Customer Success Story: Market segment Kraftwerke Oberhasli AG Industrial water Operation under high pressure Specially adapted automatic basket strainer for pressures up to 1,160 psi Location: “Until now, the valves Background These valves use the pressure Innertkirchen, Switzerland The Kraftwerke Oberhasli of the water to control the ball had to be cleaned and AG power plant (KWO) can valves which, in turn, control Challenge: repaired by the KWO generate energy on demand at the intake to the turbines. Protecting a control valve against any time using water dammed Due to the water‘s drop height abrasion from glaciers and every three to four in the Grimselsee, 1909 meters of 670 meters, very high suspended matter in a hydroelectric above sea level. The Swiss pressures occur in the valves power station by installing an months. An automatically energy company makes and their supply lines. automatic basket strainer in the self-cleaning filter is the an important contribution supply line, and operating pressure to generating electricity Challenge of up to 1,450 psi while providing more economical and stabilizing the grid in Sand settling tanks are in place the highest possible degree of Switzerland and Europe from precision in the strainer element solution. A particularly upstream, which prevent the its hydroelectric power plants in entry of coarse particles into challenging problem was the Grimsel area. Solution: the control valves, however In addition, reservoirs act they have demonstrated only Modification of the Eaton to find a filter element as natural batteries in which Model 2596 automatic basket limited success. “Until now, that offers the highest energy can be stored in the strainer with a new, stronger the valves had to be cleaned form of water and later used to housing, special four-fold possible filter fineness and repaired by the KWO every mechanical seal on the flushing arm generate electricity. However, three to four months,” explains drive shaft, reinforced filter element that could also withstand the use of natural glacial runoff Franz Christen, Sales and and pressure reduction in the the high pressures and and rainwater poses a problem Technical Manager at backwash tube -suspended matter. The glacier BT-Hydraulik AG, which was was backwashable.“ is continuously eroding very commissioned by KWO to find fine stone particles from the Result: a solution to the problem. In Franz Christen, mountains. These solids, the past, the valves even had Minimized wear in the sliding gate derived from glacial abrasion, valves, reduction of downtime and Sales and Technical Manager to be completely replaced on a are transported by the runoff regular basis, but now they are maintenance costs BT-Hydraulik AG into the reservoir and collect no longer available on the there together with other market. In order to reduce or, suspended matter brought ideally, eliminate costly and in by rainfall. These 25 to time-consuming repairs, the 200 micron particles pose a hydroelectric power plant problem for the huge turbines operator was interested in in the KWO power plants, as finding a new solution. “The they cause heavy wear of the installation of larger settling slide valves. tanks was not an option,” continues Christen. “At water pressures of 870 psi, “A particularly challenging Result 1,160 psi or even more than problem was to find a filter Even though the test phase of 1,450 psi, very large and element that offers the the new filter system at KWO complex tanks would be highest possible filter fineness is scheduled to run for several needed. But that would not be that could also withstand years, initial results are already feasible for economic and the high pressures and was clear. “The results are very environmental reasons, and for backwashable,” says Christen. good,” says KWO. “So far we lack of space. Converting to oil A reinforced version of the ® have had no outages and the hydraulics was likewise not DuraWedge filter elements system perfectly meets our feasible for the same reasons.” proved the solution: Made of needs in terms of maintaining Therefore, KWO decided to V-shaped stainless steel wire and cleaning the baskets.” install filter systems directly profiles, even the standard Especially compared to the upstream of the control valves version is capable of being used turbine lines where the sliding and turned to BT-Hydraulik, a in demanding applications. After gate valves have not yet been leading company in the field of being further reinforced, they retrofitted, it is clear that wear hydraulic drive technology. now can withstand the high and tear has been significantly The experts from the Berne- pressures in the hydroelectric reduced - the amount of based company advised KWO power plant, filtering out a maintenance required and the Eaton Model 2596 automatic self- to use an automatic basket large part of the suspended associated costs have been cleaning strainer – picture shows strainer. “Conventional filters matter due to a filter fineness minimized by the high-pressure special version for pressures up clog up over time and need to of 25 μm. “However, the automatic basket strainer. to 1,450 psi. be serviced and replaced at system had to be additionally regular intervals,” Christen adjusted so that the screen This strainer is designed for con- explains. “An automatically self- baskets would not be deformed tinuous, uninterrupted removal cleaning filter is the more in the backwash phase,” of entrained solids from liquids economical solution.” The explains Christen. “A pressure in pipeline systems. Model 2596 problem is that standard reduction of 870 psi to the strainers are available in different backwash filters are not ambient pressure would have sizes from DN50 to DN900 (stan- designed for the high pressures been problematic despite the dard pressure ratings PN10/PN16), in a hydroelectric power plant. reinforcement.” with automatic backwash and a BT-Hydraulik, together with The high-pressure basket broad selection of screen options. Eaton, continued to work on strainers used in KWO‘s refining the Eaton Model 2596 hydroelectric power plant - so strainer. This motor-driven far there are four - have also strainer provides continuous been adapted to the operating removal of solids from fluids in parameters used there. The pipework systems - though connector size for two of the only within a standard pressure filters is 2 inches and for the range up to a maximum of other two is 3 inches, with 232 psi. However, Eaton a flow rate of between 53 provides customization of this and 106 gallons per minute. filter system to serve However, the design of the customer-specific applications. high-pressure strainer basket developed jointly by Eaton and BT-Hydraulik can also be Solution adapted to other parameters - A version of the Eaton Model in line with whatever the 2596 automatic basket strainer application requires. The was developed for KWO that is backwash is triggered by an designed for pressures of up Eaton control - in KWO‘s case, to 1,160 psi. However, a variety whenever the differential of measures were required to pressure reaches 11.6 psi. make this possible: First of all, Alternatively, control using in order to withstand the high predetermined time intervals or pressures, Eaton modified the permanent backwashing would entire housing by increasing also be feasible. the wall thickness and making the cover considerably sturdier. 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