EN
On offshore support vessels (OSVs) such as anchor handling, platform supply vessels and crew transfer vessels marine environments can often be amongst the most extreme on the planet. Long periods at sea and a need for a high proportion of dynamic positioning, combined with operating in sediment-rich, biological waters make ideal breeding grounds for marine fouling. Fouling on the intake pipe, heat exchangers and within the pipe work in the form of barnacles, mussels, slimes and algae can significantly affect performance and ultimately result in increased fuel usage and unscheduled maintenance downtime. Availability is the key consideration on an OSV and therefore minimizing this fouling risk is a priority for a commercial operation. Drawing on SME Group’s twenty years plus experience in marine engineering and our extensive range of solutions that include ICCP, MGPS, SED and PHE systems, this guide highlights some pragmatic solutions to minimize the risks of fouling with effective design and the implementation of an integrated approach to protection.
1. Proactive Marine Growth Prevention at the Source
The best way to prevent fouling is to stop marine organisms from even reaching your cooling system in the first place. This is the purpose of SME’s MGPS (Marine Growth Prevention System). Based on electrolytic generation of chlorine, an SME MGPS system manufactures small concentrations of active chlorine within the seawater circulating through the sea chest. This controlled level of chlorine is released directly from the sea chest and will dissuade larvae from attaching and stop biofilm from developing on the intake gratings, the inside of the pipe work and on the heat exchangers.
Continuous Protection In contrast to manual methods or pulsed shock chlorination, SME’s MGPS delivers automatic, continuous and reactive protection, in line with fluctuations in seawater. Intelligent controllers are installed to sense water temperature, flow and salinity and automatically adjust chlorine levels to ensure consistent and optimal performance. This makes the system highly suitable for OSVs working in high biological content tropical seas, or in ports known to harbor invasive species. The MGPS can be specified as part of an all-encompassing anti-fouling package when paired with SME’s ICCP (Impressed Current Cathodic Protection), protecting hull integrity against biological and electrochemical corrosion.
2. Plate Heat Exchanger Design for Fouling Resistance
Although MGPS is designed to keep the organisms from entering the system, the design of the heat exchanger must minimize the fouling that still can take place. SME’s PHEs designed for OSVs for this type of application have a few special features that specifically tackle these fouling problems. Our plates include specific chevron corrugation patterns, which allow to generate high shear stress at the heat transfer surface in order to shed organisms as soon as they stick. This design induces turbulent flow so that no areas exist where the foul can stagnant and grow.
In addition, SME provide plates that can be treated to create surfaces with lower surface energy that don’t support sticking of foulants. For vessels which may find themselves in particularly aggressive fouling waters, titanium plates may be an excellent option. The smoother surface not only adds corrosion resistance, but also ensures that the plates are easier to clean. The SME design engineering team works hand-in-hand with OSV operators to select the correct plate shape and materials for the specific working conditions and, at the same time, optimize for thermal efficiency and foulant resistance in an endeavor to maintain efficient operation between cleaning cycles.
3. Intelligent Monitoring and Condition-Based Cleaning
Catch fouling early fouling is an issue that can grow into something that critically effects ship performance. SME PHEs are designed with bosses to incorporate temperature and pressure sensors that can report in real time into the vessel’s automation system. The monitoring of the differential in temperature and the loss in pressure of the heat exchanger can allow the first indication of fouling to be found even prior to ship crew having any indication of the change in ship performance.
SME's smart monitoring software measures fouling build rate and predicts when the rate will cause the heat transfer to drop below a defined acceptable level, thereby allowing condition-based rather than schedule-based cleaning. For OSVs with strict operating regimes, being able to postpone cleaning until it is actually required, or in fact schedule cleaning prior to a vital charter, offer significant operational flexibility. Our monitoring information logs a historical record that enables technical superintendents to recognize trends and to optimize chemical cleaning practices. With SED (Shaft Earthing Devices) for the cancellation of stray current noise in the circuit, Fouling Detection with our instrumentation guarantees performance.
4. Simplified Maintenance and Rapid Spare Parts Availability
It is always going to be necessary to clean and service OSV’s in a high fouling environment despite the most efficient preventative measures. Our PHE design focus to ensure it is easily maintained, plate packs are easily opened in hours using simple hand tools not requiring specialist lifting equipment, our clip-on gasket design avoids slow application of glue allowing for a 50% time saving in gasket change compared to bonded gaskets.
Keeping a ready stock of replacement plates and gaskets is always an issue for multi- vessel OSV owners. The SME network’s global supply chain takes care of it all, supplying 1000+ vessels per year, and the 5000 sqm of Nantong workshop makes us ensure key spare parts will be available on all major shipyards worldwide, especially in mainland China. In case of need, the technical support team of SME provide real-time remote diagnostics, even on-site services, helping the crews on-board to handle the fouling problems within the shortest possible timeframe, and back to their routine work. Thanks to the ISO 9001, 14001 and 45001 certification of our quality management, and a well-integrated process consisting of MGPS, ICCP, SED and PHE technologies, OSV operators have a one-stop solution for all the fouling protection needs. Together, we go beyond what matters.