Marine Growth Removal: A Common ROV Pilot Task Explained Step by Step

Marine growth removal is one of the most common maintenance tasks performed by ROVs on offshore structures. Over time, marine organisms colonize subsea infrastructure, adding weight, increasing hydrodynamic loading, and obscuring the steel surfaces that need to be inspected for corrosion and fatigue cracking. Effective marine growth removal requires the right tools, proper technique, and thorough documentation. This guide covers the practical aspects of performing marine growth removal operations with ROVs.

Why Marine Growth Removal Matters

• Excessive marine growth adds significant weight to the structure, affecting structural loading calculations
• Growth obscures the steel surface, preventing visual inspection for corrosion and cracks
• Marine growth increases the effective diameter of members, raising hydrodynamic forces during storms
• Some regulatory frameworks require growth to be managed below specified thickness thresholds
• Cathodic protection system performance can be affected by heavy biological fouling

Brush Tool Systems

Rotary brush tools are the most widely used equipment for marine growth removal on structural members. Hydraulically powered brushes are mounted on the ROV and applied directly to the fouled surface. Brush types include wire brushes for heavy hard growth (barnacles, mussels) and softer nylon brushes for light fouling. The key to effective brush cleaning is consistent pressure and speed — too aggressive and you damage the coating, too light and the growth is not fully removed. Multiple passes are typically required for heavily fouled areas.

Waterjet and Cavitation Systems

• High-pressure waterjet systems (up to 700 bar) for heavy fouling and coating removal
• Cavitation cleaning systems that use controlled cavitation bubbles to remove growth without surface damage
• Ultra-high-pressure (UHP) systems for precision cleaning and surface preparation
• Waterjet systems require careful pressure management to avoid damaging anti-corrosion coatings
• Cavitation systems are preferred for sensitive surfaces where coating preservation is critical

Inspection After Cleaning

• Perform a close visual inspection (CVI) of all cleaned areas immediately after cleaning
• Document the surface condition — note any coating damage, corrosion, pitting, or cracking
• Record the location and extent of any defects found using the structural reference system
• Take high-resolution still photographs of all defects and anomalies
• Compare the cleaned condition against previous inspection records if available
• Flag any findings that require engineering assessment or repair

Documentation Requirements

• Record the cleaning method used, tool type, and operating parameters
• Document the area cleaned with reference to the structural drawing
• Log the marine growth type and estimated thickness before and after cleaning
• Include before and after video and still images for each cleaned zone
• Note any operational issues encountered during cleaning
• Record cleaning duration per zone for future planning reference

Using ThrusterLog for Cleaning Records

Marine growth removal generates detailed records that need to be organized systematically for client reporting and regulatory submissions. ThrusterLog allows ROV teams to log cleaning operations alongside dive records, linking the cleaning data to specific structural locations and attaching photographic evidence. This integrated approach ensures that all cleaning activities are traceable and that the documentation meets client and regulatory standards.