prEN 764-7

Pressure equipment - Part 7: Safety systems for unfired pressure equipment

This document specifies the requirements for safety systems which protect a vessel, a system of vessels, piping, accessories or assemblies from exceeding operating conditions.
It is also applicable to safety related indicators and alarms, signals and warning devices when used in safety systems.
Equipment connected together by piping of adequate capacity, free from potential blockages and which does not contain any valve that can isolate any part from the safety system, may be considered as a single pressure system when considering the requirements for overpressure protection.
Safety systems include the interconnections between the equipment to be protected and any discharge location. This location can either be an outlet to atmosphere or the entry into a closed disposal system.
NOTE   The scope of this document and its relationship to the safety accessories and other protective devices described in the Pressure Equipment Directive are shown in Annex E.

Druckgeräte - Teil 7: Sicherheitseinrichtungen für unbefeuerte Druckgeräte

Dieses Dokument legt die Anforderungen an Sicherheitseinrichtungen zum Schutz von Druckbehältern, Systemen von Druckbehältern, Rohrleitungen, Ausrüstungsteilen und Baugruppen vor unzulässigen Betriebsbedingungen fest.
Sie beinhaltet auch sicherheitsrelevante Anzeige- und Alarmeinrichtungen, Signale und Warneinrichtungen, sofern diese in Sicherheitseinrichtungen verwendet werden.
Geräte, die über Rohrleitungen ausreichenden Querschnitts, ohne eventuelle Sperren und ohne irgendein Ventil, das Bereiche des Sicherheitssystems abtrennen kann, mit Systemen verbunden sind, dürfen in Bezug auf die Anforderungen an die Absicherung gegen Drucküberschreitung als einfaches Drucksystem betrachtet werden.
Sicherheitseinrichtungen schließen die Verbindungen zwischen dem zu schützenden Gerät und der gesamten Abblaseleitung ein. Es kann sich dabei um eine Ableitung in die Atmosphäre oder in ein geschlossenes Entsorgungssystem handeln.
ANMERKUNG   Der Anwendungsbereich dieses Dokuments, bezogen auf die in der Druckgeräterichtlinie beschriebenen Ausrüstungsteile mit Sicherheitsfunktion und weitere Einrichtungen mit Schutzfunktion, ist in Anhang E dargestellt.

Équipements sous pression - Partie 7 : Systèmes de sécurité pour équipements sous pression non soumis à la flamme

Le présent document prescrit les exigences applicables aux systèmes de sécurité qui protègent un récipient, un système de récipients, une tuyauterie, des accessoires ou des ensembles vis-à-vis de dépassements des conditions de fonctionnement.
Il est également applicable aux indicateurs et alarmes liés à la sécurité, aux dispositifs de signalisation et d’avertissement lorsqu’ils sont utilisés en tant que systèmes de sécurité.
Les équipements raccordés les uns aux autres dans un système par des tuyauteries de débit adéquat, exempts de blocages potentiels et ne comprenant pas d’appareil de robinetterie susceptible d'isoler une partie quelconque, peuvent être considérés comme un système sous pression unique eu égard aux exigences de protection vis à vis des surpressions.
Les systèmes de sécurité comprennent les interconnexions entre les équipements devant être protégés et tout point de décharge. Cet emplacement peut être un orifice de sortie à l'atmosphère ou le raccordement à un système de récupération fermé.
NOTE   Le domaine d’application du présent document et ses relations avec les accessoires de sécurité et les autres dispositifs de protection de la Directive Équipements sous pression sont indiqués en Annexe E.

Tlačna oprema - 7. del: Varnostni sistemi za nekurjeno tlačno opremo

General Information

• Status: Withdrawn
• Publication Date: 15-Jan-2020
• Withdrawal Date: 15-Apr-2020
• ICS: 23.020.30 - Pressure vessels, gas cylinders
• Technical Committee: CEN/TC 54 - Unfired pressure vessels
• Drafting Committee: CEN/TC 54/WG 55 - E - Inspection and testing
• Current Stage: 4599 - Dispatch of FV draft to CMC - Finalization for Vote
• Start Date: 15-Oct-2020
• Due Date: 13-Mar-2020
• Completion Date: 15-Oct-2020
• Directive: 2014/68/EU - Directive 2014/68/EU of the European Parliament and of the Council of 15 May 2014 on the harmonisation of the laws of the Member States relating to the making available on the market of pressure equipment
• Mandate: M/071 - Mandate to CEN for standardization in the field of Pressure equipment
• Ref Project: oSIST prEN 764-7:2019 - Pressure equipment - Part 7: Safety systems for unfired pressure equipment

Relations

• Revises: EN 764-7:2002 - Pressure equipment - Part 7: Safety systems for unfired pressure equipment
• Effective Date: 19-Jan-2023

Standards Content (Sample)

SLOVENSKI STANDARD
oSIST prEN 764-7:2019
01-november-2019
Tlačna oprema - 7. del: Varnostni sistemi za nekurjeno tlačno opremo
Pressure equipment - Part 7: Safety systems for unfired pressure equipment
Druckgeräte -Teil 7: Sicherheitseinrichtungen für unbefeuerte Druckgeräte

Équipements sous pression - Partie 7 : Systèmes de sécurité pour équipements sous

pression non soumis à la flamme
Ta slovenski standard je istoveten z: prEN 764-7
ICS:
23.020.32 Tlačne posode Pressure vessels
oSIST prEN 764-7:2019 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
oSIST prEN 764-7:2019
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oSIST prEN 764-7:2019
DRAFT
EUROPEAN STANDARD
prEN 764-7
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2019
ICS 23.020.30 Will supersede EN 764-7:2002
English Version
Pressure equipment - Part 7: Safety systems for unfired
pressure equipment

Équipements sous pression - Partie 7 : Systèmes de Druckgeräte - Teil 7: Sicherheitseinrichtungen für

sécurité pour équipements sous pression non soumis à unbefeuerte Druckgeräte
la flamme

This draft European Standard is submitted to CEN members for second enquiry. It has been drawn up by the Technical

Committee CEN/TC 54.

If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations

which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other

language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC

Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are

aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without

notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 764-7:2019 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
oSIST prEN 764-7:2019
prEN 764-7:2019 (E)
Contents Page

European foreword ....................................................................................................................................................... 5

Introduction .................................................................................................................................................................... 6

4.1 General ............................................................................................................................................................. 14

4.2 Identification of hazards ........................................................................................................................... 16

4.3 Solutions .......................................................................................................................................................... 17

5.1 General ............................................................................................................................................................. 17

5.2 Design ............................................................................................................................................................... 19

5.2.1 General ............................................................................................................................................................. 19

5.2.2 Reliability and design for functionality ............................................................................................... 19

5.2.3 Material and design ..................................................................................................................................... 19

5.2.4 Internal protection tubes .......................................................................................................................... 20

5.2.5 External chambers ....................................................................................................................................... 20

5.2.6 Electrical equipment ................................................................................................................................... 20

5.2.7 Pressure equipment integrated in a safety system ......................................................................... 20

6.1 General ............................................................................................................................................................. 21

6.1.1 Selection .......................................................................................................................................................... 21

6.1.2 Operation ........................................................................................................................................................ 22

6.1.3 Protection ....................................................................................................................................................... 22

6.1.4 Pressure limit ................................................................................................................................................ 22

6.1.5 Discharge capacity ....................................................................................................................................... 22

6.1.6 Liquid applications (thermal expansion) ............................................................................................ 22

6.1.7 Vacuum applications ................................................................................................................................... 22

6.1.8 Failure of components ................................................................................................................................ 22

6.2 Safety valves, direct loaded and pilot operated ................................................................................ 23

6.2.1 Design ............................................................................................................................................................... 23

6.2.2 Selection of the set pressure .................................................................................................................... 23

6.2.3 Sizing ................................................................................................................................................................. 24

6.3 Bursting disc safety devices ..................................................................................................................... 24

6.3.1 Design ............................................................................................................................................................... 24

6.3.2 Selection, application and installation ................................................................................................. 25

6.4 Safety valves and bursting disc safety devices in series or parallel .......................................... 25

6.4.1 Design ............................................................................................................................................................... 25

6.4.2 Application ..................................................................................................................................................... 25

6.5 Controlled safety pressure relief systems (CSPRS) .......................................................................... 26

6.6 Safety related measuring, control and regulation systems (SRMCR) ........................................ 26

6.6.1 General ............................................................................................................................................................. 26

6.6.2 Design ............................................................................................................................................................... 26

6.6.3 Documentation .............................................................................................................................................. 27

7.1 Internal ............................................................................................................................................................ 28

7.2 External ............................................................................................................................................................ 28

7.2.1 Fire..................................................................................................................................................................... 28

7.2.2 Static electricity ............................................................................................................................................ 28

7.2.3 Other hazards ................................................................................................................................................ 28

7.3 Electromagnetic compatibility ................................................................................................................ 28

8.1 General ............................................................................................................................................................. 28

8.2 Safety valves or the main valve of a CSPRS ......................................................................................... 29

8.2.1 General ............................................................................................................................................................. 29

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prEN 764-7:2019 (E)

8.2.2 Inlet piping ...................................................................................................................................................... 30

8.2.3 Outlet systems ................................................................................................................................................ 31

8.3 Installation of bursting disc safety devices ......................................................................................... 32

8.4 Safety valve and bursting disc safety devices in combination ..................................................... 32

8.4.1 Combination ................................................................................................................................................... 32

8.4.2 Inlet piping to combination ...................................................................................................................... 33

8.4.3 Outlet piping ................................................................................................................................................... 33

8.5 Isolation of relieving safety systems...................................................................................................... 33

8.5.1 Basic requirement ........................................................................................................................................ 33

8.5.2 Isolating valves .............................................................................................................................................. 33

8.5.3 Simultaneous isolation of the relieving safety accessories and the pressure source .......... 33

8.5.4 Multiple relieving safety accessories .................................................................................................... 34

8.5.5 Locking of isolating valves in a common discharge system .......................................................... 34

8.5.6 Venting .............................................................................................................................................................. 34

9.1 General ............................................................................................................................................................. 34

9.2 Pressure indicators ...................................................................................................................................... 34

9.3 Temperature indicators ............................................................................................................................. 35

9.4 Liquid level indicators ................................................................................................................................ 35

9.5 Signals and warning devices ..................................................................................................................... 35

Annex A (informative) Sizing of multiple safety valves ................................................................................. 38

Annex B (normative) Requirements for level limiters .................................................................................. 40

B.1 General ............................................................................................................................................................. 40

B.2 Floating devices ............................................................................................................................................. 40

B.3 Level electrode devices .............................................................................................................................. 40

B.4 Fault detection ............................................................................................................................................... 41

Annex C (informative) Selection of safety accessories for pressure limitation .................................... 42

C.1 General ............................................................................................................................................................. 42

C.2 Safety valve ..................................................................................................................................................... 42

C.3 Bursting disc ................................................................................................................................................... 42

C.4 Pilot operated safety valves ...................................................................................................................... 43

C.5 CSPRS ................................................................................................................................................................. 43

C.6 SRMCR ............................................................................................................................................................... 44

C.7 Bursting disc safety device upstream of a safety valve ................................................................... 44

C.8 Bursting disc safety device downstream of a safety valve ............................................................. 44

C.9 Safety valve and bursting disc in parallel ............................................................................................ 44

C.10 Safety valves in parallel .............................................................................................................................. 44

Annex D (normative) Bursting disc safety devices downstream of safety valves ................................ 45

Annex E (informative) Scope of the standard .................................................................................................... 46

Annex F (informative) Fault assessment chart ................................................................................................. 47

Annex G (informative) Inspection of safety systems ....................................................................................... 48

Annex H (informative) Risk assessment .............................................................................................................. 49

H.1 General ............................................................................................................................................................. 49

H.2 Pressure equipment boundaries determination .............................................................................. 49

H.2.1 General ............................................................................................................................................................. 49

H.2.2 Use limits ......................................................................................................................................................... 49

H.2.3 Space limits ..................................................................................................................................................... 49

H.2.4 Time limits ...................................................................................................................................................... 50

H.3 Risk estimation .............................................................................................................................................. 50

H.4 Risk evaluation .............................................................................................................................................. 50

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Annex I (informative) Calculation of reaction forces ..................................................................................... 52

Annex ZA (informative) Relationship between this European Standard and the essential

requirements of Directive 2014/68/EU (Pressure Equipment Directive) aimed to be

covered............................................................................................................................................................. 53

Bibliography ................................................................................................................................................................. 54

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oSIST prEN 764-7:2019
prEN 764-7:2019 (E)
European foreword

This document (prEN 764-7:2019) has been prepared by Technical Committee CEN/TC 54 “Unfired

pressure vessels”, the secretariat of which is held by BSI.
This document is currently submitted to the second CEN Enquiry.
This document will supersede EN 764-7:2002.

This document has been prepared under a mandate given to CEN by the European Commission and the

European Free Trade Association, and supports essential requirements of EU Directive(s).

For the relationship with EU Directive(s), see the informative Annex ZA which is an integral part of this

document.
This European Standard consists of the following parts:
— Pressure equipment – Part 1: Vocabulary;
— Pressure equipment – Part 2: Quantities, symbols and units;

— Pressure equipment – Part 4: Establishment of technical delivery conditions for metallic materials;

— Pressure equipment – Part 5: Inspection documentation of metallic materials and compliance with the

material specification;

— Pressure equipment – Part 6: Structure and content of operating instructions [CEN/TR 764-6];

— Pressure equipment – Part 7: Safety systems for unfired pressure equipment;
— Pressure equipment and assemblies – Part 8: Proof test [CEN/TS 764-8].

For the preparation of this document, CEN/TC 54 “Unfired pressure vessels” was supported by

Technical Committee CEN/TC 267 “Industrial piping and pipelines”.

Annexes A, C, E, F, G, H and I of this document are informative. Annexes B and D are normative.

The changes compared to the previous edition are the following:

— new Annexes F, G, H, I related to Fault assessment chart, inspection processes, basics for Risk

assessment and reaction forces calculation;
— new Annexe ZA template;
— new rules of presentation taken into account;
— updated normative references.
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oSIST prEN 764-7:2019
prEN 764-7:2019 (E)
Introduction

A safety system can be the ultimate limitation to protect pressure equipment from exceeding its

allowable limits or a means to prevent a potentially hazardous situation leading to injury. These limits

consist of permissible pressure, temperature, level, flow or a combination of these which were fixed at

the design stage. Regular control and/or monitoring devices which are not a necessary part of a safety

systems are excluded from this document since they become active in advance of a safety system

(see Figure 1).

It is essential to consider not only the pressure relieving device or safety related measurement, control

and regulation system (SRMCR) but the whole of the pressure relief system so as not to reduce the

relieving capacity or adversely affect the proper operation of the pressure relieving devices. Operating

problems frequently occur in pressure relief systems because of incorrect selection of the appropriate

device or because a correctly selected device was adversely affected by improper handling, incorrect

installation or lack of maintenance.

In some cases it can be necessary to establish the basic details of the safety system before selecting the

value of the maximum allowable pressure PS for the equipment to be protected. Some safety systems

need a usual margin between the maximum operating pressure and their reseating pressure which it is

essential to consider before selecting PS.

This document does not deal explicitly with hazards specifically covered in other European Directives

like, for instance, the ATEX-Directive 2014/34/EU or the EMC-Directive 2014/30/EU. In cases where

such hazards might occur and could become relevant for the design and/or construction of the safety

system, it is important that specific standards for these hazards are used or a risk analysis is made.

NOTE The role of harmonized standards in supporting the essential safety requirements of European

Directives is described in the “Guide to the implementation of directives based on the New Approach and the

Global Approach”. It can be necessary for products to meet the requirements of more than one directive and it is

the responsibility of the manufacturer to ensure that these requirements are complied with. Annex ZA draws

attention to the essential safety requirements of EU Directive 2014/68/EU “Pressure Equipment Directive”

addressed by this document. This document also draws attention to subjects which are not covered in detail but

are relevant to safety systems.
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oSIST prEN 764-7:2019
prEN 764-7:2019 (E)
Key
1 maximum allowable pressure PS X 1,10
2 no continuous operation in this zone
3 maximum allowable pressure PS
4 regulating system reacts
5 safety accessory reacts
6 monitoring system reacts
7 normal operating range
Y pressure divided by Ps
X time
A action of a regulating system
B action of a monitoring system
C action of a safety accessory

Figure 1 — Response of regulating systems, monitoring systems and safety accessories in

relation to PS
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oSIST prEN 764-7:2019
prEN 764-7:2019 (E)
1 Scope

This document specifies the requirements for safety systems which protect a vessel, a system of vessels,

piping, accessories or assemblies from exceeding operating conditions.

It is also applicable to safety related indicators and alarms, signals and warning devices when used in

safety systems.

Equipment connected together by piping of adequate capacity, free from potential blockages and which

does not contain any valve that can isolate any part from the safety system, can be considered as a

single pressure system when considering the requirements for overpressure protection.

Safety systems include the interconnections between the equipment to be protected and any discharge

location. This location can either be an outlet to atmosphere or the entry into a closed disposal system.

NOTE The scope of this document and its relationship to the safety accessories and other protective devices

described in the Pressure Equipment Directive are shown in Annex E.
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.

EN 764-1:2015+A1:2016, Pressure equipment – Part 1: Vocabulary

EN 837-1:1996, Pressure gauges – Part 1: Bourdon tube pressure gauges – Dimensions, metrology,

requirements and testing

EN 837-3:1996, Pressure gauges – Part 3: Diaphragm and capsule pressure gauges – Dimensions,

metrology, requirements and testing
EN 13480-3:2017, Metallic industrial piping – Part 3: Design and calculation

EN 50156-1:2015, Electrical equipment for furnaces and ancillary equipment – Part 1: Requirements for

application design and installation

EN 60204-1:2018, Safety of machinery – Electrical equipment of machines – Part 1: General requirements

(IEC 60204-1:2016, modified)

EN 60529:1991, Degrees of protection provided by enclosures (IP Code) (IEC 60529:1989)

EN 61508 (all parts), Functional safety of electrical/electronic/programmable electronic safety-related

systems (IEC 61508 series)

EN ISO 4126-1:2013 , Safety devices for protection against excessive pressure – Part 1: Safety valves

(ISO 4126-1:2013)

EN ISO 4126-2:2019, Safety devices for protection against excessive pressure – Part 2: Bursting disc safety

devices (ISO 4126-2:2018)

EN ISO 4126-1:2013 is currently impacted by the stand-alone amendments EN ISO 4126-1:2013/A1:2016,

Safety devices for protection against excessive pressure — Part 1: Safety valves — Amendment 1

(ISO 4126-1:2013/Amd 1:2016) and EN ISO 4126-1:2013/A2:2019, Safety devices for protection against excessive

pressure — Part 1: Safety valves (ISO 4126-1:2013).
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oSIST prEN 764-7:2019
prEN 764-7:2019 (E)

EN ISO 4126-3:2006, Safety devices for protection against excessive pressure – Part 3: Safety valves and

bursting disc safety devices in combination (ISO 4126-3:2006)

EN ISO 4126-4:2013, Safety devices for protection against excessive pressure – Part 4: Pilot-operated

safety valves (ISO 4126-4:2013)

EN ISO 4126-5:2013 , Safety devices for protection against excessive pressure – Part 5: Controlled safety

pressure relief systems (CSPRS) (ISO 4126-5:2013)

EN ISO 4126-6:2014, Safety devices for protection against excessive pressure – Part 6: Application,

selection and installation of bursting disc safety devices (ISO 4126-6:2014)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in EN 764-1:2015+A1:2016 and the

following apply.

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

• ISO Online browsing platform: available at http://www.iso.org/obp
• IEC Electropedia: available at http://www.electropedia.org/
3.1
safety accessory

device designed and used to protect pressure equipment against the ultimate limits being exceeded and

to prevent allowable limits being exceeded more than momentarily (see Annex E and Figure 1) in

reasonably foreseeable conditions
Note 1 to entry: Such devices include:

— devices for direct pressure limitation, such as safety valves, bursting disc safety devices, buckling rods,

controlled safety pressure relief systems (CSPRS), and

— limiters, such as pressure switches or temperature switches or fluid level switches and ‘safety related

measurement control and regulation (SRMCR)’ devices.

Note 2 to entry: In this document “safety accessory” solely refers to the pressure risk/hazard.

Note 3 to entry: More than one safety accessory may be necessary for these purposes.

3.2
safety system

system of safety accessories and other protective devices which prevents the process parameters

exceeding the limit values determined by the hazard analysis and ensures that the following risks are

eliminated or adequately controlled (injury to personnel, damage to the environment and damage to

property)

Note 1 to entry: The term “safety system” corresponds to the ESR 2.10 wording of “suitable protective devices”.

EN ISO 4126-5:2013 is currently impacted by the stand-alone amendments EN ISO 4126-5:2013/A1:2016,

...

SLOVENSKI STANDARD
oSIST prEN 764-7:2018
01-maj-2018
7ODþQDRSUHPDGHO9DUQRVWQLVLVWHPL]DQHNXUMHQRWODþQRRSUHPR
Pressure equipment - Part 7: Safety systems for unfired pressure equipment
Druckgeräte -Teil 7: Sicherheitseinrichtungen für unbefeuerte Druckgeräte
Ta slovenski standard je istoveten z: prEN 764-7
ICS:
23.020.32 7ODþQHSRVRGH Pressure vessels
oSIST prEN 764-7:2018 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
oSIST prEN 764-7:2018
---------------------- Page: 2 ----------------------
oSIST prEN 764-7:2018
DRAFT
EUROPEAN STANDARD
prEN 764-7
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2018
ICS 23.020.30 Will supersede EN 764-7:2002
English Version
Pressure equipment - Part 7: Safety systems for unfired
pressure equipment
Druckgeräte -Teil 7: Sicherheitseinrichtungen für
unbefeuerte Druckgeräte

This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee

CEN/TC 54.

If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations

which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other

language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC

Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are

aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without

notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 764-7:2018 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
oSIST prEN 764-7:2018
prEN 764-7:2018 (E)
Contents Page

European foreword ....................................................................................................................................................... 5

Introduction .................................................................................................................................................................... 6

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

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

3 Terms and definitions ................................................................................................................................... 9

4 Risk consideration ....................................................................................................................................... 13

4.1 General ............................................................................................................................................................. 13

4.2 Identification of hazards ........................................................................................................................... 14

4.3 Solutions .......................................................................................................................................................... 16

5 Limiting devices and systems .................................................................................................................. 16

5.1 General ............................................................................................................................................................. 16

5.2 Design ............................................................................................................................................................... 17

5.2.1 General ............................................................................................................................................................. 17

5.2.2 Reliability and design for functionality ............................................................................................... 17

5.2.3 Material and design ..................................................................................................................................... 18

5.2.4 Internal protection tubes .......................................................................................................................... 18

5.2.5 External chambers ....................................................................................................................................... 19

5.2.6 Electrical equipment ................................................................................................................................... 19

5.2.7 Pressure equipment integrated in a safety system ......................................................................... 19

6 Pressure limitation ...................................................................................................................................... 20

6.1 General ............................................................................................................................................................. 20

6.1.1 Selection .......................................................................................................................................................... 20

6.1.2 Operation ........................................................................................................................................................ 20

6.1.3 Protection ....................................................................................................................................................... 21

6.1.4 Pressure limit ................................................................................................................................................ 21

6.1.5 Discharge capacity ....................................................................................................................................... 21

6.1.6 Liquid applications (thermal expansion) ............................................................................................ 21

6.1.7 Vacuum applications ................................................................................................................................... 21

6.1.8 Failure of components ................................................................................................................................ 21

6.2 Safety valves, direct loaded and pilot operated ................................................................................ 21

6.2.1 Design ............................................................................................................................................................... 21

6.2.2 Selection of the set pressure .................................................................................................................... 22

6.2.3 Sizing ................................................................................................................................................................. 23

6.3 Bursting disc safety devices ..................................................................................................................... 23

6.3.1 Design ............................................................................................................................................................... 23

6.3.2 Selection, application and installation ................................................................................................. 23

6.4 Safety valves and bursting disc safety devices in series or parallel .......................................... 23

6.4.1 Design ............................................................................................................................................................... 23

6.4.2 Application ..................................................................................................................................................... 23

6.5 Controlled safety pressure relief systems (CSPRS) .......................................................................... 24

6.6 Safety related measuring, control and regulation systems (SRMCR) ........................................ 24

6.6.1 General ............................................................................................................................................................. 24

6.6.2 Design ............................................................................................................................................................... 24

6.6.3 Documentation .............................................................................................................................................. 25

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7 Hazard protection ........................................................................................................................................ 26

7.1 Internal ............................................................................................................................................................. 26

7.2 External ............................................................................................................................................................ 26

7.2.1 Fire ..................................................................................................................................................................... 26

7.2.2 Other hazards ................................................................................................................................................. 26

7.3 Electromagnetic compatibility ................................................................................................................ 26

8 Installation of pressure relieving devices ........................................................................................... 26

8.1 General ............................................................................................................................................................. 26

8.2 Safety valves or the main valve of a CSPRS .......................................................................................... 27

8.2.1 General ............................................................................................................................................................. 27

8.2.2 Inlet piping ...................................................................................................................................................... 28

8.2.3 Outlet systems ................................................................................................................................................ 28

8.3 Installation of bursting disc safety devices ......................................................................................... 29

8.4 Safety valve and bursting disc safety devices in combination ..................................................... 29

8.4.1 Combination ................................................................................................................................................... 29

8.4.2 Inlet piping to combination ...................................................................................................................... 29

8.4.3 Outlet piping ................................................................................................................................................... 29

8.5 Isolation of relieving safety systems...................................................................................................... 29

8.5.1 Basic requirement ........................................................................................................................................ 29

8.5.2 Isolating valves .............................................................................................................................................. 29

8.5.3 Simultaneous isolation of the relieving safety accessories and the pressure source .......... 30

8.5.4 Multiple relieving safety accessories .................................................................................................... 30

8.5.5 Locking of isolating valves in a common discharge system .......................................................... 30

8.5.6 Venting .............................................................................................................................................................. 31

9 Indicators and alarms ................................................................................................................................. 31

9.1 General ............................................................................................................................................................. 31

9.2 Pressure indicators ...................................................................................................................................... 31

9.3 Temperature indicators ............................................................................................................................. 31

9.4 Liquid level indicators ................................................................................................................................ 32

9.5 Signals and warning devices ..................................................................................................................... 32

10 Inspection and maintenance .................................................................................................................... 32

Annex A (informative) Sizing of multiple safety valves ................................................................................. 35

Annex B (normative) Requirements for level limiters .................................................................................. 37

B.1 General ............................................................................................................................................................. 37

B.2 Floating devices ............................................................................................................................................. 37

B.3 Level electrode devices .............................................................................................................................. 37

B.4 Fault detection ............................................................................................................................................... 38

Annex C (informative) Selection of safety accessories for pressure limitation .................................... 39

C.1 General ............................................................................................................................................................. 39

C.2 Safety valve ..................................................................................................................................................... 39

C.3 Bursting disc ................................................................................................................................................... 39

C.4 Pilot operated safety valves ...................................................................................................................... 40

C.5 CSPRS ................................................................................................................................................................. 40

C.6 SRMCR ............................................................................................................................................................... 41

C.7 Bursting disc safety device upstream of a safety valve ................................................................... 41

C.8 Bursting disc safety device downstream of a safety valve ............................................................. 41

C.9 Safety valve and bursting disc in parallel ............................................................................................ 41

C.10 Safety valves in parallel .............................................................................................................................. 41

Annex D (normative) Bursting disc safety devices downstream of safety valves ................................ 42

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Annex E (informative) Scope of the standard ................................................................................................... 43

Annex F (informative) Fault assessment chart ................................................................................................. 44

Annex G (informative) Inspection of safety systems ...................................................................................... 45

Annex H (informative) Risk assessment ............................................................................................................. 46

H.1 General ............................................................................................................................................................. 46

H.2 Pressure equipment boundaries determination .............................................................................. 46

H.2.1 General ............................................................................................................................................................. 46

H.2.2 Use limits ......................................................................................................................................................... 46

H.2.3 Space limits..................................................................................................................................................... 46

H.2.4 Time limits ...................................................................................................................................................... 47

H.3 Risk estimation ............................................................................................................................................. 47

H.4 Risk evaluation ............................................................................................................................................. 47

Annex ZA (informative) Relationship between this European Standard and the essential

requirements of Directive 2014/68/EU (Pressure Equipment Directive) aimed to be

covered............................................................................................................................................................. 49

Bibliography ................................................................................................................................................................. 50

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European foreword

This document (prEN 764-7:2018) has been prepared by Technical Committee CEN/TC 54 “Unfired

pressure vessels”, the secretariat of which is held by BSI.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 764-7:2002.

This document has been prepared under a mandate given to CEN by the European Commission (EC)

and the European Free Trade Association, and supports the essential safety requirements of the

Pressure Equipment Directive (PED) 2014/68/EU.

For the relationship with EU Directive(s), see the informative Annex ZA which is an integral part of this

document.

This European Standard consists of the following parts, under the general title Pressure equipment:

— Pressure equipment - Part 1: Vocabulary;
— Pressure equipment - Part 2: Quantities, symbols and units;

— Pressure equipment - Part 4: Establishment of technical delivery conditions for metallic materials;

— Pressure equipment - Part 5: Inspection documentation of metallic materials and compliance with the

material specification;

— Pressure equipment - Part 6: Structure and content of operating instructions [CEN/TR 764-6];

— Pressure equipment - Part 7: Safety systems for unfired pressure equipment;
— Pressure equipment and assemblies - Part 8: Proof test [CEN/TS 764-8].

For the preparation of this document, CEN/TC 54 “Unfired pressure vessels” was supported by

Technical Committee CEN/TC 267 “Industrial piping and pipelines”.

Annexes A, C, E, F, G and H of this document are informative. Annexes B and D are normative.

The changes compared to the previous edition are the following:

— new Annexes F, G, H related to Fault assessment chart, inspection processes and basics for Risk

assessment;
— new Annexe ZA template;
— new rules of presentation taken into account;
— updated normative references.
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Introduction

A safety system can be the ultimate limitation to protect pressure equipment from exceeding its

allowable limits or a means to prevent a potentially hazardous situation leading to injury. These limits

consist of permissible pressure, temperature, level, flow or a combination of these which were fixed at

the design stage. Regular control and/or monitoring devices which are not a necessary part of a safety

systems are excluded from this document since they become active in advance of a safety system

(see Figure 1).

It is essential to consider not only the pressure relieving device or safety related measurement, control

and regulation system (SRMCR) but the whole of the pressure relief system so as not to reduce the

relieving capacity or adversely effect the proper operation of the pressure relieving devices. Operating

problems frequently occur in pressure relief systems because of incorrect selection of the appropriate

device or because a correctly selected device was adversely affected by improper handling, incorrect

installation or lack of maintenance.

In some cases it can be necessary to establish the basic details of the safety system before selecting the

value of the maximum allowable pressure PS for the equipment to be protected. Some safety systems

need a usual margin between the maximum operating pressure and their reseating pressure which it is

essential to consider before selecting PS.

This document does not deal explicitly with hazards specifically covered in other European Directives

like, for instance, the ATEX-Directive 94/9/EC or the EMC-Directive 2004/108/EC. In cases where such

hazards might occur and could become relevant for the design and/or construction of the safety system,

it is important that specific standards for these hazards are used or a risk analysis is made.

NOTE The role of harmonized standards in supporting the essential safety requirements of European

Directives is described in the “Guide to the implementation of directives based on the New Approach and the

Global Approach”. It can be necessary for products to meet the requirements of more than one directive and it is

the responsibility of the manufacturer to ensure that these requirements are complied with. Annex ZA draws

attention to the essential safety requirements of EU Directive 2014/68/EU “Pressure Equipment Directive”

addressed by this document. This document also draws attention to subjects which are not covered in detail but

are relevant to safety systems.
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Key
1 Maximum allowable pressure PS X 1,10
2 No continuous operation in this zone
3 Maximum allowable pressure PS
4 Regulating control system reacts
5 Safety system reacts
6 Monitoring system reacts
7 Normal operating range
Y Pressure
X Time

Figure 1 — Response of regulating, monitoring and safety systems in relation to PS

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1 Scope

This document specifies the requirements for safety systems which protect a vessel, a system of vessels,

piping, accessories or assemblies from exceeding operating conditions.

It is also applicable to safety related indicators and alarms, signals and warning devices when used in

safety systems.

Equipment connected together by piping of adequate capacity, free from potential blockages and which

does not contain any valve that can isolate any part from the safety system, may be considered as a

single pressure system when considering the requirements for overpressure protection.

Safety systems include the interconnections between the equipment to be protected and any discharge

location. This location can either be an outlet to atmosphere or the entry into a closed disposal system.

NOTE The scope of this document and its relationship to the safety accessories and other protective devices

described in the Pressure Equipment Directive are shown in Annex E.
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.

EN 764-1, Pressure equipment – Part 1: Vocabulary

EN 837-1, Pressure gauges – Part 1: Bourdon tube pressure gauges - Dimensions, metrology, requirements

and testing

EN 837-3, Pressure gauges – Part 3: Diaphragm and capsule pressure gauges - Dimensions, metrology,

requirements and testing
EN 13480-3, Metallic industrial piping – Part 3: Design and calculation

EN 50156-1, Electrical equipment for furnaces and ancillary equipment – Part 1: Requirements for

application design and installation

EN 60204-1, Safety of machinery - Electrical equipment of machines – Part 1: General requirements

(IEC 60204 1)
EN 60529, Degrees of protection provided by enclosures (IP Code) (IEC 60529)

EN 61508 (all parts), Functional safety of electrical/electronic/programmable electronic safety-related

systems (IEC 61508 series)

EN ISO 4126-1, Safety devices for protection against excessive pressure – Part 1: Safety valves (ISO 4126-

EN ISO 4126-2, Safety devices for protection against excessive pressure – Part 2: Bursting disc safety

devices (ISO 4126-2)

EN ISO 4126-3, Safety devices for protection against excessive pressure – Part 3: Safety valves and

bursting disc safety devices in combination (ISO 4126-3)

EN ISO 4126-4, Safety devices for protection against excessive pressure – Part 4: Pilot-operated safety

valves (ISO 4126-4)
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EN ISO 4126-5:2013, Safety devices for protection against excessive pressure – Part 5: Controlled safety

pressure relief systems (CSPRS) (ISO 4126-5:2013)

EN ISO 4126-6, Safety devices for protection against excessive pressure – Part 6: Application, selection and

installation of bursting disc safety devices (ISO 4126-6)

ISO 4126-9:2018, Safety devices for protection against excessive pressure - Part 9: Application and

installation of safety devices excluding stand-alone bursting disc safety devices

3 Terms and definitions

For the purposes of this document, the terms and definitions given in EN 764-1 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
3.1
safety accessory

device designed and used to protect pressure equipment against the ultimate limits being exceeded and

to prevent allowable limits being exceeded more than momentarily (see Annex E and Figure 1) in

reasonably foreseeable conditions
Note 1 to entry: Such devices include:

— devices for direct pressure limitation, such as safety valves, bursting disc safety devices, buckling rods,

controlled safety pressure relief systems (CSPRS), and

— limiters, such as pressure switches or temperature switches or fluid level switches and ‘safety related

measurement control and regulation (SRMCR)’ devices.

Note 2 to entry: In this document “safety accessory” solely refers to the pressure risk/hazard.

Note 3 to entry: More than one safety accessory may be necessary for these purposes.

Note 4 to entry: Limi
...