Assessment of critical factors when running and retrieving Framo pump modules through moonpool

Abstract

The scope of this Master Thesis was to assess critical factors when running and retrieving Framo pump modules through the moonpool of a vessel. The thesis has been presented in a twofold manner. The first part thoroughly describes Framo Engineering AS equipment. Internal procedures and discussions with Framo employees have been used to obtain needed information. The second part has been dedicated to moonpool theory. Emphasize has been made on describing the behavior of the water inside the moonpool. The Bernoulli equation was used to prove that moonpool water motions have similar response characteristics as those of a mass-spring system. At the moonpool bottom opening the water motions are hard to describe. Moonpool responses have been described based on formulas given in DNV-RP-H103. Possible natural periods has been presented for a standard moonpool, showing that resonance condition may arise during a North Sea operation. Large water oscillations are the main concern during a moonpool operation. Hydrodynamic parameters have been discussed, including added mass and damping. Values for added mass and drag coefficients for Framo pump and running tool have been estimated according to DNV-RP-H103. From this thesis it can be concluded that installation through the moonpool has both advantages and disadvantages compared to the overside crane operations. To be able to predict the forces in the moonpool adequate input data such as transfer functions and hydrodynamic parameters should be obtained from dedicated software. Due to the complex geometry of Framo equipment, estimates of hydrodynamic coefficients should come from models test or CFD-analysis.