Filter Bag Information

Explanation of filter bag sizes and terminology


The size and type of filter bag will determine the design of the corresponding bag filter vessel in the way it interfaces/seals with the vessel and the number of filter bag chambers to handle your flow rate.


The most common filter bag sizes are generically referred to as #1, #2, #3 or #4 and their dimensions along with the maximum capacities for nominally rated filter bags for water-like fluids is shown in the table below.


Each filter bag has a specification sheet indicating its maximum capacity based upon the retention and also has detailed information about its efficiency for retention if it is an absolute rated type of filter bag.


In addition to potential flow limitations of the filter bag, the maximum capacity of the bag filter housing is based upon its inlet size and maintaining the inlet velocity ≤12 FPS.  We can correct your flow rates and clean differential pressure figures for different viscosities if you call us or use one of our inquiry forms; this will enable us to suggest the most appropriate filter bag design and housing (if needed).


There are other filter bag designs which are filter vessel brand specific, for example Ronningen-Petter brand vessels have Certa-Seal and SE series 8" diameter x 29½" long , 152 series 4" diameter x 15½" long and 154 series 4" diameter x 26½" long filter bags.


Filter Bag Sizes

We offer the four most common "industry standard" filter bag sizes, referred to as #1, #2, #3 and #4 as well as the Ronningen-Petter SE, 152, 154 and Certa-Seal sizes as follows:

Filter bag specifications chart

depends upon the vessel inlet size and the maximum recommended flow velocity of 12 FPS for SE and Certa-Seal series bag filter vessels


Filter Bag Retention

Retention is expressed in microns (μm); Divide by 1000 to convert to millimeters (mm).


Filter Bag Efficiency

Eaton filter bags are offered in two efficiencies, "nominal" and "99%":




Filter Bag particle retentionHigher efficiencies are obtained by increasing the thickness of the filter bag material and in some cases, using multiple layers of material, each layer having a different retention.  This creates a torturous path for the particles to follow and maximizes the volume of particles that can be retained before changing the filter bag.


Filter Bag Seals

Eaton Filter Bags are generally available with two types of sealing rings, a SNAP-RING™ and a SENTINEL™ RING.  The Ronningen-Petter Certa-Seal™ is very similar to the SENTINEL™ ring design.


SNAP-RING filter bag sealSNAP-RING™ filter bags are "economy bags" having nominal efficiencies.  To help ensure the flow passes through the filter bag material and not around the edges of the filter bag opening, a ring is sewn into the material which "snaps" into a corresponding groove in the filter housing support basket.  SNAP-RING™ filter bags are available with stainless steel, carbon steel, polypropylene and nylon rings.


SENTINEL RING filter bag sealing ringSENTINEL™ RING filter bags have a molded plastic ring welded to the filter bag, their shape also "snaps" into the corresponding groove in the support basket like SNAP-RING™ filter bags.  In addition, due to their unique shape, downwards compression creates a superior "crush seal"; pushing the OD of the filter bag into the ID of the support basket groove for a tighter seal.  To fully benefit from SENTINEL™ RING filter bags an optional "hold down ring" is required to transfer the lid closure pressure to the SENTINEL™ RING.  Some filter housings, such as the goose-neck style TOPLINE™, do not require a hold-down ring.


Restrainer Baskets

filter bag restrainer basketFilter bag restrainer baskets provide support to a filled filter bag, reducing the chance for filter bag damage.  The standard filter bag restrainer basket is constructed of 316SS, has 9/64" (3.57mm) perforations and is slightly shorter than the filter bag length to ensure full support.  We can provide 20, 30, 40, 60, 80, 100, 150, 200 and 325 mesh lined support baskets to "convert" your filter housing to a strainer if desired.