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Opportunistic maintenance strategy of a Heave Compensation System for expected performance degradation

Zhang Chao, Qian Yujie, Dui Hongyan, Wang Shaoping, Chen Rentong, Tomovic Mileta M.

Eksploatacja i Niezawodność

2021

Vol. 23, no. 3

512--521

In the marine industry, heave compensation systems are applied to marine equipment to compensate for the adverse effects of waves and the hydraulic system is usually used as the power system of heave compensation systems. This article introduces importance theory to the opportunistic maintenance (OM) strategy to provide guidance for the maintenance of heave compensation systems. The working principle of a semi-active heave compensation system and the specific working states of its hydraulic components are also first explained. Opportunistic maintenance is applied to the semi-active heave compensation system. Moreover, the joint integrated importance measure (JIIM) between different components at different moments is analyzed and used as the basis for the selection of components on which to perform PM, with the ultimate goal of delaying the degradation of the expected performance of the system. Finally, compared with conditional marginal reliability importance (CMRI)based OM, the effectiveness of JIIM-based OM is verified by the Monte Carlo method.

Utilization of an active and/or passive heave compensation in the equipment of dynamic positioning vessels

Herdzik J.

Journal of KONES

2014

Vol. 21, No. 2

89--95

DP vessels have a possibility to maintain their position or heading by using thrusters and propellers but the heave compensation is not possible that way. Heave compensation is a technique used to reduce the influence of waves on a hull or only a part of an equipment inside the hull. There are two types of heave compensation: passive (PHC) and active (AHC). Due to limit, the energy demand the hybrid heave compensation (HHC) is often in use. The offshore activities needed the compensation to some extend (level) could be drilling, handling loads in cranes or pipe laying. Different types of Heave Compensator Systems (HCS) are used to compensate for these movements. Safety of these offshore activities is so important that the area of power (using external energy) and non-power (using only the energy of wave movement) drives are quickly developed. The heave compensators allow increasing the weather window and better making use of the offshore vessels. The expected level of decreasing the vessel heave in compare to work equipment is from 5 to 50 times. Active compensation by hydraulic motor needs its active run for motion compensation and the system ought to be equipped with accelerometer senses of ship movement. Computing algorithms and the choice of control method are principal in HCS performance. In the article, it was shown examples of different types of compensators with their advantages and disadvantages and their utilization.