Rob Dubois is a featured speaker on the New Sampling Sensor/Initiative (NeSSI™), a program focused on modular and automated process analytical systems design. Rob has given presentations and/or led tutorials on this topic at many different venues, including IFPAC (International Forum of Process Analytical Chemistry), INTERMAC/Tokyo, NIST (National Institute of Standards and Technology), ISA, ODVA and the PAT (Process Analytical Technology) focus group/London, as well as CPAC (Center for Process Analytical Chemistry – University of Washington/Seattle). He is a co-author of the NeSSI Generation II specification and developer of an ISA-sponsored seminar on NeSSI. Rob worked at Dow Chemical from 1978 to 2007 in various roles associated with process analytical, including major engineering, maintenance and research & development. Rob is a member (and former chair) of the CPAC/NeSSI steering team. He can be reached at email@example.com.
Q: Why was the New Sampling Sensor Initiative (NeSSI) founded, and what are its core objectives?
A: NeSSI has four objectives. They are:
1. To facilitate the acceptance and use of modular, miniature sample system designs using the ANSI/ISA SP76.00.2002 standard;
2. To provide the mechanical, electrical and software infrastructure needed to accelerate the use of microAnalytical technology within the process analytical community;
3. To reduce costs and complexity by moving the analytical systems out of the analyzer houses to the field where they can be close-coupled to the process pipes and vessels. (This is referred to as By-Line analysis.);
4. To lay the groundwork for the adoption of open communication standard(s) for process analytical to provide fully automated, intrinsically safe, smart, plug-and-play sample systems.
Q: Who is responsible for the ongoing technical development of the NeSSI program?
A: The Center for Process Analytical Chemistry (CPAC) at the University of Washington (Seattle) sponsors a steering team. Based on both end-user and supplier input, the steering team sets the vision, develops guidelines and writes specifications for the NeSSI program. The steering team also has a communication role, which includes organizing and hosting semi-annual workshops [in Seattle], publishing a Web site and issuing updates to a mail-out list. The real technical developers, however, are the manufacturers and inventors, who turn the guidelines and specifications into actual products. Since this is an ad hoc initiative, anyone is welcome to develop and/or supply products.
CPAC provides a neutral forum and legal umbrella, which allows normally competitive end-users, suppliers and academic groups to collaborate on an initiative such as NeSSI.
Q: From a high-level perspective, please identify and explain each of the three generations outlined as part of the NeSSI roadmap?
A: Generation I covers the physical, fluid handling components of a process analytical [sampling] system. Elements of Generation I include Lego-like modular assembly; a standard footprint which allows interchangeability of the surface-mount, miniature components; low internal dead volume; plus an overall compact assembly. Typical components include valves, filters and pressure regulators. CIRCORTech, Parker-Hannifin and Swagelok are the major suppliers of the modular mounting blocks and fittings. Some manufacturers provide a configuration software tool used to design and document a system. Introduced about five years ago, this generation is mature and well proven in industry.
Generation II, under development since 2004, provides a means to automate the analytical [sample] system components. More complete automation has been an unmet need for process analytical sampling. Automation is important because if extracted sample parameters such as flow, pressure and temperature are not carefully measured and controlled, the analytical results are unreliable or even meaningless. Key elements of Generation II are bus-networked components and an architecture that integrates these components into the overall plant communication hierarchy. Since many process analytical installations are contained in sealed enclosures handling hazardous fluids (e.g. ethylene, hydrogen), we have adopted a “fit-for-purpose” intrinsically safe bus technology, which allows us to use sensors and actuators in an electrically hazardous environment. At this time, there are two competitive NeSSI-bus technologies – CAN in Automation (CiA 103), used by ABB, and I2C, which is available from Siemens. Both of these are mature products; however they had to be adapted to operate intrinsically safe. NeSSI-bus-compatible components, such as on/off valve actuators and combination flow/pressure sensors, will be available this year. Work on Generation II should be well developed by 2010.
Generation III, now at the emerging stage, provides the infrastructure — or as we call it “the connection rails” — so that a microAnalytical sensor can be plugged into both the sampling system and a plant’s communication network in a matter of minutes. Generation III will contribute the most cost savings to industrial users, since it will allow them to move their measurements out of the expensive analyzer houses and to the field where By-Line analysis can be done. For this to happen, systems need to be compact, robust and automated — which is why the NeSSI generations are designed to be backward compatible.
Q: According to the NeSSI Web site, work has begun on Generation III aspects of NeSSI. What sort of work is currently being performed as part of this generation of the project?
A: Work now being performed for Generation III includes:
• Developing a set of design requirements and guidelines for microAnalytical sensors in industrial settings. Development of this specification is in progress.
• Promotion by CPAC of Generation III as a microAnalytics platform.
• Sensor development, including miniature chromatography modules that have been specifically designed for the NeSSI platform.
Q: What are some of the stumbling blocks NeSSI has faced in its initial phases of development? What are some of the key obstacles that remain to be overcome for NeSSI to realize its full potential for sampling systems designers?
A: An early stumbling block for Generation I was to get substrate (surface mount footprint and interconnections) architecture suitable for process analytical use. Many of the early designs (ca. 2002) were borrowed from the high-purity semiconductor industry. It took some very significant design changes by the manufacturers to make a product more in tune with the process analytical industry. One such change was the move to elastomeric seals rather than metallic in order to lower costs. I think most manufacturers had two distinct product launches plus a distinct period of kaizen. Once the substrate portion was perfected, components (such as valves) had to be either modified or developed from scratch in order to better match the flow patterns of a modular system. Today there are in excess of 60 components, which are available for mounting on a NeSSI platform.
Another significant stumbling block was the difficulty in selection of a bus system for NeSSI Generation II. Our selection process was somewhat torturous in approach. Our shopping list included bus components that were small in physical size, low cost, well proven in industry, industrially robust, capable of supporting multiple devices (up to 30) and, most critically, able to be certified for use in an electrically hazardous Division/Zone 1 environment. It was not until 2007 that we had two good candidates that met the criteria. Although I wouldn’t consider this an obstacle, the existence of two competing buses may keep some product developers (and users) on the sidelines until a clear winner is established. Some developers are supplying components with “top hats” which contain either configuration, so this may not be a big issue.
Another potential technical challenge is the lack of a proportional valve that operates in an intrinsically safe environment. The constraint on current usage makes this a challenging technical design. (In an intrinsically safe scheme all components draw from the same power well. So each sensor and actuator must play nicely with the others within a power budget.) Until we have this valve available, we cannot do closed-loop, PID control at the sample system level. Three years ago, we had no miniature, modular flow transmitters — today we have two that are network capable and others that use 4-20 mA. Hopefully it will be just a matter of time before such a product becomes available.
We also need to do more work to fully develop the Sensor Actuator Manager (SAM). This is an inexpensive computer, mounted locally with each sample system (hockey-puck sized) and packaged for use in hazardous areas. SAM provides a suite of industry-standard and open applets that can be configured for any flavor of sample system or analytical sensor. Examples of an applet would be a stream switching routine or a sensor validation package.
At CPAC, we have compiled a list of over 50 common applets which could apply across the process analytical regime. Today, the Generation II design has the sample system controlled from an embedded SAM located in a smart full size analyzer such as a gas chromatograph. There needs to be an independent SAM, which can handle both simple analyzers (e.g. oxygen, moisture) as well as the emerging class of microAnalytical sensors. The challenge is getting equipment whose price point starts to fit into the process analytical budget. I see this as more of an economic justification and industry coordination issue rather than a technical roadblock. Consumer electronics and commodity software will ultimately come to our rescue. Developing this stand-alone SAM will continue to be a major push as we move into Generation III.
Q: Some of the common concerns voiced by potential users of NeSSI systems include high cost, troubleshooting at the component level, and a lack of long-term performance data. How have these concerns affected uptake for Gen I NeSSI systems? Do you see these concerns being resolved going forward?
A: The higher than conventional system cost certainly slowed the early acceptance and growth. There was also some suspicion of a new mousetrap which had no track record — after all, the chemical manufacturing community is (and should be) conservative. A rule of thumb is that it takes two major facility build cycles, or eight years, for new systems to penetrate the petrochemical market. It is now apparent that significant cost benefits can be achieved from repetitive builds of standard sample system designs. It also appears that savings may be derived from faster design and fabrication, as well as simpler installation and reduced long-term cost of ownership (maintenance and spare parts). Now that there are some “miles in the bank,” this needs to be further quantified.
With respect to difficulty of troubleshooting, this is somewhat like a modern automobile engine — sure it is harder to get at the spark plugs in my new car, but it now lasts twice as long and is much more reliable than my old one. So like my new car, Gen II system is designed to have more diagnostic sensors and both a local and a remote graphical user interface (GUI) which allows the technician to do faster troubleshooting. There are also solutions for those who feel uncomfortable with a close packed system. One of the modular manufacturers has exposed tubing that can be traced under the substrate if so desired. Separation of component manifolds can also be done, but in my opinion this defeats the purpose of a compact system.
Regarding long-term performance data, now that many of the Gen I mechanical systems have been in operation for as many as five years, no systematic history of sealing failures or plugging has been reported. There was lots of initial apprehension about the use of o-ring seals, but this has not been an issue. In fact, the more compact, rigid design embodied by NeSSI seems to be more leak-resistant than conventional designs. A good measurement of satisfactory performance is repeat orders. One large company that has been actively involved with NeSSI from the beginning has specified 150-plus systems for use in a greenfield petrochemical facility.
Any idea that we would obtain vastly superior cost savings over conventional systems, based on a piece for piece replacement at the Generation I level is a bit of a myth. The “big bang” is not at Generation I. As Generation II unfolds, we will begin to have increased reliability by means of automation and remote communication. Once we are automated, we can start adapting our traditional designs to incorporate sensors and actuators. It is quite remarkable, but even after 70 years process analytical still relies heavily upon the use of nonautomated, maintenance-intensive devices such as rotameters, pressure gauges and mechanical regulators to condition the extracting sample prior to analysis. The replacement of the classical rotameter with a flow transmitter will solve an annoying positioning constraint on modular systems (rotameters must be mounted vertically) and allow an even more compact design. Remote communication allows predictive maintenance and event logging — which has proven, when more complex analyzers such as gas chromatographs become networked, to reduce the ratio of analyzers per technician needed to maintain an analytical system. Once the sample system is automated, I suspect the uptake of NeSSI systems will be accelerated. This is the point where significant cost savings can be achieved.
Q: What are the core application environments for NeSSI technology? Do you foresee NeSSI technology expanding into other applications going forward?
The original core applications for NeSSI are vapor and lighter liquid applications used for process analytical measurements in the petrochemical, refining, air separation and chemical manufacturing industries. However, both pilot plants/labs and micro reactors could ultimately be major application environments for NeSSI. (CPAC has also been very active in this area.) NeSSI is particularly useful for these process intensive (i.e., compact) setups. Some companies have already used NeSSI for applications, involving catalyst screening studies where miniaturization and rapid, modular assembly is important.
Another promising environment for analytical applications is in the pharmaceutical industry. Right now, more widespread use of continuous analytical measurements is underway in this industry. This is being driven by the PAT (Process Analytical Technology) initiative. However, NeSSI cannot be used with solid samples or powders, so these applications would need to be limited to gases and lower viscosity liquids. There are also general applications in the laboratory where NeSSI has been used to handle and condition the fluids, such as carrier gases, required by bench-top analyzers.
In the future consideration category, the introduction of a low-cost intrinsic safety network that can handle multiple sensors and actuators may allow NeSSI technology to penetrate those industries that use hydrogen fuel cells. Modular, miniature and intrinsically safe systems may also have military applications — particularly aboard vessels that require control and transport of flammable fluids or are located in electrically hazardous areas.
Q: How do you see NeSSI technology evolving over the next 10-15 years?
A: I think in a few years NeSSI technology will be so commonplace that the term NeSSI may actually fade away. Our goals are clear — we need to:
• Extract simplicity out of complexity through standardization;
• Swap maintenance-intensive systems for reliable ones through automation;
• Drive down design and installation as well as the long-term ownership costs by making the measurement closer to its sample source.
These are all natural, evolutionary steps with any technology — whether it is process analytical or something else. We are impatient people. We just want this to occur sooner rather than later. To summarize, our roadmap is unfolding as planned. (Albeit over a longer period of time than anticipated). And this is where I see this all evolving.
• Process sampling will become automated and more tightly integrated with its analyzer or analytical sensor.
• This new, intrinsically safe, fluid handling and conditioning technology for handling low quantities of fluids safely will become more widely used in areas such as pilot plants and micro reactor work once more precise temperature control of the components becomes available.
• Analyzer technicians will configure their analytical sample systems using graphical tools such as PDAs and portable laptops. Adjustments will be via software, not hardware.
• Engineering designers will be able to design an analytical system on their computers, which not only shows the nuts and bolts but also includes a suite of calculations for doing such things as flow calcutions, pressure drop and dewpoints.
• Assembly can be done by unskilled personnel, and the NeSSI components will become more tightly integrated with their enclosures and heaters.
• It will further drive the use of standard sample system designs for commodity process analytical applications. Science will replace art.
• Off-the-shelf applets will be available (at a cost) to provide commodity and user-selectable, programmable features such as stream switching.
• Improvements will also occur in component performance, especially in the area of stream filtration, once the various sensors become available.
• Certification of a process analytical system will become easier, since intrinsically safety is a standard protective method acceptable by electrical approval agencies anywhere in the world.
• The above items will be welcome, but the revolution will come with the widespread use of microAnalytical technology. These will be the spin-off and ultimate benefit derived from NeSSI.