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Passive Heave Compensator Design and Numerical Simulation for Strand Jack During Lift Operation in Deep Water

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Passive Heave Compensator Design and Numerical Simulation for Strand Jack During Lift Operation in Deep Water Journal of Marine Science and Engineering Article Passive Heave Compensator Design and Numerical Simulation for Strand Jack during Lift Operation in Deep Water Yong Zhan *, Bailin Yi, Shaofei Wu and Jianan Xu College of Mechanical & Electrical Engineering, Harbin Engineering University, Harbin 150001, China; [email protected] (B.Y.); [email protected] (S.W.); [email protected] (J.X.) * Correspondence: [email protected]; Tel.: +86-451-8256-9750 Abstract: In this paper, the passive heave compensator for the strand jack lifting system is studied. An analytical model is developed, which considers the nonlinear characteristic of the compensator stiffness thus as to predict its response under different parameters accurately. This analytical model helps to find the feasible gas volume of the compensator. The comparative analysis is carried out to analyze the influence of key design parameters on the dynamic response of the compensator. In order to evaluate the effectiveness of the compensator, a coupling model of the strand jack lifting system is derived. The compensator efficiency is evaluated in terms of the lifted structure displacement and the strand dynamic tension. The numerical simulations are performed to evaluate the effectiveness of the compensator. Numerical results show that the compensator is able to significantly decrease the tension variation in the strands and the motion of the lifted structure. Keywords: passive heave compensator; strand jack; deepwater lift operation; nonlinear model Citation: Zhan, Y.; Yi, B.; Wu, S.; Xu, J. Passive Heave Compensator Design 1. Introduction and Numerical Simulation for Strand Strand jacks are lifting devices, which are widely used in heavy liftings, such as Jack during Lift Operation in Deep offshore installation [1] and marine salvage [2]. A general strand jack consists of a hydraulic Water. J. Mar. Sci. Eng. 2021, 9, 714. cylinder and two anchors, as shown in Figure1. A number of strands are installed through https://doi.org/10.3390/jmse9070714 the strand jack and the load is attached to the end of the strands by a suitable block. The main operation cycle of the strand jack in the lifting process can be described as follows: Academic Editor: Anchor 1 grips the strands, then Anchor 2 releases the strands, and the jack extends its Constantine Michailides piston together with the load. Once the piston travels a predefined distance, Anchor 2 grips the strands, then Anchor 1 releases the strands, and the jack reacts its piston without Received: 10 June 2021 load. The above operation cycle repeats to lift the load. The strand jack offers many Accepted: 26 June 2021 Published: 28 June 2021 advantages over ship cranes, such as small size, simple structure, large capacity, high efficiency, and good controllability. Therefore, it has broad application prospects in the Publisher’s Note: MDPI stays neutral marine engineering field. The detailed information about the working principle of the with regard to jurisdictional claims in strand jack can be referred to in paper [3]. published maps and institutional affil- With the development of ocean resource exploitation, such as oil and gas, lifting iations. operations of structures have to be conducted in the deeper sea. Meanwhile, the lifted structures have become larger in size and heavier in weight in order to reduce the frequency of lifting operations and the period of underwater installation. Dealing with large size and heavy structures at a water depth above 300 m puts new challenges on the lifting equipment since the lifting operation of the strand jack is continuously influenced by the Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. wave-induced motion of the vessel. The heave motion of the lifted structure referred to This article is an open access article seabed results in excessive dynamic tension variations in the strand, which are directly distributed under the terms and exerted on the strand jack. This phenomenon is especially important in rough seas, where conditions of the Creative Commons the critical tension of the strand can be exceeded and leads to serious damage. Therefore, a Attribution (CC BY) license (https:// heave compensation system should be used to decrease the maximum tension in the strand creativecommons.org/licenses/by/ and the motion of the lifted structure, thus as to increase the safe operating sea-states of 4.0/). the strand jack. J. Mar. Sci. Eng. 2021, 9, 714. https://doi.org/10.3390/jmse9070714 https://www.mdpi.com/journal/jmse J. Mar. Sci. Eng. 2021, 9, 714 2 of 18 heave compensation system should be used to decrease the maximum tension in the J. Mar. Sci. Eng. 2021, 9, 714 strand and the motion of the lifted structure, thus as to increase the safe operating2 ofsea- 16 states of the strand jack. Figure 1.1. Structure of strand jack.jack. Heave compensation is is an an effective effective techni techniqueque to todecouple decouple the the load load motion motion from from the thewave-induced wave-induced vessel vessel motion. motion. There There are three are three types types of heave of heave compensation compensation systems: systems: pas- passive,sive, active, active, and andsemi-active semi-active heave heave compensati compensationon systems systems [4]. The [ 4passive]. The heave passive compen- heave compensationsation system uses system a fixed uses mass a fixed of massgas as of th gase elastic as the medium elastic medium and store and or store release or releaseenergy energywhen the when dynamic the dynamic load is performed load is performed to keep toth keepe position the position of the load of the constant load constant with respect with respectto seabed to seabed[5]. The [5 passive]. The passive compensation compensation system system has the has advantages the advantages of consuming of consuming little littleexternal external power, power, simplicity, simplicity, and high and highreliability. reliability. Therefore, Therefore, it is itsuitable is suitable for large for large size sizeand andheavy heavy structure structure lifting lifting applications. applications. The Theactive active heave heave compensation compensation system system uses usesthe sen- the sensorsor to measure to measure the thevessel's vessel’s motion. motion. Then, Then, the actuator the actuator is controlled is controlled dynamically dynamically to com- to compensatepensate for the for vessel the vessel motion. motion. It has It high has highcompen compensationsation efficiency efficiency and is and accurate is accurate in posi- in positioning. However, there are some disadvantages to the active heave compensation tioning. However, there are some disadvantages to the active heave compensation system, system, such as high cost, low reliability, and high power consumption. The semi-active such as high cost, low reliability, and high power consumption. The semi-active heave heave compensation system is a hybrid system, which combines features of both passive compensation system is a hybrid system, which combines features of both passive and and active systems. More detailed information can be referred to in the literature [4]. active systems. More detailed information can be referred to in the literature [4]. The operational process is time-consuming, and the strand jack experiences heavy The operational process is time-consuming, and the strand jack experiences heavy load when lifting operation of large size, and heavy structure is carried out in deep water. load when lifting operation of large size, and heavy structure is carried out in deep water. Moreover, high reliability and low power consumption are the main considerations. Thus, Moreover, high reliability and low power consumption are the main considerations. Thus, the passive compensation system was considered in this paper. the passive compensation system was considered in this paper. The passive heave compensation system has a broad variety of applications, including offshore lifting [6], vertical array of hydrophone [7], and riser tensioner [8–10]. Therefore, passive heave compensation systems received much attention in recent years, and much effort has been made to design the compensators with good performance. In order to investigate the dynamic response of the passive compensator, several dynamic models J. Mar. Sci. Eng. 2021, 9, 714 3 of 18 The passive heave compensation system has a broad variety of applications, includ- ing offshore lifting [6], vertical array of hydrophone [7], and riser tensioner [8–10]. There- J. Mar. Sci. Eng. 2021, 9, 714 fore, passive heave compensation systems received much attention in recent years,3of and 16 much effort has been made to design the compensators with good performance. In order to investigate the dynamic response of the passive compensator, several dynamic models have been proposed in the literature. Nam [6] proposed a model based on linear stiffness havefor a beenpassive proposed compensator in the literature.without the Nam consider [6] proposedation of athe model damping based effect. on linear Both stiffness numeri- forcal asimulations passive compensator and experimental without the results consideration show that of the the dampingcompensator effect. is Botheffective numerical in de- simulationscreasing the and wire experimental tension variation results for show the that ship the crane compensator lifting operation. is effective Duc in [11] decreasing investi- thegated wire the tension crane variationvibration-reducing for the ship proble cranem liftingusing operation.a
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