There are two main types of filter bag systems: 1.Open System; 2. Closed System

Open System

This is the most economical bag filter system consisting of a micron rated filter bag, which is simply tied onto a pipe, or secured to an adapter head which is threaded onto a pipe, through which unfiltered liquid passes. An open system also includes a strainer bag (placed inside a 5 gallon pail, for example) into which unfiltered fluid is poured.

Closed System

This is an economical method of liquid filtration consisting of three main components:

• a micron rated filter bag
• a retainer basket
• a pressure vessel

The liquid to be filtered is delivered through the inlet of the filter vessel into the top of the filter bag, which is supported by the retainer basket. Because the system is pressurized, the liquid is distributed evenly over the entire surface of the filter bag, resulting in even flow distribution.

In both Open and Closed systems the fluid passes through the filter bag from the inside out. Contaminate particles remain inside the bag, allowing filter bag change out to take place without contamination of the filtrate.

Bag Filter Systems vs. Cartridge Systems

Liquid filter bags offer a very economical and efficient alternative to cartridge filters. Filter bags offer the most cost effective means of particulate removal from liquid streams (1 micron to 2000 micron nominal). One filter bag can replace up to nine cartridge filters, offering substantial cost savings. Our bags are easy to use and readily available, usually within a few days. Stock items can be shipped same day.

Absolute vs. Nominal Micron Ratings

The terms Absolute and Nominal are often associated with micron ratings given to liquid filter bags and cartridges.

As the name suggests, absolute conjures up a notion of 100% pure filtration. Absolute rated filter bags and cartridges, contrary to their name, are not absolute. They are generally gauged by the percentage of contaminate particles they are capable of removing in perfect laboratory conditions. For example, a one micron absolute rated filter bag will remove between 99.5% and 99.9% of laboratory "challenge particles" one micron or larger. They are not 100%. For this reason, we refer to this type of filter bag as "High Efficiency", stating the corresponding media efficiencies from independent laboratory test results.

On the other hand, nominal micron ratings are average or general in nature. Their efficiencies can fall anywhere between 50% and 95% with the norm being around 80% efficiency. That is to say, a one micron nominally rated filter bag will remove approximately 80% of "challenge particles" one micron or larger in perfect laboratory conditions. The terms Absolute (High Efficiency) and Nominal should be used as a guideline only when selecting the best filter bag or cartridge for an application. Unless stated as "High Efficiency", micron ratings used in our nomenclature are nominal.

Welded vs. Sewn Construction

The key benefits of this fully welded product are:

• Increased performance efficiencies due to the elimination of needle holes from the sewing process means no unnecessary bypass through sewn seams when trying to filter very fine particulate.
• The absence of sewing thread eliminates silicone contamination issues.
• More cost effective production equates to a more competitively priced product.

The end result is a higher quality, value added filter bag without added cost.

PolyformSEAL™

Industrial Filter has developed its new PolyformSEAL™ in both 4" and 7" configurations. These new top retaining flanges are a perfect fit in our own IFM filter housings, as well as most competitor's filter vessels. Three advantages of this new design are:

• Quadruple sealing, which means this flange creates a seal in four distinct points in its' profile. This translates into excellent sealing characteristics, all but eliminating the possibility of fluid bypass.
• Raised handles with a thick cross section means high strength in a user friendly design for easy removal from the filter vessel.
• Available on both polypropylene and polyester felt bags, this seal offers versatility for specific thermal and chemical applications.

 Filter Bag Operating Guidelines

• Recommended change out: it is recommended that a liquid filter bag be changed out when the differential pressure (P) between the upstream and downstream sides reaches 20 - 25 psi. Although this is a rule of thumb, some applications may require change out at a P well below 20 psi. Under no circumstances should P be allowed to exceed 25 psi.
• Maximum operating pressure: for carbon steel and stainless steel filter housings is 150 psi, provided this pressure is indicated on the vessel's data plate. If no pressure is indicated, the vessel should not be used. Normal operating pressure for most industrial systems is between 40 and 80 psi. Special order vessels are available with higher operating pressure capabilities.
• Maximum flow rate: The following is a general guideline for four standard filter bag sizes based on a continuous flow of clean water at ambient temperature:
  
  

  Size 1	7" x 16.5"	80 USGPM
  Size 2	7" x 32"	150 USGPM
  Size 3	4" x 8"	20 USGPM
  Size 4	4" x 14"	40 USGPM

Typical Applications

Typical applications suited to liquid filter bags include:

• Paint, coatings and ink industries.
• Process water, water treatment and cooling tower applications.
• Petro chemical, solvents and general chemical applications.
• Food and beverage industries.
• Pharmaceutical and cosmetics applications.
• Adhesives and resins industries.