Self-cleaning screen filtration systems are, experienced plant managers say, a familiar technology. After all, hundreds of them are installed worldwide every year. They are most appropriately used in high-flow, low-load environments and, therefore, not usually associated with being effective when filtering organic material, especially from rivers where the water quality can change on a daily basis. However, the need to conserve water, accommodate space limitations and other factors are causing industrial companies and municipalities to look anew at this technology.
New Brunswick-based Irving Tissue paper mill had been using an older carbon steel filtration technology to process raw-intake water coming from a nearby river into its plant. Faced with an obsolescence of existing parts combined with the advantages of newer filtration technologies, Irving Tissue decided it was time to replace its 18-year-old filtration system.
The new filter installation manufactured by VAF Filtration Systems offers several improvements over the previous system, including a self-cleaning capability that does not require external motors, pistons, limit switches or PLC controls.
“The automated, self-cleaning filter concept has been around more than 40 years,” says Steve Springer, vice president of sales and marketing at VAF. “However, VAF improved upon the idea with a patented bi-directional hydrodynamic drive [BHD]. The bi-directional mechanism rotates the cleaning nozzles in a controlled path around the screen surface, with some overlap, to ensure 100 percent screen cleaning in just one pass. In the 15 second cleaning cycle, the entire screen surface is traversed at least four times.”
According to Springer, multiple passes of the screen are accomplished due to equalized pressure across both chambers of the filter and the bi-directional track in the BHD system. With the old piston-type technology, hydraulic forces encountered within the filter body allow the cleaning nozzles to make only one pass across the screen during the same 15 seconds. The BHD mechanism also has fewer moving parts than other similar self-cleaning filters, Springer notes, which amounts to an inherently simpler system that requires less maintenance and reduces overall operating costs.
Trevor Downey, Irving Tissue project manager, agrees, “We chose VAF for our site for several reasons; it was the most effective system solution with the least amount of moving parts.”
With VAF’s filter technology, “No backflushing, as with other types of filter media, is necessary. This is not the case when a sand media tank is used. Over 90 percent more water is used while flushing the sand media and excessive space is required for such a system,” Springer says.
Additionally, a typical backflush requires the downstream flow to be closed during cleaning. With automated self-cleaning filters, because backflushing is eliminated, the full flow rate of the system and the filtration process can be maintained during flushing.
“It is a first-rate system and works great,” says Downey. Delivered and installed in 10 weeks, the V-Series filter system has a flushing volume of less than 1 percent of the total flow over the course of a year, thus reducing the flushing volume the plant was seeing with the previous filter system. The frequency in which the flushing cycle is initiated has decreased as well, going from 15 minute intervals up to 40 minutes in between cycles. At the same time, however, the amount of intake water filtration has increased from 700 to 2000 gal/min with the newly installed VAF system.
In addition to the water savings and increased efficiency that the new filters offered, Irving Tissue also approved of the 316L stainless steel uni-welded body design with no external seals, which eliminates any potential leak points. The existing carbon steel filter system was replaced by five V-1500 316L stainless steel filters with custom 316 stainless steel manifold. The system engineered by VAF has a small footprint, which is beneficial when retrofitting an existing space. Though small, the system is able to exceed the performance requirements called for by Irving Tissue.
Teaming up with its Canadian distributor, Newterra, VAF supplied the filtration package while Newterra’s controller group brought its expertise to design a custom PLC control package that interfaced with the Irving Tissue maintenance control system. Newterra also continues to provide onsite training and service support to the plant. Downey concludes, “The followup from VAF and Newterra has been great. They really back up their product.”
In conclusion, the installation at Irving Tissue demonstrates the ability and efficacy of VAF’s self-cleaning screen technology to provide effective filtration in organic and inorganic environments. Key features include the self-cleaning capability along with the improved efficiency and simpler technology.
“Optimizing water usage, increasing productivity and identifying and analyzing the cost-benefits of an integrated system [are] what we do,” says Springer.
In some process applications, filters and filtration systems that are more than a decade old may not meet the quality filtration levels. The maximum return on investment can be achieved with newer filter technologies, especially given the availability of systems with continuous filtration and near zero water waste. A replacement can require less maintenance, less electricity and fewer parts. PC
For more information from VAF Filtration Systems, Arvada, Colo., call 303-425-4242 or visit www.vafusa.com.