In late 2010, the United States Coast Guard (USCG) contacted Mascoat concerning corrosion under insulation (CUI) issues with the floating floor systems on their 110- foot cutter vessels. The issue had escalated to the point that it was costing the USCG about $200,000 every two years on each vessel, plus lost time.
What is a Floating Floor?
On a marine vessel, a floating floor is essentially a floating sheet of steel (or deck) that sits on a dampening block. These blocks are attached to the fixed deck and provide several functions for the flooring system in addition to providing a place for the floating deck to sit. Because the blocks are usually only a few inches tall, an air gap is created, reducing the transference of sound. In many cases conventionali nsulation like fiberglass is placed in this air gap for further sound reduction. These floating floors are used regularly in the marine industry because of their high ability to reduce both airborne and structural noise.
Unfortunately, in addition to taking up valuable space (4-6 inches or 10-15 cm),a floating floor cannot be effectively sealed, so corrosion from daily condensation is quite commonplace.
After the initial meeting with the USCG, it was decided that Mascoat Sound Control-dB (MSC-dB) should be applied to the fixed deck at a minimum of 60-80 mils, along with a top coat. (A top coat was recommended due to the possibility of pooling water on the deck areas.) The goal of the application was to stop the CUI issues, while at the same time providing enhanced sound damping. After examining the proposed solution, the USCG wondered if it should completely replace the floating floor systems on these vessels. All parties agreed that this approach would be hugely beneficial; however, more analysis would be needed since it had never been successfully attempted.
To get a more in-depth analysis, the USCG contacted Noise Control Engineering (NCE) out of Billerica, Massachusetts, to conduct tests using MSC-dB to replace the floating floors. NCE is a leader in acoustical testing worldwide.
Test results indicated that the Mascoat Sound Control-dB was as effective as the floating floor below 500 Hz, which is the frequency range in which machinery noise is most influential. NCE’s acoustic model shows that the damping treatment would be as effective as the floating floor for reducing noise and vibration in the compartments of interest. Tests also indicated that the application of a top coat (specified by the USCG) does not significantly alter the performance of Mascoat on the tested steel structure. This is the first known test data available that states a sound damping coating can effectively be used to replace a floating floor system.
After reviewing the test data, the USCG decided to immediately launch a pilot project on their 110’ vessels to see actual results. The first vessel is scheduled to be coated in late spring of 2011. NCE will be evaluating the results after the MSC-dB is installed. All parties involved believe this will become the new standard on the 110’ USCG vessels. The USCG has stated they will save millions of dollars per year after the implementation.