Flotation Billets
Expanded polystyrene (EPS) can be used for a variety of flotation devices, such as rafts, docks and billets. Buoyancy billets are usually produced in standard sizes but can be easily customized. They are suitable for fresh and salt water and are unaffected by winter temperatures. EPS billets can support 55 pounds per cubic foot, which is significantly more than typical wood flotation devices. Since EPS is lightweight and easy to work with, installation and maintenance costs are low.
EPS buoyancy systems are safe for the environment. They are ozone friendly, no CFCs are used in their production and they have no food value for marine animals. Growth of marine life in stagnant water does not impair the buoyancy of the billet and can be easily removed with a scraper.
EPS flotation structures exhibit excellent rebound characteristics with minimum rocking, provide less resistance to breaking waves and are quieter than those with other types of flotation, such as drum floats.
Product Focus: Flotation
In summer months, it is not unusual to find the nearest watering hole filled with people escaping the heat and enjoying the water as well as sights and sounds. Many water-related activities are made safer with the use of expanded polystyrene (EPS) from floating docks to life-saving devices and buoys to surf and boogie boards. Whether you recognize it or not, EPS is everywhere on the waterfront.
Flotation devices have evolved over the years due to the introduction of new materials. Prior to the invention of foam plastics in the early 1960s, wood or empty drums were commonly used in flotation docks. Due to its lightweight and buoyant characteristics, EPS has become the most popular flotation product on the market today.
With a life expectancy of 20 years for exposed EPS, manufacturers began experimenting with various coatings to protect it from petroleum products floating in the water and to prolong its lifespan. The blocks were painted, encased in steel or aluminum, wrapped with fiberglass or covered with wood. By the 1990s, the Corps of Engineers recommended and implemented regulations to require encapsulated foam in all marine installations. Approved coatings or encapsulations were at the discretion of each reservoir manager, making it tedious for manufacturers and distributors to market their various products. Appendix C to 36 CFR Part 327, “Shoreline Use Permit Conditions: Dock and Mooring Floatation Standards,” specified standards currently in place. The coatings must be warranted by the manufacturer not to crack, peel, slough or deteriorate from ultraviolet rays and to retain its performance properties against wake and ice for at least eight years.
Water absorption tests developed by the American Society for Testing Materials (ASTM) do not specifically apply to flotation devices. The Corp of Engineers implements a majority of the standards followed by manufacturers and distributors. Frederic Hunt, a marina consultant, developed a simple test to determine water absorption of foam flotation docks. The “Hunt Absorption Test” is administered to obtain a preliminary indication of the relative absorption of foams. No governing body including the Corps of Engineers references this test as a standardized and reliable test. It is most widely used as an advertising and marketing tool.
Advancements in processing helped polyethylene coated expanded polystyrene gain wide acceptance. It is now the dominant flotation device due to its long life and durability. EPS billets are able to support 55 pounds per cubic feet, as compared to wood, which is approximately 20 to 40 times heavier, but can only support about 18 to 28 pounds. The polyethylene should be a minimal thickness of 0.125 inches. For areas affected by ice, thicknesses should increase to at least 0.187 inches. The tubs have an estimated life span of over 40 years and even if the coating cracks or are punctured, it will remain buoyant for approximately 15 to 20 years. Corps of Engineers concluded that encapsulated flotation devices would last three to four times longer than exposed EPS.
As the popularity of EPS floatation devices grew, new uses and designs emerged. Floating homes received national attention after being featured in the movie, “Sleepless in Seattle”. Entire floating neighborhoods dot the west coast of the U.S. and Canada. The houses range in size from 450 square feet to more than 3,000 square feet. The Floating Homes Association defines the structure as “a legally-permitted structure, with no means of self-propulsion, which occupies a permanent berth and is subject to property taxes.” There are a lot of similarities to a land home although there is no lawn to mow and instead of pesky rabbits, there are loud Canadian geese to contend with.
The homes cannot float on the polyurethane coated EPS tubs as seen under docks. Due to the extreme weight of the structure, EPS is incorporated as the core of a reinforced concrete platform. International Marine Floatation Systems, Inc. (IMFS) is a major manufacturer of floating homes. Their design consists of blocks of EPS with steel reinforced concrete walls at 10 to 15 feet on centers and a top slab. Underslab items, like plumbing, are encapsulated by the EPS prior to casting the concrete. They prefer to use a non-structural coating to protect the EPS from various marine wildlife and abrasions. Some of the platforms are more than 6 feet high. All underfloor voids are filled with EPS to insure an unsinkable home.
These unique homes are constructed to meet and often exceed local and regional building code standards. The floating foundation platforms are one-piece engineered structures to allow construction to meet local building codes and are fireproof. Similar to a land home, the occupants are fully serviced with water, sewer, cable and telephone utilities. Unlike a conventional boat, the floating platforms never require expensive haul-out for painting or scraping below the water line. Since EPS is utilized in the foundation construction, it is completely insulated from the variations in water temperature, including ice conditions. Damage due to freeze/thaw cycles is minimized.
This foundation design is also used for larger structures, including a floating restaurant, office building, public washrooms on Lake Pleasant in Phoenix, Az. and a floating swimming pool on the Mississippi River in Alton, Ill. By joining the platforms, floating walkways and roads can be assembled.
Flotation devices provide another example of how expanded polystyrene is utilized in a variety of unexpected applications. In this case, it also “expands” the opportunities to safely enjoy the waterfront and water-based activities.
** Courtesy of http://www.epsindustry.org/other-applications/floatation-billets
