This video helps you select the correct style Harmsco liquid filtration cartridge for your specific application.

Before you can determine what type of filter you will need, you need to identify what type of contaminates you are removing:

  • Is it a tiny particulate or a large solid?
  • Is it hard, fibrous, gelatinous?
  • Is it a liquid such as a solvent, oil, or ink?

The three main filter types are:

  • Depth Filters work best on liquid contaminates such as gels, solvents, ink and oils.
  • Bag Filters designed to work best with large contaminates.
  • Pleated Filters are most efficient for filtering particulates.

Harmsco Filter Types

Remember: a low-cost filter that needs frequent replacement costs more to use than a higher-cost filter that rarely needs to be changed.

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Pleated Microfiltration is an Elite Distributor for GE Nominally and Absolute Rated Membrane Filters. Shop over 800+ products at

Most particulate Filters are referred to as either Nominal, or Absolute. In the case of both of these filters the results achieved are very application sensitive. It is important to remember that lots of very creative claims are made by some manufacturers about how their filter will perform.

Nominal Ratings

Nominally Rated Filters capture most of the particulate of the assigned micron rating, or higher. In practice, the flow
rate has a great impact on performance. In most cases, the slower the flow, the greater the efficiency of the filter.

Pleated Microfiltration Nominal Filters available online:

Absolute Ratings

Absolute Rated Filters capture a much higher percentage of the particulate matter. Some manufacturers consider 95% as absolute, while others consider 99%, 99.9%, and 99.999%. Different test protocols are used to determine exactly what is absolute for a specific application. Although it is tempting to say that you need an absolute rated filter keep in mind that it is usually much higher priced.

Pleated Microfiltration Absolute Filters available online:

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Slow the Flow for Efficiency

With in-depth cartridge filters, the slower the flow, the more efficient the cartridge is and the longer the user can go between change-outs. At, we typically size housings to start out with a clean differential pressure of two pounds or less. You will find that many people in the filter business will quote housings that are undersized for an application so that they quote the lowest capital equipment cost.

The Pressure Drop

The differential pressure (pressure drop) across both the cartridge and housing must be considered cumulatively. The pressure drop across the housing differs from housing to housing, but in most cases, it can be obtained from the housing manufacturer.

Flow Rates

Assuming a cartridge vessel is designed for cartridges with a one-inch inside diameter, keep in mind that the flow through the bottom of each filter should not exceed 15-25 gallons per minute (for membrane pre-filters, try not to exceed 15 gpm). These flow rates should not be exceeded because turbulent flow is created on the interior core of the filter, which frequently cause unloading of contaminant from the filter media.


Always consider the viscosity of the material to be filtered when sizing filters or vessels. Also keep in mind that the viscosity of most materials varies depending on temperature. If you have an application where the customer does not want to go over a certain differential pressure and the temperature of the product can go through a wide swing, be careful to find out what the viscosity of the liquid is at both extremes of temperature.

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