U.S. FILTER TAPS ALGOR SOFTWARE TO IMPROVE WATER FILTRATION PRODUCT

The analysis program began by constructing a model of the complete drum. Deflections from this stress analysis were used as boundary conditions on detailed, tightly-meshed models of the ends of the drum.

Today's increased emphasis on the environment has led many companies in the water treatment industry to design new products and improve existing ones. Since the components used for purposes such as water filtration are often large and complex, it can be both difficult and expensive to build prototypes of proposed designs.

Increased Use of Analysis

U.S. Filter is a leader in the design and manufacture of water and wastewater treatment equipment. As demand for their products increases, the company's engineering department for Lyco™ products, under the direction of Chief Engineer James Sousa, has increased its use of Algor software in the design and analysis of both new and improved parts and systems.

Recently, Mr. Sousa called upon Algor software to help make improvements to the design of an existing water treatment product. The Micro-Matic is a rotating drum microstrainer that is used in a wide variety of applications where it is necessary to remove particulate matter contaminants and large suspended solids as a part of the water purification process. Typical uses for the system include wastewater treatment, potable water systems, industrial waste treatment and water filtration prior to ultraviolet light treatment for fish hatcheries.

James Sousa, Chief Engineer for U.S. Filter's Lyco™ products, constructed the models and performed the Algor finite element analyses to improve the design of the company's Micro-Matic drum microstrainer.

Value Engineering

"The Micro-Matic improvement project involved value engineering," says Mr. Sousa. "We basically modeled and analyzed the existing product design, making improvements wherever possible. This included weight and material usage reductions as well as specialized design considerations such as reducing the overall number of welds required. Weld reduction can provide a stiffer structure that also uses less steel. The use of Algor FEA made these specific kinds of design enhancements possible. Analyzing the effects of changing weld locations or types of welds, for example, is simply not practical to do manually. In this case, we were able to predict the behavior of any proposed design modification without building expensive, time-consuming prototypes."

System Operation

The primary component of the Micro-Matic is a large drum, onto which a series of replaceable filter panels are attached. Approximately 70% of the drum, which is open at one end and closed at the other, is submerged under water in a steel or concrete chamber.

As the drum rotates at up to two rpm, water enters the open end and a differential head builds within the drum. This causes the water to be forced out through the filter panels into a surrounding effluent chamber. Depending on the filter materials used, particulate matter as small as five microns is trapped on the inside surface of the panels.

Here we see the top of the drum. The spray heads are used to backwash trapped materials from the filters. Inside the drum a trough collects this material for further processing.

Filters Cleaned

As the filter panels rotate to the top of the drum, they emerge from the water and are passed under a spray system. The spray heads backwash the solids from the interior surface of the filters. A collection trough, located inside the drum above the water level, carries the backwash away for proper disposal or further treatment. The filter panels, now cleansed, re-enter the water as the drum continues to rotate.

The unit can be purchased as a "turn-key" filtration system, which includes an integral steel tank, or the rotating drum can be installed in an on-site concrete basin. Drum sizes vary from four to 12 feet in diameter and up to 16 feet in length. "Because of the important function these units perform," says Mr. Sousa, "Reliability is a key design consideration."

Two Step Analysis

"The critical stress condition in this type of structure is fatigue," continues Mr. Sousa, "For that reason, we performed a series of linear stress analyses. We used a two-step procedure to get the analysis data we needed. First, the entire drum structure was modeled in Superdraw II, primarily using plate elements. Loadings included maximum operating head for strength design and normal operating head for fatigue considerations.

"The second step," says Mr. Sousa, "Was to model the open and closed ends of the drum using brick elements with the deflections from the first analysis as boundary conditions. Since the models represented only portions of the complete structure, it was possible to use a much tighter mesh in areas of high stress. This method was used for a number of different proposed design alternatives. We found that through careful modeling, it was possible to closely predict the product's behavior."

Good Results

According to Mr. Sousa, the product improvement program was a big success. In his words: "We are very pleased. There is no question that the new design represents a superior filtration product."

U.S. Filter continues to use Algor software to analyze and improve water treatment products. These include glass-fused-to-steel bolted water storage tanks and rotating biological contactors. "Algor is very user friendly," according to Mr. Sousa, "The menu-driven features within Superdraw II and Superview are remarkably easy to use."