Trends in Pleated Cartridge Filters (continued)

Media Types

While many media types have been around for years, the range of available media for pleated cartridge filters is expanding as new technologies enhance media filtration and cleaning capabilities.

Available types and their applications. The most commonly used media in pleated cartridge filters is a nonwoven cellulose-synthetic blend. This media is an economical choice for dry dust collection applications at operating temperatures up to 180°F.

A polyester-silicon blend media with a melt-blown synthetic applied to its surface is a good choice for achieving emissions as low as 1 mg/m3 or less - far below the OSHA limit for nuisance dusts. This media can handle dry or moist applications with operating temperatures up to 180°F while providing a smooth surface for better dust release, thus facilitating filter cleaning.

Spunbonded polyester media is suited to applications with hot, moist airstreams in operating temperatures up to 250°F. The media can also handle hygroscopic dusts and applications requiring regular filter washdowns.

Other specialized media have been developed for more demanding applications, including heat-resistant media for very high temperature applications, flame-retardant finishes for applications with flammable dusts, carbon-impregnated finishes for dissipating static, and ultrahigh-efficiency media for removing toxic dusts.

Media area and capture efficiency. Use caution when comparing the media area (stated in square feet or meters) in different cartridge filters. Although comparing the filters' total media area is useful, it's more meaningful to compare their usable media area. With horizontally mounted filters, a large proportion of their usable media area can be lost when dust collects on the filter tops, causing uneven dust loading around each filter. With vertically mounted filters, pleat spacing and other filter design factors (discussed later in this article) can have a dramatic impact on how much media area is usable.

Also don't rely on manufacturers' claims about a media's capture efficiency stated as a percentage, such as "99.5 percent efficiency." OSHA indoor air quality limits are measured not in percentages but in milligrams per cubic meter, so you must make sure that the amount of dust in your collector's exhaust is less than the established OSHA limits in these units of measure. A reputable collector or filter manufacturer should guarantee that emissions from your collector will be below OSHA's allowable threshold for your dust.