The Safe Damping for Non-Linear Cases of Subsea Equipment Installation

Abstract The concept of increasing the damping ratio to reduce response amplitude is applied to the highly nonlinear problem of vertical installation of subsea equipment. It is known that, depending on the equipment and excitation characteristics, the installation cable can become slack, leading to elevated tension peaks known as snap loads. Due to the nonlinearity of the installation, such as the cable stiffness becoming zero when the cable is not stretched, different dynamic behaviors can occur during slackness. This work shows that increasing damping to convert a double-periodic response into a quasi-harmonic one can greatly reduce tension peaks in the cable. However, further increasing the damping beyond this threshold results in only slight decreases in the tension peaks. Thus, this work proposes the use of the damping ratio capable of causing the response to become quasi-harmonic, which is referred to as the safe damping factor, to increase the safe operation window of the installation.