March 2006

Putting the Pieces Together

NeSSI’s Modular Systems Design Strategy

By Nigel K. Glover

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. 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. 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 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. 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. 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. 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. 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