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Fatigue Life Analysis of FSO Anchor Chain with Corrosion Effect Dewinta Putri Cahyaningtyas; Nur Syahroni; Rudi Walujo Prastianto; Eko Budi Djatmiko; Murdjito Murdjito; Hafizh Muhammad Naufal Shidqi
International Journal of Marine Engineering Innovation and Research Vol 8, No 2 (2023)
Publisher : Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25481479.v8i2.16942

In this study, the authors analyze the fatigue life of the anchor chain used to secure the Gamkonora FSO to the seabed. The objective is to determine the operational lifespan of the anchor chain by considering its fatigue life. The research begins with an analysis of the movement of the Gamkonora FSO under environmental loads in both free-floating and moored conditions to determine the tension in each anchor chain. Next, the anchor chain tension is calculated for various corrosion levels, namely 0%, 5%, 10% and 15%. Subsequently, the tension range and damage ratio values are determined using the T-N curve method based on Palmgren Miner’s failure law, with failure estimation carried out using the rainflow counting method. The numerical modeling results reveal that the largest translational motion behavior of the FSO occurs during heave motion, reaching 1.409 m/m, while the largest rotational motion is observed during roll motion, with a value of 3.463 deg/m when the FSO is fully loaded. The maximum tension recorded in the anchor chain is 1,695.14 kN at heading 90 under 0% corrosion conditions, with a safety factor of 4.53. Furthermore, the cumulative damage value from the T-N curve is obtained, with the largest value recorded as 0.0702. Based on the cumulative damage, the fatigue life of the anchor chain is estimated to be 14.25 years during its operational lifespan.

Saddle Strength Analysis on Jacket Structure During Roll Up Procedures in Fabrication Phase Defriana, Nabila; Handayanu, Handayanu; Syahroni, Nur
International Journal of Offshore and Coastal Engineering (IJOCE) Vol 6, No 2 (2022)
Publisher : Pusat Publikasi Ilmiah Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25800914.v6i2.14772

Offshore platform is a structure that serves as a well drilling facility to explore, extract, store and process petroleum and gas located under the seabed. There are several phases in theconstruction of offshore structures (fixed jacket platform) from preparation to construction. Fabrication phase is the earliest stage in the manufacture of a fixed offshore platform (jacketstructure) which is carried out by the fabricator. One of the procedures at the fabrication phase is roll up procedure. In this final project research, an analysis will be carried out regarding the configuration of the rigging, crane, and sadle support used in the jacket structure during roll up procedure. After the analysis of jacket structure modeling using the SACS software, the results of rigging configuration can be obtained, which were the slingsspesifications used to connect the structure with cranes, with sling diameter of 2.75 inch and SWL value of 64 MT. As for the sling used to connect the jacket with winch has a diameter of 1.5 inch snd SWL value of 18 MT. Furthermore, the cranes used have a capacity of 75 and 78 MT, respectively. In the load analysis of the jacket structure, it was found that saddle support received the largest reaction when the jacket was at an 80-degree slope with the largest reaction value of 102.74 MT. In the saddle support local analysis, the result of maximum equivalent von-mises stress obtained was 43,486 MPa, with the saddle allowable stress of 345 Mpa, therefore the UC value of 0.24 can be obtained.

Experimental Study of Electrode Variation Effect on Connection Strength for Underwater Welding Wicaksono, Benedictus Arif; Syahroni, Nur; Mulyadi, Yeyes
International Journal of Offshore and Coastal Engineering (IJOCE) Vol 6, No 2 (2022)
Publisher : Pusat Publikasi Ilmiah Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25800914.v6i2.14773

SMAW welding has various electrodes that can be used in underwater welding. This study will analyze the influence of electrode type on mechanical properties and the influence ofwelding position on the mechanical properties of joints for underwater welding. This experiment results show that the E7016 electrode pull test has a superior value than the E6013 and E7018 electrodes; when compared between E6013 and E7016, it is reasonable if the E7016 is stronger than E6013 and the frequency level is higher than E6013 even if it already uses a different amper. However, if the E7016 electrode compared to the E7018 is still superior to the E7016 electrode using the same voltage and amper. In addition, the results of macro test observations show that welding using the E7018 electrode has lower porosity levels than E7016 electrodes, while with the same experiment results, the tensile strength of the E7016 is superior to the E7018. So that the power value of E7016 electrodes can be superior to E7018 in this experiment is not only based on porosity that occurs but also slag and imperfect penetration also determines the strength of welding results by using E7016 electrodes.

Fatigue Life Analysis of FSO Mooring Chain by Considering the Effects of Offloading Load Hafizh Muhammad Naufal Shidqi; Nur Syahroni; Daniel Mohammad Rosyid; Dewinta Putri Cahyaningtyas
International Journal of Marine Engineering Innovation and Research Vol. 8 No. 2 (2023)
Publisher : Department of Marine Engineering, Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25481479.v8i2.5457

Mooring chains are critical components in the maritime industry used to secure ships and floating oil and gas platforms such as FSOs to stay in their designated positions. The loads exerted on mooring chains during routine operations and additional loads during offloading operations can cause structural fatigue. Therefore, fatigue life analysis of mooring chains is essential to ensure safety and optimal performance. This study aims to conduct fatigue analysis of mooring chains by considering an important factor, namely the influence of offloading. Offloading load refers to the additional load exerted on the mooring chain during loading and unloading operations. The mooring system configuration uses a spread mooring system of 8 chains (4x2), 87 mm in diameter, with 20% pretension. In the fatigue analysis, the "Palmgren-Miner" method was used to evaluate the accumulated damage caused by cyclic loads. Then, the "Rainflow Counting" method is used to identify and count the number of load cycles that occur so that later the fatigue life can be calculated and known. From the research results, it was found that the mooring system configuration design still meets the safety factor requirements recommended by API RP 2 SK both during SLS, ULS, and FLS analysis. In SLS and ULS conditions, the greatest tension value is when the FSO is in the Ballast load condition, with the maximum value of tension that occurs is 2207.4 kN in SLS conditions, and 4151.6 kN in extreme conditions. In the FLS condition analysis, it was found that with an offloading frequency of 24 times per year (1271.89 hours), in the design configuration, the influence of the offloading system can increase up to 7% of the fatigue damage that occurs, and the lowest fatigue life, reduced by 3 years. The least fatigue life occurs in Chain 1.2 at the splash zone segment, which is 67 years.

Fatigue Life Analysis of FSO Anchor Chain with Corrosion Effect Dewinta Putri Cahyaningtyas; Nur Syahroni; Rudi Walujo Prastianto; Eko Budi Djatmiko; Murdjito Djatmiko; Hafizh Muhammad Naufal Shidqi
International Journal of Marine Engineering Innovation and Research Vol. 8 No. 2 (2023)
Publisher : Department of Marine Engineering, Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25481479.v8i2.5460

In this study, the authors analyze the fatigue life of the anchor chain used to secure the Gamkonora FSO to the seabed. The objective is to determine the operational lifespan of the anchor chain by considering its fatigue life. The research begins with an analysis of the movement of the Gamkonora FSO under environmental loads in both free-floating and moored conditions to determine the tension in each anchor chain. Next, the anchor chain tension is calculated for various corrosion levels, namely 0%, 5%, 10% and 15%. Subsequently, the tension range and damage ratio values are determined using the T-N curve method based on Palmgren Miner’s failure law, with failure estimation carried out using the rainflow counting method. The numerical modeling results reveal that the largest translational motion behavior of the FSO occurs during heave motion, reaching 1.409 m/m, while the largest rotational motion is observed during roll motion, with a value of 3.463 deg/m when the FSO is fully loaded. The maximum tension recorded in the anchor chain is 1,695.14 kN at heading 90° under 0% corrosion conditions, with a safety factor of 4.53. Furthermore, the cumulative damage value from the T-N curve is obtained, with the largest value recorded as 0.0702. Based on the cumulative damage, the fatigue life of the anchor chain is estimated to be 14.25 years during its operational lifespan.

Influence Analysis of Shielding Gas Flow Rate and Purity Level Variation on GMAW Welding Process to Microstructure of Alumunium 5083 Nur Syahroni; Yeyes Mulyadi; Sadewa Sechan Winando
International Journal of Offshore and Coastal Engineering Vol. 5 No. 1 (2021)
Publisher : Department of Ocean Engineering

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j2580-0914.v4i3.9954

Aluminium is a commonly used material in construction and transportation industries. The advantages of using the aluminium material are its light weight, corrosion resistant, and the capability to form an alloy with another metal. Therefore, the aim of this research is to analyze the influence of shielding gas flow rate and purity level variation to mechanical properties and microstructure of the welded material. The welding process used on this research was the GMAW method. The material used was aluminium 5083 series with 300 mm x 150 mm x 8 mm dimensions. The shielding gases used were high purity (HP) and ultra-high purity (UHP) argon (Ar). The variations of shielding gas flow rate used were 16, 18, dan 20 litre/minutes. Based on the tensile test that has been done, the variation of UHP argon gas with 20 litre/minute flow rate had the best result with yield strength of 217,32 MPa and ultimate strength of 295,83 MPa. The result of the micro photos showed that the GMAW method produced small dots where the dots were Mg2Si formation, which the greater number of smaller size dot produced would increase the mechanical properties of the material.

Saddle Strength Analysis on Jacket Structure During Roll Up Procedures in Fabrication Phase Handayanu Handayanu; Nur Syahroni; Nabila Defriana
International Journal of Offshore and Coastal Engineering Vol. 6 No. 2 (2022)
Publisher : Department of Ocean Engineering

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25800914.v6i2.14772

Offshore platform is a structure that serves as a well drilling facility to explore, extract, store and process petroleum and gas located under the seabed. There are several phases in theconstruction of offshore structures (fixed jacket platform) from preparation to construction. Fabrication phase is the earliest stage in the manufacture of a fixed offshore platform (jacketstructure) which is carried out by the fabricator. One of the procedures at the fabrication phase is roll up procedure. In this final project research, an analysis will be carried out regarding the configuration of the rigging, crane, and sadle support used in the jacket structure during roll up procedure. After the analysis of jacket structure modeling using the SACS software, the results of rigging configuration can be obtained, which were the slingsspesifications used to connect the structure with cranes, with sling diameter of 2.75 inch and SWL value of 64 MT. As for the sling used to connect the jacket with winch has a diameter of 1.5 inch snd SWL value of 18 MT. Furthermore, the cranes used have a capacity of 75 and 78 MT, respectively. In the load analysis of the jacket structure, it was found that saddle support received the largest reaction when the jacket was at an 80-degree slope with the largest reaction value of 102.74 MT. In the saddle support local analysis, the result of maximum equivalent von-mises stress obtained was 43,486 MPa, with the saddle allowable stress of 345 Mpa, therefore the UC value of 0.24 can be obtained.

Experimental Study of Electrode Variation Effect on Connection Strength for Underwater Welding Nur Syahroni; Yeyes Mulyadi; Benedictus Arif Wicaksono
International Journal of Offshore and Coastal Engineering Vol. 6 No. 2 (2022)
Publisher : Department of Ocean Engineering

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25800914.v6i2.14773

SMAW welding has various electrodes that can be used in underwater welding. This study will analyze the influence of electrode type on mechanical properties and the influence ofwelding position on the mechanical properties of joints for underwater welding. This experiment results show that the E7016 electrode pull test has a superior value than the E6013 and E7018 electrodes; when compared between E6013 and E7016, it is reasonable if the E7016 is stronger than E6013 and the frequency level is higher than E6013 even if it already uses a different amper. However, if the E7016 electrode compared to the E7018 is still superior to the E7016 electrode using the same voltage and amper. In addition, the results of macro test observations show that welding using the E7018 electrode has lower porosity levels than E7016 electrodes, while with the same experiment results, the tensile strength of the E7016 is superior to the E7018. So that the power value of E7016 electrodes can be superior to E7018 in this experiment is not only based on porosity that occurs but also slag and imperfect penetration also determines the strength of welding results by using E7016 electrodes.

Burst Pressure Analysis on Corroded Pipeline Using Finite Element Method Mahadi Yahya Sormin; Yoyok Setyo Hadiwidodo; Nur Syahroni
International Journal of Offshore and Coastal Engineering Vol. 8 No. 2 (2024)
Publisher : Department of Ocean Engineering

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25800914.v8i2.4877

The oil and gas industry includes exploration, extraction, production or processing, and transportation. One of the important activities in the oil and gas industry is the hydrocarbon transportation system. The most commonly used hydrocarbon transportation facility is the subsea pipeline. Pipes operating in a marine environment can easily corrode. Corrosion will cause a metal loss on the pipe surface and worsen the strength of the pipe. The thinning of the pipe surface due to corrosion will result in localized holes of varying depths and uneven shapes on the outer and inner surfaces. A burst pressure will occur if the internal pressure in the pipe with corrosion defects exceeds the allowable internal pressure limit. Therefore, to prevent burst pressure, it is necessary to evaluate the residual strength of the pipe in order to determine whether the defective pipe with working pressure can continue to operate safely or not. The internal pressure value calculation results are as follows: until the pipe fails, it is considered to burst using an FEA of 19.42 MPa. Meanwhile, the internal pressure value using standard codes DNV-RP-F101 is 18.76 MPa. For the effect of variations in the dimensions of the corrosion defect size, the most influential is the length and depth of the defect due to a decrease in the graph that does not fluctuate. The percentage differences between the failure pressure values resulting from rectangle and semi-ellipsoidal corrosion defects and the burst pressure values from the burst test experiments are 0.61% and 0.15%, respectively.

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