ISO 23778:2022

INTERNATIONAL ISO
STANDARD 23778
First edition
2022-09
Proof of competence of hydraulic
cylinders in crane applications
Vérification d’aptitude des vérins hydrauliques pour appareils de
levage
Reference number
© ISO 2022
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Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 2
5 General . 3
5.1 Documentation . 3
5.2 Materials for hydraulic cylinders . 5
5.2.1 General requirements . 5
5.2.2 Grades and qualities . 6
6 Proof of static strength .7
6.1 General . 7
6.2 Limit design stresses . 8
6.2.1 General . 8
6.2.2 Limit design stress in structural members . 8
6.2.3 Limit design stresses in welded connections . 9
6.3 Linear stress analysis . 9
6.3.1 General . 9
6.3.2 Typical cylinder arrangements. 9
6.3.3 Cylinder tube. 11
6.3.4 Cylinder bottom .13
6.3.5 Piston rod welds . 14
6.3.6 Cylinder tube and piston rod threads . 14
6.3.7 Thread undercuts and locking wire grooves . 14
6.3.8 Oil connector welds . 15
6.3.9 Connecting interfaces to crane structure . 16
6.4 Nonlinear stress analysis . 16
6.4.1 General . 16
6.4.2 Standard cylinder with end moments . 16
6.4.3 Support leg . 16
6.5 Execution of the proof . 17
6.5.1 Proof for load bearing components . 17
6.5.2 Proof for bolted connections . 17
6.5.3 Proof for welded connections . 18
7 Proof of fatigue strength .18
7.1 General . 18
7.2 Stress histories . 18
7.3 Execution of the proof . 20
7.4 Limit design stress range . 20
7.5 Details for consideration .20
7.5.1 General .20
7.5.2 Bottom weld . 20
7.5.3 Notch stress at oil connectors . 23
7.5.4 Cylinder head . 24
7.5.5 Piston rod . 26
7.5.6 Cylinder head bolts .28
7.5.7 Cylinder head flange weld .28
7.5.8 Mechanical interfaces . 30
8 Proof of elastic stability .30
8.1 General .30
8.2 Critical buckling load .30
8.3 Limit compressive design force . 32
iii
8.4 Execution of the proof . 33
Annex A (informative) Critical buckling load for common buckling cases .34
Annex B (informative) Second order analysis of two important cases.38
Annex C (informative) Shell section forces and moments for cylinder bottom .41
Annex D (informative) Fatigue analysis of bottom weld for more complex cases . 44
Bibliography .47
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Foreword
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electrotechnical standardization.
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described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 96, Cranes, Subcommittee SC 10, Design
principles and requirements.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
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INTERNATIONAL STANDARD ISO 23778:2022(E)
Proof of competence of hydraulic cylinders in crane
applications
1 Scope
This document applies to hydraulic cylinders that are part of the load carrying structure of cranes. It is
intended to be used together with the ISO 8686 series and ISO 20332, and as such they specify general
conditions, requirements and methods to prevent mechanical hazards of hydraulic cylinders, by design
and theoretical verification.
This document does not apply to hydraulic piping, hoses, connectors and valves used with the cylinders,
or cylinders made from other material than (carbon) stee
...