ISO 5175-3:2025

International
Standard
ISO 5175-3
First edition
Gas welding equipment — Safety
2025-04
devices —
Part 3:
Decomposition blockers for low-
pressure acetylene
Matériel de soudage au gaz — Dispositifs de sécurité —
Partie 3: Bloqueurs de décomposition pour l'acétylène basse
pression
Reference number
© ISO 2025
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Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Materials . 2
5 Requirements . 2
5.1 General .2
5.2 External gas tightness .2
5.3 Pressure resistance .2
5.4 Decomposition resistance .2
6 Methods for type testing . 3
6.1 General .3
6.2 Accuracy of pressure.3
6.3 External gas tightness test .3
6.4 Pressure resistance test .3
6.5 Decomposition test .3
7 Manufacturer's instructions . 4
8 Marking . . 4
Bibliography . 6

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 44, Welding and allied processes, Subcommittee
SC 8, Equipment for gas welding, cutting and allied processes.
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iv
International Standard ISO 5175-3:2025(en)
Gas welding equipment — Safety devices —
Part 3:
Decomposition blockers for low-pressure acetylene
1 Scope
This document specifies the general requirements and tests for decomposition blockers downstream of
pressure regulators in acetylene manifold systems (see ISO 14114). Decomposition blockers can be used in
the low-pressure section (downstream of acetylene manifold system outlet) up to 0,15 MPa (1,5 bar) e.g. in
pipelines, outlet points or for the protection of low-pressure sections in big pipe systems. Decomposition
blockers can only be used in sections with pure acetylene. The possible backflow of oxygen or air into
the section where the decomposition blocker is installed needs to be prevented by a non-return valve
downstream of the decomposition blocker.
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.
ISO 554, Standard atmospheres for conditioning and/or testing — Specifications
ISO 5175-1, Gas welding equipment — Safety devices — Part 1: Devices incorporating a flame (flashback)
arrestor
ISO 9090, Ga
...