Steel tanks in marine and offshore assets are susceptible to corrosion attack due to chemical or electrochemical reactions (galvanic corrosion) between the steel and its environment. Without proper protection mechanisms in place, steel tanks will naturally corrode in the most vulnerable areas especially at the corners of bulkhead, frames, and stiffeners.
The rate and severity of the tank corrosion are highly influenced by several factors including environmental conditions, the tank’s construction and purposes, the length of exposure of unprotected steel to moisture, chemical properties of the moisture and undesirable temperature ranges and humidity level.
Challenges in Replacing Steel in Tanks
Major safety issues when replacing steel in marine and offshore assets tanks include fire & explosion hazards, ensuring proper ventilation to prevent accumulation of flammable gases, ensuring proper protection to prevent extensive heat penetration to another tank from hot work, and ensuring proper personal protective equipment is worn by workers.
Other safety issues when replacing steel in tanks also include ensuring proper lighting, ensuring proper staging platform when working at height, proper communication between workers, and ensuring proper handling of steel materials.
Renewal of corroded steel in tanks while the asset is in operation is still possible. However, this requires careful planning and coordination between the asset’s crew and contractors performing the work.
Some challenges associated with renewing corroded steel while an asset is in operation include ensuring that work does not interfere with normal operations and productions, ensuring that adjacent tanks are gas free, ensuring that work is performed safely and efficiently, and ensuring that work is completed within a reasonable timeframe.
Exploring Alternatives to Hot Work
With the above, there have been many interests to explore alternatives to renew corroded steel without hot work. This can be done using cold bonding techniques such as epoxy coatings, or composite materials such as Sandwich Plate System (SPS).
Some advantages of using cold bonding techniques such as epoxy coatings or composite materials i.e SPS for renewing corroded steel include reduced downtime for repairs, reduced costs compared to traditional hot work methods, and improved safety due to reduced risk of fire or explosion.
Sandwich Plate System Technology
Sandwich Plate System (SPS) is an alternative solution for repairing and reinforcing steel structures in maritime and offshore applications. Sandwich Plate System consists of two metal plates bonded with a solid elastomer core, creating a strong and durable composite material. Sandwich Plate System Technology can be used to efficiently reinstate bottom and side shell structures, decks, tank tops and bulkheads, and to repair vessel cracks, without the need for hot work or drydocking.
The Sandwich Plate System Technology process uses structural adhesive and bolts for fitting new steel components in place. The bolted connections transfer the full structural capacity across the joints. Once the SPS installation is complete, the composite panel, created through bonding the solid elastomer core to the top and bottom face plates, has strength in excess of the original plating. There is no upper limit on the size of an SPS Cold Work repair – the largest approved by ABS was in excess of 800m².
Figure 1 showing Sandwich Plate System on the longitudinal and transverse bulkhead with “live” cargo tank on the adjacent side of the bulkheads
Sandwich Plate System Technology: A Permanent and Quality-Guaranteed Ship Repair Solution
Sandwich Plate System Technology has many advantages over conventional steel renewal methods, such as crop and renew, which involve cutting out and replacing corroded steel plates. SPS is faster, safer, more cost-effective and more sustainable than crop and renew. SPS can reduce installation time by up to four times, labour by up to 90%, and steel by up to 56%.
Sandwich Plate System Technology also eliminates the fire and explosion hazards associated with hot work and reduces the carbon dioxide emissions by 55%. SPS can be installed while the vessel is in operation, minimising downtime and disruption.
Sandwich Plate System Technology is approved by all major classification societies and has been used in over 500 projects covering 300,000m of various marine and offshore applications. SPS is currently the only thermoset solution being used in the maritime industry. SPS is a permanent, class-approved and quality-guaranteed ship repair solution that can extend the lifespan of any vessel and enhance its structural integrity.