Offshore production platforms or FPSOs utilizing compressors and pumps often vibrate badly, causing equipment failures, lost production, excessive maintenance cost and safety issues.
Vibration problems occur because the structure’s Mechanical Natural Frequencies (MNF) are resonant with the machine’s dynamic forces.
A dynamic analysis of the support structure is required for new offshore facilities and machinery modules, or when equipment is being modified. Recommendations from the study will avoid costly repairs and downtime due to structural vibration problems.
- Create a finite element analysis (FEA) of the supporting structure, including the equipment module.
- Conduct a forced response analysis of the structure by including all dynamic forces for the planned operating conditions.
- This study is directly coordinated with the vibration study of the machine (eg API 618 or 674 analysis). This ensures consistency in the overall design, including dynamic forces, weights, inertia, damping and structural design.
Upgrade on Production Platform (9 compressor packages); Dynamic vibration analysis for multiple decks.
Dynamic Structural analysis for FPSO, including three large compressors, skid, and module deck.
Integrated Structural Dynamics and Compressor Design.
Features in BETA's Approach
- Early in the design process, BETA will provide input on the deck design, equipment locations and equipment mounting techniques. This avoids rework of design and avoid delays in the project schedule.
- BETA has proprietary software tools to calculate all dynamic loads. For reciprocating compressors, this includes gas forces, crosshead forces, driver loads and pulsation-induced forces.
- The evaluation will include both the compressor skid and platform deck.
- BETA’s forced response study will evaluate the loads for the range in operating conditions.
- Vibration amplitude, stress and deflections are evaluated against industry guidelines
- For FPSO applications, the analysis assumes a typical stiffness for the topside structure stabbing point on the ship. The calculation of the ship deck stiffness at each stabbing point can be included as an optional analysis. The scope can be expanded to include: strength of the ship deck structure (buckling analysis); and fatigue analysis of the topside structure connection to the ship deck where hull girder bending is the driving fatigue load
- BETA has developed proprietary FEA modeling techniques. These approaches have been rigorously field tested.
- Recommendations include practical modifications to increase dynamic stiffness of the skid and/or skid support structure. A summary of the applied loads and results is provided in a report (calculated mode shapes, mechanical natural frequencies and vibration amplitudes).
- Onsite inspection includes vibration and pulsation measurements.
- Dynamic structural analysis will avoid resonant conditions on the platform, FPSO, or machinery module. (Static design approaches are not able to accurately predict where resonance will occur, or the severity of vibration.)
- This analysis is cost effective, especially when coordinated with the static design.
- Based on hundreds of studies, BETA has proven leadership and experience in structural vibration analysis. Experience means faster turnaround and higher reliability operation.
- BETA's integrated approach includes platform and/or module, skid and machinery characteristics for more accurate results.
> Dynamic Analysis of Reciprocating Compressors on FPSO Topside Modules
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