In the design of subsea flow systems the integrity and reliability is paramount. As the equipment must be designed to operate at a large variety of conditions, inherent to the many processes, evaluation of the integrity is complex. . Flow induced pulsations and vibrations can cause serious design and production problems, especially in subsea gas production systems. Mechanical vibrations can be induced by internal and external flow through a complex process that is affected by numerous factors such as the piping geometry, flow conditions and fluid properties. Wellhead choke valves are commonly used to control the flow of fluids from the reservoir. During production, significant noise is produced by the flow as it passes through the choke. The noise is of broadband nature: it can be described by pressure pulsations with frequencies over a large range (1-20 kHz). The subsequent vibration levels can become significant when the pressure pulsations match with a certain acoustic or mechanical resonance mode of the production piping, and can lead to an increased risk of failure of nearby equipment. The paper describes a method to examine the mechanical loads on nearby equipment due to the vibrations induced by the usage of a wellhead choke by the means of Computational Fluid Dynamics (CFD) simulations and Finite Element Modeling (FEM). Numerical experiments were performed on a generic piping system consisting of standard pipes and bends as well as a fictive ensemble of sensor block and choke valve to explore: 1) the acoustic eigenmodes of the piping, 2) the mechanical eigenmodes of the piping and equipment, and 3) the resulting mechanical loads on the subsea equipment. It is shown that typical frequencies characteristic of noise related fatigue are such that the number of cycles, easily reaching 1010 within a few months, can be regarded as the primary source instead of the maximum stress levels. Some aspects are not considered in the current approach, such as the effect of the medium and the surrounding. These will lead to slightly lower cyclic stress estimates, and will therefore not invalidate the presented method as a worst case estimation of noise induced vibrational stresses.
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