Structural Steel Remediation on Corroded Fire Wall on Offshore Platform

Overview

The operator of an offshore platform had recently removed the cementitious passive fire protection (PFP) system on its fire wall for a detailed structural inspection. With the PFP removed the damage was observed to consist of the entire loss of section in the majority of structural columns. In addition to this there were numerous holes through the firewall with many other regions displaying less than 30% of the residual wall thickness.

IC Integrity were engaged to find a solution to the structural degradation. The challenge was to reinstate the firewall structure with no hot work and with an extremely rapid turnaround.

Scope

The project had the following specifications:

Structure	Offshore oil platform firewall
Wall Section Loss	30% average over the first meter
Wall Sheeting Design Pressure	4.8 kPa
Structural Member Design Condition	Return to original strength
Design Life	20 years
Repair Size	55 m2

Solution

The solution encompassed a hybrid carbon fibre and bonded/bolted structural steel solution. This proprietary iasgroup technology combines structural steel and CFRP bonding on site to provide structural reinforcement.

For the columns, prefabricated steel sections were bolted and adhesively bonded to reinstate the original capacity.

For the firewall membrane, multiple layers of Carbon Fibre reinforced epoxy laminates were deigned to meet the design pressure. The layers were site laminated and vacuum bagged into place.

All engineering for this project was completed in-house.

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Benefits

• No Category 1 Hot Work: The repair was undertaken under Category 2 hot work permits
• Rapid Turnaround: From site visit to the operations staff mobilising to site took 4 weeks. Site installation took a further 29 days to complete
• Durability: The use of CFRP to reinstate the firewall and the use of epoxy bonding at the steel interface provides a significant improvement on durability when compared to traditional methods
• Cost effective: CFRP is highly versatile and customised to site conditions resulting in less time on site