oSIST prEN 764-7:2019

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: Not Published
• Public Enquiry End Date: 02-Dec-2019
• ICS: 23.020.32 - Pressure vessels
• Technical Committee: TLP - Pressure vessels
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 04-Oct-2019
• Due Date: 21-Feb-2020
• Completion Date: 05-Dec-2019
• 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: FprEN 764-7 - Pressure equipment - Part 7: Safety systems for unfired pressure equipment

Relations

• Revised: SIST EN 764-7:2002 - Pressure equipment - Part 7: Safety systems for unfired pressure equipment
• Effective Date: 01-Nov-2019
• Revised: SIST EN 764-7:2002 - Pressure equipment - Part 7: Safety systems for unfired pressure equipment
• Effective Date: 18-Jan-2023
• Revised: SIST 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

---------------------- Page: 2 ----------------------
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
2

---------------------- Page: 4 ----------------------
oSIST prEN 764-7:2019
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
3

---------------------- Page: 5 ----------------------
oSIST prEN 764-7:2019
prEN 764-7:2019 (E)
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

4

---------------------- Page: 6 ----------------------
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.
5

---------------------- Page: 7 ----------------------
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.
6

---------------------- Page: 8 ----------------------
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
7

---------------------- Page: 9 ----------------------
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)
1
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)

1
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).
8

---------------------- Page: 10 ----------------------
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)
2
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”.

2
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
2

---------------------- Page: 4 ----------------------
oSIST prEN 764-7:2018
prEN 764-7:2018 (E)
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
3

---------------------- Page: 5 ----------------------
oSIST prEN 764-7:2018
prEN 764-7:2018 (E)
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

4

---------------------- Page: 6 ----------------------
oSIST prEN 764-7:2018
prEN 764-7:2018 (E)
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.
5

---------------------- Page: 7 ----------------------
oSIST prEN 764-7:2018
prEN 764-7:2018 (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 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.
6

---------------------- Page: 8 ----------------------
oSIST prEN 764-7:2018
prEN 764-7:2018 (E)

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
7

---------------------- Page: 9 ----------------------
oSIST prEN 764-7:2018
prEN 764-7:2018 (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, 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-
1)
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)
8

---------------------- Page: 10 ----------------------
oSIST prEN 764-7:2018
prEN 764-7:2018 (E)
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
...