Chemical Engineering January 2017 - 49

TABLE 4. CLEANROOM CLASSIFICATIONS1
Classifications
ISO 14644-1
ISO 1
ISO 2
ISO 3
ISO 4
Class 10
ISO 5
Class 100
ISO 6
Class 1,000
ISO 7
Class 10,000
ISO 8
Class 100,000
ISO 9
1,000,000
FS 209E2,3
0.1 µm
10
100
Class 1
1,000
1,236
10,000
12,360
100,000
0.2 µm
2
24
237
247
2,370
2,649
23,700
26,485
237,000
Maximum number of particles by size (per m3)
0.3 µm
0.5 µm
10
102
106
1,020
1,059
10,200
10,594
102,000
4
35
35
352
353
3,529
3,531
35,200
35,314
352,000
353,140
3,520,000
3,531,400
35,200,000
8
83
35
832
353
8,320
3,531
83,200
35,314
832,000
353,140
8,320,000
Notes:
1. A comparison between ISO 14644 and FS209E standards for maximum allowed particles by size
2. Federal Standard (FS) 209E, " Airborne Particulate Cleanliness Classes in Cleanrooms and Clean Zones " was withdrawn on November 29, 2001
3. The FS209E micron class values have been transposed from ft3 to m3
in the fabrication, it
will be moved
into a de-bagging area similar to
a gowning/de-gowning area adjacent
to the cleanroom, or through
a pass-through opening. The cleanroom
environment will again typically
meet the environmentally controlled
cleanroom classification of ISO 4 or
5. All fabrication within the cleanroom
is carefully controlled to minimize
or eliminate contamination of
what will become the final product
contact surfaces of the piping system
or equipment being fabricated.
Once fabricated, all welds - particularly
the process contact surface
of welds, including the heat affected
zone (HAZ) surrounding the weld
proper - will be thoroughly examined
against a rigorous set of weldacceptance
criteria.
Once fabrication is approved, the
process contact surfaces of the assembled
piping systems and equipment,
depending on the item's MOC,
will be cleaned and passivated to aggressively
initiate a stainless steel's
natural tendency to create a passive
and protective chromium-oxidesurface
layer. If it is required that the
assembly be qualified in accordance
with a factory acceptance test (FAT),
it would take place at this time. Once
this process has been completed,
the process contact surfaces are
then cleaned, rinsed, dried and
packaged for shipment.
Step 5. The H.P. packaged piping
system or equipment is then
shipped
to
the
installation
site
where, if it is set up as an on-time
delivery with the fabricator, it will
be moved directly into its permanent
location. If not, the item should
be placed in an area of the site in
which both construction traffic and
the environment are controlled. If
it is required that the assembly be
qualified in accordance with a site
acceptance test (SAT), it would take
place at any time after the assembly
is installed in its permanent location,
unless otherwise agreed to.
Cleanroom classifications
Cleanroom requirements and classifications
were initially issued on
September 11, 1992 under FS
(Federal Standard) 209E. This program
was accepted and adopted
on an international basis for cleanroom
standardization up until November
29, 2001. On that date,
the U.S. General Services Administration
(www.gsa.gov) issued, in
part, the following notice regarding
FS Airborne Particulate Cleanliness
Classes in Cleanrooms and
Clean Zones: " Federal Standard
209E dated September 11, 1992 is
hereby canceled and superseded
by International Organization for
Standardization (ISO) Standards.
International Standards for Cleanrooms
and associated controlled
environments, ISO 14644-1 Part 1:
Classification of air cleanliness; and
ISO 14644-2 Part 2: Specifications
for testing and monitoring to prove
continued compliance with ISO
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
JANUARY 2017
14644-1. " [2]
With that notification, ISO 14644-1
and 14644-2 became the de facto
international standard for cleanroom
requirements. Cleanroom classification
designations thereby changed
from the 10, 100, 1,000, and so on
classifications to the ISO 1, 2, 3, 4,
and so on classifications, as reflected
in Table 4. This table compares and
contrasts both the FS and ISO standards,
because there are many companies,
catalogs, and specifications
that still specify the classifications
referred to in the old superseded FS
209E standard.
Designing for high purity
What separates the design of highpurity
process equipment from that
of typical industrial-type process
equipment can be found in the consideration
given to integrating design
attributes of cleanability into an
overall design concept. The term
" cleanability, " can therefore be defined,
for the purpose of this discussion,
as, " adoption and application
of specifications that render welded
joints, mechanical joints, processcontact
surface finishes, internal
appurtenances, and pipe-runs as
being designed to facilitate, to a
satisfactory degree, their drainability
by gravity or with the assist of pneumatic
pressure (blow-down). "
What that definition implies is that
equipment or piping designed for
cleanability shall have equipment
process contact internals designed
49
29
35
293
353
2,930
3,531
29,300
35,314
293,000
1.0 µm
5.0 µm

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Chemical Engineering January 2017

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