Molding the future of process analytical sampling

InTech, Aug 2001 by Fussell, Ellen

Sampling from start to finish

ISA's Analysis Division and CPAC are cosponsoring a meeting at ISA 2001 next month in Houston to raise awareness and receive input, guidance, and support for their new sampling system initiatives. The meeting is for everyone who has anything to do with sam pling systems-those who make components for sampling systems, systems integrators, users, and those who maintain the systems.

"We intend to bring the attendees up to date and explore future directions," said Jim Tatera of Tatera Associates. "We want to anticipate and avoid as many problems as we can and take advantage of good ideas."

For more information on ISA 2001, visit www.isa.org.

From measuring gases in environmental stacks to corrosive and toxic

chemicals, food processing, and pharmaceuticals, system sampling has been a key concept in process analytical systems for years. But the growth spurt in technology has left a gap in the sampling arena. "Since the 1930s, sample systems have looked the same-tubing, piping, filters, flowmeters, and valves-and have been the nightmare of process analytical sampling as technologies have developed," said Jim Tatera, owner of Tater Ass;ociarcs, a process analytical systems consulting firm in Madison, Ind. Most problems involve fluctuation in process conditions: flow, bubbles trapped in the liquid, solids being filtered out, and sample temperature changes.

While analyzers have gotten smarter and the microprocessors in them can self-- diagnose, Tatera said, aside from the occasional new filters and flowmeters, sample system testing technology hasn't really progressed. Frustrated with the current state of sampling technology, members of the Center for Process Analytical Chemistry (CPAC) envisioned a smart sampling system-a system that could monitor and diagnosis its own status and performance.

"Today you hear about lab-on-a-chip sensors and MEMS technology," said Tatera. "But if you've got a sampling system from a process that's 4 by 5 inches in size, what good does it do you to have this nice, neat little sensor if you have to take up a whole wall anyway? If you can get a small modular sampling system to work well and reduce that footprint size, suddenly these smart lab-on-a-chip sensors offer a lot more potential to the processing industries," he said.

To help support the CPAC effort, Tatera and others have embarked on a quest to bring sampling systems into the twenty-first century, working closely with the ISA-SP76 Composition Analyzers committee and the ISA Analysis Division. They're developing a new modular sampling system interface standard: ISA Draft 76.00.03, Madular Component Interfaces for Surface-Mount Fluid Distribution Components. The committee's goal is to provide a modular platform that can accommodate smart devices and the older manual valves or regulators.

Dan Podkulski, senior staff engineer at ExxonMobil in Baytown, Texas, chairs the SP76 working group that's developing the standard. The concept models one used in the semiconductor industry for ultraclean gas samples, Podkulski said. "Most of the demand for a standard came from the suppliers; they needed a reference for our design," he said. "There's not a lot of value for one company to design something that doesn't work with something else; it defeats the purpose of a modular-type system."

Podkulski said the committee began working on metallic sealed-type components and now have a standard based on an elastomeric seal. "The standard defines an interface between a substrate and the component-the location, size, and placement of the flow paths and bolt patterns," he said.

The main urgency in developing the standard is there are people manufacturing components to the proposed design. "People are even purchasing sample systems using that design draft standard," he said. -Wc need to get the standard approved because as soon as you get people excited, you need to capitalize on that energy so they can start using it in the field."

New sampling initiative

To help boost the concept of a modular sampling system, in succession to developing a new standard, Peter van Vuuren of ExxonMobil and Rob Dubois of Dow Chemical in Alberta, Canada, started an initiative called the New Sampling/Sensor Initiative, or NeSSI. Their goals are to establish more reliable process sampling and reduce design, engineering, and manufacturing costs of sampling systems.

"First we make the systems smart so they can diagnose their own problems. That's the goal of NeSSI," said Tatera. "Then we provide the found dation so devices can be interchanged. That's where the standard development comes in." The NeSSI leaders are anxious to adopt the new SP76 draft standard as the interconnection scheme, or base, of their system.

Tatera said the project proponents have made progress translating these traditional sampling system designs to the new surface-mount configurations. "Now we're building prototype systems for online testing," he said. "To make NeSSI a reality, we need to expand the equipment options beyond those that mimic traditional systems to make the sampling system powered, smart, and full of sensors, communications, and controls."