- Title
- Long-term wear of model offshore mooring chains under simulated working conditions
- Creator
- Lotfollahi Yaghin, Amin
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2016
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Steel chains are used for many maritime floating structures including floating production storage and offloading platforms (FPSOs) used in the offshore oil and gas industry. Different components of the mooring systems may be damaged by storm waves and by material deterioration but this process is faster for chains located in the splash zones. A main cause of the damage is the breakage of the mooring chain of the system due to impulsive tension which is produced by large buoy motion and the abrasion between the chain links. Since protection of chains is notoriously difficult by painting or cathodic protection, design is based on an allowance which accounts for diameter loss due to both corrosion and wear. Metal loss due to corrosion and wear affects the serviceability and reliability of mooring lines and failure due to these factors has serious environmental consequences. Data on metal loss due to corrosion and wear are scarce in literature and usually do not differentiate between these two factors. This research aims to fill in the wear part of this knowledge gap. For this purpose, a test rig was designed by the author and built in the Engineering laboratory of the University of Newcastle. The function of this rig is to cause wear in a 5-link chain set being held in tension by applying an axial force together with restricting the movement of end links and moving the middle link in an oscillatory motion. The study sheds light on how different factors such as axial force, prior corrosion, wetness conditions, number of wear cycles and amplitude of movement affect the wear rate of the interlink areas of chain links. Measurements conducted include the chain mass loss and bar diameter reduction in the inter-link areas. The study shows a non-linear increase in mass loss of chains during tests with a slightly higher rate during the first 10,000 to 12,000 cycles. Also the non-linear effect of axial load on wear rate is shown by performing tests under different axial loads applied on chain sets. Although prior corrosion in marine environment causes mass loss in chains, the wear rate of corroded and un-corroded chains have similar trends. Furthermore, testing in wet conditions showed a significant decrease in wear rate of chains. These main results along with other outcomes of this research are a first attempt in documenting the metal loss of model mooring chains in order to estimate the service life of chains in actual mooring conditions for the prediction of optimum timeframe to change a chain section of a mooring line after some years of service.
- Subject
- steel chains; mooring systems; wear; marine corrosion
- Identifier
- http://hdl.handle.net/1959.13/1315675
- Identifier
- uon:22984
- Rights
- Copyright 2016 Amin Lotfollahi Yaghin
- Language
- eng
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Abstract | 129 KB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Thesis | 6 MB | Adobe Acrobat PDF | View Details Download |