Closed Loop Control System Basics

closed loop control
Closed loop diagram
The video below explains the concept of a closed loop control system, using a steam heat exchanger and food processing application as an example.

A closed loop control system uses a sensor that feeds current system information back to a controller. That information is then compared to a reference point or desired state. Finally, a a corrective signal is sent to a control element that attempts to make the system achieve its desired state.

A very basic example of a temperature control loop includes a tank filled with product (the process variable), a thermocouple (the sensor), a thermostat (the controller), and a steam control valve feeding a tubing bundle (the final control element).

The video outlines all the major parts of the system, including the measured variable, the set point, the controlled variable, controller, error and disturbance.

Safety Compliance White Paper for Solenoid Valves

ASCO Valve
Discussion of safety when
selecting solenoid valves.
(White paper courtesy of ASCO Valve)

Regulatory modifications have raised important issues in design and use of industrial safety systems. Certain changes in IEC 61508, now being widely implemented, mean that designers and users who desire full compliance must give new consideration to topics such as SIL levels and the transition to new methodologies. 

In particular, these issues can impact users’ selection of solenoid valves and prepackaged redundant control systems (RCS) for implementation in a safety instrumented system (SIS). Such selections may also be affected by how experienced valve suppliers are at dealing with complex new compliance methodologies.

These issues are especially applicable to the oil, gas, chemical, and power industries - in applications such as safety shutdown systems, boilers, furnaces, high-integrity protection systems (HIPS), and more. They’re of concern to safety engineers and reliability engineers, as well as to process engineers, engineering executives, and plant managers.

This report will address these issues in developing a compliant SIS using valves and RCSs. Making the right choices in safety system planning and in valve supplier selection can affect design time, costs, and effort — as well as the safety of the plant itself.

Eccentric Rotary Plug Control Valves

Eccentric plug valve
Eccentric plug valve
(courtesy of Neles/Metso)
A plug valve is typically a quarter-turn (90 deg rotation) on-off valve, while eccentric plug valves are often used for control applications. The plug may be cylindrical or tapered, and may be designed with a variety of port patterns. End connections are typically flanged, hub type, or butt weld.

Eccentric rotary plug valves are designed for liquid, gas, vapor and slurry control in general and demanding applications. They provide excellent control performance, and their capability to handle impure fluids makes them well suited in refining, petrochemical, chemical, natural gas, and fertilizer manufacturing applications.

The design of an eccentric plug valve uses a modified plug design (basically a plug cut in half) which is well suited for applications that require a higher seating force, but with minimal friction when cycling from open to closed position. Eccentric plug valves also provide improved shut off capabilities without significant increases in operating torque. This style valve is used for a wide range of flow control and isolation applications including clean water, dirty water, sewage, sludge, and slurries.


Automation Competency Model Helps Guide Future Technical Workforce

Author, Stephen R. Huffman, Vice President, Marketing and Business Development, at Mead O’Brien, Inc.
Eight years ago, the Automation Federation (AF) delegation told an audience at the Employment and Training Administration (ETA) about the people practicing automation careers in industry. Not long before our visit, the ETA, part of the U.S. Department of Labor (DOL), had worked with the National Institute of Standards and Technology (NIST) to develop a “competency model” framework based on the needs of advanced manufacturing. The ETA was eager to engage AF and ISA to use our tiered framework to develop a competency model for the automation profession.

After developing the preliminary model, hosting subject-matter expert (SME) meetings facilitated by the DOL to finalize our work, and then testing the model with several automation managers against their own criteria for validity, we rolled out the Automation Competency Model (ACM) to educators, government, and industry in 2008. Since then, it has been a tool for educators and parents to show students what automation professionals do, management to understand the skill sets their employees need to be effective and to use as a tool for gap analysis in reviews, program developers to create or alter curricula for effective education and training, and lawmakers to understand how U.S. manufacturing can be globally competitive and the jobs needed to reach that goal.

In the lower tiers, the model identifies necessary soft skills, including personal effectiveness, academic, and general workplace competencies. Automation-specific work functions, related competencies, and references (e.g., standards, certifications, and publications) are detailed in tier 5. In short, the model stakes out our professional territory and serves as a benchmark for skill standards for all aspects of process and factory automation. Previously, parts of the academic community and some U.S. lawmakers and agencies had the misconception that industrial automation and information technology (IT) are synonymous. Although there has been some convergence between IT and operational technology (OT), much of that perception has changed. OT-based industrial automation and control systems (IACS) were a focus in the recent cybersecurity framework development organized by NIST in response to the presidential executive order on cybersecurity for critical infrastructure.

The ACM has been a great tool for the AF to use to draw new organizational members and working groups, who visualize the big picture in automation career development. Also, we are telling our story and forming partnerships with science, technology, engineering, and math (STEM) organizations such as FIRST and Project Lead the Way. Since forming in 2006, AF now has 16 members representing more than 500,000 automation-related practitioners globally. After two three-year critical reviews, the ACM is still the most downloaded competency model on the DOL website. As a result of our work in creating the ACM and the IACS focus in cybersecurity framework meetings, the DOL asked AF to review a heavily IT focused Cybersecurity Competency Model. After adding IACS content and the philosophy of plant operation (versus IT) cybersecurity, the model released was a much stronger tool with wider applicability.

Recently, ISA, as a member of the American Association of Engineering Societies (AAES), presented the development of the ACM to AAES leadership as a way to provide tools for lifelong learning in the engineering profession. AF/ISA was once again invited to work with the DOL and other AAES member societies to lead in developing an Engineering Competency Model. The model framework and our experience in ACM development enabled us to identify the front-end skills, necessary abilities, knowledge to be developed, and academic prerequisites for any of the disciplines, plus industry-wide competencies from the perspective of all engineering-related plant functions: design, manufacturing, construction, operations and maintenance, sustainability and environmental impact, engineering economics, quality control and assurance, and environmental health and safety—with emphasis on cyber- and physical security, and plant safety and safety systems.

Now the societies dedicated to each vertical discipline listed in tier 5 will begin to identify all critical work functions, detail all competencies within each function, and note the reference materials. It is important for the participants to see the big picture, consider the future, and keep an open mind; agreement typically comes easily when SMEs participate with that mindset. Once the model through tier 5 is complete, job titles and job descriptions are created. When the DOL accepts the model, the U.S. government officially recognizes these positions. We hope the emerging Engineering Competency Model will be a great tool to address the overall skilled worker shortage. If the automation model is any indication, the new engineering model will have a large impact on achieving the skilled workforce goal.

Suggestions for An Efficient Industrial Steam System


(image courtesy of OSHA.gov)
Here is a video, courtesy of Armstrong International, which provides a broad overview, and suggestions for proper use, of the key components of a well designed steam system.  Covered in this video are:
  • 4 basic components of a steam system
  • Water-side care
  • Steam mains
  • Drip legs and drip traps
  • Branch piping, or runouts
  • Non-condensible gases
  • Proper selection of trap type and size
  • Thermostatic and thermodynamic traps
  • Thermostatic air vents
  • Vacuum breakers
  • Condensate management
  • Heat exchangers
  • Return lines

For more information on any steam or hot water system, contact:

Mead O'Brien
(800) 892-2769
www.meadobrien.com

Innovative Pressure Transmitter Automatically Selects Calibration Range

Foxboro S Series
Foxboro S Series
Typical 2-wire intelligent transmitters require the operator to manually program and use a single calibration range suited to the specific application. Not anymore. A winner of a 2015 Flow Control Innovation Award has come up with a significant change in transmitter set-up.

Foxboro, through its patented “Foxcal” firmware allows the Foxboro models IDP10S, IGP10S, IAP10S transmitters to automatically select and use any of 11 preset calibration ranges (stored in firmware). These calibration ranges cover the full pressure range of the transmitter. Upon installation, the S Series transmitter automatically selects the appropriate calibration range based on application inputs; and, if application inputs change, automatically transitions to another, more appropriate calibration range – all while maintaining a reference accuracy of 0.05%.

It is the first pressure transmitter to incorporate not only multiple calibration curves, but the ability to automatically select and transfer between them in real time. With the new technology, users have a wide-range capability with high reference accuracy for all industries requiring precise differential, gauge, and absolute pressure measurement. Additional benefits are inventory reduction and simplified tech training. Because of their wide turndown range with such high reference accuracy, adopting one model of S Series transmitter eliminates the need to inventory, learn, and maintain multiple transmitter models that handle more limited ranges (e.g., 150 psi, 800 psi, 4000 psi).

The Foxboro IDP10S datasheet can be downloaded here.

Or, you can review it online below:


For more information, contact:
Mead O’Brien
(800) 892-2769
sales@meadobrien.com
www.meadobrien.com

Cybersecurity, ISA, and Automation Federation and How We Got Here

Author, Stephen R. Huffman, Vice President, Marketing and Business Development, at Mead O’Brien, Inc.
Published: InTech Magazine, May-June 2015

Cybersecurity and
Automation
Technical leaders had the foresight to create the ISA99 standards committee back in 2002. They recognized the need for cybersecurity standards in areas outside of the traditional information technology (IT), national security, and critical infrastructure areas of concentration at the time. In the following years, a number of ISA99 committee members spent time and effort advocating and even testifying on Capitol Hill about our profession, which was not well defined, and our cybersecurity efforts therein, which were not well discerned from IT perceptions.

When Automation Federation (AF) refocused its efforts in 2007 with both automation profession advocacy and industrial automation and control system (IACS) cybersecurity as two of its strategic imperatives, we ventured forth to Capitol Hill with a message and a plan. We found that in general our lawmakers equated process and industrial automation as “IT” and thought that IT was already addressing cybersecurity in terms of identity theft and forensics, and that the Department of Defense was handling cyberprotection for national security. For the next several years, AF built its story around cyberthreats in the operational technology (OT) area and how ISA99 through its series of standards, technical reports, and work group output was providing guidance for asset owners, system integrators, and control system equipment manufacturers specifically for securing IACS.

The operating philosophy of IT cybersecurity versus OT cybersecurity is quite different. Although the approach of shutting down operations, isolating cybersecurity issues, and adding patches may work well to mitigate IT breaches, the same cannot be said for operating units in a real-time process. In short, it really is not feasible to “reboot the plant.” The message resonated enough for us to help create the Liebermann-Collins Cybersecurity Senate Bill introduced in 2012, but opposition (more political than reasonable) doomed this first effort.

In 2013, the President issued Executive Order 13636 for enhancing cybersecurity protection for critical infrastructure. It included directing the National Institute of Science and Technology (NIST) to establish a framework that organizations, regulators, and customers can use to create, guide, assess, or improve comprehensive cybersecurity programs. Of the more than 200 proposals submitted by organizations receiving a request for proposal, almost all were IT-based. The AF/ISA submittal took the perspective of operational technology backed by the strength of the existing ISA99 set of standards. After a set of five framework meetings of invited participants, including the AF “framework team,” over the course of 2013, the OT and IACS teams were much more successful in defining the needs, and the automation message was much better understood. NIST personnel with legislative experience with AF on the 2012 Senate bill understood that private industry is a key piece of the cybersecurity and physical security puzzle.

AF organized a series of NIST framework rollout meetings in 2014 around the country with attendees from the AF team, NIST, and the White House. The meetings were hosted by state manufacturing extension partnerships, which are state units of NIST. After these meetings and more work with Senate lawmakers, a bipartisan Senate bill, The Cybersecurity Enhancement Act, was signed by the President and put into law in December 2014 (www.congress.gov/bill/113th-congress/senate-bill/1353). In summary, the act authorizes the Secretary of Commerce through the director of NIST to facilitate and support the development of a voluntary, consensus-based, industry-led set of standards and procedures to cost effectively reduce cyberrisks to critical infrastructure. As you can imagine, ISA99, now IEC/ISA 62443, will play a more prominent role in securing the control systems of industry in the future through a public-private information-sharing partnership. Thanks for the foresight and fortitude of the ISA99 standards committee.