The "fifth horseman" of process control

"ITt's time to change the conventional way of sampling systems, and with the new technology in microprocessors we now have that opportunity," said Rob Dubois of Dow Chemical in Alberta toward the end of 2001.

"We ultimately want to get small analytical

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Dubois and colleagues Peter van Vuuren and Jeffrey Gunnell authored a revision and update of the New Sampling/Sensor Initiative (NeSSI) Generation II specification this summer. NeSSI is the vehicle by which Dubois and many others are marshalling tiny analytical sensor technology.

The initiative began in 1999 at the Center for Process Analytical Chemistry (CPAC, www.cpac.washington.edu) sponsor meeting to explore the potential of miniature process analyzer sample system components.

ARC Advisory Forum (www.arcweb.com) analyst Paula Hollywood provided this overview to InTech magazine.

Originally established in 1984 as a National Science Foundation Industry/University Cooperative Research Center, CPAC has evolved into a self-sustaining, multi-industry, multidisciplined consortium dedicated to meeting manufacturing's evolving requirements for real-time analysis.

CPAC provides a collaborative forum for users, suppliers, and the research community in the development of process analytical technology. Technologically, the thrust of the consortium's efforts focus on measurement methodology, including miniaturization of traditional instrumentation as well as development of new sensors and the integration of process measurement with process modeling and control that will be the platform for microanalytics in the future.

Estimates state that manufacturers spend $2.5 billion annually on maintenance and repair of process analyzer systems. NeSSI is on a path to develop standardized, smart, safe, modular, and reliable process stream sensor and sampling systems.

The NeSSI road map has three generations. The focus of Generation I, now in the testing phase, was to miniaturize the components for substrate mounting. Generation II is under consideration and focuses on the connectivity and communication issues of intelligent sampling systems.

If the goals of this initiative come to pass, it could conceivably eclipse the importance of traditional process control measurements and become the "fifth horseman" of process control along with pressure, temperature, flow, and level measurements.

Systems are custom built

Process control systems, sensors, and analyzers have all evolved to become sophisticated pieces of equipment with a fair degree of intelligence; however, the sampling system has not changed in any meaningful way in thirty years.

The reality is that in many enterprises the number of chemists is shrinking and the number of analyzers is growing, making more efficient analyzer systems essential.

Most sample systems are custom built to specific user needs without the benefit of industry standards as a guide. If one considers a breakdown of the cost to build a process analyzer system, the analyzer itself accounts for nearly 40%; sample acquisition and preparation, including transport and return lines, accounts for 30%; and providing an appropriate installation accounts for more than 25%.

Estimates are that the NeSSI platform will reduce the cost to build an analyzer system by as much as 40%. The savings will largely come as a result of a reduction in analyzer system infrastructure.

With the sampling system close coupled to the process, long sample transport and return lines and the problems associated with them will disappear, including analyzer shelters.

The increased intelligence derived from the NeSSI platform will yield savings in total cost of ownership in the range of 30%, chiefly through previously unavailable diagnostics. Technicians will no longer have to check out all system components in case of a problem, as the analyzer will have the ability to self-diagnose. The much-improved data connectivity should enable remote vendor support, allowing users to place greater reliance on suppliers rather than on dedicated site analyzer engineers.

It will also enable one technician to increase the number of analyzers he or she can support, and it will reduce the analyzer spare parts inventory the manufacturer will be obliged to carry.

Talking about my generation

The NeSSI initiative has brought together a diverse group of manufacturers and vendors to modernize the analytical sampling system. To the amazement of many, the group determined that the requirements of the process industry were the same regardless of the product manufactured.

The desire for a standardized sampling system conceived, assembled, and configured on a workbench is common to all. The requirements are actually quite reasonable and include a building block approach with no special skill required for assembly and plug-and-play components that are selfdocumenting.

Generation I: With the ANSI/ISA SP76 standard for open architecture interface as a starting point, the focus of Generation I, which began in 2000, has been mechanical components. The immediate goal was to reduce the size of the sampling system. The result was modular substrates upon which microanalytical components can easily mount, so sampling systems can reside closer to the process line.

Employing a standard mechanical interface enables interoperability between system components regardless of manufacturer, where commercial-off-the-shelf components are part of the substrate. It should not be surprising this is the very same desire that plant engineers have expressed regarding field instrumentation for some time. With a standard interface, time to design, build, and implement is far less. The number of components in compliance with the SP76 standard continues to increase. Prices are down; indeed, pricing on miniaturized components has fallen from three times that of standard product to approximately a 20% premium.

The efforts of Generation I have yielded four working models on which field testing is underway. Unofficial reports indicate manufacturers are pleased with the designs vendors have put forth, but some members have expressed concern that the flow path in the components, not the substrate, may be too small. There is acknowledgement that larger flow paths would add dead volume, but new O-ring designs may address that issue.

All of the models excel in different areas, and all provide plug-and-play functionality meeting the NeSSI vision. Subsequent models could combine the best features of all four.

Generation II: The principal issue of this phase is smart control of the sampling system. This will require low-cost measurement and control components to transfer signals and power to and from the system. A widely circulated draft of the Generation II "electrified" specification went out to the NeSSI membership one year ago and is the basis for prototype designs.

A primary requirement of Generation II is that all components meet Division 1 (Zone 0, 1) hazardous certification, such that the systems are neutral for any geographic location. The petrochemical and refining industries are driving this requirement.

The requirements of Generation II are that all components be suitable for substrate mounting and be intrinsically safe electrical classification requirements.

Additional Generation II requirements include the following:

* miniaturized flow, pressure, and temperature sensors

* programmable heated substrate base

* combined electropneumatic actuators packaged as a unit for on/off and modulating control

* multidrop serial communication/connectivity network

* temperature-controlled enclosure

* sensor actuator manager to include at least one Ethernet port, one or two network ports, and one wireless port

Honeywell is managing Generation II development in conjunction with the NeSSI steering committee. Much of the funding for this project will result from Honeywell's contract with the U.S. Department of Energy for development of wireless and sensor technologies to help reduce U.S. industry operating costs by up to $1 billion, principally in energy costs. Delivery of prototypes will happen this year as a condition of the contract. The resulting work will be open to all suppliers to adopt.

Estimates are that the NeSSI platform will reduce the cost to build an analyzer system by as much as 40%.