key
Security
at Gate
Only 1
Contact Isolation
Relay
CATEGORY #1 ACCORDING – EN 954-1:

15. COMPRESSED AIR DUMPING - CATEGORY 1 SCHEM-3.DWG 10/3/98
33CR2
MAIN AIR
DUMP
VALVE
33SOL2
LINE #XXXX
CIRCUIT BKR
EMERGENCY
TO PLC OR ANNUNCIATOR LIGHTS
LINE #XXXX
LINE #XXXX
PULL
CORD
LINE #XXXX
CORD
PULL
STOP
EMERGENCY
STOP
33CR2
RESET
SAFETY
G
33CR2
RELAY
GUIDED
POSITIVE
Compressed air in Category 1
Only one
Valve
CATEGORY #1 ACCORDING – EN 954-1:

16.  Security Category 2
Check at least every game machine, or periodically
during operation, if indicated by risk analysis
The safety function performed by the control system
should be checked at regular intervals automatically or
manually
If a fault occurs, the safety function can be lost in the
checks, but will be detected in the next test
All applicable requirements of Category B, in addition to
using well-tested components
Input and output devices connected to single channel
SAFETY CATEGORY - EN 954-1:

17.  Safety Category 3
A failure does not lead to loss of safety function. An
accumulation of undetected faults can lead to a
dangerous situation
Redundancy: duplication of circuits / components such
that if one fails the other still generate a stop signal
Wiring System Dual channel: they can detect grounding
faults, opens circuits and shortscircuits
SAFETY CATEGORY - EN 954-1:
All applicable requirements of Category B, in addition
to using well-tested components

18. SAFETY CATEGORY - EN 954-1:
 Safety Category 3
Employment Security Control Modules foolproof
Command circuits hard-wired: no control via software or
electronic. Exception: Safety Programmable Controllers with
multiple processors and redundant software
Self-diagnosis of the components is done periodically and
automatically
No risk period between a failure and the next
verification of the safety function
Auto-verification of the power contactors via auxiliary
contacts

19. A1
A3
Y2
Y1
Y36
S52
S12
S11
S22
S21
Y37
A2
13
14
23
24
33
34
41
42
11CR1
SAFETY RELAY
24V
Y32
Y35
0V
(+) (-)
+24VDC
E-STOP
ACTIVATED
FUSE CUT-OUT
ACTIVATED
COMMON
PNOZ8
CHAN. 1
CHAN. 2
K1 K2 K3
POWER
FAULT
E-STOP AUX. SAFETY
RELAY #1
E-STOP AUX. SAFETY
RELAY #2
LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX
MACHINE E-STOP
TO PLC
DC
RTN
24VDC CARD
LINE #1127
DETAIL "A"
TYPICAL INPUT CIRCUIT USED FOR ANNUNCIATION
PLC INPUT
PLC INPUT
E-STOP
RESET
JUMPERS
MONITORED MANUAL
RESET REQUIRED
EMERGENCY STOP CATEGORY 3 SCHEM-11.DWG 10/3/98
TO MACHINE MOTION
INTERLOCKING AS REQUIRED
11CR2
INTERLOCKING AS REQUIRED
TO MACHINE MOTION
11CR3 11CR2 11CR3
11CR2 11CR3
11CR2
11CR3
EMERGENCY
STOP STOP
EMERGENCY
STOP
EMERGENCY EMERGENCY
STOP STOP
EMERGENCY
PULL
CORD CORD
PULL
CORD
PULL
E-STOP
R
CIRCUIT BKR
Emergency Stop
Category 3
Two Relays
of
Isolation
Stop Button
Emergency
Dual Channel
Relay
Security
Relay
Contacts
2 Channels
CATEGORY #3 ACCORDING – EN 954-1:
et
Reset
Manual

20. A1
A3
Y2
Y1
Y36
S52
S12
S11
S22
S21
Y37
A2
13
14
23
24
33
34
41
42
33CR1
SAFETY RELAY
24V
Y32
Y35
0V
(+) (-)
+24VDC
E-STOP
ACTIVATED
FUSE CUT-OUT
ACTIVATED
COMMON
PNOZ8
CHAN. 1
CHAN. 2
K1 K2 K3
POWER
FAULT
LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX
GUARD DOOR
GUARD DOOR AUX. SAFETY
RELAY #1
RELAY #2
GUARD DOOR AUX. SAFETY
INTERLOCKING AS REQUIRED
TO MACHINE MOTION
TO PLC
TO MACHINE MOTION
INTERLOCKING AS REQUIRED
PLC INPUT
JUMPERS
AUTOMATIC RESET ACCEPTABLE
TYPICAL INPUT CIRCUIT USED FOR ANNUNCIATION
24VDC
DETAIL "A"
PLC INPUT
CARD
GUARD DOOR SWITCHES CATEGORY 3 SCHEM-10.DWG 10/3/98
CIRCUIT BKR
33CR2 33CR3
33CR2
33CR3
GUARD
DOOR DOOR
GUARD
DOOR
GUARD
DOOR
GUARD
DOOR
GUARD
DOOR
GUARD
DOOR
GUARD
DOOR
GUARD
33CR2 33CR3 33CR2 33CR3
GUARD
DOOR
Security Key
with 2 contacts
Two Relays
Security or
Just 1 but
Oversized
Safety relay
Double contacts
Insulation
of relays
Auto
Reset
Protections in
Category 3
CATEGORY #3 ACCORDING – EN 954-1:

21. Compressed air
in Category 3
Double Isolation
Valves with
electrical swith
sensor
Reset with Redundant
Contacts Relief Valves and
Isolation Relays
CATEGORY #3 ACCORDING – EN 954-1:

22. Interlocking UNACCEPTABLE TO PLCs:
GUARD DOOR & E-STOP INTERLOCKING THROUGH A PLC IS NOT ACCEPTABLE
1
2
3
4
REED SWITCH
PROX. SWITCH
MICRO SWITCH
GUARD DOOR
GUARD DOOR
GUARD DOOR
GUARD DOOR
E-STOP
E-STOP
PULL CORD
5
6
7
8
GUARD DOOR
PHOTO EYE
GUARD DOOR
LIMIT SWITCH
LIMIT SWITCH
GUARD DOOR
E
24
VDC
DC
RTN
RTN
DC
VDC
24
8
RTN
DC
VDC
24
VDC
24
RTN
DC
1
2
3
4
5
6
7
DC INPUT MODULE DC OUTPUT MODULE
REJECT
MAIN AIR
MAIN
MOTOR
RAISE
ROLL
SPLICER
MOTOR
LOWER NIP
ROLL
EXTEND
RETRACT
SCHEM-1.DWG 10/3/98
Emergency
Input
Module
Output
Module
Contactor,
relay
etc.

23. ACCEPTABLE SAFETY INTERLOCKING OF PLC OUTPUT MODULES
8
RTN
DC
VDC
24
VDC
24
RTN
DC
1
2
3
4
5
6
7
DC OUTPUT MODULE
SCHEM-5.DWG 10/3/98
24
VDC
8
7
6
5
DC
RTN
4
3
2
DC OUTPUT MODULE
VDC
24
1
DC
RTN
E-STOP
GUARD SAFETY
E-STOP
GUARD SAFETY
GUARD SAFETY
ZONE "A"
ZONE "B"
ZONE "C"
MAIN
DRIVE
DRIVE
MAIN
ROLL
FEEDER
SPLICE
ROLL
KNIFE
PRESS
ROLL
SLITTER
KNIVES
MAIN AIR
SPLICER
EMBOSSER
TRIM
RAISE
SEAL
CHOPPER
EMBOSSER
LOWER
RAISE
VACUUM
ROLL
MAIN AIR
Contacts
Stop
Emergency
Contacts
Key in
Protection
Device
(motor,
for example.)
Output
Module
Output
Module
ACCEPTABLE interlocking PLCs:

24. Category #3 Full – Double Keys
Secirity relay
A1
A3
Y2
Y1
Y36
S52
S12
S11
S22
S21
Y37
A2
13
14
23
24
33
34
41
42
33CR1
SAFETY RELAY
24V
Y32
Y35
0V
(+) (-)
+24VDC
E-STOP
ACTIVATED
FUSE CUT-OUT
ACTIVATED
COMMON
PNOZ8
CHAN. 1
CHAN. 2
K1 K2 K3
POWER
FAULT
LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX LINE #XXXX
GUARD DOOR
GUARD DOOR AUX. SAFETY
RELAY #1
RELAY #2
GUARD DOOR AUX. SAFETY
INTERLOCKING AS REQUIRED
TO MACHINE MOTION
TO PLC
TO MACHINE MOTION
INTERLOCKING AS REQUIRED
PLC INPUT
JUMPERS
AUTOMATIC RESET ACCEPTABLE
TYPICAL INPUT CIRCUIT USED FOR ANNUNCIATION
24VDC
DETAIL "A"
PLC INPUT
CARD
TWO SWITCHES PER GUARD DOOR CATEGORY 3 SCHEM-12.DWG 6/3/99
CIRCUIT BKR
33CR2 33CR3
33CR2
33CR3
GUARD DR 1
SWITCH 1
33CR2 33CR3 33CR2 33CR3
SWITCH 2 SWITCH 2
SWITCH 1
SWITCH 2
SWITCH 1
GUARD DR 2 GUARD DR 3
GUARD DR 3
GUARD DR 2
GUARD DR 1
GUARD DR 4
SWITCH 1
GUARD DR 4
SWITCH 2
GUARD DR 5
SWITCH 1
GUARD DR 5
SWITCH 2
GUARD DR 6
SWITCH 1
GUARD DR 6
SWITCH 2
GUARD DR 7
SWITCH 1
GUARD DR 7
SWITCH 2
GUARD DR 8
SWITCH 1
GUARD DR 8
SWITCH 2
GUARD DR 1
SWITCH 1
GUARD DR 1
SWITCH 2
2 Keys for
Protection
Double contacts
Insulation
of relays
Isolation Relays
Double
Positively
Guided

25. Categoría #3 Full – Double Keys

26. SAFETY INTERLOCKING CATEGORY 3
THESE DEVICES MUST BE SAFETY RATED
SUCH AS CARDS, FITZMILLS, NON-WOVEN MACHINES, ETC.
GENERAL APPLICATION FOR LARGE MACHINES WITH HIGH RISK, HIGH INERTIA LOADS
CHANNEL 1
SAFETY
DOOR LATCH
S
SOLENOID
LOCKING
SWITCH
CHANNEL 2
MAT
SAFETY
CURTAIN
RF
CURTAIN
LIGHT
CHANNEL 1
CHANNEL 2
RELAYS
SAFETY
E-STOP CHANNEL 2
CHANNEL 1
FEEDBACK
START/STOP
CONTROLS
NORMAL
JLR
SAFRES-1.DWG 6/23/98
CONDITIONER
SIGNAL
SAFETY
CHANNEL 1
HAZARDOUS
M
COMPONENTS
MOTION
MACHINE
CHANNEL 2
OTHER
CHANNEL 1
MODULE
TACHOMETER,
CHANNEL 2
SENSORS
PROXIMITY
ENCODER, OR
ISOLATION CONTACTORS
ELECTRO-MECHANICAL
FEEDBACK
DRIVE
BRAKING
SYSTEM
OR L
M
LOAD
INERTIA
HIGH
GENERAL CONNECTION DIAGRAM

27. Close Open Open
RELAYS WITH REGULAR CONTACTS:

28. Open Close Close
Relé Energizado
RELAYS WITH REGULAR CONTACTS:

29. close Close Open
Welded contact
RELAYS WITH REGULAR CONTACTS:

30. Cerrado Abierto Abierto
RELÉS CON CONTACTOS POSITIVAMENTE GUIADOS:

31. open close Close
relay energized
RELAYS WITH POSITIVELY GUIDED CONTACTS:

32. welded contact
RELAYS WITH POSITIVELY GUIDED CONTACTS:
open Close Close

33. DRIVE KEYS
POSITIVE BREAK
DOOR OPENED
GUARD REMOVED
SWITCH DEACTIVATED
SWITCH ENGAGED
GUARD IN PLACE
DOOR CLOSED
POSITIVE MODE
TAPE
SWITCH ENGAGED
GUARD REMOVED
DOOR OPENED
DEFEATED
OVERCOMING CONTACT
FORCES DISCONNECTION
GUARD, DOOR
DOOR CLOSED
GUARD IN PLACE
SWITCH ENGAGED
ROTATION OF CAM
WELD OR STICKING
NEGATIVE MODE
GUARD, DOOR
.5mm
TOLERANCE
TIGHT GAP
SAFRES-6.DWG
MACHINE
FRAME
DISTANCE
6/23/98
JLR
TOLERANCE
ACTUATOR
RELAY
FRAME
GUARD, DOOR
GUIDED RELAY
POSITIVELY
DISTANCE
GAP
GUARD, DOOR
MACHINE CONVENTIONAL
POSITIVE GUIDANCE

34.  Safety Category 4
Used equipment can cause severe injury, including death, as
guillotines and presses
Are all the requirements of Category 3
When failures occur, the safety function is always
executed
The faults are always detected in time to prevent the loss of
safety function
Using input devices in dual channel with reversal of
polarity between the contacts on the safety key
SAFETY CATEGORY - EN 954-1:

35. CATEGORY KEYS
 Class 1 keys actuator
involucre
Involucre and actuator
are physically linked

36. actuator
involucre
Involucre and actuator
are physically
separated
CATEGORY KEYS
 Class 2 Keys

37.  RESISTANT TO TAMPERING
 It is not easily suppressed and not diverted
 POSITIVE BREAK CONTACTS
 There is a positive drive between the actuator
and the contacts of the key forcing them to open
 A TEST FAILURES
 The contacts remain open, in a safe condition
in case of failure
CATEGORY KEYS
 Features:

38.  Stop emergency (EN60204)
 CATEGORY 0:
 Immediate stop to the removal of power
 Is only achieved through electro-mechanical
components commanded physically and not through
software.
 Is an uncontrolled stop
 Valid only for equipments that have a quick and safe
stop
 Can be used as Emergency Stop
EMERGENCY STOP

39.  CATEGORY 1:
 Controlled stop with the maintenance of power the
actuators of the machine to a full stop.
 The withdrawal of power occurs only after the full
stop of the equipment
The final withdrawal must be guaranteed by the key
electro-mechanical devices.
Speed monitors should confirm the stop
  Can be used as Emergency Stop
STOP EMERGENCY
 Stop Category (EN60204)

40.  CATEGORY 2:
 Controlled stop with the maintenance of power the
actuators of the machine to a full stop.
 After stopping, the power continues available
actuators.
 CAN NOT be used like Stop Emergency
EMERGENCY STOP
 Stop Category(EN60204)

41.  Circuit Features:
Emergency buttons and strings should be approved to
implement security functions
 Reset the Security function must be executed
by contact closure of a button so as to be
a monitored manual reset.
 The relay or contactor circuit stop mergency contacts
should be positively guided.
 When several machines are a "line production "Emergency
function of each machine should be integrated into a single
circuit. Must be provided a separate power supply.
STOP EMERGENCY

42.  Reds
 mushroom type
 With lock
 Turn or pull to unlock
 Clearly identified
EMERGENCY STOP
 Button features:

43.  Press to activate / Turn to relieve
 Press to activate / Pull relief
 Press to activate / Key to relieve
 Pull to activate / reset button
EMERGENCY STOP
 Types of Buttons:

44.  Global vs. Cell vs. Local
 The strategy depends on the application of machine:
1. Integrated production line - Global System
M1 M2 M3
Raw
material
Embalagem Etiquetagem
Pesagem
Product
finish
Enchi/o
M4
EMERGENCY STOP
 Strategies of connection:

45.  Global vs. Cell vs. Local
 The strategy depends on the application of machine:
2. Integrated cell - pass-on system
Célula
1
Cell
2
Cell
3
Cell
4
Product flow
EMERGENCY STOP
 Strategies of connection:

46.  Global vs. Cell vs. Local
 The strategy depends on the application of machine
3. Local stop = A machine or equipment
Máquina
1
EMERGENCY STOP
 Strategies of connection:

47. According to EN 294, the devices must be mounted so
that it is impossible for the operator to reach the point of
risk above, below, on the sides or through the protections
EN 999 describes how to calculate the minimum safe
distance between protection and risk point. The safe
distance depends on:
From the way the machine stop completely
Response time of protective device
The order of the protection
Approach speed of the operator
SAFE DISTANCES
 Non-Physical Protection:

48.  Calculating Safety Distance:
The following formula is used to calculate the minimum
safe distance from the danger zone, according to EN 999:
S = (K*T)+C
S is the minimum distance, in millimeters, of the
danger zone to the detection point
K is the approach speed of the body, or parts thereof, in
mm / sec.
T is the total downtime of the machine
C is the additional distance in mm, based on
intrusion towards the danger zone before the
performance of protective equipment
SAFE DISTANCES

49.  Opto-electronic
 Photocells
 Cortina de luz
 Laser Scanner
 Cameras
SAFE DISTANCES
 Examples of Non-Physical Protection:

50.  Security Flap,
 Security Flaps
 Safety mats
SAFE DISTANCES
 Examples of Non-Physical Protection:

51. SAFE DISTANCES
 Application of Non-Physical Protection:

52. Danger
Zone
3Vertical installation
with carpet
Security
Danger
Zone
2Vertical installation
and horizontal
Danger
Zone
1 Installation angle
SAFE DISTANCES
 Application of Non-Physical Protection:

53. SAFE DISTANCES
 Application of Non-Physical Protection:

54. Profibus-PA
SIGUARD
Laser scanner Circuit
breakers
Operator panel
Safety door monitoring
Fail-safe
AS-i Module
Proximity-type
protective
equipment
SIGUARD
Position switch
Safety door
monitoring
SINUMERIK
SIMODRIVE
MICRO
MASTER
SIMATIC
S7 400F/H
ET200S PROFIsafe
with motorstarters
SIMATIC S7 315F
ET200M/F
ET200S PROFIsafe
DP/DP
Link
Proximity-type
protective
equipment
DP/AS-i
Link
ET200S PROFIsafe
PROCESS FIELD BUS
 Totally Integrated Automation Security with

55. circuit
contactor
PLC
M
~
M
~
M
~
M
~
M
~ M
~
DS
F-Kit
M
~
DS
F-Kit
M
~
DS
F-Kit
M
~
DS
F-Kit
End
module
M
~
L+
M
PM-D
F1
DS
F-Kit
IM
151
circuit
contactor
Motor Starters of
Security
Padron PLC
Security
relay
Typical New
Padron PLC &
Seciurity
 Security Installations

56. Red
orHardwirded
L +
Restart
M -
PLC Padrón
Inverter/VFD
Integrated security
Inverter/VFD
Features:
• Does not require E / S
analog or digital
• Internal power bus
• Idle safety State
• Safe braking ramp
• Safe Speed Reduction
 Inverters y Frequency drives in Cat. #3
Typical New

57. ¿QUESTIONS ?
EN 954-1

58.  NBR NM 273 – Dispositivos de intertravamento associados a
proteções.
 NBR 13.759 – Equipamentos de parada de emergência.
 NBR 14.009 – Princípios para apreciação de riscos.
 NBR 14.153 – Sistemas de comandos relacionados à segurança.
 SOP-WW-S-004-00 – Machine Safeguarding Process.
 J&J Engineering Guide - Volume 5 - Electrical Safety Circuit
Design Guide.
 Fotos de dispositivos de seguridad obtenidas de internet o de
catálogos de los fabricantes:
 Euchner
 ACE Schmersal
 Rockwell
 Pilz
 Sick
 Siemens
INTERTRABAMIENTO DE SEGURIDAD CATEGORÍA #3
 Referencias: