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The Center for
Process Analytical Chemistry (CPAC, www.cpac.washington.edu) was formed
in 1984 at the University of Washington as part of the National Science
Foundation (NSF, www.nsf.gov). Over the years, the group has grown and
is now recognized as an Industry/University Cooperative Research Center
(I/UCRC), a designation offered by the NSF to certified programs that
foster long-term partnerships among industry, academe, and government.
CPAC members come from all sectors of industry, including chemical
plants, biotech facilities, and other organizations that perform
analytical chemistry, either in their labs or out in the process. In
addition, CPAC’s membership includes manufacturers of components,
systems integrators, and several national laboratories and government
agencies.
| Figure 1. Under NeSSI Generation One, the mechanical size and shape of
early gas sticks have been defined. Generation Two of the program,
which is currently under development, aims to incorporate power and
communication standards, while Generation Three involves the
implementation and use of micro analyzers.
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One of CPAC’s core
programs is the New Sensor Sampling Initiative (NeSSI), which aims to
modularize and miniaturize process analyzer sample system components,
thus reducing the cost of building and owning such systems. So far,
NeSSI has developed specifications to enable users and integrators to
design systems using components from various manufacturers. The origins
of this concept, which is commonly referred to as “downport,” can be
traced to the semiconductor industry. Semiconductor gas panel builders
and integrators realized space was at a premium in their gas panels and
pursued modularity and miniaturization, developing a standard set of
dimensions and materials to be used to enable downporting of systems.
These standards were formalized by SEMI approximately three years ago.
A Three-Pronged Approach
Recently, a similar
trend has been gaining momentum in the industrial world. As downport
systems have evolved, the need for a set of standards has grown in this
environment as well. NeSSI is currently working toward that end with a
three-phase program (Figure 1). Under NeSSI Generation One, the
mechanical size and shape of early gas sticks have been defined.
Generation Two of the program, which is currently under development,
aims to incorporate power and communication standards, while Generation
Three involves the implementation and use of micro analyzers.
| Figure 2. The first applications of the ANSI/ISA-SP76 specification to show up
in the real world were commonly called gas sticks because they typically followed a
single flow path.
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Currently, the mechanical standards are in place for gas and liquid
sample systems. There are major manufacturers making gas sticks,
panels, and systems using components they manufacture or integrating
components from a variety of manufacturers. The specifications for this
phase of the NeSSI initiative have been formulated into a document and
submitted to ISA (www.isa.org), resulting in the ANSI/ISA-SP76
standard. This specification describes the mechanical configuration of
systems — primarily the spacing between components, connection size and
location, materials, and a few more parameters.
Applications
The first
applications of the specification to show up in the real world were
commonly called gas sticks because they typically followed a single
flow path. These gas sticks, shown in Figure 2, are based on a few very
basic components. Subsequent applications, such as the one shown in
Figure 3, featured a variety of components such as filters, pressure
transmitters, check valves, and back-pressure regulators.
| Figure 3. Subsequent applications featured a variety of components such
as filters, pressure transmitters, check valves, and back-pressure
regulators. Photo ©2006 Swagelok Company
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The dimensions of these systems are defined in the SP76 specification.
All devices, including future analyzers, have to fit within this
system. Future systems will involve adding more SP76-compliant devices.
With the addition of NeSSI-compliant, three-way valves, as well as a
few more equipment suppliers joining the NeSSI initiative, industry has
started to see some pretty sophisticated and very small systems.
Figure 4 shows a system manufactured by Parker Hannifin
(www.parker.com), which can be made to almost any length and width.
Earlier gas sticks and these more complex systems represent an
important evolution in that they can be disassembled and the components
can be reused. As a result, users can pipe up a number of components to
create a sample system and then reuse the components in a new design to
support, for example, an additional flow path and/or vent line. In
essence, the components can be taken apart and put back together like
building blocks or puzzle pieces.
Design Efficiency
| Figure 4. A modular system manufactured by Parker, which can be made to almost any length and width.
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In labs and pilot
plants, this concept is valuable because it allows engineers to run a
system, make changes, and run the system again. In the analyzer world,
once a sample system is built and installed, it would seem the last
thing an engineer would want to do is take it apart. But the truth is,
the systems described here can be taken apart and rebuilt with ease,
providing a more efficient systems design approach.
For example, if a sample line gets stopped up, it can be removed from
the system, returned to a safe work area, diagnosed, repaired, or
swapped out for a replacement component, and then the system can be
reinstalled back into the process. Clearly, such systems are not an
end-all, be-all solution, but they do represent a more cost-effective
and logical method of repair as compared to traditional methods that
require whole systems to be swapped out when, in fact, performance
problems are typically the product of a single underperforming
component.
| Figure 5. In the lab, an experiment with flowmeters, valves, and an analyzer shows how components can be disassembled
and reused.
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In the lab, an experiment with flowmeters, valves, and an analyzer
shows how components can be disassembled and reused (Figure 5). Extend
this system out from the lab and apply it to sample systems in the
plant or in the chemical process area, and the benefits are magnified.
Modular sample systems are particularly promising in hazardous
locations, as such applications typically require devices to be housed
in explosion-proof boxes. These boxes cost money, and a compact,
modular system can cut down on the size (and cost) of
explosion-proofing.
Size Matters
Further,
SP76-compliant systems can be used in a lab to make smaller batches.
Smaller batches can aid in more test runs, less chemical being
consumed, and less floor space for each process. Traditional systems
provide everything in a box with some room for tinkering. Modular
systems save space and lose nothing in regard to tinkerability (usually
each component can be accessed with one Allen wrench).
Figure 6 is an
example of a three-stream system with a lot of components. The
components are piped together using standard stainless steel tubing.
The system includes thermal mass flow controllers with pressure gauges
and regulators on both sides and a handful of valves. This is a large
system. In Figure 7, you still have the same three gas streams, but in
a much smaller NeSSI-compliant package. It includes a Parker Hannifin
Intraflow substrate and components, GO (www.goreg.com) pressure
regulators, Honeywell (www.honeywell.com) pressure transmitters, Parker
valves and actuators, and Brooks Instrument (www.brooksinstrument.com)
thermal mass flow
controllers.
| Figure 6. An example of a three-stream
system with a lot of components. Photo Courtesy of UOP.
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Ethernet and DeviceNet communications are commercially available in
Generation One NeSSI systems. Software can be used for configuration,
control, data collection, and diagnostics. In fact, the owner of the
system shown in figures five and six indicated that one of its most
impressive characteristics is that it provides exceptional diagnostic,
control, and data collection capabilities. The system enables remote
monitoring and control using only standard Internet tools, and
configuration can be accomplished with relative ease.
The Future
Modular sampling
systems allow users to put a lot of mechanical components into a small
space, thus saving time and money, while at the same time adding
flexibility. NeSSI’s Generation One mechanical specifications for
modular sample systems are now well defined, and there are a number of
companies supplying components and systems. Moreover, industrial users
are starting to implement these systems in their labs and in the
analyzer world. Generation Two of the NeSSI program is currently under
way, as participants are finding and using components that offer
communications capabilities. Meanwhile, Generation Three of the program
is expected to enable the actual analyzer on the platform rather than
just the sample conditioning lines.
| Figure 7. A modular system comprised of a substrate and components,
pressure regulators, pressure transmitters, valves and actuators, and thermal mass flow controllers. Photo Courtesy of UOP.
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A traditional analyzer system is a large box or two full of components.
Putting it together is, very often, an art rather than a science. Each
plant has a group of folks responsible for taking care of these
systems. Sometimes, there is an entire house full of analyzers and the
sample lines necessary to supply fluids. NeSSI’s Generation Three phase
aims to miniaturize the analyzers and incorporate the SP76 guidelines
to enable a complete analyzer system in an even smaller package. These
micro analyzers will, in theory, be able to perform a variety of
functions, and they will be mounted on a mechanical platform where they
can communicate over a common network. In this environment, the ideal
analyzer would have multiple certifications for use in a variety of
environments. It would not consume very much power to meet the needs of applications that require an Intrinsically Safe rating. And the system would be smart, strong, and economical.
In the future, gas
chromatographs, mass spectrometers, and some other single-point devices
are prime targets for modularization and miniaturization along the
lines of the NeSSI program. It is also possible that the initiative
will eventually result in temperature and pressure specifications that
can be plugged into any situation, as well as support for gas and
liquid flows from minute to full, 1⁄4” line sizes.
Nigel K. Glover has
more than 28 years of experience with industrial fluids and flow
control applications. For the past 11 years, he has been working for
Brooks Instrument, a division of Emerson Process Management. He earned
a bachelor’s degree in Chemical Engineering from The Georgia Institute
of Technology. Brooks Instrument is a charter member of CPAC and
continues to actively support ongoing programs; primarily the NeSSI
initiative. Mr. Glover can be reached at
nigel.glover@emersonprocess.com.
For More Information: www.brooksinstrument.com
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