Biofouling or marine growth on the surface of submerged objects is one of the biggest problems affecting every ship at sea, including FSRUs. These growths cling to the external surface of ships and other parts such as water intakes, pipes, and so on, causing problems contributing to decreased ship efficiency.
Although there are mechanical removal tools and processes to remove such biofouling, this is not always possible, nor is the expense of docking the vessel periodically for cleaning feasible. To combat biofouling, maritime guides in Singapore recommend using one of many types of marine growth prevention systems, such as ultrasonic antifouling.
What is Ultrasonic Antifouling?
Ultrasound or ultrasonic hull antifouling leverages soundwaves to deter barnacles, algae, and other marine life from growing on the hulls and interior of ships, box coolers, and sea chests. While antifouling paints work great at preventing fouled and rough hulls (which raises frictional resistance and leads to increased fuel consumption and wear and tear), they can release toxins that are harmful to the environment.
The adoption of this ultrasonic technology has steadily risen following the ban on organotin in bottom paints by the International Maritime Organization (IMO) over a decade ago and limitations on using copper as an antifouling agent. Since ultrasonic antifouling does not rely on chemicals that harm the marine environment and wildlife, it is among the most sustainable antifouling methods to date.
The cleaning abilities of sound waves have long been recognised years ago, ever since the start of World War II, and industries have leveraged it for many purposes in agriculture, medicine, aerospace, electronics, and more since the 1950s. And although this capability has long been acknowledged to be applicable in maritime applications, its usage has only gained traction at the start of the 21st century.
The Basics of How Ultrasonic Antifouling Works
An ultrasonic antifouling system typically consists of a modular control unit or box that controls numerous transducers installed on the vessel’s hull and other internal features. The system emits multiple ultrasonic pulses in a range of targeted frequencies transmitted through the material to which the transducers attach.
The pulses create a pattern of alternative negative and positive pressure on the material’s surface, making microscopic bubbles during the negative pressure cycle, which then implode during the positive pressure cycle. This surface agitation that occurs at the microscopic level gives rise to a cleaning effect that eliminates algae, which is the first link in the food chain of marine life. Constantly keeping submerged surfaces algae-free makes them a less inviting habitat for larger algae-eating organisms. In addition, the movement of water-borne from this process also prevents mussel larvae and barnacles from embedding in the ship’s hull.
An ultrasonic antifouling system has three distinct advantages compared to other marine growth prevention systems, namely:
- Dry installation and maintenance, which eliminates the need for dry docking
- Cheaper than traditional copper-anode antifouling solutions
- Green technology with zero impact on the marine environment
The technology has addressed many of the biggest technical challenges in its implementation, with modern systems now being sufficiently robust to withstand even harsh conditions at sea and high temperatures with constant fluctuations in places like the engine room, where constant vibration is also a concern.
Conclusion
With the ever-increasing push for sustainability worldwide, the FSRU industry and its close ties to the LNG sector are compelled to make more progress in becoming more environmentally friendly. Switching to an ultrasonic antifouling system is undoubtedly a good first step towards this endeavour. However, there are many other challenges to overcome for the industry to be more sustainable and achieve its net zero goals.
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