Filters and Cartridges

All filters and cartridges shall be labeled and color-coded with the NIOSH approval label. The label must not be removed and must remain legible. A change schedule for filters and canisters has been developed to ensure that these elements of the respirators remain effective. 

FIGURE 24.13 Example of an air-purifying respirator. (Courtesy of the National Institute for Occupational Safety and Health.) 

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Both media filters and cartridge filters can be used in a pretreatment process. Granular media filters involve the filtration of large particles through different layers of fine particles, usually coal, pumice, sand or garnet (Bonnelye et al. 2004). Cartridge filters act as the final filtration step before the water passes through the membranes, and remove fine particles as small as 1 pm. 

Pressure filters are usually operated batch-wise. The batch pressure filters can be classified as tank (pressure vessel) filters or presses. Tank filters have filter elements of different types mounted in pressure vessels. Tank filters are divided into pressure nutsches, leaf filters, candle or tubular filters, bag filters, and cartridge filters. Presses (see Figure 22.38) consist of a series of filter surfaces (plates). The elements are mounted on a frame and are pressed together mechanically. 

Clarification of liquids often calls for the use of depth filtration equqnnent. The process techniques used and the filtration mechanisms involved in depth filters are outlined in Ch t 6, which includes information on sand filters and cartridges. 

The most common types of filters used in industrial processing are pressure filters such filter presses, leaf filters, and cartridge filters, as well as vacuum filters like the rotary drum vacuum filter, and the rotary vacuum disc filter. Most filtration units produce a cake, which at long cycles may become reasonably dry at the expense of declining the flow rafes. Keeping consfanf... 

Stocks of spare filters and cartridges shall be maintained to allow immediate change when required or desired by the employee. Cartridges shall be changed based on the most limiting factor below ... 

Fixed rigid media are available in the forms of disks, pads and cartridges. They are composed of firm, rigid particles set in permanent contact with one another. The media formed have excellent void uniformity, resistance to wear and ease in handling as piece units. Depending on the particle size forming the filter media, temperature, pressure and time for caking, it is possible to manufacture media with... 

The TEOM sampler draws air through a hollow tapered tube, the wide end of the tube being fixed, while the narrow end oscillates in response to an applied electric field. The narrow end of the tube contains the filter cartridge. The sampled air flows from the sampling inlet, through the filter and tube, to a flow controller. The tube-filter unit acts as a simple harmonic oscillator with ... 

A soil sample (10 g) was extracted by mechanically shaking with methanol-deionized water. This mixture was filtered and a portion was removed for partitioning into toluene-hexane. A phenyl solid-phase extraction (SPE) cartridge was employed... 

Leachate Fractionation. Crude leachate was filtered through cartridge (Sep-Pak) in order to separate polar from nonpolar compounds. Nonpolar fraction was eluded from C. cartridge with acetone, evaporated under nitrogen gas and stored at -20 C. Polar leachate was lyophilized and stored at -20 C. 

In addition to online filters and precolumns, a simple protein precipitation step often precedes online SPE LC/MS/MS to prolong cartridge life. Protein precipitation can also reduce analytical interference and shorten chromatographic separation time. Since an internal standard (IS) solution is often added to plasma samples and centrifugation is used to remove possible particles before loading into the autosampler, protein precipitation does not add labor to the process. 

Cartridge 112. Influent from the WWTP Igualada (Catalonia, NE Spain) was taken into Pyrex borosilicate amber glass bottles and preserved immediately after sampling (February 2000) with addition of formaldehyde (3%, v/v). The sample was filtered through a 0.45 p,m membrane filter and pre-concentrated (50 mL) on C18 cartridges within 24 h. 

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