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Abstract Conventionally, heavy lift offshore operations require vessel cranes with immense lifting capacities, especially in harsh sea conditions dominated by swells. Due to the nature of this type of project, mobilizing a suitable Heavy Lift Vessel (HLV) is impractical at short notice. Additionally, in many regions, limited crane capacity is a common issue faced by offshore installation contractors. This paper aims to present and discuss the alternative engineering solutions to utilize the available HLV, with crane capacity lower than the jacket weight, assisted by a semi-submersible vessel. This alternative method provides flexibility to the project team when selecting the HLV for the purpose of offshore installation planning. The jacket structural characteristics and installation sequence is initially assessed to understand the jacket weight reduction associated with various jacket submersion depths. The main requirements for the semi-submersible barge are then determined considering the optimal compromise between jacket submersion depth and vessel crane capacity. The semi-submersible vessel dynamic motion, Dynamic Amplification Factor, boom tip heave motion, side-lead and off-lead angles on the vessel crane are all taken into consideration. All critical stages throughout the offshore installation starting from semi-submersible barge station-keeping, jacket float-off sequence, semi-submersible vessel grounding, lifting with jacket partially submerged, jacket wet tow, and finally jacket set-down are analyzed. All installation criteria set forth by marine operation team and international codes / standards shall be met. Furthermore, appropriate operation limiting sea states and installation workability are established, based on the analysis results considering multiple sea state combinations. A suitable semi-submersible vessel with a maximum submersion depth of 21.0 m was selected to assist the 3,200 metric tons HLV for the operation. Approximately 20% of jacket weight reduction is achieved and the remaining 80% of weight is picked up by the vessel crane. This outcome has taken into account the clearance requirements between jacket structures and vessel as well as jacket and grillage / sea fastening, including dynamic heave motion of HLV. Thorough studies were performed considering various options of positioning the semi-submersible vessel during jacket float-off and lift-off operations. Grounding the semi-submersible vessel was identified as the preferred option, as it effectively eliminates other potential risks associated with the operation. Additionally, the analysis results from different installation stages, i.e. semi-submersible vessel station-keeping, float-off, lift-off, and jacket wet-tow are used to configure and design the installation aids and select marine spreads. This innovative method can be employed for future projects with the same restrictions. It provides a wider range of HLV for heavy jacket installation, which is economical and provides flexibility to the project planning. Almost half of total cost is saved compared to conventional lifting utilizing a larger vessel crane capacity.