prEN ISO 23251

SLOVENSKI STANDARD
oSIST prEN ISO 23251:2020
01-junij-2020
Petrokemična industrija ter industrija za predelavo nafte in zemeljskega plina -
Sistemi za sproščanje in izravnavanje tlaka (ISO 23251:2019)
Petroleum, petrochemical and natural gas industries - Pressure-relieving and
depressuring systems (ISO 23251:2019)
Erdöl-, petrochemische und Erdgasindustrie - Druckentlastungs- und
Druckausgleichssysteme (ISO 23251:2019)

Industries du pétrole, de la pétrochimie et du gaz naturel - Systèmes de dépressurisation

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

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Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Supplements to API Std 521, 6th edition (2014)................................................................................................................. 2

4.1 General requirements ....................................................................................................................................................................... 2

4.2 Chemical reaction ................................................................................................................................................................................. 2

4.3 Fires .................................................................................................................................................................................................................. 2

4.4 Causes for vacuum ............................................................................................................................................................................... 3

4.5 Considerations for individual PRDs ...................................................................................................................................... 3

4.5.1 General...................................................................................................................................................................................... 3

4.5.2 Multiple PRDs ..................................................................................................................................................................... 3

4.6 Piping .............................................................................................................................................................................................................. 3

4.6.1 General...................................................................................................................................................................................... 3

4.6.2 Backpressure ....................................................................................................................................................................... 3

4.6.3 Line sizing .............................................................................................................................................................................. 3

4.6.4 Multiple relief scenarios ............................................................................................................................................ 3

4.6.5 Reaction forces .................................................................................................................................................................. 3

4.7 Disposal to flare ...................................................................................................................................................................................... 4

4.7.1 General...................................................................................................................................................................................... 4

4.7.2 Combustion properties .............................................................................................................................................. 4

4.7.3 Combustion methods ................................................................................................................................................... 4

4.7.4 Flare systems designs .................................................................................................................................................. 4

4.7.5 Sizing .......................................................................................................................................................................................... 4

4.7.6 Ignition of flare gases ................................................................................................................................................... 4

4.7.7 Liquid seal drum drums ............................................................................................................................................ 4

4.8 Single PRD protecting several components in a process system ................................................................. 4

Bibliography ................................................................................................................................................................................................................................ 5

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This document was prepared by Technical Committee ISO/TC 67, Materials, equipment and offshore

structures for petroleum, petrochemical and natural gas industries, Subcommittee SC 6, Processing

This second edition cancels and replaces the first edition (ISO 23251:2006), which has been technically

revised. It also incorporates the Technical Corrigendum ISO 23251:2006/Cor.1:2007 and the Amendment

The technical requirements of this document and API Std 521 used to be identical. In the meantime

API Std 521 has been technically revised as API Std 521, 6th edition (2014). The purpose of this document

is to bring it up to date, by referencing the current edition of API Std 521 and adding supplementary

— Permission to use administrative controls such as car-sealing or chain-locking valves to prevent an