Miscellaneous Mechanical ComponentsDOE-HDBK-1018/2-93FILTERS AND STRAINERSDeep-bed filters, like precoat filters, are cleaned by backwashing. Water is pumped through thedistribution piping near the top of the filter. The flow rate of the water is kept high enough tolift the granulated charcoal or anthracite up into the free space. The water washes away thedeposits that have accumulated. When the backwash cycle is completed, the flow is stopped, andthe granules settle back down into the filter bed. The filter can then be put back into service.Metal-EdgedFiltersMetal-edged filters are used in the lubrication (oil) systems of many auxiliary units. A metal-edged filter consists of a series of metal plates or disks. Turning a handle moves the plates ordisks across each other in a manner that removes any particles that have collected on the metalsurfaces. Some metal-edged type filters have magnets to aid in removing fine particles ofmagnetic materials.StrainersStrainers are fitted in many piping lines to prevent the passage of grit, scale, dirt, and otherforeign matter, which could obstruct pump suction valves, throttle valves, or other machineryparts. One of the simplest and most common types of strainers found in piping systems is theY-strainer, which is illustrated in Figure 23.Figure 23 Y-strainerFigure 24 illustrates three additional common types of strainers. Part A shows a typical sumppump suction bucket strainer located in the sump pump suction line between the suction manifoldand the pump. Any debris that enters the piping is collected in the strainer basket. The basketcan be removed for cleaning by loosening the strongback screws, removing the cover, and liftingthe basket out by its handle. Part B of Figure 24 shows a duplex oil strainer commonly used in fuel oil and lubricating oillines, where it is essential to maintain an uninterrupted flow of oil. The flow may be divertedfrom one basket to the other, while one is being cleaned. Rev. 0ME-05Page 45
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