White Papers

on 'Distributed Control'

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  • First Principle Process Relationships

    First principle relationships can define process cause and effects that can lead to improved controller tuning and performance by the selection of better tuning rules and process variables for scheduling of tuning settings.

    Greg McMillan
  • Designing a Control System for High Availability

    This paper will discuss redundant and non-redundant methods for achieving high availability of control systems, as well as improvements in control technology and recommended control system designs. The paper will also highlight features within the Rockwell Automation Integrated Architecture platform and ICS Triplex product lines that can help achieve higher availability.

    Rockwell Automation, ICS Triplex
  • I/O Solutions for Temperature Monitoring

    Sensors used for temperature monitoring and data acquisition can be quite varied. Applications ranging from simple room temperature monitoring to highly sophisticated batch process control can all be highly dependent on obtaining accurate temperature readings. The primary types of sensors used for this purpose are resistance temperature detectors (RTDs), thermocouples, integrated circuit temperature detectors (ICTDs), thermistors, and infrared sensors.

    Opto 22
  • Electronic Flow Control Valve (EFCV) with Pressure Compensation Capability

    A new concept for an Electronic Flow Control Valve (EFCV) with pressure compensation capability is introduced. Based on its embedded sensors and micro controller, the EFCV can provide flow control without the need of load/displacement/speed information from the power elements, like hydraulic cylinders or hydraulic motors.

  • 10 Steps to Lean Electrical Controls

    Globalization is forcing companies to constantly become more efficient. To drive efficiencies, many companies are implementing Lean Manufacturing to stay competitive in this ever shrinking world.

  • Building a Bridge to Safety

    This paper examines the benefits and shortfalls of both safety PLCs and configurable safety relays. It also examines a new way of handling safety in industrial automation, "SafetyBridge" technology.

    Phoenix Contact
  • Proper Media Compatibility, Sensing Topology and Grounding Ensure Long-term, Trouble-free Pressure Measurements in Wet and Noisy Electrical Environments

    Water is a key element to life. It plays an important role in the world economy, as it functions as a solvent for a variety of chemical substances. 71% of the Earth's surface is covered with water and 97% of that water is in oceans and saline. Only 3% of the earths water is fresh and can be found in the polar caps, glaciers, ground aquifers, lakes, swamps and rivers. In parts of the world where there is limited or no access to fresh water, desalination is being used to convert saline water to drinking water. To manage resources and the flow of water, modern electrical pumps and control systems are employed. Water chemical compatibility and electrical interference are two major challenges for the control systems. Let's ook at two major sources of fresh water and the issues that can limit the performance of the control system.

    American Sensor Technologies
  • Radioactive Isotopes in Process Measurement

    An Objective Look at the Roles of Cesium-137 and Cobalt-60 in Nuclear Measurement Systems for Industrial Processes

    Level and density measurements in process control are performed by a number of technologies. When the process temperature, pressure, or chemistry is an issue, then nuclear measurement systems have the advantage. These are non-invasive to the vessel and unaffected by the process pressures and chemistries.

    Overall, a nuclear measurement system used for process control consists of a gamma energy emitter and detector. An emitter is placed on one side of a vessel to broadcast a beam of energy to the opposite side of the vessel. The detector is placed in the beam on the opposite side of the vessel. The detector will scintillate in the presence of gamma energy and register counts proportional to the field strength. When the process value (level or specific gravity) is low, the detector will register a high number of counts since less gamma energy is blocked by the process material. When the process value is high, more of the gamma energy is blocked which leads to fewer counts.

    The two most common gamma emitters used for level and density process measurements are isotopes of cobalt and cesium. The goal of this article is an objective comparison of the roles of cesium-137 and cobalt-60 in process measurement. This will be accomplished by reviewing the properties of the two materials and then comparing the use of the materials in process measurement.

    Vega Americas Inc.
  • Unlocking Automation Systems for Higher Business Responsiveness

    Every manufacturing industry is experiencing an increasing speed of business in several areas including changing schedules, customer needs, costs of materials, business models, and technologies. At the same time, many manufacturing sites - particularly in the discrete industries - have growing complexity in their operations which makes it more difficult to adapt. There are more SKUs and data to keep track of due to product proliferation, smaller lot sizes and compliance to government regulations.

    The demands for improved speed and agility conflict with the plants' ability to respond. Visibility into current operations, including the control system, is the primary reason manufacturers buy Manufacturing Execution Systems (MES). This visibility provides the information necessary for informed decision making in real-time by all levels of personnel - plant floor to the executives.

    MES applications contain the critical business processes for executing a production schedule. These systems perform the production-centric functions of planning, controlling, operating and informing. Control systems execute these functions to produce the goods needed to fulfill customer orders. By integrating MES with control systems, manufacturing becomes more agile for responding to change in this increasingly dynamic business environment. Integrating the control system with the MES allows for more effective and broader set of production management functions to improve operational performance.

    To improve their response to operational issues, managers look to technology for connecting plant floor and business systems for automated business processes. Some manufacturers have implemented point solutions on a case-by-case basis. Because of the higher development costs and support issues, this approach is not acceptable. An integration platform is needed.

    ARC Advisory Group
  • How to Use a Regulator to Reduce Time Delay in an Analytical System

    Process measurements are instantaneous but analyzer responses never are. From the tap to the analyzer, there is always a time delay. Unfortunately, this delay is often underestimated or misunderstood.

    Time delay is defined as the amount of time it takes for a new sample to reach the analyzer. One way to control time delay is with a regulator. Regulators control pressure, and pressure in an analytical system is closely related to time. In the case of gas systems with a controlled flow rate, the lower the pressure, the shorter the time delay.

    Delay may occur in any of the major parts of an analytical instrumentation (AI) system, including the process line, tap and probe, field station, transport line, sample conditioning system, stream switching system, and analyzer.

    Doug Nordstrom, Mike Adkins, Swagelok
  • Process Solutions White Paper and Literature Downloads

    Learn about scalable technologies that can provide high availability and a significant return on investment. Download content on these topics:
    • Achieving High Availability in Process Applications — Process industries don't have to accept one-size-fits-all solutions that do – and cost – more than necessary.
    • Clean in Place Made Simple — This paper discusses an approach that makes CIP automation a straightforward task and provides ample modularity and flexibility through the use and application of ANSI/ISA-88 (S-88) concepts.
    • Process eTalk — This quarterly eNewsletter will help you stay up to date on the latest trends and topics within the process industries.

    Rockwell Automation
  • A Systematic Approach To Plantwide Control

    This paper summarizes Sigurd Skogestad's struggles in the plantwide control field.

    A chemical plant may have thousands of measurements and control loops. By the term plantwide control it is not meant the tuning and behavior of each of these loops, but rather the control philosophy of the overall plant with emphasis on the structural decisions. In practice, the control system is usually divided into several layers, separated by time scale.

    My interest in this field of plantwide control dates back to 1983 when I started my PhD work at Caltech. As an application, I worked on distillation column control, which is excellent example of a plantwide control problem. I was inspired by Greg Shinskey's book on Distillation Control, which came out with a second edition in 1984 (Shinskey, 1984). In particular, I liked his systematic procedure, which involved computing the steady-state relative gain array (RGA) for 12 different control structures ("configurations"); the DV-configuration, LV-configuration, ratio configuration, and so on. However, when I looked in more detail on the procedure I discovered that its theoretical basis was weak. First, it did not actually include all structures, and it even eliminated the DB-configuration as "impossible" even through it is workable in practise (Luyben, 1989). Second, controllability theory tells that the steady-state RGA by itself is actually not useful, except that one should avoid pairing on negative gains. Third, the procedure focused on dual composition control, while one in practise uses only single end control, for example, because it may be optimal economically to use maximum heating to maximize the recovery of the valuable product.

    Sigurd Skogestad, Norwegian University of Science and Technology (NTNU)
  • Understanding REACH

    Registration Evaluation Authorization and Restriction of Chemical Substances

    It is certainly no secret to anyone that the past decade has placed a renewed focus on the environment and how all members of the world community, to include business organizations, affect it. Concerns about protecting the world in which we live have been the impetus behind such worldwide movements as recycling and renewable energy. From a manufacturing standpoint, RoHS (Reduction of Hazardous Substances) has impacted businesses as well as REACH, a more recent set of regulations that are becoming more significant to North American based manufacturing operations that are part of a supply chain that directly or indirectly supplies products into the European Union.

    As with any new regulatory requirements, the initial exposure to the documentation can create a degree of uncertainty among those who will be asked to comply. From this perspective, REACH is no different from any of its predecessors. In an attempt to offer some understanding of the REACH regulations and some clarification of the requirements it places on manufacturers, C&M Corporation gathered Michael Karg, Director of Product Development, along with Randy Elliott, Regulatory Compliance Engineer, and Ariann Griffin, Regulatory Compliance Technician, to discuss some of the particulars of REACH and respond to some of the questions C&M has been discussing with members of its client base.

    What is the purpose of REACH?

    Mike Levesque, Randy Elliott, Ariann Griffin and Michael Karg, C&M Corporation
  • How A Biogas Processing System Manufacturer Identified the Best Flow Meter for Gas Measurement

    Klargastechnik Deutschland GmbH's equipment and processes help customers address organic biomass fermentation and recovery while supporting electric power co-generation. The result is clean, green electric power that also reduces both solid waste and hazardous toxic gases such as carbon dioxide and methane, which pollute the environment and contribute to global warming.

    In order to provide these benefits, the company's equipment and systems rely on highly precise and reliable flow measurement of process waste gases. Measuring biogas flow at several points in the system provides operators with critical information for optimal gas production, control, safety and reporting. However, Biogas applications present several challenges in selecting the proper flow meter.

    Download this application note to learn how a biogas processinf system manufacturer can identify the best flow meter for gas measurements.

    Fluid Components International, Achim Sprick, Managing Director, Klargastechnik Deutschland GmbH
  • A Blueprint for the Real Time Enterprise

    Manufacturing and production processes have had to be controlled and managed in real time from inception because they change in real time frames. This has been a natural premise of industrial systems from the very beginning.

    A major shift in the business of manufacturing has occurred over the past decade which is driving the dynamics of the business of production and manufacturing into the real time domain. Business variables, such as energy prices, feedstock prices and even product prices have rapidly transitioned from highly transactional time frames into real time frames. For example, a decade ago it was not unusual for an industrial plant to establish a contract with its energy supplier that essentially set the price over an extended time period, of often 6 months or even a year. Today, in most parts of the world, long term fixed price energy contracts are not being offered and the price of energy can change multiple times in a day. The implications of this transition are clear. Industrial business functions must operate in real time to be effective and efficient. Industrial companies that do not move to real time business operations will be at a severe disadvantage in their marketplace.

    Invensys, Peter G. MartinInvensys, Peter G. Martin
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