Rethink Sample System Automation

Rethink Sample System Automation -- NeSSI Provides New Tools to Tackle the Challenges and Improve Performance

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Thermostats for temperature control. We can replace thermostats with PID control loops. We already are doing this using commercially available smart heaters. Advantages include the ability to maintain higher temperatures thanks to tighter control of the heater. Although an explosion-proof heater can't run on intrinsically safe power, its temperature and set-point signals can be integrated into the NeSSI-bus. Reliability will be enhanced by being able to better monitor and control critical dew points and bubble points of the process sample.

 

NeSSI bus-enable module
Figure 4. Valve Control Module and
Transmitter: Module (left) comes with
a lockout to prevent actuation of
multiple valves at the same time.
Photo courtesy of Swagelok.

 


Gas cylinders for calibration and validation. More-precise flow and temperature control in a sample system affords the opportunity to opt for more permeation generators to calibrate and validate analytical sensors. Today we use bulky gas cylinders to do this chore. It would be a tremendous advantage from an installation and operational point of view to eliminate calibration cylinders when the components needed are available as permeation sources.

Maintenance resources and routine rounds.NeSSI can eliminate the need for continual checks and adjustments. The new generation of smart analyzers such as gas chromatographs will have visualization built into the sample system as part of their local human machine interface (HMI) and remote workstations, helping analyzer technicians properly troubleshoot. Indeed, troubleshooting will become more of a science than an art. Portable zone-2-rated laptop computers or PDAs can effectively serve as the new "adjustable wrench" for the technician.

Block and vent valves for gas chromatograph sample introduction. Typically to ensure constant molecular volume we reference the sample pressure to atmosphere using a block-and-vent-valve arrangement prior to injecting a sample into a gas chromatograph. The ability to use an absolute pressure sensor will allow more-precise measurement and better control without the need for block-and-vent hardware. Of course, this would require the sample system to communicate with the gas chromatograph.

System-centric health monitoring. Sensors and networking will enable expansion of monitoring to all elements of an analytical system. It will permit overall analytical system performance to appear in the control room as a traffic light status signal that tells the operator whether the complete process analytical system is good, bad or is still good but will soon require maintenance. This will improve the operator's confidence in the performance of the analyzer system.

The Path Forward
Bus systems undoubtedly will mature fairly quickly; many components including miniature flow meters, pressure sensors, smart heaters and both proportional and on/off automated valves either are available or will be in the next couple of years. Ability to purchase functional applets that could work across multiple analyzer systems will be truly revolutionary — they even may be fun to use. Today SAM functionality is embedded in more-complex analyzers such as gas chromatographs. Extending it to other analyzers demands a compact NeSSI-bus-enabled SAM. Until that's available we'll struggle to bring standardization and simplicity to our discipline. Until then we'll continue to supply ad hoc and proprietary solutions that will work — but not support our general move to Generation III microanalytical and by-line installations. Our objective is to allow a microanalytical manufacturer to be able to plug into the mechanical and communication rails — and configure its devices sampling tasks using off-the-shelf applets. This architecture finally will enable the sampling and analytical measurement to go hand-in-hand as an integrated package.

The cost and technical effort to move to complete sample-system automation will be high. However end users will gain significant rewards including higher reliability and lower maintenance costs. It'll take a clear vision and concerted effort to change the game — but the horse is out of the barn and it's only a matter of time before we'll look back and wonder why we clung to our manual systems for so long. However, until that time comes we'll continue, out of sheer habit, to build steel copies of wooden bridges.

More Information on NeSSI
The Center for Process Analytical Chemistry at the University of Washington serves as the forum for NeSSI development activities. It conducts workshops and presentations twice a year in Seattle. For additional reading or contact information, refer to:

http://en.wikipedia.org/wiki/NeSSI
http://www.cpac.washington.edu/NeSSI/NeSSI.htm


Robert N. Dubois is a consulting analytical specialist based in Sherwood Park, Alberta, and a member of the NeSSI steering team at the Center for Process Analytical Chemistry, Seattle. E-mail him at robndubois@shaw.ca.

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