MultiFunction Booms: Materials and Technology for Debris Guidance and Exclusion.
Many operators at dams around the world understand the limitation, failures, and inefficiencies of debris booms typically used in front of trash racks. It's common to see booms built of plastic, wood, steel, and aluminum. Arguably, the key failing for booms is that they require the individual sections to be connected by shackles, chains or wire ropes. This traditional method of boom design leaves gaps between sections that (allowing debris to flow through or underneath) and moreover these connections become the potential failure points. Because these failure points are both the tension members and the wear items, this type of boom necessitates regular, sometimes frequent inspection, maintenance, and repair and limits their use to low tension applications. In applications where booms are required for dam safety, because of this limitation, booms are often removed during high flows, often just when you need the debris exclusion the most.
To maximize debris reduction the MultiFunction boom uses recent developments materials and technology. With HDPE materials and boom sections that can be flange bolted together, PNP has eliminated the typical gaps between boom sections where debris can pass, while increasing the safe working load of the boom and at the same time, removed the wear items and failure mechanism. To prevent floating debris from passing under the boom, a continuous length, heavy-duty, 4-ply poly-nylon debris guidance skirt, or galvanized steel screen can be permanently attached to the keel on the bottom of the boom. PNP will work with operators and engineers to oriented the boom to flow, allowing water current to guide debris to the shore for easy removal.
Boom skirts have site-specific designs, designed to maximize efficiency after consideration of environmental and operational objectives. Skirts can be flexible designed for lower water velocity sites, resistant to impacts, tears, and abrasion, weighted with galvanized chain in areas where the skirt may be in contact with the pool bottom at the low pool or with steel weight bars for mid-water spans, or skirts can be rigid, designed for higher water velocity sites.
To assist in the prevention of debris from splashing over the top of the boom, an optional debris overtopping guard runs the entire length of each boom section on the upstream side of the boom. Working like the bow of a boat, its flare prevents waves and debris from rolling over the top of the boom and provides the boom additional freeboard.
Types of Boom Sections and Connections:
Flange Bolted Sections: When boom sections can be flange bolted together, the entire boom becomes the structural load member. This methodology is ideal for applications where debris exclusion or guidance is necessary or for security and safety applications and where the attachment of lights, signs, or fences above the boom is desired. Section lengths are usually 25 to 50 feet, however, it can be any size required. Flange bolted sections are bolted together using A325 galvanized steel backer rings and galvanized hardware.
Articulating Sections: To improve debris guidance and accommodate pool fluctuation and shore connections articulating connections are used. Shore sections of the boom are generally shorter to allow increased boom articulation and fit a sites unique bathymetry. Pad Eyes and Universal joints are built with A572 high-strength low alloy steel plate. Fittings are sized to match the safe working load of the boom and can be fitted with a weak-link or boom release link if desired.
The effect of ice loads on booms is correlated with the ice boom objective (to guide or exclude), ice cover thickness, current velocities, the orientation of the boom to the flow, or the size of the ice cover that the boom must resist.
The properties of the boom’s construction material will affect the ability of the boom to survive the compression effects of ice. The size of the booms tension members and method of connections of the booms sections will allow it to survive the loads. The catenary in the boom span and ability of boom sections to articulate will assist in allowing the boom to adjust to conditions when necessary. The modular design allows a MultiFunction Boom to be constructed in a variety of shapes.
For installations where ice conditions significant, a detailed analysis of these conditions should be undertaken by experts with the requisite experience.
MultiFunction Booms™ are capable of withstanding temperatures to 140 degrees below freezing. With a very high flexural modulus of elasticity and the capacity for high deformation without fracture, combined with high tensile strength, a high bending radius, and high fatigue resistance, and fitted with connections between boom sections that enhance these properties, these booms can be designed to safely adjust variable external forces and accommodate the resultants of stresses distributed over the boom by ice, debris, or grounding during pool fluctuation.
To survive in the harsh environment where booms are often deployed they have few if any, moving parts, and they are sized with a boom diameter and wall thickness to support your site’s specific loads and budget. The modular design allows the MultiFuction boom to be built in a variety of sizes and shapes, from single pontoons to high strength rectangular shapes to provide low maintenance, high efficiency, long service life.