Filter housings are vessels that hold replaceable cartridges, elements, bags or media. They hold one or many filters at varying pressures. This permits high flow rates and long service life while ensuring proper filtration of fluids.

Types of Filter Housings

Filter housings fall into two major categories, including housings for filtration of fluids and pressurized air and other gases.

Standard options include:

Melt blown filter cartridges: This unit is suitable for removing particles of a uniform size throughout the filter's body. The instruments are appropriate for well water and normal city water. They are affordable and serve in both commercial and domestic environments.

String wound filter cartridges: These are surface-type devices effective for removing different-sized particles. The tools operate with surface waters from streams and rivers and are employed at the pre-filter stage. The lower price range and a polypropylene fiber construction make the product a preferred choice for general as well as specialized filtration tasks.

Pleated filter cartridges: Filtration of different-sized elements in a limited amount relies on pleated cartridges. Such instruments apply to stream and river surface waters. The provided surface area of the item exceeds its diameter. The components are priced higher than the string wound or melt blown options and represent an optimal solution for sub-micron filtration. In biological blocks, their primary objective is sterile water production of exceptional purity.

Media filter cartridges: The instruments function as water treatment systems that affect chemical changes in water. Such tools feature a reduced flow rate compared to a particle filter of equivalent dimensions. Replacing these structures is not dependent on pressure drop readings.

Operation

Filter housings have inlet and outlet ports for the movement of liquid. One of the ports possesses a termination with a sealing surface that corresponds to the filter elements. Maintenance requirements involve regular replacement of the structures as they accumulate debris.

An extensive selection of sealing surfaces exists to accommodate numerous product models and configurations. In bag filters, the flow moves upstream into the bag through its walls, with the filtrate then exiting the housing.

In pleated solutions, the fluid flow is introduced from the outside. The fluid then moves through the element while the sealing surface assists in discharging the buildup.

The condition of a cartridge is determined by checking the overall pressure drop across it. The unit requires replacement when the pressure drop exceeds the acceptable threshold. This indicator is calculated by subtracting inlet pressure from outlet pressure. An alternative approach involves changing the components on a regular basis.

The following steps outline the process:

1. Close the filter's inlet valve to the filter
2. Close the outlet valve
3. Undo lid on the top of the housing to allow remaining pressure to dissipate
4. Drain water from the housing
5. Remove the cartridge
6. Rinse or wipe the bowl with a sterilant
7. Insert a new cartridge
8. Loosely replace the bowl or lid
9. Slowly fill the housing with water by using the inlet valve
10. Close the inlet valve and complete the seal
11. Turn inlet valve on and restore the pressure
12. Check for leaks and resume service

Features

Typical features of filter housings include:

• Single, multi-basket, cartridge, duplex, and multiplex units
• Low pressure drops
• Sure-sealing covers
• Permanently piped housings
• Carbon steel, stainless steel, or plastic construction
• Adjustable-height legs or low profile
• Differential pressure indicators
• Large-area heavy-duty baskets or cartridge internals
• Liquid displacers for preventing product loss during basket or bag removal
• Dual stage straining/filtering

Each category of housing comes with unique specifications. Some of these are listed below:

• Standard housing -- maximum operating temperature 52º C, maximum operating pressure 150 PSI
• High-temperature nylon housing -- maximum operating temperature 74º C, maximum operating pressure 100 PSI
• Polypropylene housing -- maximum operating temperature 52º C, maximum operating pressure 150 PSI
• Giant housings -- maximum operating temperature 82º C, maximum operating pressure 100 PSI
• Stainless steel housing -- maximum operating pressure 100 PSI
• Sanitary housing for single-tube cartridge filter -- maximum operating pressure 71 PSI

Applications

A broad array of applications engages filter housings. The following is a list of fields where these devices are employed:

• Electronics
• Automotive
• Food and beverage
• Paints, inks, resins, and coatings
• Petrochemicals
• Chemical processing
• Municipal and industrial water treatment
• Lubricants, metalworking fluids
• Pulp and paper
• Pharmaceutical
• Solvents 

Select models are designed for distinct procedures and environments:

Melt blown cartridges are suited for areas, including filtration of pure water and reverse osmosis systems.

Pleated cartridges are ideal for preventing entry of airborne particles in water tank vents, ultraviolet sterilization and point-of-use filtration.  

Media filters are designed for these applications:

• Activated carbon for the removal of chlorine, taste, and odor
• Mixed bed DI resin for water purification
• Calcite media for neutralization of acidic water

String wound cartridges are found in applications, including up-stream of ion exchange resin columns to remove particles and downstream to remove resin fines and reverse osmosis technology.

Selection

A myriad of product variations, including specialized structures, is available today. Check manufacturer's specifications to determine if the functional parameters of a particular device are aligned with the intended application.

Image Credits: 

Eaton Filtration | Watts