Overview
AISUS were commissioned by a North Sea operator to undertake a comprehensive internal cleaning and inspection campaign on ten conductors ranging from 20″ to 30″ in diameter. The work formed a critical part of a large-scale decommissioning project and was completed in advance of a planned cut-and-pin operation.
The primary objective was to provide the client with a detailed assessment of conductor integrity, addressing concerns regarding the condition of the internal surfaces following years of exposure to the harsh offshore environment. Marine growth, corrosion, sediment, and other debris could hide areas of damage, making it difficult to assess the condition of the conductors and increasing risks during decommissioning activities.
Requirement
The task required AISUS to conduct an internal clean and visual inspection to obtain visual data and record any anomalies within 10 conductors.
A thick build up of marine growth, scale and corrosion build up within the conductors had to be removed
to allow a detailed Remote Visual Inspection (RVI) of the conductor.
Challenges
Internal diameter changes were identified throughout several conductors during the inspection. The SIRIUS X Tool was able to successfully navigate these variations due to its remotely adjustable capability.
Visibility within the closed conductors was severely reduced by murky water, making visual inspection challenging. AISUS mitigated this by deploying a submersible pump to remove the water, allowing for a clear and comprehensive internal inspection.
For conductors open to the sea, the existing water was pumped out and replaced with clean seawater to improve visibility and maximise inspection effectiveness.
Solution
A 6-man team was deployed on a 24-hour operational schedule to ensure maximum efficiency and minimise project downtime. The operation utilised our advanced internal inspection scanning tool, SIRIUS X, to deliver a comprehensive assessment of the component’s internal condition.
The scope included:
- An initial visual inspection to identify debris, marine growth, sediment accumulation, and any foreign objects that could obstruct cleaning or inspection activities.
- High pressure water jetting (HPWJ) of the component to remove marine growth, scale and corrosion build up
- Ultrasonic Testing (UT) was carried collecting wall thickness measurements throughout the component, enabling the identification of corrosion, erosion, pitting, and any areas exhibiting wall loss or reduced structural integrity
- Following cleaning, a detailed visual inspection was performed to capture high-definition imagery and video of the component internals.
Results
- The SIRIUS X successfully removed the marine growth, scale and corrosion build up within all 10 conductors, allowing for visual data to be collected effectively
- The UT data showed areas of internal and external loss of wall thickness
- Minor Surface pitting was observed throughout the majority of the 20″ conductor
Benefits
Our service delivered to the client gave the ability to inspect an area of concern for which they had previously been unable to obtain any data.
AISUS was able to provide the client with a comprehensive assessment of the asset’s condition.
