NeSSI
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NeSSI is an acronym for New Sampling/Sensor Initative. It is a collaborative open industry-wide initiative, with most of the work being done by industrial companies in the chemical and petrochemical fields (both vendors and end-users), aimed at developing and promoting a new technology for how process analyzers and sample conditioning systems are designed, constructed, and used within Industry. The heart of this new technology is a standardized modular surface-mount architecture. This standardized architecture provides a simple way to combine flow control and sensing components to build compact, and easy to maintain, industrial-grade fluid handling systems. The NeSSI advances to date have addressed many of the current cost-of-ownership limitations of traditional sampling system construction. The NeSSI vision also seeks to develop new technology that provides plug-and-play interoperability on an intrinsically safe communication bus, and lays the groundwork for the next generation of "smart" sampling and analyzer systems.
NeSSI originated at the Center for Process Analytical Chemistry (CPAC) situated at the University of Washington in Seattle, Washington, USA. The driving forces behind this initiative are to improve analytical system reliability through automation as well as to make analytical systems less expensive and simpler to build and maintain. The development of NeSSI has been a collaborative effort between Industrial end-users, manufacturers who supply the industries, and academic researchers working in the field. CPAC continues as the focal point for NeSSI development and provides a neutral umbrella under which interested companies (many of which are competitors in the marketplace) have been able to meet, discuss needs and issues, and make progress towards defining the future of Industrial sampling and analyzer systems. The focus of NeSSI is to provide the specifications, guidelines, and industry-wide concensus for the design and performance goals of a Lego-style building block approach for analytical systems. These efforts have resulted in commercially available hardware, published ISA/ANSI standards, and numerous published papers and presentations in open and industry related literature and conferences. The end result is that NeSSI is rapidly becoming an accepted and de facto standard in many industries. The NeSSI name is trademarked by the University of Washington to insure that it remains freely associated with the open nature of the Initiative — anyone can use the name NeSSI to refer to products or services that are consistent with the specifications and guidelines of NeSSI as long as they refrain from exclusively tying the name to a proprietary product or service.
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[edit] Background
Modern chemical and petrochemical processing plants are complex systems involving many steps (often called unit operations) involved in producing one or more products from various raw materials. In order to control these many processes, for both improved product quality and operational safety, many measurements are made at the different stages of processing. These measurements, either from simple sensors (such as temperature, pressure, flow, etc.) or from sophisticated chemical analyzers (providing composition of one or more components in the chemical stream), are typically used as inputs to process control algorithms to give a "snapshot" of the process operation and to control the process to insure it is operating efficiently and safely. Traditionally, most of the measurements (with the exception of temperature, pressure and flow) were performed "off-line" by taking a sample from the process and analyzing it in the laboratory. Beginning in the early 1980's, a trend aimed at moving the analysis from the laboratory to the process plant was embraced by industry and a new discipline called Process Analytical Chemistry (PAC) emerged which combined chemical engineering and analytical chemistry. One of the main driving forces for PAC [See also a more recent but related development in the pharmaceutical industry, called PAT] is to remove the bottleneck, and time lag, associated with sending the samples to the lab and waiting for the analysis results. By moving the analysis to the process, results can be obtained closer to real-time which effectively improves the ability for the control action to correct for process changes (i.e., feedback and feedforward control). By far, the most common implementation of PAC (especially for more complex analyzers) utilizes what is known as extractive sampling. This typically involves a fast loop where portion of the process sample is split off the main process stream, conditioned (filtered, pressure regulated, etc.), and introduced to the analyzer where the chemical composition or the intrinsic physical properties of process fluids (vapors and liquids) is measured. The hardware (traditionally metal tubing, compression fittings, valves, regulators, and filters) associated with this fast loop sampling is collectively referred to as the analyzer sampling system. Despite the simple explanation just given, modern sampling systems can be quite large, complex, and expensive. The design features of analytical sample systems have changed little, from the early 1930's when the discipline of Process Analytics began in Germany, right through until the present day.
[edit] History
The rationale for NeSSI originated from focus group meetings held in 1999 at CPAC which called out for more reliable sampling and analysis for the manufacturing processes. Early work with NeSSI was started in July, 2000 by Peter van Vuuren (ExxonMobil Chemical) and Rob Dubois (Dow Chemical) with the (initial) aim of adopting new types of modular and miniature hardware which were being addressed in a standard being developed at that time by an ISA (Instrumentation, Systems and Automation) SP76 working group. (Reference 1) The term NeSSI, along with the futuristic concepts of a NeSSI-bus and smart sampling devices were first introduced outside of CPAC at a presentation given in January 2001 at the International Forum of Process Analytical Chemistry (IFPAC) at Amelia Island, Florida, USA. The Generation II conceptual and functional electrical specification was released by CPAC in 2003 and is an open publication on the CPAC/NeSSI website. (Reference 2) Since its debut in 2000, NeSSI has seen rapid acceptance in Industry. Currently, there are three commercial providers (Swagelok, Parker-Hannifin, and CIRCORTech) of NeSSI compliant systems (with hundreds of surface mount components available that are interchangeable between their proprietary flow substrates), many third-party suppliers of specialty components for NeSSI, and a growing list of companies implementing NeSSI systems in their manufacturing and pilot-plant facilities. Recently, two of the largest suppliers of process analyzers, ABB and Siemens, have committed to supporting NeSSI hardware and the development of the intrinsically safe NeSSI-bus communication into their products. NeSSI is rapidly gaining status as the preferred, or de facto, standard for many process sampling system applications. In addition, NeSSI acceptance has spread beyond its initial chemical and petrochemical industry roots to find applications in the automotive, food, and pharmaceutical industries as well as applications as an analytical development system in research laboratories.
[edit] Technical Objectives
- Facilitate the acceptance and implementation of modular, miniature & smart sample system technology based on the ANSI/ISA SP76 standard substrate.
- Provide a technology bridge to the process for sensor or lab-on-a-chip micro-analytical devices
- Promote the concept of field-mounted (By-Line) smart analytical systems.
- Lay the groundwork for Pipe to Pixel™ open connectivity architecture for intrinsically safe device (sensors and actuators) communication and industry standard communication protocols.
Comparison of Current vs. NeSSI Technology (Extractive Systems)
| CURRENT | NeSSI |
|---|---|
| Analyzer shelters | Analytical system close to the sampling point (By-Line) |
| Long, traced transfer lines | Short lines, fast response |
| Extensive design required | Minimal design, standard based design |
| Custom assembly | Modular Lego-like assembly |
| Field repair | Modular replacement |
| Sample may not reach the analyzer | Sample flow is validated |
| Large amount of sample | Small amount of sample, less material to condition |
| Sample may condense | Temperature is controlled to prevent condensation |
| Conduits, seals, armored cable, purging | Simple plug-in connector, unarmored wiring using miniature, flexible cable |
| Large space required | Small, compact, low internal volume |
[edit] Applications
NeSSI is used for process analytical measurements in the petrochemical, chemical and oil refining industries. These measurements may be for quality monitoring of raw material or final product, environmental compliance, safety, energy reduction or process control purposes. Vapor applications may include hydrocarbon feed stocks and intermediates (ethylene, ethane, propylene, etc.), natural gas streams, liquefied petroleum gas (LPG) streams, hydrogen and air gas streams. Liquid systems applicable to NeSSI™ are hydrocarbons such as diesel fuel as well as aqueous streams. Highly viscous fluids and solids are not suitable for use with NeSSI. Very dirty, high particulate streams need to be filtered. Some liquid service applications may be limited by pressure drops associated with components hooked up in a serial configuration. NeSSI systems have found applications in areas other than the process analytical environments including micro reactor, mini plant and laboratory environments where small size, unskilled assembly and flexible configuration is important.
[edit] Technology Development Roadmap
NeSSI technology development has been grouped into three technology generations which are backward compatible. The time spans project time to first commercialization. Gen I is commercialized and proven in numerous industrial and laboratory applications.
[edit] Technical Development Roadmap
[edit] Generation I – Fluid Components
Generation I covers mechanical systems associated with the fluid handling components. Generation I has adopted the ANSI/ISA SP76.00.2002 miniature, modular mechanical standard. SP 76 defines a dimensionally standard footprint which allows interchangeability of surface mount components between different manufacturers. 
SP76.00.02-2002 Standard Footprint
Currently three manufacturers produce the substrates which provide the platform for the surface mount components. There are over 60 different types of surface mount components available from various suppliers who provide valves, filters and regulators as well as pressure and flow sensing devices. Commercial Systems (from left to right) Swagelok, CIRCORTech, Parker-Hannifin
[edit] Generation II – Connectivity using NeSSI-bus and the SAM
- Adoption of a digital communication bus (NeSSI-bus) that is specifically tailored for process analytics and intended to replace 4-20 mA systems.
- Classifying the interior of an enclosure handling hazardous fluids as Division 1/Zone 1 rather than Division 2.
- Adopting the use of a low energy, globally accepted Method of Electrical Protection called Intrinsic Safety for the NeSSI-bus.
- Adopting the use of plug and play, self-identifying smart sensors, actuators and heaters.
- A move away from the use of local indicating devices such as gauges and rotameters in order to reduce labor intensive manual checking (rounds).
- Moving from a centralized control (automation) model to a local/field model which is represented by a small device called SAM (Sensor Actuator Manager).
- Adopting the concept of portable, 3rd party software “applets” for use with SAM.
- Sharing high level analyzer information and data over an Ethernet ANLAN layer to/from DCS (Distributed Control System) and O&M (Operation and Maintenance) users.
- Introduction of a Graphical User Interface (GUI) (WIKILINK) for better visualization of physically compact sampling systems.
Generation II Connectivity Model using NeSSI-bus and SAM
[edit] Generation III - microAnalytical
The introduction of new microAnalytical devices to the process industries can be enabled by employing standard physical, electrical and software interfaces. Generation III will allow tighter integration of the sample conditioning and analytical measurement devices.
[edit] References
- “ANSI/ISA 76.00.02-2002 Modular Component Interfaces for Surface-Mount Fluid Distribution Components – Part1: Elastomeric Seals,” Instrumentation, Systems, and Automation Society (ISA), Compositional Analyzers Committee, (2002), www.isa.org
- Dubois, Robert N.; van Vuuren, Peter; Gunnell, Jeffrey J. “NeSSI (New Sampling/Sensor Initiative) Generation II Specification”, A Conceptual and Functional Specification Describing the Use of Miniature, Modular Electrical Components for Adaptation to the ANSI/ISA SP76 Substrate in Electrically Hazardous Areas. Center for Process Analytical Chemistry (CPAC), University of Washington, Seattle WA, (2003)
[edit] External Links
- www.cpac.washington.edu/NeSSI/NeSSI.htm — provides more technical information about NeSSI as well as a complete history of its development through a compendium of papers and talks presented at various meetings, workshops, and conferences since its inception.
