S. Berliner, III's berliner-ultrasonics.org Fluid Filtration Page keywords = " filter filtration fluid air gas water oil fuel hydraulic pore size porous medium media mesh fabric felt bubble point differential pressure Berliner III Berlin ultrasonic processing cavitate cavitating cavitation cleaning fluid filtration home.att.net "
Updated:  28 Mar 2012, 19:50  ET
[page created 24 Jan 1999;
  original AT&T Worldnet Website begun 30 May 1996.]
Update info on the top on ALL pages for your convenience.
URL http://berliner-ultrasonics.org/flfilter.html
(formerly http://home.att.net/~Berliner-Ultrasonics/flfilter.html 
moved to this domain on 03 Mar 2010)

S. Berliner, III
Consultant in Ultrasonic Processing
"changing materials with high-intensity sound"

SONOCHEMISTRY * REACTION ACCELERATION * DISRUPTION
HOMOGENIZATION * EMULSIFICATION * POLLUTION ABATEMENT
DISSOLUTION * DEGASSING * FINE PARTICLE DISPERSION
BENEFICIATION OF ORES AND MINERALS
CLEANING OF SURFACES AND POROUS MATERIALS

also see
Keywords (Applications) Index

[consultation is on a fee basis]

Technical and Historical Writer, Oral Historian
Popularizer of Science and Technology  



S. Berliner, III's

FLUID FILTRATION Page


This page was originally created to provide a place for comments and queries about

FLUID FILTRATION

.

INDEX

INTRODUCTION to FLUID FILTRATION {follows}.
THE BUBBLE POINT TEST.   new (28 Mar 2011)


INTRODUCTION to FLUID FILTRATION

Fluid filters (as opposed to electronic filters, an unrelated field), are porous materials and other means used to remove particulates and other solid and semi-solid contaminants from a fluid.  Non-solid contaminants, such as dissolved gases or other materials can not be filtered; they must be removed by absorbtion, adsorption, distillation, and other means beyond the purview of this monograph.  Entrained gases (in bubble form) may be removed by modified filter media.

A fluid can be either a gas (air, steam, oxygen, nitrogen, etc.) or a liquid (water, oil, hydraulic fluid, gasoline, etc.).

Porous materials can be cleanable (reusable) or disposable.  They can be made of wire mesh or felts or papers or perforated sheets, wound strands, etc.

Reusable mesh or porous metal can be sinter-bonded to prevent movement of fibers or particles relative to one another, thus assuring absolute pore size control and, thus, the flow rate through the medium.

Pore size and shape determines the maximum particle size that can pass the filter.  Porous material construction determines the maximum differential pressure which can be imposed upon the medium.  Cores and other reinforcements and backup materials placed against the downstream face of the porous medium can enhance the ability to withstand great differential pressures.

Accessories such as bypass valves and differential pressure indicators and alarms are commonly fitted to fluid filters.

Design philosophies must take into account whether it is better to have fluid flowing at all times, regardless of contamination, or to have flow interrupted rather than allow contaminant downstream of the filter medium.

Cleanable (reusable) fluid filters can be readily and throughly cleaned by ultrasonic means; however care must be taken to assure cleanliness, integrity of the medium, and resultant maximum pore size (absolute particle size rating).   new (03 Mar 10)


THE BUBBLE POINT TEST

new (28 Mar 2011)

There are two primary tests applied to reusable fluid filter elements to determine if they are suitable to be returned to service.  One is a dynamic FLOW TEST to assure that the pores are all or mostly unplugged.  The other, which will be expanded upon here, is the BUBBLE POINT TEST which determines the size of the largest pore, thus indicating the maximum particle size that might pass the medium (absolute filter rating).

In a rigid reusable filter medium, such as Pall Corporation's sintered PSS™ Porous Stainless Steel or RIGIMESH® woven wire mesh, the absolute filtration rating can be no lower than the diameter of the largest opening through the medium.  Other factors such as tortuosity of path and van derWaal's and other attractive forces might shift the absolute rating slightly but the maximum poresize is a rather definitive limit.

If a filter medium is fully wetted and immersed in a test liquid, gas (usually air) introduced under the medium will remain in place until the static head (pressure) of the gas exceeds that in the largest pore, at which time the gas will escape through that pore, "unwetting" it such that a stream of gas will follow.  Cylindrical elements are rotated under the liquid surface to test all portions of the medium.

[More to follow.]



U.S.Flag U.S.Flag

THUMBS UP!


THUMBS UP!   - Support your local police, fire, and emergency personnel!


To contact S. Berliner, III, please click here.


© Copyright S. Berliner, III - 1999, 2001, 2010, 2012  - All rights reserved.


Return to Top of Page