The vibration activity monitor is a relatively simple hardware and software system designed to provide updated predictions of the fatigue-loading activity in the jacket major-member welds of offshore oil platforms. Positioned on the platform cellar deck, the vibration recorder measures platform deck motion with two orthogonal accelerometers. These motions are processed in real-time to provide continuous records of the direction and frequency of platform motion. The recorded data is combined with transfer functions from a finite element structural model, in order to predict and rank the fatigue activity in the joints. These predictions are used to verify the platform design fatigue analysis, to understand where unanticipated fatigue activity has occurred and to define the welds for underwater inspection. This monitoring information will result in cost savings, maximized operating window, increased safety, minimized fatigue on critical elements, and generally improve the understanding of the platform behavior.
Offshore Structural monitoring provides the offshore industry the following:
- Design verification
- Installation control
- Structural integrity
- Riser Monitoring
- Noise and Vibration
- Collision detection
- Vessel performance monitoring
- Platform Monitoring
- Instrumentation solutions for Wind Farms
Significant changes to the platform’s structural integrity can be detected by monitoring its natural frequencies and comparing the response characteristics to certain criteria. With this data you can:
- Reduce in frequency the periodic sub-sea inspection.
- Assess platforms following a hurricane.
- Allows the operator to prioritize remedial actions when resources are at a premium. A platform fitted with OLM can quickly be assessed and brought back into production.
- Reduce the time at risk of a failed member, minimizing the probability of catastrophic failure.
- Monitor systems installed on offshore facilities, especially those requiring extension of operating life.
The central data acquisition unit should have enough channels to record the accelerometers and several additional channels to record other sensors such as:
- Tilting and inclinometers to monitor the overall structure.
- Strain gauges located in the legs to monitor leg and overall structure loads and weight distribution.
- Relative motion monitoring system allows the motion of a jacket and cantilevered drilling jack up platform to be compared with allowable limits.
- Tides and ocean waves-height, measuring the air-gap measurements using a radar-based wave height sensor.
- Meteorological data (wind speed, wind direction, barometric pressure, temperature and humidity).
- Integrity monitoring for free standing risers.