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Filtration · Process Duty

Bag Filter Housings

Bag filtration accommodates a higher solids loading than cartridge filtration at a lower operating cost, which establishes it as the conventional selection for liquid filtration within a process rather than at its termination. The bag is supported within a perforated restrainer basket and is replaced without special tooling.

Single and multi bag housings are manufactured in side entry and top entry configuration, in stainless and carbon steel, to standard size 1 and size 2 bags or to accommodate the bag specification already held by the customer.

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Flair bag filter housing installed on a process line Photograph of completed unit
Bag Filter Housings
Construction & Types

Configuration and entry

A bag filter housing accommodates one or more filter bags, each supported within a restrainer basket that takes the load of the differential pressure across the bag. Housings are specified by their entry arrangement and by their duty.

Side Entry Standard duty

Inlet and outlet are on the shell, so the bag is changed with the housing left in place on its supports and only the cover removed. The more common arrangement in process plants.

Top Entry Simplified piping

The inlet is located on the cover itself, giving a simpler pipe layout in some installations. Bag change out is carried out from the top in the same manner as a side entry unit.

Simplex Single housing

A single housing accommodating one or more bags. The most economical configuration, applicable where the line may be isolated briefly for bag change out.

Duplex Continuous duty

Two housings with a changeover valve, permitting flow to continue through one chamber while bags are changed out in the other. Specified where the process cannot be interrupted.

Specification

Standard range

Where a stated range does not cover a particular requirement, equipment is engineered to the customer specification.

Bag size Size 1 and size 2 as standard, size 3 and 4 on request
Entry Side entry or top entry
Construction Simplex or duplex, fabricated
Design code ASME Sec VIII Div 1 where required
Filtration range 1 to 200 micron according to bag media
End connections Flanged, screwed or triclover
Closure Swing bolt, eye bolt or clamp
Options Differential pressure gauge, restrainer basket, magnetic insert, vent and drain connections, cover davit
Materials of Construction

Grades routinely handled

Carbon Steel SS 304 SS 316 SS 316L

Stainless steel is the standard specification for food, pharmaceutical and corrosive duties, while carbon steel housings are supplied for water, oil and general utility service where full stainless construction is not required. The bag media and restrainer basket are selected independently of the housing material, against the process fluid and the filtration rating required.

Applications

Where these units are installed

Paint, ink, resin and adhesive filtration Edible oil and food liquid filtration Plating and surface treatment bath filtration Water treatment ahead of finer stages Chemical intermediate and solvent filtration
FAQ

Common questions

Size 1 bags are shorter, around 180 mm in diameter and 410 mm long, and are typically used in lower flow applications. Size 2 bags are longer, around 810 mm, and offer a larger filtration surface for higher flow rates. Confirm your flow rate and we will recommend the size that gives the best interval between change outs.
A side entry housing has the inlet and outlet on the shell, so the bag can be changed with the housing left in place on its supports and only the cover removed from the top. A top entry housing has the inlet on the cover itself, which some plants prefer for a simpler pipe layout. Either can be supplied against your line arrangement.
Change out frequency depends on the solids loading of the fluid, not a fixed schedule. The operative indicator is differential pressure across the housing: once it approaches the design limit, the bag is due for replacement. Fitting a differential pressure gauge at the time of order lets the interval be read directly rather than estimated.
Yes, and it is recommended. The restrainer basket supports the bag against the differential pressure across it, preventing it from collapsing or bursting under load, and is included as a standard fitment.
Bag media covers a wide range, from around 1 micron for fine liquid polishing up to 200 micron for coarser clarification duty. The rating is selected against the contaminant size you need to remove and the solids loading expected in the line.
Yes, this is a routine specification. The housing is selected against the process fluid and pressure rating, while the bag media is selected on its own filtration and chemical compatibility criteria, so the two are specified independently.
A differential pressure gauge, restrainer basket, magnetic insert for ferrous fines, vent and drain connections, and a cover davit for larger housings can all be fitted. Specify the process conditions and duty and we will confirm which options are relevant.
Standard housings are built to ASME Sec VIII Div 1, and IBR construction is offered on request where the application requires it. Advise us at enquiry stage so the unit is engineered and documented accordingly from the outset.
Enquiry

Request a quotation for Bag Filter Housings

Give us the line size, flow rate, fluid and operating conditions and we will engineer directly against them. Most enquiries are answered the same working day.