01 May 2004
Modular sample system can save money from going down the drain.
By David M. Simko
All companies are striving to decrease costs in all parts of their operations. In the process industries, the effective use of reliable, repeatable continuous online process analyzer systems can reduce the cost of labor, lost or off-specification product, and wasted raw materials and energy. However, an analyzer system is only as effective as the sampling system, the control system (including computers and software), and the analyzer itself.
The objective of using miniature modular sampling systems is to reduce the overall cost of such systems. Industry sources have said the challenges are to reduce the cost to build such systems by 40% and to reduce the cost of ownership by 35%. Industry analysts estimate the installed base of process analyzer systems, on a global basis, is $20 to $25 billion. The cumulative expenditures in the industry from 2001 through 2004 approaches $21 billion, including process analytical instruments, sampling systems, systems integration services, and in-house spending and maintenance services. The cost to build a system is 35% of the total cost over its estimated life of fifteen years. The cost to operate and maintain that system over the same period makes up the remaining 65% of the total cost. These percentages may vary with the type and complexity of an analyzer system; however, a rough survey of industry experts suggests that, on average, these numbers are valid. As stated earlier, industry experts concede that you can trace as much as 80% of analyzer system problems back to the sampling systems.
Dealing with these problems on a continuing basis makes sampling systems a high-maintenance and expensive part of the total analyzer system. For example, if 30% of total maintenance costs goes into sampling systems, the industry will spend $3.4 billion in this area over the four-year period mentioned above.
Reducing the costs of the sampling systems can result in significant savings.
The first step in the life-cycle cost analysis of a process analyzer system is determining what elements contribute to the cost. The cost to build includes the cost to design, fabricate, install, and commission the system. The cost to own includes the cost to operate, support, and maintain the system. Sampling systems can vary considerably from application to application and company to company. The elements may consolidate in different ways, but end users generally accurately know the costs of these systems within their particular organizations.
Traditional vs. modular system
This analysis assumes the systems you want to compare contain all the elements identified, you know the cost to build the traditional system, and you can project the cost to operate and maintain it over its expected fifteen-year life cycle. Only those cost elements affected by a change to a modular system will undergo analysis.
The cost comparison will consider only three elements in design and development—the overall analyzer system, the sample system, and the protection system and enclosures. This analysis assumes the costs of the other elements in this category—the analyzers, support equipment, and data processing equipment—are the same for both types of systems.
The design of an overall process analyzer system is determined by the definition of the analysis to be performed, considering process fluid and components to be analyzed, what you need to learn about the fluid, and how you will use the information; the methods and techniques to be employed; and finally, how you will sample the fluid.
Sampling requirements may be a simple single-stream system handling a clean process fluid that requires no preconditioning and has short transport lines and that you can simply calibrate. A dedicated at-line analyzer is an example of this type of system. However, a continuous online analyzer system would likely be a multistream system encompassing the extraction, collection, preconditioning, transport, and conditioning of a sample before its presentation to the analyzer. It would also include calibration, purging, stream selection, and disposal capabilities. Each of the multiple sample transport lines would be long, running from the sample tap on the process to an analyzer shelter or enclosure.
You should consider the modular approach during the design and development of an overall analyzer system. With this approach, the overall analyzer system can be physically smaller. In addition, you should think about moving the smaller analyzer enclosure closer to the process line. Sample transport lines could be substantially shorter, resulting in cost savings at installation and during operation and maintenance of the system. At some point in the future, you can replace the large, expensive shelters with multiple small enclosures located very close to the process line.
A sample system
In an example of a hypothetical worldscale ethylene plant, the cost of the sampling and sample transport systems can represent as much as 30% of the total cost of the analyzer system. In the traditional approach, the sample system usually consists of a panel or panels, housed in enclosures or on racks inside a shelter, along with the analyzers. The panels consist of a group of specified fluid control components connected with tubing and tube fittings. They are usually built in a panel shop, either in-house or by a subcontractor, following detailed shop drawings.
In the modular approach, the sample system consists of a substrate made up of multiple 11/2-inch blocks. The substrate defines the flow path through the system.
Each fluid control component will occupy one 11/2-inch square position on the substrate. Occasionally certain types of components, such as mass flowmeters or mass flow controllers, may bridge more than a single position. The interface seal definition is in the ANSI/ISA-76.00.02 Modular Component Interface for Surface-Mount Fluid Distribution Components standard, which ensures open architecture.
Users house sample panels in enclosures to protect the plant from the explosion of flammable materials, gases, or vapors that might build up by leakage or concentrations of dust or fibers in suspension. Currently, the choice of protection method is essentially explosionproof containment, intrinsic safety, or purged (pressurized) enclosures.
The savings that accrue from using the modular design are:
Intrinsic safety and encapsulation, where feasible and practical, are the preferred methods of protection. In the context of NeSSI and modular sample system technology, the intrinsic safety option is not yet viable and will not be until there is a resolution of specific connectivity and communications issues. There is a need for an intrinsically safe version of a communications bus that will permit the manufacture of electrical components small enough to fit within the 11/2-inch square area defined as a position on a miniature modular substrate.
Purging commonly protects sample systems. By using modular technology you can reconfigure a number of panels representing real systems. Typically, the physical size reduces by 70%—length, width, and height—while providing a platform for increased functionality.
End-user companies handle control system integration in different ways. Some do their own integration, some use a supplier of primary equipment that does the integration for them, and still others use an integrator. Additional savings can come from using the modular approach for sampling systems. The time and cost to assemble modular systems are less than the time and cost to fabricate panels, regardless of whether end users, integrators, or fabricators build the modular or traditional systems.
Usually panel fabrication comes from working drawings and involves fitting, mounting, and connecting individual fluid control components with tubing or pipe and requires skilled technicians.
On the other hand, you can assemble modular systems from most manufacturers without any special tools. However, currently available systems vary considerably in their complexity. The simplest system uses U-shaped flow components accurately positioned in aluminum substrate and manifold channels with locator pins. In this particular system, there are no face seals, which are potential leak points between positions. All surface-mount components that meet the ANSI/ISA-76.00.02 seal interface standard assemble in the same manner, from the top down with four bolts. No tubing, tube bending, or tube fittings are required. You can put together the compact and lightweight assemblies on a bench. Following an assembly diagram generated by the configuration software, assembly reduces to mounting the functional fluid control components side by side on 11/2-inch centers on a substrate, which defines the flow path through the system. You can assemble a modular system in a matter of hours, while a comparable traditional panel may take days.
Installation of a modular sample system is the responsibility of the organization integrating the analyzer system into the plant. The mechanical portion of the installation usually involves only the hookup of the various system inlets and outlets with tube fittings, which contributes to overall cost savings.
Initially, the price of individual surface-mount components will be higher than the price of the same component in its traditional configuration. Eventually, economics of scale should drive down the price of the surface-mount components.
In addition, the modular approach provides a standard platform and some opportunities for increased or improved functionality. For example, in a traditional system, flow control can occur by using a miniature control valve and a transmitter, generally requiring both instrument air and electricity to run to and/or from the devices. In a modular system, this flow control can happen using differential pressure or thermal mass flowmeters or mass flow controllers. The installed cost, including the mass flowmeter or controller, is likely to be less expensive than the installed cost of the control valve and transmitter, including those devices.
Proof pressure testing and leak testing of the installed sample system and functional testing of individual fluid control components will be much simpler because of the small, self-contained unit. Testing and any required troubleshooting should be faster and therefore result in lower cost. The party responsible for integrating the sample system into the process analyzer and enterprise control systems will do the commissioning.
The cost to operate process analyzer systems resides with each end user, based upon his or her own policies and practices. Cost data comparing the operation of traditional sampling systems with modular sampling systems will undergo analysis by end users for their own purposes.
In addition, the amount and type of spare parts required to operate the sample system will likely be similar for both kinds of systems. At least initially, as the new modular systems go in service, the conditions that have a deleterious effect on a traditional system will likely have a similar effect on a modular system. As operating data collects, the information generated can help balance the need for spare parts and establish the stocking levels.
All the time
Continuous online process analyzer systems are dynamic, operating twenty-four hours a day, seven days a week with maximum uptime. They routinely require a supply of expensive analyzer fluids for use as carrier gases or solvents and in calibration and purging or cleaning. Analyzer fluids are expensive.
The greatly reduced internal volume and surface area in a modular sample system means you will need much less of these expensive fluids to operate the system, resulting in considerable, measurable savings.
The reduced size of a modular sample system will also result in savings in the operation of the protection system. Purged systems pressurize with a slight positive pressure. The use of smaller enclosures reduces the amount of purge gas used over the life of the system and directly affects the cost of the protection system.
NeSSI Generation I modular sample systems can integrate into existing control systems by taking advantage of traditional I/O architecture. End users who have shared data show the response time of miniature modular systems is faster than that of traditional systems.
If the system is functioning properly, the cost of labor to operate the system is essentially the cost of analyzer engineers and/or the cost of analyzer technicians. If response time measurably improves, it follows that performing the routine checks on a system will be faster. If the system is operating properly on a consistent basis, labor costs will essentially be the analyzer technician's time. If the system is malfunctioning, labor costs will likely include the cost of an analyzer engineer's time. However, these costs in a modular system should be lower than in a traditional system. Troubleshooting a modular system should be faster and more efficient and also result in higher uptime on the system. It should be easy to monitor these costs during the evaluation of a modular system in an actual installation.
One objective of workers responsible for process analyzer systems is to maximize the uptime of the systems. Each incremental increase in uptime has a positive impact on a plant's operation. Conversely, downtime has an adverse effect.
Personnel can plan and schedule maintenance. Routine troubleshooting and maintenance of modular systems should be easier and less expensive than for traditional systems because of features such as smaller size, lower internal surface area and volume, shorter transport lines, less lag time, and faster response time. Because of these features, combined with the regular, repeatable layout of a modular system—all functional fluid control components assembled side by side on 11/2-inch squares—you can establish predictable performance during commissioning. You need to collect comparative maintenance data during the evaluation of modular systems in real applications to validate the savings.
Unscheduled maintenance reduces analyzer uptime, is costly, and can have serious effects on process control and product quality.
The design of these systems is such that you can do much of the maintenance in a shop rather than in the field. Sample systems generally fall into a number of key functional areas such as extraction and collection, preconditioning, stream selection, calibration, and conditioning. Each of these areas can get its own standardized modular "functional blocks." A group of functional blocks can connect to build a complete sample system. You can stock spare functional blocks.
When a problem occurs in the field, you can quickly change out entire function blocks, minimizing downtime. You can repair or recondition the problematic functional block in a shop and put it back into inventory.
The savings in maintenance spending over the life of a system is a composite of the simplification and improvements in sample system design, operation, and performance, the potential predictive performance, as well as the ability to perform effective preventive maintenance.
An important component of support cost is the ongoing training of the technicians who operate and maintain the analyzer systems. One of the characteristics of traditional sampling systems is they are usually unique to the specific analyzer system and application. There does not appear to be much standardization from sample system to sample system, even within a given facility. As a result, similar problems can and do manifest themselves in different ways, making troubleshooting and resolving the problems more difficult.
The modular approach to sample system design can make ongoing training simpler and less costly. The same features of modular systems that offer cost savings in the areas of designing, building, installing, operating, and maintaining—computer-aided layout, with an assembly diagram provided; regular, repeatable arrangement of components on 11/2-inch square substrate positions; standard interface seals between substrates and functional fluid control components; compact size, with smaller internal volume and surface area; and clearly defined flow path through the substrates and manifolds—combine to permit a higher level of standardization in the design of the sample systems.
The cost of documenting analyzer system performance and regulatory compliance should not differ greatly between traditional and modular systems.
The challenge for the application of NeSSI-based modular sampling systems is to reduce the cost to build and own the sampling systems by 40% and 35%, respectively. Sampling systems can vary substantially, and you can consolidate their cost elements in different ways. End users generally know the costs of their systems.
Areas to look for and document for cost-to-build savings are in design, fabrication, installation, and commissioning. Cost-to-own savings can be in specific areas of operation, maintenance, and support.
You can reduce sample system design time using currently available software, which can also cut drafting time. The overall analyzer system and the sampling systems can be physically smaller, with less internal volume and surface area. The smaller systems can be in smaller housings, perhaps located closer to the process lines, with shorter transport lines, all resulting in reduced cost. Mechanical installation of the compact modular system usually consists of the pull-up of a few tube fittings. The modular approach to sample systems provides a platform for increased functionality, which can result in increased efficiency and reduced costs. Proof pressure and leak testing of a modular sampling system will lower, which also contributes to the overall cost savings. The aggregate cost of the individual components, configured to meet the requirements of ANSI/ISA-76.00.02 and used in a modular system, will likely be more expensive in the short term, compared to those same components in their standard configurations used in traditional systems.
Operating costs also will reduce because the compact systems will require less consumables and utilities. Predictable performance standards will make preventative maintenance procedures more effective, reducing the potential for expensive unscheduled maintenance. Users can change out modular systems in the field and then effectively and inexpensively maintain them in a shop. Modular systems permit standardization of common solutions, making the job of ongoing training for the analyzer and maintenance technicians easier and less expensive.
Behind the byline
David M. Simko is with Solon, Ohio–based Swagelok Co.
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