Chemical Engineering January 2017 - 44

Feature Report
High Purity Chemicals:
Processing Equipment
Essentials
Some practical tips regarding the design and fabrication of piping systems and equipment for
high-purity applications are presented here
W. M. (Bill) Huitt
W.M. Huitt Co.
IN BRIEF
THE PURITY QUOTIENT
ELECTRONICS
CHEMICALS
PERSPECTIVE
HIGH-PURITY
EQUIPMENT
CLEANROOM
CLASSIFICATIONS
DESIGNING FOR HIGH
PURITY
FINAL REMARKS
C
hemical processing,
and
the chemical
process industries
(CPI) on the whole,
have evolved lightyears
beyond their very beginnings
- beginnings
in which chemistry was
more or less a form of alchemy
and the mixing of
basic natural elements.
From such humble beginnings,
and more pointedly
over the past several
decades, the chemical
industry has progressed
dramatically from those early times to today's
high-tech chemical processing, which
include bioprocessing and the electronics
industry. These are two industries that not
only rely on what is referred to as high-purity,
ultrahigh-purity, and ultra-pure chemistry,
they could not exist without it. This discussion
does not focus on the chemistry itself,
but on the various nuances in the equipment
used to manufacture, monitor and handle
these chemicals.
Step 1: Non-H.P tubing, fittings and
other components delivered to supplier
for cleaning, capping and bagging.
Step 2: Tubing, fittings and other
components receipt inspected, cleaned,
surface finished and transferred to
cleanroom where they are inspected again
for cleanliness, then capped and bagged.
Step 3: Tubing & fittings cleaned, capped,individually
double bagged, and then bagged again in bulk lots
then delivered to fabricator.
Step 4: Fabricator constructs,
assembles and packages H.P. systems
and equipment within cleanroom.
Step 5: Completed fabrication of piping
systems assembly and equipment
shipped to site.
FIGURE 1. The evolution of high-purity equipment can follow the steps shown here
The three terms, as they pertain to chemical
processing today are nominal, vague and
self-defining at best - they mean only what
the user of any of the three terms intends for
them to mean. In other words, as previously
alluded to, these terms currently possess
no universally accepted or standardized real
and specific value.
The bioprocessing industry relates, to a
The purity quotient
Since the topic of this discussion focuses
on what is vaguely termed " high purity, "
" ultrahigh purity, " and " ultra-pure " chemical
processing, we need to provide some clarification
with regard to those three terms. I
mention clarification rather than definition of
these terms, because there are no universally
accepted definitions that quantify and
delineate these three terms.
44
large degree, with the term high purity. But
the semiconductor industry has an affinity
for all three terms. These are terms that, with
regard to the purity of chemicals, can mean
whatever the user wants them to mean.
To get a feel for the scope of such a nominal
term as " purity, " Table 1 lists 47 various
purity and chemical grade designations
used throughout the CPI. Some designations
are company trademarks and others
find their source in various industry organizations.
They do have one thing in common:
there is no uniformity or conformity in the
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