SIST EN 764-7:2002
(Main)Pressure equipment - Part 7: Safety systems for unfired pressure equipment
Pressure equipment - Part 7: Safety systems for unfired pressure equipment
This European Standard 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 standard and its relationship to the safety accessories and other protective devices described in the Pressure Equipment Directive are shown in annex F.
Druckgeräte - Teil 7: Sicherheitseinrichtungen für unbefeuerte Druckgeräte
Diese Europäische Norm 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, zu 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 der vorliegenden Norm, bezogen auf die in der Druckgeräte-Richtlinie be-
schriebenen Ausrüstungsteile mit Sicherheitsfunktion und weitere Einrichtungen mit Schutzfunktion ist in Anhang F dargestellt.
Equipements sous pression - Partie 7: Systemes de sécurité pour équipements sous pression non soumis a la flamme
La présente Norme européenne prescrit les exigences applicables aux systemes de sécurité qui protegent un récipient, un systeme de récipients, une tuyauterie, des accessoires ou des ensembles vis-a-vis de dépassements des conditions de fonctionnement.
Elle est également applicable aux indicateurs et alarmes liés a la sécurité, aux dispositifs de signalisation et d'avertissement lorsqu'ils sont utilisés en tant que systemes de sécurité.
Les équipements raccordés les uns aux autres dans un systeme 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 etre considérés comme un systeme sous pression unique eu égard aux exigences de protection vis a vis des surpressions.
Les systemes de sécurité comprennent les interconnexions entre les équipements devant etre protégés et tout point de décharge. Cet emplacement peut etre un orifice de sortie a l'atmosphere ou le raccordement a un systeme de récupération fermé.
NOTE Le domaine d'application de la présente norme et ses relations avec les accessoires de sécurité et les autres dispositifs de protection de la directive équipements sous pression sont indiqués en annexe F.
Tlačna oprema - 7. del: Varnostni sistemi za neogrevano tlačno opremo
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 764-7:2002
01-november-2002
7ODþQDRSUHPDGHO 9DUQRVWQLVLVWHPL]DQHRJUHYDQRWODþQRRSUHPR
Pressure equipment - Part 7: Safety systems for unfired pressure equipment
Druckgeräte - Teil 7: Sicherheitseinrichtungen für unbefeuerte Druckgeräte
Equipements sous pression - Partie 7: Systemes de sécurité pour équipements sous
pression non soumis a la flamme
Ta slovenski standard je istoveten z: EN 764-7:2002
ICS:
23.020.30
SIST EN 764-7:2002 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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EUROPEAN STANDARD
EN 764-7
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2002
ICS 23.020.30
English version
Pressure equipment - Part 7: Safety systems for unfired
pressure equipment
Equipements sous pression - Partie 7: Systèmes de Druckgeräte - Teil 7: Sicherheitseinrichtungen für
sécurité ppour équipements sous pression non soumis à la unbefeuerte Druckgeräte
flamme
This European Standard was approved by CEN on 29 April 2002.
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. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Management Centre or to any CEN member.
This European Standard exists 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 Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2002 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 764-7:2002 E
worldwide for CEN national Members.
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EN 764-7:2002 (E)
Contents
page
Introduction .5
1 Scope .6
2 Normative references .7
3 Terms and definitions.7
4 Risk consideration.9
4.1 General.9
4.2 Identification of hazards.11
4.3 Solutions.12
5 Limiting devices and systems.12
5.1 General.12
5.2 Design .13
6 Pressure limitation.14
6.1 General.14
6.2 Safety valves, direct loaded and pilot operated .16
6.3 Bursting disc safety devices .17
6.4 Safety Valves & bursting disc safety devices in series or parallel.17
6.5 Controlled safety pressure relief systems (CSPRS) .18
6.6 Safety related measuring, control & regulation systems (SRMCR) .18
7 Hazard protection .20
7.1 Internal .20
7.2 External.20
7.3 Static electricity.20
8 Installation of pressure relieving devices .21
8.1 General.21
8.2 Safety valves or the main valve of a CSPRS.21
8.3 Installation of bursting disc safety devices .23
8.4 Safety valve and bursting disc safety devices in combination.23
8.5 Isolation of relieving safety systems .24
9 Indicators and alarms.25
9.1 General.25
9.2 Pressure indicators .25
9.3 Temperature indicators .26
9.4 Liquid level indicators .26
9.5 Signals and warning devices.26
10 Inspection and maintenance.27
Annex A (informative) Sizing of multiple safety valves.29
(normative)
Annex B Requirements for level limiters .31
B.1 General.31
B.2 Floating devices.31
B.3 Level electrode devices.31
B.4 Fault detection.32
Annex C (informative) Selection of safety accessories for pressure limitation .33
(normative)
Annex D Bursting disc safety devices downstream of safety valves .36
Annex E (informative) Scope of the standard.37
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EN 764-7:2002 (E)
Annex ZA (informative) Clauses of this European Standard addressing essential requirements or other
provisions of EU Directives .38
Bibliography .39
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EN 764-7:2002 (E)
Foreword
This document EN 764-7:2002 has been prepared by Technical Committee CEN/TC 54 “Unfired pressure vessels”,
the secretariat of which is held by BSI with support of Technical Committee CEN/TC 267 “Industrial piping”.
This European Standard shall be given the status of a national standard, either by publication of an identical text or
by endorsement, at the latest by November 2002, and conflicting national standards shall be withdrawn at the latest
by November 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) 97/23/EC.
For the relationship with the EU Directive(s) see the informative annex ZA which is an integral part of this
document.
This European Standard consists of the following parts:
Part 1: Definitions of pressure, temperature and volume.
Part 2: Quantities, symbols and units.
Part 3: Definition of parties involved.
Part 4: Establishment of technical delivery conditions for metallic materials.
Part 5: Inspection documentation of metallic materials and compliance with the material specification.
Part 6: Operating instructions.
Part 7: Safety systems for unfired pressure equipment.
Annexes A, C, E of this European Standard are informative. Annexes B and D are normative.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,
France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain,
Sweden, Switzerland and the United Kingdom.
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EN 764-7:2002 (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 standard 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 has to be considered before
selecting PS.
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 97/23/EC “Pressure Equipment Directive” addressed by this standard. This standard also draws attention to subjects
which are not covered in detail but are relevant to safety systems.
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EN 764-7:2002 (E)
Figure 1 — Response of regulating, monitoring and safety systems in relation to PS
1 Scope
This European Standard 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 standard and its relationship to the safety accessories and other protective devices described in
the Pressure Equipment Directive are shown in annex F.
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EN 764-7:2002 (E)
2 Normative references
This European Standard incorporates, by dated or undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text, and the publications are listed hereafter. For
dated references, subsequent amendments to or revisions of any of these publications apply to this European
Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the
publication referred to applies (including amendments).
prEN ISO 4126-1, Safety devices for protection against excessive pressure - Part 1: Safety valves (ISO/DIS 4126-
1:1999).
prEN ISO 4126-2, Safety devices for protection against excessive pressure - Part 2: Bursting disc safety devices
(ISO/DIS 4126-2:1998).
prEN ISO 4126-3, Safety devices for protection against excessive pressure - Part 3: Safety valves and bursting
discs safety devices in combination (ISO/DIS 4126-3:1999).
prEN ISO 4126-4, Safety devices for protection against excessive pressure - Part 4: Pilot operated safety valves
(ISO/DIS 4126-4:1999).
prEN ISO 4126-5, Safety devices for protection against excessive pressure - Part 5: Controlled Safety Pressure
Relief Systems (CSPRS) (ISO/DIS 4126-5:1999).
prEN ISO 4126-6, Safety devices for protection against excessive pressure - Part 6: Application, selection and
installation of bursting disc safety devices (ISO/DIS 4126-6:2000).
prEN ISO 4126-7, Safety devices for protection against excessive pressure - Part 7: Common data (ISO/DIS 4126-
7:2000).
EN 954-1:1998, Safety of machinery – safety related parts of control systems – Part 1: General principles for
design.
prEN 50156-1, Electrical equipment for furnaces and ancillary equipment - Part 1: Requirements for application
design and installation.
EN 60529:1991, Degrees of protection provided by enclosures (IP code) (IEC 60529:1989).
IEC 61508, Functional safety of electrical/electronic/programmable electronic safety – related systems.
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.
3 Terms and definitions
For the purposes of this European Standard, the following terms and definitions apply.
3.1
safety accessory
device designed and used to protect pressure equipment against the allowable limits being exceeded (see annex
E)
3.2
safety system
system of safety accessories and other protective devices which prevents the process parameters exceeding the
ultimate limiting values determined by the hazard analysis and ensures that the following risks are eliminated or
properly controlled:
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EN 764-7:2002 (E)
injury to personnel;
damage to the environment;
damage to property
3.3
monitoring system
system which periodically checks given parameters and draws attention to those which are outside normal
operating limits but which are below the limiting values determined by the hazard analysis. Normal operating
conditions of the process can be restored either directly by the system or by an operator
3.4
regulating system
system which adjusts or controls a particular parameter to maintain operation within predetermined limits
3.5
independence
ability to function as required without interference from or dependence upon other equipment
3.6
fail-safe
characteristic whereby the failure of any safety system or any energy source will leave the protected equipment in a
safe condition
3.7
hazard
potential source of harm
[ISO/IEC Guide 51:1999]
NOTE 1 Harm is the physical injury or damage to the health of people or damage to property or to the environment.
NOTE 2 The term hazard can be qualified in order to define its origin or the nature of the expected harm.
3.8
risk
combination of the probability of occurrence of harm and the severity of that harm
[ISO/IEC Guide 51:1999]
3.9
risk analysis
use of available information to identify hazards and to estimate the risk
[ISO/IEC Guide 51:1999]
3.10
risk evaluation
judgement, on the basis of risk analysis, of whether a tolerable risk has been achieved
[ISO/IEC Guide 51:1999]
3.11
risk assessment
overall process of risk analysis and risk evaluation
[ISO/IEC Guide 51:1999]
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EN 764-7:2002 (E)
3.12
reliability
ability of a system or component to perform a required function under specified conditions and for a given period of
time without failing
3.13
shutdown
automatically or manually initiated action to achieve a safe condition of the pressure equipment
3.14
lockout
system feature which preserves the shutdown action until it is released by a manual intervention
3.15
safety related measurement, control and regulation system (SRMCR)
system which by means of automatic control equipment, operating independently from other process control
functions, prevents operating parameters exceeding allowable limits in pressure equipment
3.16
limiter
device which either activates the means for correction or provides for shutdown or shutdown and lockout
3.17
safety
freedom from unacceptable risk
[ISO/IEC Guide 51:1999]
3.18
self-diagnosis
regular and automatic determination that all chosen components of a safety system are capable of functioning as
required
3.19
maximum allowable pressure (PS)
maximum pressure for which the equipment is designed, as specified by the manufacturer
3.20
maximum/minimum allowable temperature (TS)
maximum/minimum temperatures for which the equipment is designed, as specified by the manufacturer
3.21
redundancy
provision of more than one device or system which is sufficient to perform or provide the necessary function
3.22
controlled safety pressure relief systems (CSPRS)
pressure relief system conforming to prEN ISO 4126-5
4 Risk consideration
4.1 General
All service conditions shall be considered to select the most appropriate safety concept to ensure safe operation.
This requires a realistic assessment of risk by means of risk analysis and risk evaluation (see Figure 2).
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EN 764-7:2002 (E)
Risk analysis involves:
Determination of the boundaries of the pressure equipment including intended use and reasonably foreseeable
misuse;
Identification of potential hazards and estimation of the risk.
Risk evaluation involves the process in which, on the basis of risk analysis, judgement is made to achieve a
tolerable risk.
NOTE The manufacturer and the user should consider the most onerous conditions which can exist for pressure and
temperature within the allowable limits.
NOTE Risk reduction and the selection of safety systems are not part of risk analysis and risk assessment.
Figure 2 — Process for risk assessment and risk reduction
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EN 764-7:2002 (E)
4.2 Identification of hazards
During operation of a piece of pressure equipment, dangerous situations may occur due, for example to:
operational aspects;
human errors;
unreliability of some functions;
unsafe loading conditions;
maintenance;
physical characteristics of the fluid:
a) pressure;
b) temperature;
c) flow;
d) level;
e) fouling capability;
f) adhesion;
g) abrasion;
chemical characteristics of the fluid:
a) corrosivity
b) toxicity;
c) flammability;
d) stability;
e) fouling;
site conditions such as:
a) vibration;
b) temperature (e.g. freezing);
c) wear;
d) corrosion;
e) external fire (see 7.2)
Each of these factors can result in the operating limits of the pressure equipment being exceeded.
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EN 764-7:2002 (E)
4.3 Solutions
Risk assessment shall be used to produce the basic information which is needed to correctly design the pressure
equipment and to select the most efficient safety accessories. The equipment shall be designed in order to:
a) eliminate or reduce hazards;
b) provide appropriate protection measures if the hazard cannot be eliminated;
c) inform the user of residual hazards and indicate the appropriate special measures for that case;
d) prevent the danger from misuse.
Preference shall be given to inherently safe design solutions.
Operating instructions shall include instructions for inspection and maintenance to ensure that the required level of
protection is available.
NOTE Inspection and maintenance of safety systems are necessary to ensure that the required level of integrity is
maintained. A record should be kept on both the procedures and findings
5 Limiting devices and systems
5.1 General
Where the allowable limits can be exceeded, the pressure equipment shall be fitted with, or provisions shall be
made for the fitting of:
a) Regulating systems:
Where appropriate, manually or automatically operated regulatory devices for the control of operating parameters
such as measurement, control and regulation devices (MCR), pressure switches, temperature switches, level
switches and flow switches to maintain conditions during normal operation within the maximum / minimum
allowable limits;
b) Monitoring systems:
Where appropriate, adequate monitoring devices for the control of operating parameters such as measurement,
control and regulation devices (MCR), indicators, alarms, pressure switches, temperature switches, level switches,
flow switches which enable adequate action to be taken either automatically or manually or activate the means for
correction and/or provide for shutdown and lockout, to keep the pressure equipment within the allowable limits.
If the process parameter value cannot exceed the allowable limits, a monitoring system is sufficient and a safety
system unnecessary. The process parameter can be brought back into the normal operating range by:
manual action - after a status signal; or
automatically;
c) Safety systems:
Safety devices such as safety valves, bursting disc safety devices, buckling rods, CSPRS, etc. or safety related
measuring, control and regulation devices (SRMCR), which serve as ultimate protection to ensure that the
maximum allowable operating limits are not exceeded.
Safety systems or their relevant components shall be independent of other functions, unless their safety function is
not affected by such other functions.
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EN 764-7:2002 (E)
NOTE 1 See definition of independence.
NOTE 2 Regulating and monitoring systems which are not part of a safety systems are not covered by this standard.
5.2 Design
5.2.1 General
The safety system shall be designed to operate sufficiently reliably under all conditions of operation determined by
the risk analysis in 4.1, including start up, shut off, and during maintenance and repairs.
All limiters, and their components, installed in a safety system shall comply with the requirements of this clause and
6.6. Additional requirements for particular types of limiters are given in annex B.
5.2.2 Material and design
5.2.2.1 Limiters shall withstand the thermal, mechanical, chemical and electrical loads that can occur during
operation.
5.2.2.2 The use of materials with great differences in their electrochemical potential shall be avoided in order to
prevent corrosion which would affect the function of the limiter.
5.2.2.3 Chambers, connecting pipes and protection tubes for the limiters shall be designed so that they can be
cleaned and inspected. They shall also be suitably designed to prevent the build up of deposits in the
tubes/chambers.
5.2.2.4 Protection tubes and chambers shall be designed to allow the device to have an adequate response
time.
5.2.3 Internal Protection Tubes
5.2.3.1 Where an internal protection tube is necessary, for example, in order to prevent the effect of foam or
turbulence, then the protection tube shall be considered to be part of the equipment to be protected.
5.2.3.2 Openings on the protection tube which are necessary in order to ensure level equalisation shall be
properly sized and shall be positioned at the lowest point of the bottom and at the highest practicable point of the
protection tube.
5.2.4 External Chambers
The pipe connections to external chambers shall ensure that the parameter to be measured is representative of the
parameter in the main equipment.
5.2.5 Electrical equipment
5.2.5.1 Electrical equipment shall comply with prEN 50156-1.
5.2.5.2 All wiring and electrical equipment in connection with safety systems shall be adequately protected
against ingress of moisture and effects of high temperature.
5.2.5.3 Electrical components within the confines of limiting devices shall be able to withstand the temperature
of the surrounding environment. Any equipment which is in contact with parts carrying the process fluid shall be
able of withstanding the highest temperature resulting from contact with:
the process fluid at the highest temperature; or
the saturated vapour of the process fluid at the highest foreseeable pressure; or
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EN 764-7:2002 (E)
any fluid used periodically to clean the equipment.
Safety accessories shall have, as a minimum, a protection rating to IP54 of EN 60529:1991. When
5.2.5.4
components are installed inside an enclosure or control box, the IP rating required for the box shall be considered
adequate.
5.2.5.5 The limiter shall be designed so that a fault in any related part shall not lead to a loss of the safety
function. This may be achieved by fault avoidance techniques, self-diagnosis, redundancy, diversity or a
combination of these methods. Fault assessment for the electrical components shall be in accordance with the
procedure in the fault analysis charts of prEN 50156-1. The figure “Fault assessment for the hardwired section of a
safety device” in this standard shall also be applied for faults in hydraulic, pneumatic and mechanical components.
5.2.5.6 Limiters shall function independently of each other and of other control systems unless their safety
function cannot be affected by other such functions. Limiters may, however, share common components (e.g.
power supplies, bus systems, circuit boards, etc.) provided each limiter is fail-safe as defined in 3.6 and no adverse
safety effect can occur from faults in other limiters or related equipment.
The limiter shall be designed in such a way that once it has been activated, sent the appropriate signals
5.2.5.7
and prevented the allowable limits being exceeded, manual resetting is required after the relevant process
parameter has been restored to a safe level and all possible causes of the fault have been corrected.
6 Pressure limitation
6.1 General
6.1.1 Selection
Safety accessories which may be suitable for pressure limitation are:
safety valves:
a) direct loaded;
b) pilot operated;
bursting disc safety devices;
safety valves and bursting disc safety devices in combination;
controlled safety pressure relief systems (CSPRS);
safety related measurement, control and regulat
...
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