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Chemical process analysis visionaries, spurred by the successful use of modular sampling systems and manifolds (Figure 1) for ultra-pure gases in the semiconductor industry, have launched a major effort to define and adopt a new vision of process analyzer sampling systems, sensors, and connectivity, with diagnostics and the smarts to optimize their performance.
Formally created at ISA Expo 2000, the New Sampling/Sensor Initiative (NeSSI) is a vendor-neutral and non-affiliated effort that operates out of the Center for Process Analytical Chemistry (CPAC) at the University of Washington in Seattle. Peter van Vuuren of ExxonMobil Chemical, Baytown, Texas, observes that it has grown into "an ad hoc industry initiative to drive permanent change in how we do process analytical [chemistry]."
As of May 2002, the NeSSI effort has more than 300 e-mail subscribers representing over 30 end users in the oil and petrochemical industry, manufacturing companies, equipment vendors, academia, and national laboratories. Their goal: reduce the design, assembly, installation, and operating and maintenance costs of sample handling systems. Their plan: facilitate the development and evaluation, over three generations, of:
1. Modular sampling system designs using standardized surface-mount hardware that is compliant with ANSI/ISA-76.00.02-2002, Modular Component Interfaces for Surface-Mount Fluid Distribution Components-Part 1: Elastomeric Seals (SP76).
2. Software and plug-and-play hardware for smart sampling systems that optimize their performance by altering pressure, flow, temperature, and in the future, other operating parameters. This hardware also would be certified for use in hazardous areas (intrinsically safe) and enabled for non-proprietary communications solutions.
3. Open standards for wireless communication and hardware for miniaturized analytical instrumentation.
History and Lore
Exactly when the concept of a modular sampling system first originated is hard to pin down. Work that started as early as 1994 resulted in a patent, Modular Sample Conditioning System, U.S. Patent 5,841,036, filed in August 1996 and issued to Don Mayeaux, president, A+ Corp., Prairieville, La., in November 1998. That may represent the beginnings of efforts to modularize sample conditioning systems.
However, it appears that the industry-wide initiative on the need for new approaches to sampling started within the Oil and Petrochemical Industry Focus Group at CPAC. "However, there was a consensus that the problem was not unique to petrochemical and that sampling was a concern in the food and consumer products, pharmaceutical, biotech, and the chemical process industries, and that there was a need for projects in sampling and sampling systems," recalls Mel Koch, director of CPAC, who formerly had global responsibility for analytical sciences at Dow Chemical.
Figure 1: Heart of the Beast
The essence of NeSSI is using modular components mounted on a standard substrate to build sample conditioning and analyzer systems. (Source: Swagelok)
"The CPAC group wanted to develop a concept for a flexible and smart sampling system that would be low-maintenance, require lower volumes (smaller samples), and be amenable to microanalytical devices," says Jim Tatera, senior process analysis consultant and president of Tatera and Associates, Madison, Ind. "The modular approach really took off when people piggybacked the concept with the SP76 standard for a modular sampling interface, the so-called surface mount technology, allowing it to move forward with some flexibility and interchangeability."
The SP76 standard is based on the semiconductor industrys concepts for surface mount technology. However, Mayeaux argues that the development of a standard for modular sampling and sample conditioning systems should have "wiped the slate clean; to design something that would be best for sample conditioning and analytical applications rather than adapt technology developed for control purposes."
"The way we approached it was to consider what we hoped to accomplish and what we wanted in the substrate and component interface design," relates Bac Vu, analytical specialist, Dow Chemical, Freeport, Texas. "There were features in the semiconductor design that were useful and that we felt we could implement in the chemical industry. We did not duplicate their design, but used it as a starting point to derive something to suit our needs. It has also given vendors an impetus to drive further development of sample conditioning technology, which we feel is an area that has been stagnant in terms of technological advancement and development."
Benefits Run Deep
Despite differences in the mechanical and engineering details of components and substrates, the interface designs are compliant with SP76 and the modular sample system concept embodied in NeSSI will help reduce the high lifecycle costs associated with conventional sampling systems. These costs include design and engineering, assembly, training, installation, startup, and maintenance.
"The biggest advantage of the NeSSI approach is it provides a standardized design and a smaller footprint for the sample system. It also provides a standardized approach that greatly simplifies the design effort because it provides for a [standardized] substrate and components that are carefully designed and defined for the particular application," says Rajko Puzic of Imperial Oil's Products and Chemicals Div., Sarnia, Ontario. This standardization and modularity (Figure 2) also greatly simplifies assembly, "So there is no variability. If I put 10 systems in service and theyre all the same, I most likely wont have to go through special cleaning or additional effort to make them work the first time out."
Figure 2: NeSSI Unleashed
Modular components simplify sample system design, construction, housing, and maintenance. (Source: Parker Hannifin)
Stephen Jacobs, development associate chemist at Eastman Chemicals, Kingsport, Tenn., adds, "First, we see benefits in shrinking the footprint so we can put more things into the same area. Second, we see benefits in cutting down the labor it takes to build these systems. And third, [NeSSI] is going to allow us greater automation."
Along with reducing the size and increasing flexibility with respect to the installation, design, and layout, "the NeSSI platform has provided incentives for suppliers to look at newer technology for sample conditioning components, components with smaller dead volumes that are more reliable and easier to maintain and change out," observes Vu. "We feel the new technology will [increase] reliability and reduce the space required for sample conditioning and analytical equipment installations. It will also give us greater flexibility in terms of where we install it--we wont be limited specifically to installing systems in analyzer shelters. Another goal of this technology is to expand the implementation of sampling system and analytical technology near the sampling point or directly in the process pipe or vessel."
"ANSI/ISA-76.00.02-2002 standardized the interface between the substrate and the surface-mounted functional components such as valves, regulators, filters, flow controllers, sensors, etc.," says David Simko, marketing resources manager, Swagelok (www.swagelok.com). "It defined the physical dimensions of the interface, the location and size of the ports, and the location of the bolts. As long as those dimensions are met by the substrate and surface-mount functional component manufacturers, the two will fit together."
Sensor, substrate, and flow control component vendors are finding that modifying their existing product offerings is fairly easy and inexpensive. "In most cases, customizing existing components to be compliant with the SP76 interface standard is not difficult," says Steve Doe, analytical market manager, Parker Hannifin (www.parker.com). "We regularly customize flow paths, port configurations, or performance requirements on standard products for special customer applications, and adapting products to the SP76 interface is a similar effort."
"We were able to modify existing products quite inexpensively and make them commercially available quite easily," says Doug Mitchell, product manager for oxygen analysis products at GE Panametrics (www.panametrics.com). The company offers Generation I NeSSI-compliant oxygen and moisture analyzers.
Intuitively, users seem to know that NeSSI-compliant systems are cost-effective. However, "Getting buy-in from the business has been a challenge because we dont have the type of hard justification we would really like to have, and the businesses are insisting on it to invest in the new technology," says Vu.
On the other hand, Imperial Oils Puzic notes that, "People usually look at what it costs to buy a NeSSI system versus a conventional system, but they dont take into account additional engineering, cleaning, and assembly costs. In my experience, in looking at price quotations for both systems, even at this early stage I think the NeSSI system is cost-effective."
Figure 3: Plans for Growth
The timeline for three generations of NeSSI shows well soon be seeing smart sensors, management software, communications, and more.
Adds Jacobs, "Though NeSSI-compliant systems are pricey now, as production numbers rise and components become more standardized I think prices will drop. Im willing to pay the extra cost now to hopefully get [the technology] more established."
At least one leading user has presented its experiences with the technology as a way of generating buzz. Tatera says ExxonMobil released a paper, "Application of Smart Modular Sample Systems at an Olefins Plant," for presentation at IFPAC 2002 because, "If they didnt release the information and increase the size of the market, the devices and technologies they want to mount on these platforms wouldnt be available because vendors wouldnt have the volume [to make it worth it] for them to manufacture."
The development of the first generation of NeSSI-compliant components was relatively straightforward because SP76 was developed and approved quickly and vendors either already offered or quickly adapted existing components. In addition to various flow controllers, valves, regulators, pressure gauges, etc., NeSSI-compliant, surface-mountable oxygen, moisture, pH, and conductivity sensors are also available.
As currently envisioned, the specification for Generation II NeSSI systems involves definitions for:
1. Temperature-programmable substrates to maintain sample temperatures and dewpoints.
2. Smart, compact pressure, temperature, and flow sensors to provide measurements for validation and control.
3. "Combi"-valve, a pneumatic valve and solenoid combination component for controlling flow of sample and validation fluids.
4. Sensor Actuator Manager (SAM), a management and communications interface to manage the communications with and among sensors and actuators to standardize repetitive operating tasks and provide a gateway to an Ethernet LAN. The goal of SAM is to simplify maintenance by providing operating information about the sampling system.
5. A standardized graphical human machine interface (HMI) to allow interrogation and field-adjustment of the sampling system as well as analyzers interfaced to it.
6. Serial multi-drop sensor bus to simplify communications and connectivity.
7. A temperature-controlled enclosure for sampling system and analyzers where standardized designs will help standardize an area classification inside the enclosure.
Formal specifications, development, and evaluation of NeSSI II-compliant devices is in progress. If all goes according to plan (Figure 3), NeSSI II-compliant components should be commercially available in summer 2005. Jacobs cant wait. "Im at a juncture where I need to do it now. Im working with two companies that are not only shrinking sensors to give us a smaller footprint, but are also giving us jumping-off points to do other things as well. For instance, one vendor is modifying a sampling system to make it look like a web site, so I can not only query from a remote location but, with the added I/O, input signals into the sampling system from other sensors as well as output signals to give me control over the valving and some of the things I want to do."
Jacobs also comments that because Ethernet is ubiquitous, not only does he have the ability to control various remote devices, the analyzer technicians in the field can also access manuals and other needed information from other computers on the network.
One element of the NeSSI vision of success allows a designer to design, build, and document a complete analytical system on the bench using very simple tools. "To do this, not only does the mechanical system have to be simple to assemble, but power/communication needs to be pluggable," says Rob Dubois, senior analyzer specialist at Dow Chemical Canada, Fort Saskatchewan, Alberta. "In electrically hazardous areas, this means using, where feasible, intrinsically safe (low-power) methods using simple wiring and connectors. Honeywell Labs and Honeywell Automation are in the process of building a proof of concept apparatus prototype that will demonstrate the use of simple sensors and actuators operating over an intrinsically safe multi-drop network."
The vision for third-generation NeSSI-compliant systems includes wireless connectivity as well as labs-on-chips and other microanalytical devices. In fact, "NeSSI has provided a very interesting reason and enabling tool for miniaturization of analytical instrumentation," observes CPACs Koch.
"The majority of the 20 research projects now underway at CPAC involve building instrumentation that will be NeSSI-compatible, part of the Generation III concept," he continues. "When some of these projects started at CPAC in the mid-1990s, critics in the oil and petrochemical industry thought we were wasting our time because they were accustomed to large sampling systems attached to large process analyzers. However, once a few of the NeSSI units were built and attached to an analyzer, even something as small as a process GC, the engineers started asking why the analyzer had to be so big. Now they are not only appreciative of miniaturization technology, but are encouraging its development."
"People have asked the question, Will NeSSI standardize analytical system design? The answer is, sort of," says Dubois. "Having standards such as SP76 certainly help, as will a sensor/actuator communication standard. However, most analytical systems have personalities to accommodate nuances in specific processes or measurements. Consequently NeSSI systems need to be flexible and highly configurable to work within the constraints of simple, but not inflexible, mechanical, electrical, and software standards."
Field Editor Mark D. Weiss is a Rockland County, N.Y.-based freelance writer and long-time contributor to CONTROL.
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