Pilz PSS SB HYD, Basic license User Manual
Programmable Safety Systems
PSS-Range
PSS Standard Function Blocks
MBS Hydraulic Presses
Version 3.2
Operating Manual
Item No. 19 203-07
The spirit of safety.
All rights to this manual are reserved by the publishers. Copies may be made for
internal purposes.
While every effort has been made to ensure that the information in this manual is
accurate, no responsibility can be accepted for errors or omissions contained within it.
We reserve the right to amend specifications without notice. We are grateful for any
feedback on the contents of this manual.
The names of products, goods and technologies used in this manual are trademarks of
the respective companies.
Contents
Introduction 1-1
MBS Modular Block System 1-2
Categories/requirement classes 1-3
Overview of manual 1-4
Definition of symbols 1-5
Terminology 1-6
Overview 2-1
Software package 2-1
Range 2-2
Safety 3-1
Safety guidelines 3-1
Use of qualified personnel 3-1
Warranty and liability 3-1
Application guidelines 3-2
Standards 3-3
Fault detection 3-4
Fault detection techniques 3-5
Feasibility test 3-5
Pulsed input signals 3-6
Self test on the outputs 3-6
Fault prevention 3-6
Intended Use 4-1
System software 4-1
Intended use of the standard
function blocks 4-2
SB051: Operating mode selector switch 1 from 8 4-2
SB052: Operating mode selector switch 2 from 6 4-3
SB059: Two-hand monitoring 4-4
Modular Block System: Hydraulic Presses 1
Contents
SB061: Emergency stop monitoring 4-4
SB063: Emergency stop monitoring 4-5
SB064: Safety gate monitoring 4-6
SB065: Feedback loop monitoring 4-7
SB066: Safety gate monitoring 4-8
SB067: Feedback loop monitoring 4-8
SB068: Monitoring ESPE/AOPDs with guarding and control function 4-9
SB069: Monitoring ESPE/AOPDs with guarding function 4-10
SB070: Initialisation of administration data block (DB015) 4-11
SB071: Initialisation of administration data blocks
(DB015/DB016/DB017) 4-11
SB072: Temporary suspension of safety functions 4-12
SB075: Controlling and monitoring safety gates with guard locking 4-12
SB086: Overrun control on linear-driven presses 4-13
SB087: Driving/monitoring the position of a single hydraulic valve 4-14
SB088: Driving/monitoring the position of a dual hydraulic valve 4-14
SB089: Driving/monitoring the position of two hydraulic valves 4-16
SB092: Enable switch 4-17
SB097: Monitoring muting lamps 4-18
MBS Basics 5-1
Block design 5-1
Structure 5-1
Formal parameters and actual parameters 5-2
Administration data blocks DB015, DB016 and DB017 5-3
Structure of the administration data blocks 5-3
Blocks contained in the administration data blocks 5-5
Input parameter SSNR 5-7
Fault diagnostics 5-9
Error types 5-9
Fault diagnostics using the administration data blocks 5-10
Temporary flag range in MBS blocks 5-11
Output parameter FG/ENBL 5-11
Assignment of input and output parameters 5-12
Minimum scan time 5-12
Global parameters 5-13
2
Modular Block System: Hydraulic Presses
Standard Function Blocks 6-1
Guidelines for selecting standard function blocks 6-1
Emergency stop monitoring 6-1
SB061 NA_1 6-1
SB063 E-STOP 6-1
Safety gate monitoring 6-2
SB066 ST-K4 6-2
SB064 S-GATE 6-3
Feedback loop monitoring 6-3
SB067 RFK_K4 6-3
SB065 FBL 6-4
Initialisation of administration data blocks 6-4
SB070 INIT_MBS 6-4
SB071 INIT_MBS 6-5
SB051: Operating mode selector switch 1 from 8 6-6
Block header 6-6
Input parameters 6-6
Output parameters 6-7
Error messages 6-8
Global parameters used in administration data block DB015 6-9
Blocks required 6-10
SB052: Operating mode selector switch 2 from 6 6-10
Block header 6-10
Input parameters 6-10
Output parameters 6-12
Error messages 6-13
Global parameters used in administration data block DB015 6-14
Blocks required 6-14
Modular Block System: Hydraulic Presses 3
Contents
SB059: Two-hand monitoring 6-16
Block header 6-16
Input parameters 6-16
Output parameters 6-20
Error messages 6-20
Global parameters used in administration data block DB015 6-22
Blocks required 6-22
SB061: Emergency stop monitoring
Category 4 6-24
Block header 6-24
Input parameters 6-24
Output parameters 6-25
Error messages 6-25
Global parameters used in administration data block DB015 6-27
Blocks required 6-27
SB063: Emergency stop monitoring
Category 4 6-28
Block header 6-28
Input parameters 6-28
Output parameters 6-29
Function test 6-29
Error messages 6-30
Global parameters used in the administration data blocks 6-31
Blocks required 6-31
SB064: Safety gate monitoring 6-32
Block header 6-32
Input parameters 6-32
Output parameters 6-34
Functions 6-35
Error messages 6-38
Global parameters used in the administration data blocks 6-39
Blocks required 6-39
SB065: Feedback loop monitoring 6-40
Block header 6-40
Input parameters 6-40
Output parameters 6-41
Functions 6-42
Error messages 6-43
Global parameters used in the administration data blocks 6-45
Blocks required 6-45
4
Modular Block System: Hydraulic Presses
SB066: Safety gate monitoring 6-46
Block header 6-46
Input parameters 6-46
Input circuitry 6-47
Output parameters 6-48
Functions 6-48
Error messages 6-52
Global parameters used in administration data block DB015 6-53
Blocks required 6-53
SB067: Feedback loop monitoring on contactors 6-54
Block header 6-54
Input parameters 6-54
Output parameters 6-54
Error messages 6-55
Global parameters used in administration data block DB015 6-56
Blocks required 6-56
SB068: Monitoring ESPE/AOPDs with
guarding and control function 6-58
Block header 6-58
Input parameters 6-58
Wiring the input parameters 6-62
Output parameters 6-62
Function 6-63
Cycle modes 6-65
Error messages 6-65
Global parameters used in administration data block DB015 6-67
Blocks required 6-67
Diagrams for ESPE/AOPD 6-68
Timing diagram for “guard only” mode of ESPE/AOPD 6-68
Timing diagram for “double break” mode of ESPE/AOPD 6-70
SB069: Monitoring ESPE/AOPDs with
guarding and control function 6-72
Block header 6-72
Input parameters 6-72
Wiring the input parameters 6-74
Output parameters 6-74
Function 6-75
Error messages 6-76
Modular Block System: Hydraulic Presses 5
Contents
Global parameters used in administration data block DB015 6-77
Blocks required 6-77
Timing diagram 6-78
SB070: Initialisation of administration data block DB015 6-80
Block header 6-80
Input parameters 6-80
Function 6-80
Error messages 6-82
Blocks required 6-82
SB071: Initialisation of administration data blocks 6-84
Block header 6-84
Input parameters 6-84
Function 6-84
Error messages 6-86
Blocks required 6-86
SB072: Temporary suspension of safety
functions (ESPE/AOPD muting) 6-88
Block header 6-88
Input parameters 6-88
Wiring the input parameters 6-91
Output parameters 6-91
Wiring the output parameters 6-92
Operating modes 6-92
Terminology 6-92
Sequential muting mode (muting when entering the danger area) 6-93
Parallel muting mode (muting when leaving the danger area) 6-95
Parallel muting mode (muting when entering and leaving the
danger area) 6-97
Safety guidelines 6-99
Error messages 6-100
Global parameters used in administration data block DB015 6-102
Blocks required 6-102
Cycle diagrams 6-103
Parallel muting cycle 6-103
Sequential muting cycle 6-104
SB075: Controlling and monitoring safety gates with
guard locking 6-106
Block header 6-106
Input parameters 6-106
Input circuitry 6-110
6
Modular Block System: Hydraulic Presses
Output parameters 6-110
Operating modes 6-112
Procedures 6-115
Additional safety guidelines 6-116
Error messages 6-117
Global parameters used in administration data block DB015 6-119
Blocks required 6-119
SB086: Overrun control on linear-driven presses 6-120
Block header 6-120
Input parameters 6-120
Output parameters 6-122
Procedures 6-122
Timing diagram 6-125
Error messages 6-125
Global parameters used in administration data block DB015 6-126
Blocks required 6-126
SB087: Driving/monitoring the position of a single
hydraulic valve (poppet and directional control
valve) 6-128
Block header 6-128
Input parameters 6-128
Output parameters 6-129
Function 6-130
Safety guidelines for input parameters TOn and TOff 6-132
Settings for the parameters TOn and TOff 6-133
Error messages 6-134
Global parameters used in administration data block DB015 6-135
Blocks required 6-135
SB088: Driving/monitoring the position of a dual
hydraulic valve (poppet and directional control
valve) 6-136
Block header 6-136
Input parameters 6-136
Output parameters 6-138
Function 6-139
Safety guidelines for input parameters TOn and TOff 6-141
Settings for the parameters TOn and TOff 6-143
Error messages 6-144
Global parameters used in administration data block DB015 6-146
Blocks required 6-146
Modular Block System: Hydraulic Presses 7
Contents
SB089: Sequential driving/monitoring the position
of two hydraulic valves (poppet and directional
control valves) 6-148
Block header 6-148
Input parameters 6-148
Output parameters 6-150
Function 6-151
Safety guidelines for input parameters TOn and TOff 6-153
Settings for the parameters TOn and TOff 6-154
Error messages 6-155
Global parameters used in administration data block DB015 6-157
Blocks required 6-157
SB092: Enable switch 6-158
Block header 6-158
Input parameters 6-158
Output parameters 6-159
Function 6-160
Switching diagrams 6-161
Error messages 6-163
Global parameters used in administration data block DB015 6-163
Blocks required 6-163
SB097: Monitoring muting lamps 6-164
Block header 6-164
Input parameters 6-164
Output parameters 6-165
Wiring the output parameters 6-166
Wiring diagram 6-166
Function 6-166
Guidelines for the design and layout of muting lamps 6-167
Error messages 6-168
Global parameters used in administration data block DB015 6-169
Blocks required 6-169
Timing diagrams 6-170
Link Blocks 7-1
Check list 7-1
8
Modular Block System: Hydraulic Presses
Examples 8-1
Application and parameters of individual blocks 8-2
Emergency stop monitoring
with manual start (start-up and operation), category 4 8-2
Emergency stop monitoring
with automatic start-up, manual start (operation)
and function test, category 4 8-4
Feedback loop monitoring
Shutdown with two contactors connected in series,
category 4 8-6
Feedback loop monitoring
Shutdown with two main contactors connected in series and
pulsed outputs, category 4 8-8
Feedback loop monitoring (selective shutdown),
category 4 8-10
Emergency stop monitoring with monitoring of feedback loop,
category 4 8-14
Safety gate monitoring
with manual start and manual restart, category 2 8-16
Safety gate monitoring
with automatic start and manual restart, category 2 8-20
Safety gate monitoring
with manual start and manual restart, category 4 8-24
Safety gate monitoring
with automatic start and manual restart,
category 4 8-28
Safety gate monitoring
with manual start and manual restart, category 4 8-32
Safety sensors PSEN 2.1p-10 and PSEN 2.1p-11
with block SB066 (ST_K4) 8-36
ESPE/AOPD in guard mode with automatic function test
(SB068) 8-40
ESPE/AOPD in single break mode with cycle reset via a pulse at
top dead centre (TDC) 8-42
ESPE/AOPD in guard mode with automatic function test
(SB069) 8-44
Monitoring muting lamps 8-46
Safety gate monitoring with guard locking, automatic start and
manual restart, category 4 8-48
Modular Block System: Hydraulic Presses 9
Contents
Appendix 9-1
Assignment table
Category and requirement class 9-1
Standard function blocks: current versions 9-2
Changes to the standard function blocks 9-3
Changes to the operating manual 9-15
Allocation of safety subroutine numbers enable flags 9-17
10
Modular Block System: Hydraulic Presses
Modular Block System: Hydraulic Presses 11
Introduction
This manual describes how to manage the standard function blocks in the
“MBS Hydraulic Presses” software package in accordance with their
intended use.
Standard function blocks in the “MBS Hydraulic Presses” package are part
of the Pilz MBS Modular Block System. They can be used in the failsafe
section of a PSS-range programmable safety system.
To fully understand this manual you will need to be conversant with the
information found in the general documentation for the PSS-range
(System Manual, Installation Manual for the modular/compact PSS, PSS
SW PG Programming Manual/PSS WIN-PRO Programming Manual).
In particular you should refer to the following documents from the System
Manual:
• Safety Manual
• FS System Description
• Error List
To fully understand the bus-specific requirements and correlations for
SafetyBUS p applications you will need some knowledge of the design and
management of SafetyBUS p.
Knowledge of the safety regulations for the particular area of application is
assumed.
This installation manual is intended for instruction and should be retained
for future reference.
1-1Modular Block System: Hydraulic Presses
Introduction
MBS Modular Block System
Safety-related areas can be equipped with a multitude of safety devices
such as E-STOPs, safety gates, light barriers etc. Safety devices are
required in various quantities and combinations, depending on the object
requiring protection. The Pilz MBS Modular Block System was developed
to drive the various safety devices and to carry out process engineering
functions, helping users to save time and money.
The MBS consists of individual standard function blocks (SBs), which are
geared specifically towards the relevant safety device or process
engineering function. It allows standard function blocks to be used in any
combination. The standard function blocks can be combined in any
sequence (max. 600).
Standard function blocks are encoded by an authorised body so that they
cannot be modified. If an encoded standard function block is used within
an application program, program testing may be restricted to the new parts
of the program, considerably reducing the test time.
1-2
Modular Block System: Hydraulic Presses
Categories / requirement classes
EN 954-1 divides safety devices into categories.
All standard function blocks are designed for the highest category
permitted for the safety device to be monitored. If safety devices with lower
categories are to be monitored, input parameters may be assigned
identical inputs (further information can be found in the description for the
relevant standard function block).
In process engineering, safety requirements must conform to DIN V 19250
(Basic Safety Requirements for Measurement and Control Protection
Devices).
Requirement classes in accordance with DIN V 19250 may be referred to
the categories as per EN 954-1. The Appendix contains a table showing
the assignment of category ↔ requirement class.
1-3Modular Block System: Hydraulic Presses
Introduction
Overview of manual
1 Introduction
The chapter you are reading provides an introduction to the Modular
Block System (MBS). It is designed to familiarise you with the
contents, structure and specific order of this manual and also contains
terminology definitions.
2 Overview
This chapter provides information on the most important features of
the software package and provides a brief overview of the application
range.
3 Safety
This chapter must be read as it contains important information on
safety regulations.
4 Intended Use
This chapter must be read as it contains information on intended use.
5 MBS Basics
This chapter explains the basic functions and safety requirements of
the MBS.
6 Standard Function Blocks
This chapter explains the function of the standard function blocks in
the software package.
7 Link Blocks
This chapter is designed to help you link the standard function blocks
into your project and to commission the safety functions.
8 Examples
This chapter is designed to give an overview of how the standard
function blocks may be applied and contains typical application
examples.
9 Appendix
The Appendix contains a table that explains the relationship between
categories and requirement classes, plus a list that documents the
current version status of the standard function blocks.
1-4
Modular Block System: Hydraulic Presses
Definition of symbols
Information in this manual that is of particular importance can be identified
as follows:
DANGER!
This warning must be heeded! It warns of a hazardous situation that
poses an immediate threat of serious injury and death and indicates
preventive measures that can be taken.
WARNING!
This warning must be heeded! It warns of a hazardous situation that
could lead to serious injury and death and indicates preventive
measures that can be taken.
CAUTION!
This refers to a hazard that can lead to a less serious or minor injury plus
material damage, and also provides information on preventive measures
that can be taken.
NOTICE
This describes a situation in which the product or devices in its immediate
environment could be damaged. It also provides information on preventive
measures that can be taken.
INFORMATION
This gives advice on applications and provides information on special
features, as well as highlighting areas within the text that are of particular
importance.
1-5Modular Block System: Hydraulic Presses
Introduction
Terminology
• The term “input” is frequently abbreviated to “I” (e.g. I-Parameter).
• The term “output” is frequently abbreviated to “O” (e.g. O-Parameter).
• The term “PSS” is always used when the description is valid for all
applicable PSS programmable safety systems. If the description only
relates to a specific PSS series, the specific name for that series will be
used (e.g. PSS 3000 or PSS SB 3056).
• In this manual, the system software “PSS SW PG” and “PSS WIN-PRO”
is referred to as “programming device” or “PG”.
1-6
Modular Block System: Hydraulic Presses
Overview
Software package
The “MBS Hydraulic Presses” software package is part of the Pilz MBS
Modular Block System. The software package contains all the standard
function blocks necessary for electronically-monitored safety devices on
distributed automation plants. This includes:
• Monitoring the position of operating mode selector switches for safe
mode selection (automatic, manual, cycle mode etc.)
• Monitoring two-hand circuits for simultaneity
• Evaluation of E-STOP buttons, grab wires etc.
• Monitoring safety, maintenance and supply gates
• Monitoring of power contactors through control of the feedback loop
• Controlling and monitoring electrosensitive protective equipment
• Safe, temporary suspension of safety functions (muting mode)
• Driving and monitoring a press safety valve
• Monitoring enable switches
Standard function blocks in the “MBS Hydraulic Presses” software
package are used in the failsafe section of a PSS-range programmable
safety system.
2-1Modular Block System: Hydraulic Presses
Overview
Range
The software package consists of:
• The files for the software package on CD and
• An operating manual:
PSS Standard Function Blocks MBS Hydraulic Presses, Version 3.2
The software package on the CD contains the following standard function
blocks:
• SB051 BA_1AUS8
Operating mode selector switch 1 from 8
(approved safety block)
• SB052 BA_2AUS6
Operating mode selector switch 2 from 6
(approved safety block)
• SB059 2_HAND
Two-hand monitoring
(approved safety block)
• SB061 NA_1
Monitoring E-STOP button up to category 4 in accordance with
EN 954-1, 03/97 and AK 6 in accordance with DIN V 19 250,
05/94
(approved safety block)
• SB063 E-STOP
Monitoring E-STOP button up to category 4 in accordance with
EN 954-1, 03/97 and AK 6 in accordance with DIN V 19 250,
05/94
(approved safety block)
• SB064 S-GATE
Safety gate monitoring
(approved safety block)
• SB065 FBL
Feedback loop monitoring
(approved safety block)
2-2
• SB066 ST-K4
Safety gate monitoring
(approved safety block)
Modular Block System: Hydraulic Presses
• SB067 RFK_K4
Feedback loop monitoring
(approved safety block)
• SB068 BWS_AOS
Monitoring ESPE/AOPD with guarding and control function
(approved safety block)
• SB069 AOPD_GDO
Monitoring ESPE/AOPD with guarding function
(approved safety block)
• SB070 INIT_MBS
Initialisation of the administration data block (DB015)
(approved safety block)
• SB071 INIT_MBS
Initialisation of the administration data blocks (DB015/DB016/
DB017)
(approved safety block)
• SB072 MUTING
Temporary suspension of safety functions
(approved safety block)
• SB075 GRD_LCK
Control and monitoring of safety gates with guard locking
(approved safety block)
• SB086 OVERRUN
Overrun control on linear-driven presses
(approved safety block)
• SB087 H_VALV_S
Control and position monitoring of single hydraulic valves
(poppet valve and directional control valve)
(approved safety block)
• SB088 H_VALV_D
Control and position monitoring of dual hydraulic valves
(poppet valve and directional control valve)
(approved safety block)
• SB089 H_VALV_P
Sequential control and position monitoring of two hydraulic
valves (poppet valve and directional control valve)
(approved safety block)
2-3Modular Block System: Hydraulic Presses
Overview
• SB092 ENBL_DEV
Enable switch
(approved safety block)
• SB097 MUT_LAMP
Monitoring muting lamps
(approved safety block)
• SB255 System block
SB255 is described in the PSS System Description
2-4
Modular Block System: Hydraulic Presses
Safety
Safety guidelines
These safety guidelines are an important part of this manual. Failure to
keep to these guidelines will render all warranty, guarantee and liability
claims invalid.
• All health and safety / accident prevention regulations for the particular
area of application must be observed.
• Before using one or more of the standard function blocks in this software
package, you must perform a safety assessment in accordance with the
Machinery Directive.
Use of qualified personnel
The package may only be assembled, installed, commissioned, operated,
maintained and decommissioned by qualified personnel who, because
they are
• Qualified electrical engineers and/or
• Have received training from qualified electrical engineers
are suitably experienced to operate devices, systems, plant and machinery
in accordance with the general standards and guidelines for safety
technology.
Warranty and liability
All claims to warranty and liability will be rendered invalid if:
• Standard function blocks are used contrary to the purpose for which they
were intended
• Damage can be attributed to not having followed the guidelines in the
manual
• Operating personnel are not suitably qualified.
3-1Modular Block System: Hydraulic Presses
Safety
Application guidelines
• The instructions given in the “Safety Manual” and in the “Installation
Manual” must be followed.
• Please read the information in Chapter 4 regarding the intended use of
these blocks.
• The use of Pilz SBs does not detract from the fact that it is the
responsibility of the user to design appropriate safety systems for plant,
machinery and software.
• It is the users' responsibility to determine their application requirements
by carrying out a detailed risk analysis, which should take into account
relevant regulations and standards, etc.
WARNING!
Please note: To achieve the corresponding category or requirement class,
the whole system including all safety-related components (parts, devices,
user program etc.) must be included in the assessment. For this reason,
Pilz cannot accept liability for the correct classification into a category or
requirement class.
3-2
Modular Block System: Hydraulic Presses
Standards
To use the SBs correctly you will need to have a good knowledge of the
relevant standards and directives. The following gives an overview of the
most important standards:
• E-STOP circuits EN 418
• Safety of machinery -
Two-hand controls EN 574
• Mechanical presses EN 692
• Hydraulic presses EN 693
• Hydraulic stamping and bending presses EN 12 622
• Machinery directive- basic terminology EN 292-1 and EN 292-2
• Printing and paper machinery prEN 1010
• Safety gates EN 1088
• Electrosensitive protective equipment EN 61 496-1
• Electrical equipment EN 60 204-1
• Machinery safety EN 954-1
• Basic Safety Requirements for Mea-
surement and Control Protection Devices DIN V 19 250
• Electrical equipment on firing plants prEN 50 156-1
Please note this is not an exhaustive list of safety standards and
directives.
3-3Modular Block System: Hydraulic Presses
Safety
Fault detection
The detection of errors and defects is an important function of the PSS, in
addition to pure control tasks.
Potential faults are subdivided into:
• Errors in the system hardware and wiring errors in the periphery units:
• Feasibility errors and functional errors in the process periphery units
- Errors in the system hardware are automatically detected and managed
by the PSS
- If test signals are used, wiring errors in the periphery units will
automatically be detected and managed by the PSS.
Users do not need to take this type of error into account within the
application program (additional information can be found in the PSS
“System Description”).
(input devices, actuators, wiring etc.).
These errors must be detected and managed through the PSS control
program.
WARNING!
It is particularly important to detect open circuits and shorts within the
safety circuits (e.g. two-hand, E-STOP etc.)
It is the responsibility of the user to select and apply an appropriate fault
detection system.
3-4
Modular Block System: Hydraulic Presses
Fault detection techniques
Various options are available to the user to help detect and rectify errors in
the process periphery units:
• Errors can be detected via the feasibility checks in the application program, e.g. by using redundant input devices.
• Errors can be detected by pulsing the signal lines using the test pulses
from the PSS DI2O T module.
• Errors can be detected by using the automatic tests in the output
modules.
• Avoid potential errors by using appropriate wiring.
Additional information on how to exclude potential errors can be found in
the directive VDI 2854 (safety requirements on automated manufacturing
systems).
Feasibility test
Redundant input devices for safety functions must undergo a feasibility
test within the application program.
Example:
A two-hand button has a N/C and a N/O contact. Once the application
program has detected the open N/C contact, it must check that the N/O
contact closes within an appropriate period of time. The function test
must be carried out for all possible combinations of the two contacts.
The plant must be stopped immediately if a feasibility error occurs. Similar
tests will also be required for other input devices.
If safety valves have feedback contacts, these must be evaluated
accordingly.
3-5Modular Block System: Hydraulic Presses
Safety
Pulsed input signals
Input devices for inputs with infrequent operation (e.g. E-STOP, off
buttons, etc.) must be pulsed using test signals. The connection of test
pulses to input devices is described in the “Installation Manual”.
Test pulses should also be used for input devices which have an important
safety function and frequent operation (e.g. two-hand, camshaft etc.).
Self test on the outputs
PSS output modules regularly carry out function tests. Using these tests,
dual-pole switching output modules on the PSS are automatically able to
detect and deal with open circuits, short circuits and external power
sources in the periphery wiring.
Single-pole switching output modules can detect short circuits but not
open circuits.
Fault prevention
Not all potential faults can be detected and managed. Such faults must be
excluded by suitable wiring.
Example: If the feed to the input device and the feedback from the input
device to the input use the same multicore cable, a short circuit between
the two wires could short out the input device. Such a fault would go
undetected.
3-6
Modular Block System: Hydraulic Presses
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