When considering an investment in mechanically cleaned bar screen technology, site owners are most often looking for simplicity. The mission of the bar screen at a plant's intake is to ease the remainder of the wastewater process – removing the bulk of troublesome, non-conforming debris from the wastewater stream to protect delicate downstream equipment.
However, with so many preliminary liquids/solids separation technologies to consider, it's difficult to determine what equipment will be most effective in accomplishing this mission. In some cases, operators can find themselves spending just as much time maintaining the intake screen as the rest of the processes – not exactly the simplicity originally intended. Intake bar screens can become clogged by grit, grease and stringy contaminants; large or irregularly shaped objects can damage the screen and even jam or bind the screening process, requiring operator intervention for removal.
These issues cut into the operational benefits that site owners expect from the equipment, creating expensive maintenance and unreliable performance. To ensure an investment in mechanically cleaned bar screen technology that will pay off over time, consider these five capabilities critical to effective bar screen technology.
1. Ease of Maintenance
Ideally, the installation of a mechanically cleaned bar screen will greatly reduce the amount of maintenance work within the plant. To optimize this reduction in maintenance, seek a screen that incorporates simple design constructs, such as the Duperon® FlexRake®, with a link system specifically engineered for water lubrication. A screen that is simply designed is optimal, with no lower sprocket, drive shaft, drive sprockets, or bearings below the water line to require maintenance due to wear and grit – and most importantly, should eliminate confined space entry.
2. Energy Efficiency
Look for a mechanically cleaned bar screen with a motor and controls package that is not only efficient for plant operation, but sustainable for the environment and the plant budget long-term. Fractional horsepower motors, such as the Sumitomo Cyclo Gear Motors used by the Duperon® FlexRake®, provide the raking mechanism with the persistence necessary to manage the toughest debris, yet keep costs down with consistent, low horsepower operation. Slow operating speeds and increased discharge over multiple scrapers will provide the ultimate product life.
3. Variable Debris Handling
Rocks, chunks of asphalt, concrete or metal, large clothing items, sewer plugs, tires and large volumes of septage and grease are not classified as "typical" wastewater debris. However, on any given day, any and all of these items may find their way into a wastewater channel – some with regularity! An efficient mechanically cleaned bar screen will accept both the typical wastewater debris and the debris that falls just outside those guidelines without jamming, alarms, or interruption of performance.
4. Cost of Ownership
The cost of mechanically cleaned bar screens varies widely at bid time, and it may seem simplest to accept the lowest offer to address your plant's need for screening at the intakes. However, experienced operators have learned that there is much more to the cost of a screen than its initial purchase price. When choosing a screen for your headworks, consider the long-term cost of ownership of the technology. Energy and maintenance costs, man/labor hours, and replacement parts all play an important role in the overall cost of your installation. To get a true idea of the potential costs of the mechanically cleaned bar screen you are considering, speak with operators and site owners who have installed the equipment. Their experiences may prove invaluable in realizing the true cost of your proposed installation.
5. Ease of Installation
Though it is a one-time occurrence, the installation of your mechanically cleaned bar screen can be an expensive undertaking, both in terms of cost and manpower. Installation should be simple, ideally with a fully assembled screen and raking mechanism when space and handling constraints are not an issue. Look for a unit that allows for onsite installation with your own crew, offering an opportunity for increased training and familiarity with the new equipment – and saving your site some money in the process.
Mechanically cleaned bar screens that employ these five capabilities will provide many benefits for the sites they service, such as reduced maintenance, reduced power consumption, and decreased cost of ownership. Together, these five qualities will provide a long-wearing, trouble-free installation, accomplishing the ultimate goal and simplifying the process altogether.
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