Modular design moves to the forefront
Miniature modular designs emerging as trend solution in process analyzer sample systems

New Swagelok modular platform components, together with new configurator software, make it easy to develop and assemble complete process analyzer and sample-handling systems. System designers can reduce the size, weight, and flow path volume of their process analysis and sampling systems. In the past two decades or so, analytical devices have become more capable and reliable, and the computers and software that drive and operate the systems have become more sophisticated, powerful, and user-friendly. However, the basic design of the analyzer sampling system has changed very little. There is consensus within industry that improvements need to be made in sampling systems, where as much as 80 percent of the problems associated with process analyzer systems occur. The incentive for industry is to improve performance of analyzer systems, reduce the cost to design, build, and install the systems, and reduce operating and maintenance costs. One important way to meet these needs is by making sampling systems miniature, modular, and intelligent.

The Center for Process Analytical Chemistry (CPAC), a joint industry-academic research consortium at the University of Washington, has moved forward with a New Sampling/Sensor Initiative (NeSSI) through the efforts of CPAC leadership and industrial affiliates, who are all end users or suppliers of process analytical chemistry instrumentation. The initiative is to “facilitate the state-of-the-art evaluation and ongoing development of the next generation modular sampling system designs”. A key element in the modularization strategy is open architecture. The Instrumentation, Systems, and Automation Society (ISA) SP76 Composition Analyzers Committee added a subcommittee charged to develop interface seal standards to apply to functional fluid control components and the fluid path substrates of a miniature, modular, smart sampling system. The new standard, ANSI/ISA - 76.00.02 - 2002, Modular Component Interfaces for Surface-Mount Fluid Distribution Components – Part 1: Elastomeric Seals, was issued in June 2000.
As a result of this initiative, different manufacturers are offering different approaches to the substrate design, proving the feasibility and practicality of miniature, modular, smart sample systems. These systems comprise NeSSI Generation I systems.
Swagelok Company is one manufacturer who has taken part in NeSSI and has developed the new modular platform components (MPC) system. The MPC system consists of surface mount components, substrates, and manifolds and meets all requirements of the ANSI/ISA 76.00.02 specification for the 1.5 in. (38.2 mm) footprint.

Advantages to modular
approach
The advantages to the modular approach include:
- Development and layout time and costs are reduced through tools such as system configurator software. Swagelok MPC system configurator software, for example, allows the user to place, define, and connect surface-mount components of their design on a computerized layout grid. It then identifies all of the additional flow connectors that are necessary to build the fluid system and generates a bill of materials and assembly diagram to simplify ordering and final assembly of the MPC system.
- The reduced size, weight, and footprint make it easier to couple the sample system to dedicated field-mounted analyzers and place them at the sample point, reducing long, heated sample transport lines.
- Small modular sample systems have less internal surface area than a traditional system, reducing possible adsorption of material from the fluid.
- The internal volume of the system is less, making it easier to purge or flush and conserve expensive analyzer fluids.
- The MPC system is easy to assemble using the customized assembly diagram, written instructions, and a single tool – a hex-type screwdriver. The system includes mounting blocks for installation onto a panel or into an enclosure, as well as detailed dimensional information.
- Maintenance is easier since all of the functional components are surface mounted. With the MPC system, all of the surface-mounted components are accessible from the top of the assembly; there are no hidden hardware pieces or fasteners on the bottom surfaces. Components and seals can be serviced quickly and easily without disturbing any other components.
In the chemical and petrochemical industries, sample systems are a key part of analyzer systems, and these advantages can help reduce the cost to build, operate, and maintain them. For example, in a chemical plant, the sample conditioning systems are generally housed in expensive protected enclosures that are intrinsically safe or purged and are positioned outside an analyzer shelter. However, chemical plants that adopt a miniature modular approach, such as the MPC system, can place these conditioning systems in enclosures that are typically more than 70 percent smaller than those used in traditional systems and, therefore, can reduce the cost of both the enclosure and the protection system. In addition, these smaller enclosures housing smaller modular sampling systems and miniaturized analyzers can be field-mounted closer to the process lines and can greatly reduce the cost of sample transport. Assembly costs are reduced since the extensive fitting and connecting of individual fluid control components on a large panel or racks is eliminated. Assembly is reduced to mounting the functional fluid control components side-by-side on 3.89 mm centers on a substrate, which has defined the flow path through the system. Finally, expensive zero, span, and purge gas usage can be reduced – further reducing operation costs – because of the smaller internal volume of the miniature modular system.
Intelligent control
represents next phase
CPAC also has developed a specification for NeSSI Generation II systems that addresses the connectivity and communications issues that will lead to intelligent control of these sample systems. Some key features of these next-generation systems are:
- compact, smart pressure, temperature, and flow sensors;
- smart valves with built-in electric-to-pneumatic actuators;
- multi-drop sensor bus communications, which may be wireless;
-Sensor Actuator Manager (SAM) to provide control and connectivity to the sample system.
Generation I and Generation II systems differentiate between modular and smart issues. Generation I addresses modularity issues. Some Generation I systems have been installed in operating plants, and preliminary results show the intended improvements and cost savings can be realized. Additional beta testing at specific sites will be proceeding over the next
several months. Development of Generation II systems is underway. Alpha testing will begin when basic connectivity and communication solutions and certain smart devices become available. It is
anticipated that the migration from Generation I systems to fully smart and functional Generation II systems will be evolutionary. j