Write your message
Volume 15 - Winter and Spring 2021                   ijmt 2021, 15 - Winter and Spring 2021: 51-65 | Back to browse issues page

XML Print

Download citation:
BibTeX | RIS | EndNote | Medlars | ProCite | Reference Manager | RefWorks
Send citation to:

Eedalat P, Hasanvand E. Mooring system fatigue analysis for CALM and SALM oil terminals. ijmt. 2021; 15 :51-65
URL: http://ijmt.ir/article-1-741-en.html
1- Mechanical Engineering Department, Petroleum University of Technology
2- Offshore Structure Engineering, Petroleum University of Technology
Abstract:   (676 Views)
Offshore oil terminals are a cheaper and safer solution than conventional shore terminals for unloading and loading tankers. There are several types of offshore terminals, including Catenary Anchor Leg Mooring (CALM) and Single Anchor Leg Mooring (SALM). Safety is crucially important for offshore terminals. However, over the past few decades, mooring accidents of permanent floating structures have occurred quite frequently in the last few decades. Most of these failures have been caused by fatigue load. T-N curves-based mooring system fatigue analyses for a CALM and SALM oil terminal are presented. Stress amplitudes are calculated based on the tension amplitudes of the mooring lines under the combined loading process due to wave frequency (WF) and low frequency (LF) motion. A comparison is made between CALM and SALM mooring fatigue designs based on the conditions of the Persian Gulf region. For simulation, the hydrodynamic response characteristics of terminals and tankers are first calculated using ANSYS AQWA software, and then the outputs are imported into ORCAFLEX software for fatigue analysis. The results show that under the same environmental conditions with the same tanker tonnage, the SALM terminal mooring system shows a greater fatigue life. The minimum fatigue life of the mooring system for CALM and SALM terminals occurs at near the touch-down position (TDP) and the near of connection to the seabed, respectively. It is revealed that by changing the value of minimum breaking strength (MBS) the fatigue life of the CALM and SALM terminals changes by 119% and 100%, respectively. It is also observed that by changing the amount of K value (the value for platted T-N curve), the fatigue life of the CALM and SALM terminals changes by the same amount. In all cases, the value of R (the ratio of tension range to reference breaking strength), in the mooring line of SALM terminal, although more tension is generated, the ratio of R is less and will improve the life of fatigue.
Full-Text [PDF 1342 kb]   (157 Downloads)    
Type of Study: Research Paper | Subject: Offshore Structure
Received: 2021/02/18 | Accepted: 2021/06/27

1. Wichers, J., (2013) Guide to single point moorings. WMooring.
2. Gruy R. H. and et al, (1979), The LOOP deepwater port: Design and construction of the Single Anchor Leg Mooring (SALM) tanker terminals, in Proceedings of the Annual Offshore Technology Conference, vol. 1979-May, pp. 1793-1803. [DOI:10.4043/3562-MS]
3. Xue, X. and et al, (2018), Mooring system fatigue analysis for a semi-submersible, Ocean Eng., vol. 156, pp. 550-563. [DOI:10.1016/j.oceaneng.2018.03.022]
4. Laval G. de, (1971), Fatigue tests on anchor chain-cable, in Offshore Technology Conference.
5. Olsen M. K., (2011), Estimation of annual probability of mooring line failure as a function of safety factors, Norges teknisk-naturvitenskapelige universitet, Fakultet for .
6. Wu, Y. and Wang, T., (2015), Governing factors and locations of fatigue damage on mooring lines of floating structures, Ocean Eng., vol. 96, pp. 109-124,. [DOI:10.1016/j.oceaneng.2014.12.036]
7. Amaechi, C. V., Wang, F., Hou, X., and Ye, J., (2019) Strength of submarine hoses in Chinese-lantern configuration from hydrodynamic loads on CALM buoy. Ocean Eng., vol. 171, pp. 429-442. [DOI:10.1016/j.oceaneng.2018.11.010]
8. Pecher, A., Foglia, A., and Kofoed, J. P., (2014), Comparison and sensitivity investigations of a CALM and SALM Type mooring system for wave energy converters, J. Mar. Sci. Eng., vol. 2, no. 1, pp. 93-122, Feb.. [DOI:10.3390/jmse2010093]
9. Olagnon, M. and Guede, Z., (2008) , Rainflow fatigue analysis for loads with multimodal power spectral densities, Mar. Struct., vol. 21, no. 2-3, pp. 160-176,. [DOI:10.1016/j.marstruc.2007.12.004]
10. D. N. Veritas, "DNV-RP-C205, (2010) Environ. Cond. Environ. loads.
11. Tafazzoli, S. and Shafaghat, R., (2019) ,Investigating the behavior of the mooring system for a conceptual design of a spar floating wind turbine under survival conditions, J. Mar. Eng., vol. 15, no. 29, pp. 49-62.
12. "AQWA User Manual." [Online]. Available: https://www.sharcnet.ca/Software/Ansys/14.0/en-us/help/wb_aqwa/wb_aqwa.html. [Accessed: 19-Sep-2018].
13. API, API RP2SK.Design and analysis of stationkeeping systems for floating structures,(2015), 3rd ed. American Petroleum Institute.
14. Orcaflex, OrcaFlex Manual version 9.7a,2015. section 1;3;4;6;7, 2015.

Send email to the article author

Rights and permissions
Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

Creative Commons License
International Journal of Maritime Technology is licensed under a

Creative Commons Attribution-NonCommercial 4.0 International License.