How to Select a Bag Filter Housing


We offer many different styles of bag filter housings and this article will help you determine which is the best fit for your particular application.


Let's begin by providing an overview of the simplex bag filter designs we offer within the navigation bar above, listed by least expensive to most expensive.  Its the complexity of the design (directly related to their capabilities/features) which influences cost the most.


Ecoline bag filter housingsEcoline: Used for "light duty" applications and rated for a maximum pressure of only 100 PSI, the Ecoline has a clamp style closure and is only available in 316SS material with FNPT threaded connections. It does have some notable features, such as an investment cast concave chamber cover which displaces some fluid so that when the chamber is opened the fluid level is below the edge of the vessel.  We can modify the vessel to have differential pressure ports, but that is about as much "customization" this design offers.  The Ecoline cannot be ASME code stamped and filter bag sealing is assisted by a separate internal spool which transfers the downward pressure of the lid closure across the circumference of the filter bag.  This type of sealing is characteristic of all our housing designs EXCEPT the Topline and therefore applications requiring high efficiency particle retention (greater than 65%) and especially for particle retention <50 microns, the Topline design should be utilized.


Miniline: A version of the Ecoline above designed to be used with smaller size filter bags (#3 and #4 sizes).  Reserved for low flow rate applications when a compact size/footprint is desired, they are not much different in cost from the "full size" (#1 and #2 size) Ecoline and Flowline II bag filter housings.


Flowline II bag filter housingsFlowline II: This is an inexpensive version of the Flowline housing design, having some additional material options compared to the Ecoline (carbon steel, 304SS and 316SS), Flowline II vessels are rated to 150 PSI due to its swing bolt closure and are offered with flanged or threaded connections.  Their body is hydroformed, reducing the number of weld areas, promoting a smoother internal finish.  While the manufacturing process reduces the cost of the Flowline II, it also means that customizations such as adding differential pressure taps, surface polishing and non-standard connections are not available.  As with the Ecoline above, this entry-level housing is designed for nominally rated filter bag applications where an ASME code stamp is not required.


Flowline: This is the entry-level housing for industrial applications that require an ASME code stamp.  Since the manufacturing technique involves additional welding, its more expensive than the Flowline II but it also enables non-standard connection types, differential pressure taps and surface polishing.


Sideline: These filter bag housings can be customized more than the above, to include features such as steam jacketing, side outlet location and can be ASME UM or U stamped; CRN registration is also supported with this design.  Features such as a concave displacement cover and a hold down spool are standard and similar to the other designs mentioned above.


Cutaway of a Topline bag filter housingTopline: Featuring a "goose neck" or "over-the-top" inlet design, the Topline style housing represents the best sealing capability of all bag filter housing designs.  This is because a hold-down spool is not required to seal the filter bag to the vessel, rather the chamber cover directly interfaces with the bag sealing ring and forms a bypass-free seal.  This type of direct seal with the filter bag is only possible with this inlet configuration as it enables the filter bag to be placed at the top rim of the vessel.   The additional complexity of this design contributes to its higher cost, but for applications requiring efficient retention of particles smaller than 50 microns, it is the best design to use.  This design can be ASME code stamped, polished internally or externally and customized with special connections, a steam jacket or differential pressure connections.


Polyline and FLV: Represent our non-alloy designs (PVC, CPVC and PVDF).  These are typically used for non-alloy pipelines and thus have some limitations; they cannot be ASME code stamped, polished or steam jacketed and their flow rates are typically limited to a maximum of 100 GPM.  These are more expensive than their alloy counterparts and chosen for aggressive chemistries which otherwise would require expensive, "exotic" alloys.


All of the bag filter vessels above are single chamber, simplex designs.  Therefore the flow rate is limited to the capacity of the single filter bag used within it and the process needs to be interrupted to change-out the filter bag.


To accommodate flow rates above 180 GPM, using specialty filter bags having a reduced flow capacity or for viscous fluids, using multiple chambers (filter bags) simultaneously is required.


Douline: Consists of two bag filter housings connected by a common inlet and outlet manifold and thus having double the capacity of a single chamber design; there are no valves to divert flow, flow passes through both chambers simutanesouly.


Maxiline multiple chamber filter bag vesselProline and Maxiline bag filter housings contain 3 to 14 filter bag chambers within a single vessel.  The Proline style is the lower cost version used when fluid pressure is <100 PSI and an ASME code stamp is not required.  The Maxiline series is offered in four versions, each of which offers an increasing variety of ergonomic related features such as spring assisted cover hinges and a tools-free auto closure.


The Moduline configuration consists of installing several individual filter housings connected to a common inlet and outlet manifold.  This provides some flexibility with the overall footprint and enables the process to continue during filter bag change-outs because only one filter bag chamber is isolated at any given time.


Both single housing and multi-chamber designs can be duplexed, essentially connected by a common inlet and outlet manifold with three-way flow diverting valves, thus one housing is isolated and one is in service at all times.  Duplex and Moduline designs are required when the process flow cannot be interrupted for filter bag change-outs.


Flow Rate (chamber size and number of chambers required)

The size of the bag filter housing depends upon the diameter and length of the filter bags required for your specific application.  Usually the filter bag selection influences the height of the bag filter housing and the number of filter bag chambers required.  The four "industry standard" filter bag sizes are referred to as being #1, #2, #3 or #4 sizes, with #1 and #2 sizes being the most common for industrial applications.  This page will provide an overview of the physical dimensions, maximum flow rate, surface area and volume for #1, #2, #3 or #4 size filter bags.  Once you have selected a filter bag and identified its maximum flow rate you can determine the number of filter bag chambers required.


Selecting the most appropriate filter bag involves more than just knowing the flow rate; the other characteristics of the fluid (viscosity, specific gravity & temperature) combined with the desired efficiency, volume of particles to be removed and the size of particles to be removed guide the selection of the filter bag.


Sometimes a multiple chamber design is preferred simply to extend the duration between filter bag changes.  Some filter bags have a larger removal capacity than others, thus you might compare the use of expensive media in a smaller housing (minimizing initial costs) to using a larger housing with less expensive media (minimizing operation costs).


When you complete our inquiry form or otherwise contact us by email or phone, our filtration experts will gather information about the filter bag aspect of your application to ensure the most appropriate bag filter housing is suggested. Our filter bag website provides detailed information and specification sheets for a variety of filter bag types.