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White Paper |
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Applying
Best Vent Ducting Practices from the Semiconductor Industry to
Pharma Facilities |
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Fluoropolymer
Coated Stainless Steel Piping and Ducting Offers Significant
Maintenance and Operating Cost Savings
Vince Rocca
Given an ever-changing body of
rules and regulations, pharmaceutical and biotech facilities
must be flexible as possible, to meet existing mandates and
anticipate proposed regulations. A growing number of drug
manufacturers are focusing on facility exhaust systems as an
area where improvements can be made. |
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Coated duct installation on the
roof of a California |
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Biopharmaceutical Pilot Plant.
(Photo courtesy of |
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Hellwig Plumbing) |
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Aiding
them in their improvement efforts are innovative materials of
construction. This article will focus on the use of
fluoropolymer coated stainless steel piping and ducting in both
cleanroom and non-cleanroom applications. |
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Fluoropolymer
coated stainless steel was first used by the semiconductor
industry in the 1990's, but is now finding increased use in
pharmaceutical and biopharmaceutical manufacturing, driven by
such regulations as the U.S. Environmental Protection Agency's
(EPA) Ruling 40 CFR and the National Fire Protection
Association's (NFPA) Standard 318 for cleanrooms. |
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Enacted in
1998, EPA's ruling 40 CFR imposed strict standards, with the
goal of reducing industrial emissions of hazardous air
pollutants and toxins by around 65%. To meet these
regulations, many drug manufacturers use a regenerative thermal
oxidizer (RTO) to incinerate the chemicals, or a caustic
scrubber system to remove some emissions. Often the two
technologies are used in tandem, so that the scrubber removes
hydrochloric acid emissions from the oxidizer. |
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Increased
use of thermal oxidizers and scrubbers has resulted in the need
for materials that can carry these hazardous pollutants to the
vent collecting and destruction system without compromising
plant safety. As a result, more facilities are specifying
the use of high temperature and corrosion-resistant
fluoropolymer coated duct and piping. |
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Coated
Duct in the Manufacturing Suite
Fluoropolymer coated stainless
steel ducting can be used in manufacturing suites, the synthesis
and formulation areas within pharmaceutical manufacturing, and
pilot-plant operations. Such areas typically use
specialized materials of construction for reactor vessels,
process equipment and process piping, including borosilicate
glass, glass-lined steel, exotic alloys, and fluoropolymers.
Reactors, filter-dryers and other
process equipment in this category are usually of ASME
pressure-rated type, capable of containing process liquids and
vapors up to 150 PSIG, and it usually incorporates a vent nozzle
of relief device connection.
The manufacturing suite may have
a general exhaust system, or snorkel vents at individual
equipment stations. However, many facilities today are
also incorporating large walk-in reactor enclosures and fume
hoods that are tied into the process vent system. In these
applications where higher pressures and full vacuum are
customary, fluoropolymer coated schedule 10 pipe (150 PSIG
rated) would be an appropriate choice for corrosive vent lines. |
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Coated stainless steel exhaust
duct staged for |
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installation at a NY State
University research center. |
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(Photo credit V. Rocca, Fab-Tech,
Inc.) |
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Ducting for Cleanroom
Venting and EXhaust |
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In
pharmaceutical and biopharmaceutical cleanrooms, it is essential
that every trace of any hazardous vapor be completely removed
from an entire room, or piece of equipment. Fluoropolymer
coated stainless steel ducting can be more effective than
traditional piping, in these types of facilities.
Cleanroom exhaust, fume hoods, snorkels, walk-in reactor
enclosures and Biological Safety Cabinets (BSC) used to store
chemicals with corrosive fumes, can all benefit from the use of
fluoropolymer coated stainless steel duct, rather than pipe. |
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These
negative and low-pressure systems are governed by Sheet Metal
and Air Conditioning Contractor's National Associations (SMACNA)
HVAC guidelines. In applications where biologic agents are
involved, but no corrosive chemicals are present, exhaust is
usually passed through a high-efficiency particulate air (HEPA)
filter and perhaps even a carbon absorption (CA) filter.
In this situation, uncoated stainless steel duct could be
used. But if the process is one where corrosive chemical
vapors are produced (which can potentially damage HEPA filters)
duct material with a higher level of corrosion resistance, such
as fluoropolymer coated stainless steel, should be considered. |
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Additional
areas for use of fluoropolymer coated duct include "clean
air" supply duct system feeding the biopharmaceutical
cleanroom. Hot, corrosive, ultra-pure WFI (water for
injection) is used to set incoming air humidity levels.
Some biotech/biopharm manufacturing facilities have experienced
corrosion in the galvanized and even stainless steel supply air
ducting from hot WFI vapors. Fluoropolymer coated duct can
be used in this application to provide years of maintenance free
service. Coated duct is also impervious to harsh chemicals
used to disinfect and sterilize cleanrooms and ducting.
Chemicals used can range from sodium hypochlorite (bleach) to
quaternary ammonia to phenols to formaldehyde-based
chemicals. Steam temperatures for sterilization can often
exceed 120°C (248°F). All types of chemistry, up to
300°F, can be easily handled by fluoropolymer coated duct. |
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Potential Hazards |
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As in the
semiconductor industry, hazards in the life sciences industry
are ever-present. They include fire or explosion due to
the use of solvents, flammable liquids or dust, and the
resulting contamination of production, storage, and cleanroom
areas by smoke or other substances released by the fire.
The role of fluoropolymer coated duct is to contribute to the
overall safety of both the facility and its inhabitants by
providing a reliable, corrosion resistant conduit for the
gaseous by-products of manufacturing, even in the most extreme
situations. |
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Many
building codes and insurance companies require ducting made of
stainless steel or other noncombustible materials. In some
instances, fiberglass and other combustible duct materials may
be used but require the use of internal sprinklers.
As stated in the National Fire
Protection Association's Standard 318 "3-3.6:
Exhaust duct systems shall be constructed of non-combustible
materials or protected with internal sprinklers in accordance
with 2-1.2.6 Exception: Ducts approved for use without
automatic sprinklers." The NFPA standard
continues with a hierarchy of material preferences, "3-3.6:
Considering fire protection issues only, duct materials listed
in descending order of preference are: (a) metallic, (b)
approved coated metallic or nonmetallic not requiring fire
sprinklers, (c) combustible with internal automatic |
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Exhaust duct with internal
sprinklers will add |
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significant costs to an exhaust
system as compared |
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to a fluoropolymer coated
unsprinkled system. |
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sprinkler
protection."1 (See illustration) Note: "...although
most NFPA standards are not laws, they are widely accepted
industry standards with considerable legal standing.
Failure to comply with them can potentially put manufacturers in
serious liability."2 Factory Mutual (FM)
approved stainless steel duct coated internally with a
fluoropolymer satisfies this requirement without the use and
costs of an internal sprinkler system. |
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When
selecting pipe or duct for corrosion exhaust applications, it is
critical to choose a product that is rated by Factory Mutual, an
affiliate of FM Global, an insurance company devoted to reducing
commercial and industrial property losses and maintaining the
continuity of its policy-holders' business operations. The
insurer's extensive research is often used to help set new
industry standards, develop new products and advance
loss-prevention practices. |
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"In
the past, cleanrooms and wet benches (plastic or stainless steel
workstations upon which computer chips are manufactured) often
need to be protected by sprinklers or more expensive special
fire-protection systems like carbon dioxide, fine-water spray or
halon. But, by the time a cleanroom fire propagated and
triggered a sprinkler or special fire protection system, damage
could already have occurred in the rest of the cleanroom.
Due to such factors as potential lost earnings, chip makers are
requiring suppliers to use materials in wet-bench fabrication
that are less flammable and therefore don't need additional -
and costly - fire protection systems installed, so they will be
inherently safe when they arrive in the cleanroom."3 |
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Manufacturers
of fluoropolymer coated stainless steel duct use FM Research's
services to earn the FM Approval mark, certifying the
reliability of their products. Fluoropolymer coated
stainless steel duct is regulated and approved by FM Research
Standard Number 4922. With fluoropolymer coated stainless
steel duct, structural integrity is maintained in the event of a
fire. With extremely low flame and smoke characteristics
(flame spread under 10, smoke generation under 15), these
systems will not burn or melt or generate large quantities of
smoke, and extremely important issue in the life sciences
environment. They are inherently safe when they arrive on
site. |
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Material
of Choice: Fluoropolymer Coated Pipe and Duct
The choice of materials for the
corrosive vent exhaust system is a function of the science and
processes employed within the building. It is the role of
the design engineering firm, working in conjunction with the
architect and client, to choose the highest performing, safest,
yet cost-effective materials.
ETFE (Ethylene-Tetrafluoroethylene)
and ECTFE (Ethylene-Chlortrifluoroethylene) fluoropolymer coated
stainless steel was developed in the early 1990s to address a
specific need of the semiconductor industry. Plastic and
fiberglass products were just not providing the needed safety
and performance. Compared to the more common materials of
construction, fiberglass reinforced plastic (FRP), polypropylene
(PP) and polyvinyl-chloride (PVC), stainless steel ducts coated
with fluoropolymer offer superior value. Based on
published data, fluoropolymer coatings far surpass these other
materials in chemical resistance, and the stainless steel tubing
does not burn, collapse or leak. |
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Coated duct connected to scrubber
unit at a California |
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Biopharmaceutical pilot
plant. Building was completely |
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renovated from warehouse to
cleanroom research |
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facility use. (Photo
courtesy of G. Cortes, SMW 104) |
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Fluoropolymer
coated duct is 300 series stainless steel that is coated with a
two part (primer and top coat) fluoropolymer system, then heated
and "baked" to form a chemical and mechanical bond
with the stainless substrate. Some manufacturers have
developed proprietary primer technology that assures superior
adhesion to the stainless steel, resulting in a coating that
will not delaminate. The coating is both visually
inspected and spark-tested to guarantee a pinhole free
surface. Fluroropolymer coatings have been evaluated in
over 400 chemical applications, and have been proven superior to
both FRP and plastics when tested for corrosion resistance,
concentration and upper temperature limit. |
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In
evaluating the level of corrosiveness of a given application, it
is vital to consider the entire range of chemicals that the duct
system will be exposed to. Even more important is to
consider the potential of combinations. "It
is also important to evaluate complex systems with several
different types of process streams (e.g., reactors, storage
tank, relief system) discharging into a common header.
Where vents from several sources are combined, it is necessary
to carefully consider all possible interactions between the
different streams in terms of both chemical reactivity and
flammability."4 |
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It is
reassuring that fluoropolymers have a wide corrosion resistance
envelope to handle most chemical situations. Additional
reasons for considering coated stainless steel duct include;
robust mechanical strength, light weight, ease and speed of
installation using rotating van stone flanges or EZ-type clamps,
the ability to be field modified (shortened, add nozzles or
drain ports) and the fact that the stainless steel exterior will
never need painting. Unlike FRP and other
"glued" plastic systems, there is no need for
grinding, sanding, prep work or the use of malodorous epoxies
and heating blankets, especially in the cleanroom setting.
Installation time of a fluoropolymer-coated stainless steel
system using EZ-type clamps, is the least time and labor
consuming high performance duct system available. |
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With
regard to cost, fluoropolymer coated duct is priced
competitively against other materials such as FRP, composite
materials are PTFE lined pipe. The savings become greater
as the duct diameter increases. It is important not only
to compare per-foot costs, but also to look at the total
installed cost of the system including the mechanical
contractor's labor and any related piping and sprinkler costs. |
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Conclusion
In the past, chemical and
pharmaceutical plant operators often specified fiberglass,
plastics, stainless steel or even PTFE lined carbon steel to
handle corrosive vent applications. Today, many building
codes and insurance companies require vent duct made of
stainless steel or other non-combustible materials.
The intent of the EPA's Ruling 40
CFR was to reduce harmful emissions and make the air we breathe
safer. NFPA Standard 318 is focused on making our work
environment safer and less prone to the ravages of fire and
smoke. Fluoropolymer coated duct is one step forward in
improving the overall safety of both the facility and its
inhabitants by providing a reliable corrosion resistant conduit
for the gaseous by-products of manufacturing. |
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Coated Schedule 10 vent pipe
installed on the roof of |
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a Pennsylvania Specialty Chemical
plant, replaced |
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leaking Schedule 40 stainless
steel pipe. Vent streams |
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are from glass-lined steel and
Hastelloy reactors and |
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centrifuges. (Photo courtesy
of J. Brobson, Design |
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Plastic Systems, Inc.) |
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Fluoropolymer
coated stainless steel duct are materials of construction new to
life sciences, but have been successfully used in manufacturing
for over 15 years. It meets all the required design and
operating criteria for extreme service when applied and
installed according to the parameters for its intended
use. If corrosive vapors and fire safety are concerns,
fluoropolymer coated stainless steel could be the ideal
solution. Professionals who design, build or manage life
science facilities that contend with corrosive and hazardous
vapors can benefit by doing additional research into this new
type of product. |
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References |
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1. NFPA 318
Standard for the Protection of Cleanrooms |
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2. Fire Chief,
December 9, 2005 |
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3. Cleanroom
Materials Flammability Test Protocol (Class 4910), FM Global |
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4. Collect
and Destroy Emissions Safely, Tony Ennis, Haztech
Consultants, Ltd. |
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Chemical
Engineering Progress, May 2004 |
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