Reed switches - Part 3: Reliability data for reed switch-devices in typical safety applications

IEC TR 62246-3:2018(E) provides basic technical background and experience about reliability data for reed switch-devices applied to machinery systems as well as E/E/PE safety-related control systems during the life cycle phases in general and industrial safety applications.
The document selects typical safety applications from group safety standards, and includes national safety standards and regulations accordingly. This document shows major reliability aspects for a proper design according to the standards, but it does not cover all details of an individual design. The responsibility for the verification of system design remains with the system integrator/manufacturer.

General Information

Status
Published
Publication Date
20-Jun-2018
Current Stage
PPUB - Publication issued
Completion Date
21-Jun-2018
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IEC TR 62246-3
Edition 1.0 2018-06
TECHNICAL
REPORT
colour
inside
Reed switches –
Part 3: Reliability data for reed switch-devices in typical safety applications
IEC TR 62246-3:2018-06(en)
---------------------- Page: 1 ----------------------
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IEC TR 62246-3
Edition 1.0 2018-06
TECHNICAL
REPORT
colour
inside
Reed switches –
Part 3: Reliability data for reed switch-devices in typical safety applications
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.120.70 ISBN 978-2-8322-5811-8

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TR 62246-3:2018 © IEC 2018
CONTENTS

FOREWORD ........................................................................................................................... 5

INTRODUCTION ..................................................................................................................... 7

1 Scope .............................................................................................................................. 8

2 Normative references ...................................................................................................... 8

3 Terms and definitions ...................................................................................................... 8

3.1 Failure of systems ................................................................................................... 9

3.2 Confirmation of safety measures for reed switch-devices ........................................ 9

3.3 Reliability data of reed switch-devices .................................................................. 10

3.4 Functional safety of reed switch-devices ............................................................... 11

4 Approach adopted for this document.............................................................................. 12

4.1 General ................................................................................................................. 12

4.2 Application of reed switches in accordance with IEC 62246 (all parts) ................... 12

4.3 Application in accordance with ISO 13849 (all parts), IEC 62061 and

IEC 61508 (all parts) ............................................................................................. 13

4.4 Application of the design of the E/E/PE safety-related system ............................... 13

4.5 Application of SIL capability to function units ........................................................ 14

4.5.1 General ......................................................................................................... 14

4.5.2 Procedures .................................................................................................... 14

4.5.3 Random hardware failures ............................................................................. 14

4.5.4 Systematic faults ........................................................................................... 15

4.5.5 Safety manual ............................................................................................... 15

4.5.6 Application of SIL capability for the allocation of SIL to systems .................... 15

5 Examples of reliability data for reed switch-devices ....................................................... 16

6 Examples of classification of involved groups for responsibility ...................................... 16

Annex A (informative) Hydraulic and pneumatic fluid power ................................................. 17

A.1 Example of electric actuator in hydraulic fluid power ............................................. 17

A.2 Examples of group safety standards ..................................................................... 17

A.3 Example of safety requirements ............................................................................ 17

A.4 Example of safety measures for the reed switch-device ........................................ 17

A.4.1 Usage conditions of end-user ........................................................................ 17

A.4.2 Usage conditions of the reed switch-device ................................................... 18

A.5 Example of calculation of failure rates for the reed switch-device .......................... 19

A.5.1 Dangerous failure rate of the reed switch-device ........................................... 19

A.5.2 Estimates for diagnostic coverage (DC) ......................................................... 20

A.5.3 Estimates for common cause failure (CCF) .................................................... 20

A.6 Example of classification of involved groups for responsibility ............................... 20

Annex B (informative) Safety of machinery........................................................................... 21

B.1 Example of guard interlocking device .................................................................... 21

B.2 Example of group safety standards ....................................................................... 21

B.3 Example of safety requirements for the system ..................................................... 21

B.3.1 Description of Type 3 interlocking device – example ...................................... 21

B.3.2 Typical characteristics ................................................................................... 22

B.3.3 Remarks ........................................................................................................ 22

B.3.4 Description of Type 4 interlocking device – example ...................................... 23

B.3.5 Typical characteristics ................................................................................... 23

B.3.6 Remarks ........................................................................................................ 23

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IEC TR 62246-3:2018 © IEC 2018 – 3 –

B.4 Example of safety measures for the reed switch-device ........................................ 23

B.4.1 Usage conditions of end-user ........................................................................ 23

B.4.2 Usage conditions of the reed switch-device ................................................... 24

B.5 Example of calculation of failure rates for the reed switch-device .......................... 24

B.5.1 General ......................................................................................................... 24

B.5.2 Dangerous failure rate of reed switch-device ................................................. 24

B.5.3 Estimation for diagnostic coverage (DC) ........................................................ 24

B.5.4 Estimates for common cause failure (CCF) .................................................... 24

B.6 Example of classification of involved groups for responsibility ............................... 25

Annex C (informative) Automatic electrical controls for household and similar use ............... 26

C.1 Example of automatic electrical burner control system .......................................... 26

C.2 Examples of group safety standards ..................................................................... 26

C.3 Example of safety requirements for the system ..................................................... 26

C.4 Example of safety measures for the reed switch-device ........................................ 27

C.4.1 Usage conditions of end-user ........................................................................ 27

C.4.2 Usage conditions of reed switch-device ......................................................... 28

C.5 Example of calculation of failure rates for the reed switch-device .......................... 28

C.5.1 Dangerous failure rate of reed switch-device ................................................. 28

C.5.2 Estimates for diagnostic coverage (DC) ......................................................... 29

C.5.3 Estimates for common cause failure (CCF) .................................................... 29

C.5.4 Accident damage reduction ............................................................................ 29

C.6 Example of classification of involved groups for responsibility ............................... 29

Annex D (informative) Household and similar electric appliances ......................................... 31

D.1 Example of automatic electric washing machine .................................................... 31

D.2 Examples of group safety standards ..................................................................... 31

D.3 Example of safety requirements for the system ..................................................... 31

D.4 Example of safety measures for the reed switch-device ........................................ 31

D.4.1 Usage conditions of end-user ........................................................................ 31

D.4.2 Usage conditions of reed switch-device ......................................................... 32

D.5 Example of calculation of failure rates for the reed switch-device .......................... 33

D.5.1 Dangerous failure rate of reed switch-device ................................................. 33

D.5.2 Estimates for diagnostic coverage (DC) ......................................................... 33

D.5.3 Estimation for common cause failure (CCF) ................................................... 33

D.6 Example of classification of involved groups for responsibility ............................... 33

Annex E (informative) Electric power systems ...................................................................... 35

E.1 Example of measuring and protection relay system ............................................... 35

E.2 Industrial standards .............................................................................................. 35

E.3 Safety requirements for the system – example ...................................................... 35

E.4 Safety measures for the reed switch device – example ......................................... 35

E.4.1 Usage conditions of end-user ........................................................................ 35

E.4.2 Usage conditions of the reed switch-device ................................................... 36

E.5 Example of the calculation of failure rates for the reed switch-device .................... 37

E.6 Example of classification of involved groups for responsibility ............................... 37

Annex F (informative) Railway application ............................................................................ 39

F.1 Example of automatic train control (ATC) system .................................................. 39

F.2 Examples of group safety standards ..................................................................... 39

F.3 Example of safety requirements for the system ..................................................... 39

F.4 Example of safety measures for the reed switch-device ........................................ 39

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– 4 – IEC TR 62246-3:2018 © IEC 2018

F.4.1 Usage conditions of end-user ........................................................................ 39

F.4.2 Usage conditions of the reed switch-device ................................................... 40

F.5 Example of calculation of failure rates for the reed switch-device .......................... 41

F.6 Example of classification of involved groups for responsibility ............................... 42

Bibliography .......................................................................................................................... 43

Figure A.1 – Architecture of an electric actuator in hydraulic fluid power ............................... 18

Figure A.2 – Control circuit of reed switches of magnetic proximity switches ......................... 19

Figure A.3 – B value estimated by Weibull analysis ........................................................... 19

Figure B.1 – Electric interlocking device with a proximity switch actuated by a magnet

actuator ................................................................................................................................ 22

Figure B.2 – Electric interlocking device with two proximity switches .................................... 22

Figure B.3 – Typical architecture of guard interlocking device ............................................... 23

Figure C.1 – Architecture of a microcomputer type gas meter ............................................... 27

Figure C.2 – Control circuit of a reed switch in flow sensor ................................................... 28

Figure C.3 – Accident occurrences and casualties by year (Japan) ....................................... 29

Figure D.1 – Architecture of an automatic electric washing machine ..................................... 32

Figure D.2 – Control circuit of a magnetic proximity switch.................................................... 33

Figure E.1 – Architecture of a measuring and protection relay system .................................. 36

Figure E.2 – Control circuit of a reed switch in a measuring and protection relay .................. 37

Figure F.1 – Architecture of the automatic train control (ATC) system ................................... 40

Figure F.2 – Control circuit of reed switches in the ATC system ............................................ 41

Table 1 – Diagnostic coverage (DC) ..................................................................................... 10

Table 2 – Maximum allowable safety integrity level for a safety function carried out by

a type A safety-related element or subsystem ....................................................................... 13

Table 3 – Performance level ................................................................................................. 13

Table 4 – Architectural constraints on subsystems: maximum SIL that can be claimed

for a safety-related control function (SRCF) using this subsystem ......................................... 14

Table A.1 – Possible sharing of responsibility on an electric actuator .................................... 20

Table B.1 – Possible sharing of responsibility on a guard interlocking device ........................ 25

Table C.1 – Detection methods and action in the event of emergency ................................... 26

Table C.2 – Possible sharing of responsibility on microcomputer type gas meter .................. 30

Table D.1 – Possible sharing of responsibility on an automatic electric washing

machine ................................................................................................................................ 34

Table E.1 – Failure rates of reed relays in a measuring and protection relay system ............. 37

Table E.2 – Possible sharing of responsibility on a measuring and protection relay

system .................................................................................................................................. 38

Table F.1 – Field failure rates of reed relays in the ATC system ............................................ 41

Table F.2 – Possible sharing of responsibility on reed relays in the ATC system ................... 42

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IEC TR 62246-3:2018 © IEC 2018 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
REED SWITCHES –
Part 3: Reliability data for reed switch-devices
in typical safety applications
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

The main task of IEC technical committees is to prepare International Standards. However, a

technical committee may propose the publication of a technical report when it has collected

data of a different kind from that which is normally published as an International Standard, for

example "state of the art".

IEC TR 62246-3, which is a Technical Report, has been prepared by IEC technical committee

94: All-or-nothing electrical relays.
The text of this Technical Report is based on the following documents:
Draft TR Report on voting
94/425/DTR 94/429/RVDTR

Full information on the voting for the approval of this Technical Report can be found in the

report on voting indicated in the above table.
---------------------- Page: 7 ----------------------
– 6 – IEC TR 62246-3:2018 © IEC 2018

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 62246 series, published under the general title Reed switches, can

be found on the IEC website.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct

understanding of its contents. Users should therefore print this document using a

colour printer.
---------------------- Page: 8 ----------------------
IEC TR 62246-3:2018 © IEC 2018 – 7 –
INTRODUCTION
This Technical Report:

– provides reliability data for reed switch-devices applied to machinery systems and also

E/E/PE systems;

– selects typical safety applications for reed switch-devices according to the requirements

from typical group safety standards;

– selects references, terms and definitions for machinery systems, E/E/PE systems and reed

switch-devices, lifecycle activities, safety integrity and performance level, failures and

safety measures for the reed switch-devices from typical group safety standards;

– addresses a way to share the responsibility on the components in the life cycle phases;

– addresses the application of IEC 62246 (all parts);

– considers the relation between safety requirements for the system from industrial

standards and basic safety measures for the reed switch-devices of a single E/E/PE

safety-related system and for two E/E/PE safety-related systems operating in:
• a low demand mode of operation,
• a high demand or continuous mode of operation.
– considers usage conditions at the end-user side:
• environmental conditions for reed switches’ use;
• proof test period;
• preventive maintenance.
– considers usage conditions at the E/E/PE system manufacturer side:
• switching load;
• failure mode;
• diagnostic coverage for reed switch-devices.
– considers usage conditions at the component manufacturer side:

– considers how to evaluate the risk of the reed switch-devices fault occurrence based on

the requirements from ISO 13849 (all parts), IEC 62061 and IEC 61508 (all parts):

– addresses a way to calculate reliability data of the reed switch-devices based on the

requirements from ISO 13849 (all parts), IEC 62061 and IEC 61508 (all parts)

– analyses dangerous failure rates, B values of the reed switch-devices according to the

10D
switching loads;

– calculates dangerous failure rates of the reed switch-devices based on usage rate per

year;

– considers long-term field demonstration tests and operating experiences of the systems.

---------------------- Page: 9 ----------------------
– 8 – IEC TR 62246-3:2018 © IEC 2018
REED SWITCHES –
Part 3: Reliability data for reed switch-devices
in typical safety applications
1 Scope

This part of IEC 62246, which is a Technical Report, provides basic technical background and

experience about reliability data for reed switch-devices applied to machinery systems as well

as E/E/PE safety-related control systems during the life cycle phases in general and industrial

safety applications.

The document selects typical safety applications from group safety standards, and includes

national safety standards and regulations accordingly. This document shows major reliability

aspects for a proper design according to the standards, but it does not cover all details of an

individual design. The responsibility for the verification of system design remains with the

system integrator/manufacturer.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their

content constitutes requirements of this document. For dated references, only the edition

cited applies. For undated references, the latest edition of the referenced document (including

any amendments) applies.

IEC 61508 (all parts), Functional safety of electrical/electronic/programmable electronic

safety-related systems

IEC 62061:2005, Safety of machinery – Functional safety of safety-related electrical,

electronic and programmable electronic control systems
IEC 62061:2005/AMD1:2012
IEC 62061:2005/AMD2:2015

IEC 62246-1-1:2018, Reed switches – Part 1-1: Generic specification – Blank detail

specification

ISO 13849 (all parts), Safety of machinery – Safety-related parts of control systems

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 13849 (all parts),

IEC 62061, IEC 61508 (all parts), and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
---------------------- Page: 10 ----------------------
IEC TR 62246-3:2018 © IEC 2018 – 9 –
3.1 Failure of systems
3.1.1
average probability of failure on demand
PFD
avg

mean unavailability (see IEC 60050-191) of an E/E/PE safety-related system to perform the

specific safety function when a demand occurs from the EUC or EUC control system

Note 1 to entry: The mean unavailability over a given time interval [t1, t2] is generally noted by U (t1, t2).

Note 2 to entry: Two kind of failures contribute to PFD and PFD : the dangerous undetected failures that have

avg

occurred since the last proof test and genuine on demand failures caused by the demands (proof tests and safety

demands) themselves. The first one is time dependent and characterized by their dangerous failure rate λ (t)

whilst the second one is dependent only on the number of demands and is characterized by a probability of failure

per demand (denoted by γ).

Note 3 to entry: As genuine on-demand failures cannot be detected by tests, it is necessary to identify them and

take them into consideration when calculating the target failure measures.
[SOURCE: IEC 61508-4:2010, 3.6.18]
3.1.2
probability of dangerous failure per hour
PFH

average probability of dangerous failure per hour in a safety-related control system or

subsystem

[SOURCE: IEC 61508-4:2010, 3.6.19, modified – Replacement of "of an E/E/PE safety

related system to perform the specified safety function over a given period of time" by " per

hour in a safety-related control system or subsystem" and deletion of the notes to entry.]

3.2 Confirmation of safety measures for reed switch-devices
3.2.1
proof test period

periodic test performed to detect failures in a reed switch-device so that, if necessary, the

reed switch-device can be restored to an “as new” condition or as close as practical to this

condition

Note 1 to entry: The effectiveness of the proof test will be dependent upon how close to the “as new” condition

the system is r
...

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