Pipeline Freespan Monitoring

The Problem

Our client, a major global operator, was concerned about the effects of vortex induced vibration (VIV) on freespans of their pipelines.

The operator wished to investigate whether the spans were subject to fatigue damage and if so, whether this fatigue had a significant effect on the design life of the pipelines. The pipelines considered ranged in diameter from 6” to 16”.

The Solution

We designed an integrity management scheme for our client, involving selective field monitoring of freespan movement and local environmental conditions. Key aspects of the scheme included:

• Developing hardware in-house to monitor the pipeline
• Conducting assurance studies on the accelerometer and flowmeter data gathered from the nine deployments over a two year period, to determine reliability and extract key features
• Summarising the evidence of VIV characteristics exhibited by the nine monitored freespans using the findings of the assurance studies and previous analyses of individual equipment deployments
• Re-visiting span assessment screening curves we previously produced for the client, based on the latest DNV RP-F105 and taking into account the deployment data collected
• Conducting individual assessments of all freespans currently on record as spanning over 100 m in length

Our team designed a system to measure and log the movements of the pipelines. The results were fed into fatigue calculations which our engineers could analysis in detail, manipulating inputs to investigate the effect of different sea states.

The Benefits

Our expertise and experience in VIV analysis using FEA models ensured that the client had sufficient information and an accurate insight into the fatigue of the pipelines and their remnant life. This allowed our client to effectively plan and develop a schedule of remediation and life extension works. As a result of our findings and recommendations, our client avoided unnecessary expensive repair works.