Page 149 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

SOLID-LIQUID SEPARATION AND INTERCEPTORS

SOLID-LIQUID SEPARATION AND INTERCEPTORS 3.17

to make them suitable for filter media. They can also be produced in smaller diameters and
spun into “yarn.”
Pleated filters are generally made from resin-bonded materials, with the pore size determined
by the type and size of the fiber and the binding method used. Pleated cartridges usually depend
more on sieving than do the wound type, and can better remove particles of a specific size.

Specific Materials
Polysulfone. Polysulfone is a membrane that is basically hydrophilic and has excellent
flow rates, low extractability, broad chemical resistance, high mechanical strength, and heat
resistance, permitting a variety of sterilization methods.
Nylon. Nylon is a hydrophilic membrane with generally very high flow rates, high tensile
strength, low extractables, and limited chemical resistance.

PTFE. PTFE is a naturally hydrophobic membrane often laminated to a polypropylene
support for added strength. It has excellent chemical and heat resistance.

Acrylic Copolymer. Acrylic copolymer is a membrane that is basically hydrophilic and
has excellent flow rates, low extractables, and a low differential pressure.
Polypropylene. Polypropylene is naturally hydrophobic and is available as a membrane
that is chemically inert, has a broad pH stability and high flow rate, and is considered very
durable.

Glass. Glass fibers are usually manufactured from borosilicate glass. Thicker fibers are
spun and thinner fibers are made into mats with the addition of a binder. They typically have
low differential pressures, good wet strength, and high dirt-holding capacity.

Housings
Housing selection for filter cartridges is based on the proposed application. Although housings
most often contain a single cartridge, units that hold multiple filters are available. General indus-
trial requirements differ greatly from the sanitary requirements of the pharmaceutical and food
service industries. Manufacturers provide filters and housings of standard diameter and length.
There are no industry standards for general industrial housings. The material can range
from plastic to stainless steel. For safety, pressurized housings for compressed gas and
high-pressure liquid applications must be ASME code stamped.
Sanitary requirements require conformance to 3-A Sanitary standards, such as an inte-
rior surface finish of a minimum 150-grit polish, the capability of being completely disas-
sembled and cleaned, welds ground smooth, and flush sanitary connections to piping.
Housings come in three basic styles: tee, in-line, and L-shaped. The tee style offers
easy filter changing, and it is easier to fit into an existing pipeline. It usually has the highest
pressure drop of the three styles. The in-line style offers the lowest pressure drop of the
three styles. The L-shaped style is used most often for multiple cartridge installations in
industrial applications.

Seals
Seals are used to prevent the feedwater from bypassing the filter medium. They must be
reliable enough to withstand repeated changing of the cartridge. The most common sealing

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