SIST EN ISO 23251:2007/A1:2008
(Amendment)Petroleum, petrochemical and natural gas industries - Pressure-relieving and depressuring systems - Amendment 1 (ISO 23251:2007/Amd 1:2008)
Petroleum, petrochemical and natural gas industries - Pressure-relieving and depressuring systems - Amendment 1 (ISO 23251:2007/Amd 1:2008)
2008-02-06 Minor amendment.
Erdöl-, petrochemische und Erdgasindustrie - Druckentlastungs- und Druckausgleichssysteme - Änderung 1 (ISO 23251:2007/Amd 1:2008)
Industries du pétrole, de la pétrochimie et du gaz naturel - Systèmes de dépressurisation et de protection contre les surpressions - Amendement 1(ISO 23251:2007/Amd 1:2008)
Petrokemična industrija ter industrija za predelavo nafte in zemeljskega plina - Sistemi za sproščanje in izravnavanje tlaka - Dopolnilo 1 (ISO 23251:2007/Amd 1:2008)
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Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 23251:2007/A1:2008
01-september-2008
3HWURNHPLþQDLQGXVWULMDWHULQGXVWULMD]DSUHGHODYRQDIWHLQ]HPHOMVNHJDSOLQD
6LVWHPL]DVSURãþDQMHLQL]UDYQDYDQMHWODND'RSROQLOR ,62 $PG
Petroleum, petrochemical and natural gas industries - Pressure-relieving and
depressuring systems - Amendment 1 (ISO 23251:2007/Amd 1:2008)
Erdöl-, petrochemische und Erdgasindustrie - Druckentlastungs- und
Druckausgleichssysteme - Änderung 1 (ISO 23251:2007/Amd 1:2008)
Industries du pétrole, de la pétrochimie et du gaz naturel - Systèmes de dépressurisation
et de protection contre les surpressions - Amendement 1(ISO 23251:2007/Amd 1:2008)
Ta slovenski standard je istoveten z: EN ISO 23251:2007/A1:2008
ICS:
75.180.20 Predelovalna oprema Processing equipment
SIST EN ISO 23251:2007/A1:2008 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 23251:2007/A1:2008
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SIST EN ISO 23251:2007/A1:2008
EUROPEAN STANDARD
EN ISO 23251:2007/A1
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2008
ICS 75.180.20
English Version
Petroleum, petrochemical and natural gas industries - Pressure-
relieving and depressuring systems - Amendment 1 (ISO
23251:2007/Amd 1:2008)
Industries du pétrole, de la pétrochimie et du gaz naturel - Erdöl-, petrochemische und Erdgasindustrie -
Systèmes de dépressurisation et de protection contre les Druckentlastungs- und Druckausgleichssysteme -
surpressions - Amendement 1(ISO 23251:2007/Amd Änderung 1 (ISO 23251:2007/Amd 1:2008)
1:2008)
This amendment A1 modifies the European Standard EN ISO 23251:2007; it was approved by CEN on 14 May 2008.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for inclusion of this
amendment into the relevant national standard without any alteration. Up-to-date lists and bibliographical references concerning such
national standards may be obtained on application to the CEN Management Centre or to any CEN member.
This amendment 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 CEN Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, 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
© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 23251:2007/A1:2008: E
worldwide for CEN national Members.
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SIST EN ISO 23251:2007/A1:2008
EN ISO 23251:2007/A1:2008 (E)
Contents Page
Foreword.3
2
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SIST EN ISO 23251:2007/A1:2008
EN ISO 23251:2007/A1:2008 (E)
Foreword
This document (EN ISO 23251:2007/A1:2008) has been prepared by Technical Committee ISO/TC 67
"Materials, equipment and offshore structures for petroleum and natural gas industries" in collaboration with
Technical Committee CEN/TC 12 “Materials, equipment and offshore structures for petroleum, petrochemical
and natural gas industries” the secretariat of which is held by AFNOR.
This Amendment to the European Standard EN ISO 23251:2007 shall be given the status of a national
standard, either by publication of an identical text or by endorsement, at the latest by November 2008, and
conflicting national standards shall be withdrawn at the latest by November 2008.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 23251:2007/Amd 1:2008 has been approved by CEN as a EN ISO 23251:2007/A1:2008
without any modification.
3
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SIST EN ISO 23251:2007/A1:2008
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SIST EN ISO 23251:2007/A1:2008
INTERNATIONAL ISO
STANDARD 23251
First edition
2006-08-15
AMENDMENT 1
2008-05-01
Petroleum, petrochemical and natural gas
industries — Pressure-relieving and
depressuring systems
AMENDMENT 1
Industries du pétrole, de la pétrochimie et du gaz naturel — Systèmes
de dépressurisation et de protection contre les surpressions
AMENDEMENT 1
Reference number
ISO 23251:2006/Amd.1:2008(E)
©
ISO 2008
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SIST EN ISO 23251:2007/A1:2008
ISO 23251:2006/Amd.1:2008(E)
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ii © ISO 2008 – All rights reserved
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SIST EN ISO 23251:2007/A1:2008
ISO 23251:2006/Amd.1:2008(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
Amendment 1 to ISO 23251:2006 was prepared by Technical Committee ISO/TC 67, Materials, equipment
and offshore structures for petroleum, petrochemical and natural gas industries, Subcommittee SC 6,
Processing equipment and systems.
© ISO 2008 – All rights reserved iii
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SIST EN ISO 23251:2007/A1:2008
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SIST EN ISO 23251:2007/A1:2008
ISO 23251:2006/Amd.1:2008(E)
Petroleum, petrochemical and natural gas industries —
Pressure-relieving and depressuring systems
AMENDMENT 1
Page 50, 5.15.7.4
Replace the last sentence at the end of subclause, “In calculating the heat absorption.wetted area term.” with
the following:
In calculating the heat absorption due to fire exposure, use Equations (6) and (7), applying an exponent of 1,0
to the wetted area term along with the following values of C and C :
1 2
In SI units:
C = 66 300
1
C = 108 900
2
In USC units:
C = 21 000
1
C = 34 500
2
Page 65, Clause 5
Add a new subclause, 5.23, after 5.22:
5.23 Overfilling process or surge vessel
5.23.1 General
Many process or surge vessels, including columns and towers, have a liquid level present during normal,
start-up, or shutdown conditions. Experience has shown that this equipment can be overfilled under certain
conditions. If the source pressure of a liquid feed or supply line can exceed the relief device set pressure
and/or the design pressure of the equipment, then overfilling shall be included in the system design. System
design options to deal with liquid overfill include but are not limited to
a) increasing the system design pressure and/or pressure relief device set pressure within pressure design
code allowances,
b) designing a pressure-relief system that can safely accommodate the overfill (including the effects of
operator intervention response as discussed in 5.4),
c) installing a safety instrumented system (SIS) to prevent the liquid overfill.
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SIST EN ISO 23251:2007/A1:2008
ISO 23251:2006/Amd.1:2008(E)
For all three options, all phases of operation shall be evaluated. Particular attention shall be given to start-up
and other non-routine operations where process conditions (e.g., flow rates, temperature and density) can be
different from normal and where conditions that lead to overfilling can be more likely to occur when compared
with normal operations.
If option a) is chosen, the user shall validate the design (foundation, piping, etc.) consistent with the liquid
overfill scenario.
If option b) is chosen, the user shall select the pressure-relief devices, design their inlet and outlet piping,
validate the foundation design, etc. consistent with the liquid overfill scenario. If operator intervention is used
as part of the system design, then the risk of failure of the operator to properly intervene shall be addressed.
The pressure-relief device may discharge back into a disposal system, such as a lower-pressure section of
the process, a flare or to other disposal system. If it is a basis for the disposal-system design, then the user
shall consider liquid overfill when designing the knockout drum, collection headers, etc. The design of the
disposal system shall prevent the discharge of liquids above their flash point directly to atmosphere (into the
air or on the ground) if there is an unacceptable risk as a result of a vapour-cloud explosion or other
hazardous condition. See 6.3.2.4 for cautions regarding the atmospheric discharge of liquids. See 6.6
regarding options for the disposal of liquids.
5.23.2 Mitigation measures
When designing the system to mitigate liquid overfill, the following can affect the design and shall be
evaluated:
a) risk of failure of the operator to respond properly;
b) operator training and operating procedures that include instrumentation behaviour;
EXAMPLE If a differential-pressure or displacer-level measurement reads low compared to actual level when the
fluid specific gravity is less than the design gravity. This can mean that the indicated level cannot reach 100 % even if the
actual level is well above the measured range.
c) availability of instrumentation that is required for adequate operator intervention;
d) availability of instrumentation that is required for safety instrumented system (SIS) response;
e) potential consequence associated with relief-stream disposition (e.g., discharge back into the process,
discharge to atmosphere, discharge to a treatment system, such as a flare, etc.);
f) pressure design code requirements.
If operator intervention and/or SIS options are selected, then a risk analysis method shall determine the
adequacy of the protection.
5.23.3 Level instruments
Some criteria to consider when evaluating level instrumentation and alarms to demonstrate availability and
independence from the basic process control system include the following:
a) whether the level instruments used for safeguards against overfilling are on separate process taps from
the process control system;
b) whether level instruments used for safeguards against overfilling are susceptible to the same common
mode device failures as those used for the basic process control system. Diverse instrumentation can
minimize the potential for common-mode device failures (e.g., differential pressure and radar, displacer
and float, etc.);
c) whether the instruments are proven in use for the specific process applications;
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SIST EN ISO 23251:2007/A1
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