Case Study: Wire Rope Failure
XIANBIN LIU
Director & Principal Consultant @ OSKEFER| Forensic Investigation/Failure Analysis/Root Cause Analysis
Wire rope is widely used in various industries, e.g., construction, marine offshore, mining, oil & gas, etc. ?Wire ropes are commonly used for lifting and hoisting heavy loads. Any failure related to wire rope is very dangerous and even catastrophic. Wire rope can experience various failure modes, and it's essential to understand these modes to ensure proper inspection, maintenance, and replacement. Some common wire rope failure modes include abrasion, fatigue, corrosion, overload, crushing, kinking, ?Birdcaging, etc.
Herein, I would like to share one case study I handled recently. One wire rope had been used for about 20 years. The wire rope was sent to conduct a destructive test (i.e., breaking load test), however, the wire rope fractured at a much lower breaking load. The client is requested to determine whether the wire rope itself degraded or the testing methodology issue, i.e., improper clapping.
Fractographic examination and statistical analysis of the broken wires revealed that:
1)107 wires fractured with a 45° inclined shear fracture (i.e., about 45%), 83 wires exhibited necking (i.e., about 35%), and 7 strands (49 wires) remained intact.
2) majority of the individual wires within the inner layer exhibited shear lip and slant fracture (core with7/7 shear, 1st layer with 39/42 shear), and 2nd layer with 43/78 shear).
3) most of the wires that broke in the outer layer displayed signs of necking.
Shear breaks are normally caused by axial loads combined with perpendicular compression of the wire.
Necking with cup and cone feature normally corresponds to tensile overload breaks in the axis direction.
Therefore, in this case, there were pre-existing broken wires at inner layers of the wire rope before breaking load test. Due to pre-existing broken wires at inner layers of the wire rope, it failed to meet the Minimum Breaking Load (MBL) requirement during the breaking load test.
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The wire rope predominating with shear breaks could be linked to continuous bending or flexing of the rope, particularly at sharper angles or insufficient pretension of lower rope layers during spooling or under severe operational conditions, causing shear stress to concentrate in the core and inner layers.
If you have any technical questions, welcome to contact me.
Xianbin Liu PhD CEng MIMMM
Director & Principal Consultant
OSKEFER Consulting Pte Ltd
M? +65 9692 0657
Inspection Engineer at Petrochemical Corporation of Singapore Private Limited
1 年Thanks for sharing Xian Bin. The wire rope should have been taken out of service once exceeded the no.s of broken wire within one strand and/or lay length. Visual inspection coupled with Magnetic flux leakage may be necessary to detect such defects especially in the inner core.
Senior Scientist and Deputy Group Manager at Singapore Institute of Manufacturing Technology | Adjunct Principal Consultant & Co-Founder @ OSKEFER Consulting
1 年This is an interesting case!