Page 64: of Offshore Engineer Magazine (Oct/Nov 2014)

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Subsea

Active magnetic bearings (AMB) are helping to make subsea gas compression possible.

Joaquim Da Silva, François

Carrere and Frédéric Ponson of

SKF Magnetic Mechatronics, explain the engineering process involved to create the AMBs needed for this complex project.

Collaborative design with magnetic bearings

Ormen Lange land facility seen from the

Collaborative design dynamics can ubsea gas compression enables (cartridges) where one of the challenges air. Photo: Svein Roger Ivarsen/Shell.

be modeled as a kind of distributed both improved energy ef? ciency was to use canned bearings for protect-

S especially by means of appropriate mod- network with nodes, each representing and lower costs to help offshore ing the stator coils (bearings and sen- eling/simulation tools that are able to the design stakeholders. Each partici- operators to recover the remaining sors) from any contaminant present in loop on the requirements issued by the pant is responsible for several design reserves in the existing gas ? elds. the cooling gas. One of the issues to be stakeholders. requirements, solutions and decisions, To enhance ef? ciency in this appli- addressed was the validation of predic-

The project development phase was all of which are highly interdependent. cation, it is now possible to operate tive behavior of the thrust bearing and deployed using M2S2 (Multiphysics/ The dynamic of this network is strongly and control the rotation of the subsea auxiliary bearing during the production

Multiscale System Simulation). This affected by the relationships between compression units using active magnetic life cycle of the machine; constraints methodology provided all project stake- design participants. Requirements and bearings (AMBs). and speci? cation of axial load during holders with behavioral models, each a interdependencies must be well de? ned, AMBs offer a number of advantages, rotor drop and external force pertur- compromise between the details of physi- particularly the sharing of technical including high performance, a small bation were given by the compressor cal behavior and complexity. communication/information between footprint, high reliability, and advanced maker as well as the axial bearing load the different members of the project, monitoring capabilities suitable for capacity of 45kN, whereas the radial

The Ormen Lange pilot project unmanned installations. bearings 1 and 2 had a 16kN load capac-

The subsea compression station at However, the application of AMBs ity and the radial bearing 3 had a 7kN

Ormen Lange comprises a “main within compression units requires a load capacity.

module” equipped with two or long and complex development and The designers faced a wide range of four 12.5MW subsea compres- validation methodology involving challenging physic ? elds, including sion units. The integrated vertical several multidisciplinary engineer- mechanical, electrical, magnetic, ther- motor-compressor (max speed ing teams, comprising the AMB mal and many others where the electri- 11000 RPM) is equipped with supplier, the compressor original cal time constants (< microseconds to

AMBs (three radial bearings and a equipment manufacturer, engineer- milliseconds) are usually much smaller thrust bearing) linked to a variable ing, procurement and construction than mechanical ones (several millisec- speed drive, a separator module, a companies, and the end user. onds to seconds). Taking into account cooler, and a liquid pump. To simplify development, tra- all these phenomena in numerical simu-

The motor compressor is ditional “black box” speci? cation lations requires using extremely detailed equipped with three main active should be replaced by a collabora- models, and different types of solutions

Collaborative design interdependencies (network).

Illustrations courtesy of SKF.

magnetic bearing modules tive design approach. resulting in a calculation process that is

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