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Filter Characteristics
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Depth Fiters
Difficult to give an accurale pore size rating
Thick(3-30mm)& often adsorptive
Give a prrcentage(i.e.30-70%)
Have the greatest capacity
Examples- Microfiberglass, String-wound, pad filters
Surface Filters
Fibers locked togegher by heat or membrane coating
Given a nominal rating or rated by the filter it protect
Thin(1 mm or less)& Slightly Adsorp )
Give a percentage(90-98%)pargicle reduction
Examples 每Cellulose ester coated cellulose or polyester web
Membrane Filters
Three Types
Produced by Casting
Produced by Melting
Cast Membrane Filters
Mainly made by casting membrane
Can be either hydrophilic or hydrophobic
Rated on the size of the smallest pargicle it retains
Adsorption depends on materials
Stretched Membrane Filters
PTFE-※Teflon§,e.g.Aerex CTGB PTFE
Slot shaped pores
Very thin
Often bonded to a support material
Membrane Filters-Melted Cast
Polypropylene,e.g.Solvex CPGB.
Naturally hydrophobic
Both membrane and cartridge are polypropylene
Broad chemical compatatility
Key Membrane Filter Characteristics
Cleaning(especially reverse flow)can be difficult
Vey higninternal area
Possible adsorptiong of compounds to the filter
65-75%porosity 65-75%
High flow
Membrane Filter Selection
Hydrophilic/Hydrophobic
Operating Conditions
Filter Materials-Hydrophilic
※Weter Loving§-wet spontaneously(of with little effort)with water
Cellulosic materials(i.e.Regenerated cellulose, mixed cellulose ester,etc.)
Filter Materials-Hydrophobic
※Water hating§ 每filters which are not spontaneously wet with water.
PTFE-polytetrafluoroethylene PTFE
Polypropylene, Polysulphone ,Polycarbonate
These polymers in the natural form are inherently hydrophobic to various degrees.
Applications
Alcohol,solvent ,acid,base and chemical filtration
Thank vents,breathers, fermerntation inlet/exhaust filtration
Which one to use 每philic or ＆phobic?
The fluid must completely wet the filter
The fluid must completely wet the filter |
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