Author(s)

G. Moe & J. M. Niedzwecki

Abstract

A historical perspective on the performance of vertical and inclined flare structures is provided to illustrate the breadth of the problem and provide a basis to appreciate the engineering solutions to the issue of flow-induced vibrations. Keywords: flare booms, flare towers, flow-induced vibrations, wind-induced vibrations, vortex-induced vibrations, fatigue damages, fatigue cracks. 1 Introduction On offshore platforms used for the production of oil and/or gas there is a special structure whose function is to lead any excess natural gas away from the platform to a burner located sufficiently far away from the platform. These structures are denoted flare towers if their main axis is nearly vertical, or flare booms if their longitudinal axis is inclined. In the North Sea these are truss structures of a length on the order of 100 m. A large number of cracks have been found in several of these flare structures, but it is striking that even though many cracks have been discovered and even though they sometimes are more than 20 year old, none the cracks have grown large enough to fracture through an entire cross section. One plausible hypothesis is that the structural damping increases considerably when cracks have been developed. 2 A review of some historic events From the Norwegian sector of the North Sea there were reports on at least 8 flare booms or flare towers that experienced damage from vibrations believed to be of

Keywords

flare booms, flare towers, flow-induced vibrations, wind-induced vibrations, vortex-induced vibrations, fatigue damages, fatigue cracks.