ABB AC500-S Installation and operating instructions

AC500-S

Usage of AC500 Digital Standard I/Os

in Functional Safety Applications

up to PL c (ISO 13849-1)

Application Note

Application Note for “Usage of AC500 digital standard I/Os in functional safety applications up to PL c (ISO 13849-1)”, V1.0.0

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Contents

1Introduction _____________________________________________________3

1.1 Purpose .............................................................................................................................3

1.2 Document history...............................................................................................................4

1.3 Validity...............................................................................................................................4

1.4 Important user information..................................................................................................4

1.5 Definitions, expressions, abbreviations...............................................................................4

1.6 References / Related documents........................................................................................5

2Usage of digital standard I/Os in functional safety applications up to PL c _____6

2.1 Overview............................................................................................................................6

2.2 Task...................................................................................................................................8

2.3 Solution..............................................................................................................................8

3Example ______________________________________________________14

3.1 General............................................................................................................................14

3.2 Safety function.................................................................................................................14

3.3 Functional description.......................................................................................................15

3.4 Design features................................................................................................................16

3.4.1 Implementation details 16

3.4.2 Common cause failures 18

3.4.3 Systematic failures 19

3.4.4 Safety function response time 20

3.5 Calculation of the probability of failure and correspondence to PL (ISO 13849-1)..............20

4Conclusion_____________________________________________________23

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1 Introduction

1.1 Purpose

The number of used digital safety input channels in safety applications is often signifi-

cantly higher than the number of digital safetyoutput channels. In some customer PLC

applications, there are often free spare digital standard I/O channels. There is a ques-

tion if thesefree spare digital standard I/O channels can be used together with SM560-

S Safety CPU to realize functional safety functions. If yes, one could avoid using addi-

tional Safety I/O modules with digital safety input channels and, thus, save control sys-

tem costs and reduce control cabinet dimensions in some customer applications.

We analyzed a possible usage of AC500 digital standard I/Os to realize functional

safety functions. This application note describes a possible usage of digital standard

I/O modules from AC500 platform (www.abb.com/PLC) in functional safety application

up to PL c (ISO 13849-1). The functional safety calculation according to ISO 13849-1

is used as an example to show the compliance of the proposed approach with the

relevant functional safety requirements for PL c (ISO 13849-1). The functional safety

calculation according to IEC 62061 standard (applications up to SIL CL 1) can be sim-

ilarly done, if required.

In special cases, digital standard I/O modules from AC500 platform can be also used

in functional safety applications up to PL d (ISO 13849-1) and SIL CL 2 (IEC 62061).

However, more detailed functional safety application analysis is required (contact

AC500 technical support at www.abb.com/PLC for more details) and, thus, is not

shown in this document.

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1.2 Document history

Rev.

Description of

version / c

hanges

Who

Date

1.0.0 Final release ABB 15.12.2015

1.3 Validity

The data and illustrations found in this documentation are not binding. ABB reserves

the right to modify its products in line with its policy of continuous product development.

ABB assumes no liability or responsibility for any consequences arising from the use

of this document information. ABB is in particular in no way liable for missed profits,

loss of income, loss of life, loss of use, loss of production, capital costs or costs asso-

ciated with an interruption to operation, the loss of expected savings or for indirect or

follow up damages or losses no matter of what kind.

1.4 Important user information

This documentation is intended for qualified personnel familiar with Functional Safety.

You must read and understand the safety concepts and requirements presented in

AC500-S Safety User Manual [1] as well as further referenced documents prior to op-

erating AC500-S Safety PLC system.

The following special notices may appear throughout this documentation to warn of

potential hazards or to call attention to specific information.

DANGER

The notices referring to your personal safety are highlighted in the

manual by this safety alert symbol, which indicates that death or

severe personal injury may result if proper precautions are not

taken.

NOTICE

This symbol of importance identifies information that is critical for

successful application and understanding of the product. Itindicates

that an unintended result can occur if the corresponding information

is not taken into account.

1.5 Definitions, expressions, abbreviations

AC500 ABB PLC, refer also to www.abb.com/PLC for further details

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AC500-S ABB Safety PLC for applications up to SIL3 (IEC 61508 ed. 2 and

IEC 62061) and PL e (ISO 13849-1), refer also to

www.abb.com/PLC for further details

AB Automation Builder (ABB Automation Builder is the integrated soft-

ware suite for machine builders and system integrators which co-

vers the engineering of ABB AC500 PLC, AC500-S Safety PLC,

control panels, drives, motion and robots)

CCF Common Cause Failure

CPU Central Processing Unit

DCavg Diagnostic Coverage - average

DPRAM Dual-ported Random Access Memory

IEC International Electro-technical Commission Standard

I/O Input/Output

EMC Electromagnetic compatibility

FB Function Block

FSDT Functional Safety Design Tool (ABB tool for functional safety calcu-

lation according to ISO 13849-1 and/or IEC 62061)

MTBF Mean Time Between Failures

MTTFd Mean Time To Failure dangerous

PFH Probability of Failure per Hour (1/h)

PL Performance Level according to ISO 13849-1

PLC Programmable Logic Controller

SIL Safety Integrity Level (IEC 61508 ed. 2)

TÜV Technischer Überwachungs-Verein (Technical Inspection Associa-

tion)

1.6 References / Related documents

[1] AC500-S Safety User Manual, 3ADR025091M0204

[2] Cyclic Non-safe Data Exchange between SM560-S Safety CPU and PM5xx

Non-Safety CPU, 3ADR025195M0201

[3] BGIA Report 2/2008e, Functional safety of machine controls - Application of

EN ISO 13849

[4] AC500 Documentation, refer to www.abb.com/PLC and then navigate to

Downloads area

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2 Usage of digital standard I/Os in functional safety

applications up to PL c

2.1 Overview

In this document, we discuss the usage of AC500 digital standard I/O modules on the

input side of AC500-S Safety PLC. The output side has to be implemented using safety

output modules as further explained in the notice below. SM560-S Safety CPU has to

be used for safety logic processing and diagnostic measures for digital standard I/O

modules.

NOTICE

Usage of standard output channels on standard I/O modules in

AC500 platform for functional safety applications is not considered

in this document because of the complexity of its implementation in

practice and results in very limited cost saving (two output channels

from two different standard output modules will be needed (contact

ABB technical support at www.abb.com/PLC for more details)). As

a result, safety output channels from DX581-S module [1] or built-

in drive safety functions (Safe Torque Off, Safe Stop 1, Safely Lim-

ited Speed, etc.) accessible through PROFINET / PROFIsafe [1]

shall be used on the output side of the Safety PLC.

Figure 1 gives an overview on the minimumexemplary AC500 configuration to be used

for PL c safety functions with digital standard I/O modules (PM573 standard CPU and

DC523 digital standard I/O modules are taken as examples here but other CPUs and

I/O modules from the AC500 range could also be used).

DX581-S digital safetyinput/output module is includedin Figure 1 as one of options for

Safety PLC output part (another option is the usage of PROFINET/PROFIsafe com-

munication to trigger safety functions in drives with safety option). In addition to avail-

able digital safety input channels on DX581-S, one can use digital standard I/O chan-

nels from standard I/O modules, like DC523.

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Figure 1. Basic setup with AC500/AC500-S modules for usage of AC500 digital

standard I/O modules in functional safety application up to PL c

Remote digital standard I/O modules can be used as well (refer to www.abb.com/PLC

for more details on available AC500 modules).

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2.2 Task

We want to show and describe an approach how AC500 digital standard I/O channels

can be used for functional safety applications up to PL c (ISO 13849-1) in combination

with SM560-S Safety CPU.

NOTICE

It is always highly recommended to use digital safety input channels

even for functional safety applications up to PL c (ISO 13849-1).

Thus, the presented approach with the usageof digital standard I/O

channels is only an option if spare digital standard I/O channels are

available and their reuse for functional safety functions up to PL c

is needed to satisfy specific customer requirements (e.g., limited

space in the control cabinet to add additional digital safetyI/O mod-

ule, cost saving, etc.).

Customer benefits from using spare AC500 digital standard I/O channels for functional

safety applications up to PL c (ISO 13849-1) are:

- Smaller control cabinet dimensions are possible

- Cost savings on additional Safety I/O modules.

2.3 Solution

The proposed solutionis based on the design analysis andadditional diagnostic safety

measures which can be implemented using AC500/AC500-S setup shown in Figure 1

to enable usage of AC500 digital standard I/O channels in functional safety applica-

tions up to PL c (ISO 13849-1).

Figure 2 shows an overview on reachable Performance Levels depending on Cate-

gory, DCavg and MTTFd values, as defined in ISO 13849-1. As one can see from

Figure 2 (see a selection in blue), one of the most attractive approaches to satisfy PL

c (MTTFd = High or Medium) and even PL d (MTTFd = High) requirements is the usage

of Category 2, DCavg = Low.

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Figure 2. Relationship between Categories, DCavg, MTTFd of each channel and PL

from ISO 13849-1 with a focus on Category 2

Category 2 architecture based on ISO 13849-1 is shown in Figure 3.

Figure 3. Category 2 architecture from ISO 13849-1

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Key requirements for Category 2 (ISO 13849-1) are: