What are the design criteria to consider when designing a filter media?

Question

What are the design criteria to consider when designing a filter media?

Answer 1

What is the pH of the fluid?  what is the temperature of the fluid?  What is the viscosity of the fluid?  what pressure drop across the filter is acceptable (is the filter material itself strong or weak,  is the pump strong or weak)?  What is the particle size distribution of the material to be caught on the filter?  What is the largest particle permitted to pass thru the filter? what does the flow rate of fluid thru the filter need to be?  What volume of particle matter is in a given volume of fluid? what volume of fluid needs to be filtered?  Will the filter be changed regularly?  Is it disposable or can it be cleaned and reused? What do you have to do to safely handle the material being caught in the filter? Are there other ways besides filtering that can be used to eliminate some of the particle matter?    There are other considerations depending on the specific answers to these questions.  You would think that filtering is pretty easy.  hope this helps

Answer 2

*Is it fluid filter/electronic filter?

I am considering fluid filter.

1.Flow rate and regularity of flow. A filtration system obviously must be able to accommodate the stream’s flow rate. Indeed, flow rate is the most critical parameter in determining the appropriate filter size; so, flow rate data will be among the supplier’s first requests. Flow rate analysis also will consider the regularity of the stream’s flow — whether it’s steady, intermittent, variable, or potentially subject to sudden increases.

2.Reservoir size and usage rate.

These data can be used to support calculations of overall system flow rate. In addition, they’re particularly important in applications that recirculate oil through a side-stream (kidney loop) filtration system because the filter must be able to adequately clean the fluid within the required reservoir turnover rate and time.

3.Viscosity.

Analysis of the process or lubrication stream’s viscosity also is essential to proper filter fitting because viscosity can affect flow rate. While water and other low-viscosity fluids experience little variation in viscosity, the viscosity of other fluids such as oils can change significantly with the operating temperature (or temperature variations throughout the system). So, a filtration system that processes higher viscosity fluids requires special attention for a sound specification fit. Viscosity can be an important factor, for instance, in turbine and gear oil applications.

4.Material compatibility.

The filter vessel and element obviously must suit the fluid. Otherwise, filtration system parts could deteriorate and enter the fluid stream — meaning that today’s O-ring could become tomorrow’s contaminant. This parameter is particularly important in applications using synthetic and ester-based lubricants, although compatibility also should be considered with systems using mineral-based fluids.

5.Pressure and differential pressure.

The system’s operating pressure (pump pressure) determines filter vessel sizing. It’s a good practice to size the filter vessel for a pressure at least 33% higher than the maximum operating pressure to ensure that the vessel is well within the limitations of its pressure rating. Filter element sizing is based on the differential pressure across the filter.

6.Existing pipe line size.

It sounds simple, but it’s often overlooked: the filter vessel should properly fit the existing pipe. Generally, the filter should be sized to match the pipe to which it will be installed. Unless there’s some limiting factor — such as available installation space, low flow rate or an operating pressure exceeding 3,000 psig — the filter shouldn’t be installed with connections that are smaller than the existing pipe. If the pipe is 2 in., install a filter with connections that are at least 2 in.. This simple practice will eliminate excessive pressure drop.

7.Fluid physical characteristics.

A Material Safety Data Sheet (MSDS) provides important precautions for the handling and use of the fluid, but a Fluid Product Data Sheet (FPDS) offers the most useful information for specifying filtration systems. So, be sure to have this information available when contacting a filtration supplier.

8.Temperature.

Provide the filter supplier with a realistic estimate of the fluid’s operating temperature. Consider the operating temperature range that you expect 99% of the time, adding ±10°F for safety. Unrealistically broad ranges will undoubtedly drive up system costs and may compromise performance.

9.Space for installation.

This is one of the most commonly overlooked aspects of a specification. Give the filtration supplier dimensional data detailing space limitations at the installation location. Consider the headspace above the filter necessary to allow easy removal.

10.Filter-element filtration rating.

Such ratings can be confusing because the system for rating a process filter differs from that for an oil filter. An “absolute” rating from a process filter supplier may differ from an efficiency rating supplied by a hydraulic or lube oil supplier.

In critical applications, use a filter that can provide at least a 95% efficiency rating, preferably 99%. In general applications, a 50% rating suffices. The minimum efficiency target for turbine oil or hydraulic oil filtration should be 99.5%.

11.Choice of cartridge or bag filter.

There’s no definitive basis on whether it’s better to specify a cartridge filter or a bag filter. Cartridge filters typically cost two-to-four times more than bag filters but their larger surface area yields a longer service life.

12.Filter vessel sizing.

A common error is to specify a filter vessel with too few filter elements. Such undersizing often stems from a desire to keep initial costs down. However, it’s actually advantageous to specify a filter vessel that can contain a few elements more than the minimum. Oversizing will add some initial cost but the long-term savings will pay for the upfront investment.