In the 1970s, there was a concerted effort at the chemical company I worked for to provide extra process measurement connections throughout the plants for pressure and temperature measurement. These connections could be used as needed to help identify and solve unforeseen problems. The installation of a wired transmitter on a temporary basis was not practical because of the cost to install conduit and wiring that is safe, reliable, and noise free. Consequently, the company developed standards for pressure and temperature gauges that had scale ranges and materials of construction to meet most application requirements. Unfortunately, only the operator in the field standing in front of the gauge could see the indication and the resolution was poor. I still have flashbacks of how a kind old instrument engineer spent the remaining years of his career figuring out how to compromise scale ranges.

With modern wireless smart transmitters, we could have obtained this information far more easily and accurately. Smart transmitters enable ranges to be readily configured without much of a difference in accuracy. If a gateway is set up and other wireless transmitters are already being used in the plant, the commissioning of a new transmitter may just be a matter of minutes. Line of sight is usually not required because other wireless devices can be used as necessary to find a way to the gateway. Channel hopping eliminates noise concerns. Encryption and invitation-only communication eliminate security concerns. The measurements can be readily indicated, historized, trended, and analyzed by operators and engineers. Wireless offers portability, analysis by asset management systems, historization, and computations for metrics, with the accuracy and diagnostics afforded by smart instrumentation.

Pressure is the driving force for material flow, and temperature is the driving force for heat flow. Flow disturbances start out as a pressure change and heat transfer disturbances start out as a flow or temperature change. The fouling of a heat transfer exchanger can show up as a change in the temperature or pressure difference between the tube side inlet and outlet streams.

Heat transfer rates and overall heat transfer coefficients can be computed if the heat transfer area and flow are fixed or measured. Recirculation flows are often relatively constant. When a heat exchanger in a recirculation line is used for vessel temperature control, cascade control system may already provide the necessary measurements. The cooling heat transfer rate is simply proportional to the primary loop temperature minus the secondary loop temperature; heat exchanger process inlet minus outlet temperature.

As I started to develop the use conductivity and pH for CO₂ reduction at the University of Texas Pickle Research Campus, I realized there was a whole new opportunity for wireless. pH electrodes were failing and the relationships to CO₂ load and solvent concentration needed to be quantified. The best sensor type and location needed to be found. Lab test results had to be historized and analyzed.

Concept: Wireless transmitters can be easily stocked, configured, and installed to explore and demonstrate diagnostics, metrics (Tip #61), and improvements, such as inferential measurements, new sensor technologies, new strategies, and better sensor locations.

Details: Use wireless pressure measurements to track down problems such as field regulator problems, screen and filter plugging, heat transfer surface fouling, and insufficient valve pressure drop as a percent of total system pressure drop. Use wireless pressure transmitters to provide the pressure profile for a piping system and enable the computation of the installed characteristic of a control valve. Use wireless temperature transmitters to provide an inferential measurement of heat transfer rate and overall heat transfer coefficient. Heat transfer rate measurements can enable the optimization of the scheduling of batches for energy conservation and the tradeoff between yield and production rate in batch reactors. Use wireless temperature transmitters to provide a temperature profile in a utility system for pinch analysis to find the location of the limitations in the utility system for better process efficiency and capacity. Use wireless temperature transmitters on distillation columns to find the tray with the largest and most symmetrical change in temperature for a change in reflux to distillate ratio or steam to distillate ratio. Use wireless acoustic and temperature transmitters to monitor steam traps to detect when traps are stuck open or closed. Traps stuck closed can back up condensate into the heat transfer volumes of process equipment, severely disrupting process temperature control systems. Traps stuck open will blow through steam, causing a loss of energy and higher condensate system pressure, which can cause other steam traps to shut, backing up condensate into other process equipment. Traps that are alternately stuck open and closed cause confusing and erratic plant operation. Use wireless pH transmitters in the lab in worst-case process samples to determine electrode performance, life expectancy, and warning signs of electrode failure for predictive maintenance. Use different electrode types in the lab sample to find the best sensor technology. Use wireless pH transmitters in the field to find the measurement location with the best mixing, least noise, and least deadtime (Tip #67). Use wireless mass flow computers and annubars to provide flow measurements where needed to develop and demonstrate online diagnostics and metrics. Consider a system of plant spares where wireless transmitters can be loaned to enable the rapid transition from idea to a working prototype in the field.

Watch-outs: Spare process connections may not have been provided in the design of the plant. Batteries should be monitored. The default update rate for wireless pressure measurements may not be fast enough to track down disturbances.

Exceptions: Wireless transmitters that use a lot of electrical power are not available. Wireless transmitters are too slow for surge detection and control, compressor control, polymer pressure control, and furnace pressure control.

Insight: Wireless transmitters eliminate the cost and time hurdles for moving innovations from research, engineering, and operations into action, enabling the rapid demonstration of benefits and inspiring creativity.

Rule of Thumb: Use wireless transmitters to rapidly prototype, demonstrate, analyze, and justify installations of online diagnostics, metrics, and improvements.

Look for another tip next Friday.

Topics include:

• Approaches for new and existing systems
• Seven steps to a highly effective alarm system
• Alarm management justification
• An overview of ISA-18.2, the alarm management standard

Webinar Bonus: Reserve your seat now and you’ll receive “Alarm Management Best Practices: Highly Condensed,” the first chapter of Bill R. Hollifield’s book, Alarm Management: A Comprehensive Guide.

Meet the Webinar Presenters:

Bill R. Hollifield is principal alarm management and HMI consultant at PAS

Paul Berwanger is principal abnormal situation management consultant and project manager at MAVERICK Technologies

To reserve your seat for Alarm Management Bootcamp, click here.

Fig. 1. A standard block diagram of the CDM control

Abstract: This paper deals with the design of PI controllers which achieve the desired frequency and time domain specifications simultaneously. A systematic method, which is effective and simple to apply, is proposed. The required values of the frequency domain performance measures namely the gain and phase margins and the time domain performance measures such as settling time and overshoot are defined prior to the design. Then, to meet these desired performance values, a method which presents a graphical relation between the required performance values and the parameters of the PI controller is given. Thus, a set of PI controllers which attain desired performances can be found using the graphical relations. Illustrative examples are given to demonstrate the benefits of the method presented.

 Free Bonus: To read the full article on design of PI controllers, click here.

2006 Elsevier Science Ltd. All rights reserved.

At one time, I worked in a large continuous process plant that had alarms coming in constantly. The operators could hit the “Silence” button in their sleep. We had a case where a process flow was accidently diverted to the wrong tank, and it eventually filled and overflowed the tank. Even though the tank had redundant level transmitters and we had one of the more alert panelboard operators on shift, the rising level was not noticed until the tank overflowed and was noticed by a field operator. The panelboard operator had silenced two high alarms, two hi-hi alarms, two “over” alarms, and two range alarms over the course of two hours but had failed to recognize that there was a problem.

Concept: Enable alarms on instruments that matter and on process nonconformances that the operator can do something about. Having alarms for the sake of having alarms only ensures that ALL alarms will be ignored—even the ones that matter.

Details: Alarm management has become all the rage lately, and with good reason. The proliferation of instrumentation busses has provided access to a plethora of information, and because everything is now typically alarmed, the operators are being buried under a barrage of alarms. When faced with a constant stream of annunciation, most operators quickly become numb and increasingly just hit “Silence.” Critical alarms are lost in the noise and are routinely missed.

Ironically, there was an advantage to the relay annunciator panels built into the old controlroom panelboards. There were only so many points available, so only the critical alarms made the list. With the advent of computers, EVERYTHING can be alarmed, and unfortunately that is exactly what happens.

An engineer has several ways to address this problem, and many books have been written on the subject. Addressing this expansive topic in a few pages is not possible, but here is a brief list of suggestions that can help reduce the problem of too many alarms.

• Enable alarms on instruments that matter.
• If an operator cannot do something to resolve the situation, there is no point in alarming it.
• Program “smart” alarms. Automatically disable alarms on out-of-service equipment. Add conditional logic that generates a common alarm when a piece of equipment trips rather than generating 10 or 15 alarms that essentially indicate the same condition. (For instance, if a boiler trips it makes little sense to alarm the trip, low gas flow, low gas pressure, low air flow, etc.) One piece of information that IS useful, however, is “first out” trip information. Many operators use the alarm list to determine what tripped the equipment. If the first out information can be indicated on a graphic, the operators do not need to see the individual alarms.
• Segregate the alarms and deliver the information to the appropriate audience. The operators do not need to see most calibration and/or maintenance alarms, but the maintenance department does. Generate an alarm report to Maintenance, but just indicate a possible problem to the operator so he or she can be aware of it.
• Change from alarms to indicators. If a process is running out of spec but not in a critical range, then it may make more sense to indicate this condition as a color change on the graphic instead of than firing an alarm that must be acknowledged.
• Monitor alarms and routinely eliminate “bad actors.” In most cases, a large percentage of alarms is created by a handful of points. An occasional review of the most active alarms will allow the plant to identify these points and modify the programming to reduce their frequency or address their cause. Doing this can dramatically reduce the total alarm count without requiring much effort.

Watch-Outs: Many control systems default to having all the alarms enabled. On a new system, it may make more sense to enable none of the alarms initially and add them back as necessary.

Exceptions: Some plants do not allow the operators to suppress alarms because they are concerned that critical alarms will be turned off and never restored. One solution to this problem is to allow operators the ability to suppress alarms, but program the alarms to automatically restore after some appropriate period of time. In this way, a broken instrument can be silenced for a shift while repairs are made.

Insight: One plant only enabled setpoint alarms when a controller was in automatic. (Such alarms annunciate when the process variable is beyond the allowable range around the current setpoint.) High and low alarms were not enabled unless the controller was in manual. This method provided increased alarming when a loop was in manual but did not generate alarms on a point in automatic unless it deviated too far from setpoint.

Rule of Thumb: Alarm management is a never ending effort. Routinely review the plant’s alarm list, and try to eliminate or address points that appear too often. When configuring new systems, include some means of smart alarm management into the design.

Look for another tip next Friday.

If recent events in St. Louis, Mo., are any indication of the future of automation, then prospects are indeed bright.

During the FIRST Robotics Competition, high school students worked in teams to design, build, program, test and fine tune their robots to meet the challenges of competition.

More than 10,000 students from around the globe, from ages 6 to 18, gathered April 24-27 at the Edward Jones Dome to put their engineering skills and scientific know-how to the test at the annual FIRST^® (For Inspiration and Recognition of Science and Technology) Championship. This year’s event, which included three different age-specific, team-oriented programs, drew nearly 650 student teams from 37 countries around the world, and attracted more than 2,800 mentors, coaches and adult supporters, and over 750 event volunteers.

One of the highlights of the three-day event was the FIRST Robotics Competition (FRC), which combined the excitement of sport with the rigors of designing and building robots. The competition provides students, from grades 9 through 12, with the opportunity to use sophisticated software and hardware, learn from professional engineers, collaborate, earn recognition, and qualify for millions of dollars in college scholarships. This year, more than 2,500 teams in 17 countries participated in 77 FRC regional and district competitions.

As Strategic Alliance Partners of FIRST, ISA and the Automation Federation are immensely excited to take part in and support such a dynamic educational program that inspires young people’s interest and participation in science and technology.

Robotics teams tried to instruct their robots to score as many flying discs into their goals as possible during two-minute and 15-second matches. Matches ended with robots attempting to climb up pyramids located near the middle of the field.

I’m gratified that both ISA and the Automation Federation were well-represented at the event. ISA staff participated in an informational exhibit of FIRST partners, distributing information and talking to students and their parents about the automation profession and careers in the automation field. Also attending were Bob Lindeman, Automation Federation Chairman; Steve Pflantz, vice president of ISA’s Professional Development Department; and ISA’s St. Louis members Nick Erickson, Mike Unterreiner, Keith Thomas, and Brian Nixon.

Upon returning from the event, Bob Lindeman remarked that he found the students’ energy, dedication and creativity awe inspiring:

“I must say I wasn’t prepared for the high level of enthusiasm displayed by these students. It was truly eye opening to witness these young people, from elementary grades through high school, so motivated to learn and apply engineering skills. There is no limit to where the future will take us, and no boundary to where these students will lead us. It’s an honor for ISA and the Automation Federation to be a part of this process. I encourage all of our members to get involved locally and contribute.  I guarantee you will be reinvigorated.”

Steve Pflantz was equally as effusive: “This event continues to amaze me each and every time I attend. The positive energy from all these kids having fun, being challenged and competing in this way is uplifting and awe inspiring. This is a remarkable and talented group of kids, and a lot of them are potential future automation professionals.

“FIRST also provides the real learning experiences and skills development that young technical professionals will need. From budgeting and scheduling to meeting deadlines and working together, these students are required to meet very realistic project scenarios that even seasoned professionals would find challenging.”

While this year’s FIRST competition has ended, I hope that it serves as the beginning of a new wave of ISA member participation and volunteerism in upcoming FIRST programs and events.

ISA and the Automation Federation hosted an informational exhibit where students involved in FIRST learned about the automation profession and how to plan for careers in the field.

If you haven’t been on hand at a FIRST event, you are missing out on a celebration of youthful discovery, innovation and teamwork that will fill you with optimism regarding the outlook of our automation and control profession. Your involvement in FIRST will help support these bright, enthusiastic young people as they learn, grow and position themselves for success in their lives and careers. After all, some of these students may well design the ground-breaking technologies of the future.

Whether you have just four hours to spare on a weekend or want to serve as a mentor for a given student, there is a volunteer role for you with FIRST. You’ll join other like-minded professionals – more than 120,000 annually – to experience a special camaraderie and personal satisfaction and joy that come when you take part in something truly meaningful.

To discover what teams and events are in your area, find a regional contact,  review mentor and coach roles, and gain more details on FIRST programs, visit www.usfirst.org.

About the Author
Terrence G. Ives is the third-generation president and owner of Ives Equipment Corporation in King of Prussia, Pennsylvania, a process control manufacturing representative and stocking distributor. Terry has been actively involved in ISA leadership for many years. He has held numerous positions at the local and Society level including Society Treasurer, Executive Board Parliamentarian, Finance Committee Chair, Investment Committee Chair, District 2 Vice President, and Philadelphia Section President and Exhibit Chairman. He received a bachelor of science degree in industrial systems engineering from Ohio University.

• Failure rate data – where it comes from and how it is calculated
• Fire and gas detector coverage – what it means, new metrics, and how to calculate it
• Safety system performance – a performance calculation including which equation components to apply and how to apply them

In an effort to emphasize how important it is to keep your knowledge and qualifications current, the three safety experts are sharing their expertise to keep you up to date on this timely topic.

Bill Goble, managing partner and co-founder of Exida, and author of the ISA book Safety Instrumented Systems Verification – Practical Probabilistic Calculations, will present on the different sources of failure rate data and the pros and cons of each. “Techniques commonly used to optimize safety system design use probabilistic analysis to match solutions with risk,” says Goble. “This allows designs that are optimal in terms of the tradeoff between cost and safety. The analysis also requires realistic failure rate data. Fortunately, there are several sources for this data, including end-user failure analysis, manufacturer failure analysis, FMEDA and B10 testing. As each of these techniques becomes better understood, techniques are combined to improve our data.”

Ed Marszal, president of Kenexis and author of the ISA book Safety Integrity Level Selection, emphasizes that the design of fire and gas systems can and should be done in accordance with the ISA-84 (IEC 61511) standards, though safety integrity level (SIL) alone is not enough, as discussed in the ISA-84.00.07 technical report on the topic. Marszal explains: “In addition to SIL, another metric called ‘detector coverage’ is required to fully specify the performance requirements of a fire and gas system. Fire and gas mapping is the process by which the detector coverage is calculated, and it is an exercise in analytical geometry that is greatly facilitated by using sophisticated software. Performance-based design is in its infancy, but end users are rapidly incorporating it into their design practices because of the value generated by this process, which leads to a repeatable and consistent design of FGS that is not typically occurring when existing subjective techniques are used.” More information on performance-based FGS design is being developed by ISA along with a new ISA book planned for publication later this year.  The ISA fire and gas system engineering (EC56) course also covers this subject.

Paul Gruhn, global process safety consultant and co-author of the ISA book Safety Instrumented Systems: Design, Analysis and Justification, Second Edition, will present on how to use failure rate data in performance calculations, what different portions of the PFD (probability of failure on demand) formulas are, how to use the formulas, and the impact the different portions have. The webinar provides an overview of the topic and Gruhn encourages those who need additional in-depth knowledge to look at the ISA safety instrumented systems (EC50) course, ISA technical papers and webinars, and ISA Safety & Security division activities.

Source: Safety Instrumented Systems: Design, Analysis and Justification by Paul Gruhn

If you are responsible for overseeing the design and maintenance of safety systems and fire and gas systems in process facilities, you don’t want to miss this important webinar.

Click here to register for the free safety instrumented systems webinar.

Presidential Executive Order on Critical Infrastructure Cybersecurity draws comprehensive response from ISA and AF

U.S. Presidential Executive Order 13636, announced in President Obama’s 2013 State of the Union address and signed on 12 February, is intended to confront the growing threats and risks of destructive and potentially deadly cyber attacks on the nation’s critical infrastructure. The Executive Order calls for development of a national Cybersecurity Framework that includes “standards, methodologies, procedures, and processes that align policy, business, and technological approaches to address cyber risks,” and “help owners and operators of critical infrastructure identify, assess, and manage cyber risk.” The National Institute of Standards and Technology (NIST) of the U.S. Department of Commerce is charged with developing the Framework.

NIST has recognized the efforts of the Automation Federation (AF) to ensure that language is included in the Cybersecurity Framework to address the protection of industrial automation and control systems (IACS). Key NIST staff asked to meet with AF and ISA subject matter experts immediately prior to the first of four NIST Cybersecurity Framework workshops to discuss the central role that ISA99 industry standards for IACS security might play in the Framework.

The first NIST Cybersecurity Framework workshop was held at the offices of the U.S. Department of Commerce in Washington, D.C., on 3 April. Attendees included Leo Staples, 2013 Automation Federation Energy Committee chair; Eric Cosman, co-chair of ISA99 Security Committee; Johan Nye, chairman, Governing Board of the ISA Security Compliance Institute; Steve Mustard, member of the Automation Federation Government Relations Committee; and Mike Marlowe, Automation Federation managing director and government relations director.

Following the workshop, AF agreed to a request from NIST to help identify a location for one of three additional national Cybersecurity Framework workshops, to be held in September on the Raleigh campus of North Carolina State University. The other NIST workshops are planned for May 29–31 at Carnegie Mellon University, and in July at a time and location to be determined.

ISA cybersecurity initiatives

In response to a NIST open request for information on the Cybersecurity Framework, AF submitted comprehensive responses in early April from both the ISA99 standards development committee and the ISA Security Compliance Institute (ISCI). ISA99 and ISCI have been developing IACS multi-industry consensus standards and conformity assessment programs, respectively, to protect vital industrial and critical infrastructure. The application of automation to increase productivity, reduce costs, and share information in real time across multiple industrial and enterprise systems is vital in maintaining and increasing industrial competitiveness. In order to meet industry competitiveness objectives and protect IACS from cyber threats, the NIST Cybersecurity Framework, like the ISA99 standards, is intended to apply across multiple industry sectors. Cyber attacks on industrial operations continue to be a great concern, but at the same time management demands are increasing for real-time communications between automation and business systems. In addition, the decreasing number of experienced automation experts is driving the need for remote plant operations over the Internet, raising vulnerability concerns. These are some of the major reasons that ISA and AF have taken the lead to address IACS cybersecurity with these key initiatives:

ISA99 committee The ISA99 standards development committee brings together more than 500 industrial cybersecurity experts from multiple industries and applications to develop the ISA-62443 series of American National Standards on IACS security. These standards are providing a framework for companies to achieve and maintain security improvements through a lifecycle that integrates design, implementation, monitoring, and continuous improvement. This original and ongoing work is being adopted by the Geneva-based International Electrotechnical Commission (IEC) as the IEC 62443 series. An overview of the ISA-62443 series is available here.

ISA Security Compliance Institute (ISCI) The ISA Security Compliance Institute, a subsidiary of ISA, manages the ISASecure® program, which recognizes and promotes cyber-secure products and practices for industrial automation suppliers and operational sites.

The ISASecure designation is earned by industrial control suppliers for products that demonstrate adherence to ISCI cybersecurity specifications derived from open, consensus industry standards. ISASecure certifications evaluate product/system cybersecurity characteristics and laboratory test products/systems and assess suppliers’ adherence to cybersecurity lifecycle development best practices. ISCI develops industrial automation control systems certifications, which assess conformance to the ISA-62443 standards and reference other relevant international standards, such as IEC 61508 and IEC 61511 for Safety Instrumented Systems, as appropriate to the particular certification program.

Test lab accreditation assures users of the competence and impartiality of the certification body (CB) being accredited. ISASecure is an ISO/IEC Guide 65 conformance scheme. As such, all ISASecure certification bodies (test labs) are independently accredited to ISASecure requirements, ISO/IEC Guide 65 and ISO/IEC 17025 by an ISO/IEC 17011 accreditation body, such as ANSI/ACLASS, the Japan Accreditation Bureau (JAB) and other country-specific ISO/IEC 17011 accreditation bodies. The link to the ANSI/ACLASS website for ISASecure is www.ansi.org/isasecure.

To read the full article on ISA’s cybersecurity initiatives, click here.

Help ISA gain views and insights from automation professionals and automatically enter to win an Apple iPad®.  Take the 10-minute industry survey before June 15 and we encourage you to also pass the link along to your friends and co-workers. ISA is conducting this survey because we are continuously adapting to the changes and trends in the industry to increase our expertise in automation so that we can provide valued information, services and educational and networking programs to our members.

Click here to take the ISA automation industry survey.

For survey terms and conditions, please visit www.isa.org/IS13_terms_conditions. We appreciate your time and effort.

When I am in an instrument and valve repair shop, I see many more control valves than instruments, particularly with the advances in sensor technology, transmitter intelligence, and asset management systems. Valves are mechanical devices and as such require more maintenance. Packings, seals, seats, and O-rings wear out. To ease maintenance, a control valve must be located so it can be readily and safely removed from the pipeline. However, there is much more to consider in locating a control valve.

With liquid streams, a change in control valve position causes an immediate change in liquid pressure and, in a full and pressurized pipeline, a pressure wave traveling at the speed of sound. In less than a second, the pressure imbalance from the wave provides a driving force that overcomes the liquid’s inertia and accelerates the liquid to a new velocity. Consequently, within a plant the location of a control valve does not appreciably affect the response of a process variable (PV) within the pipeline. However, if you are measuring PV response in a pipeline and the control valve is in a different pipeline, throttling a flow that is being added to the pipeline that is being measured, the distance of the valve from the measurement may cause a transportation delay. This piping and valve arrangement commonly occurs in the dilution and blending of streams.

There are some really bad control valve locations that show no understanding of the negative impact of deadtime by process and mechanical design engineers (see Tip #70). One of the worst is where there are several vessels between the control valve and the measurement. The residence time of the smaller vessels in series with the larger vessel becomes deadtime. Also bad is gravity flow. Now a change in control valve position starts a wave traveling slowly down the partially filled pipeline. For small flows in vertical runs, the flow is a falling film causing a large and unpredictable deadtime. The worst case of deadtime resulting from valve location is encountered in pH control. A control valve often throttles the reagent flow to a dip tube. The dip tube has a minimum size for structural integrity and normal mixing rules put the dip tube down near the impeller. Unfortunately, this creates a dip tube volume of 2 gallons. If the reagent flow is 1 gallon per hour, when the control valve opens, it takes 2 hours for the reagent to flush the process fluid out of the dip tube. When the control valve closes, the reagent will continue to migrate into the process for several hours. The solution is to have the control valve add the reagent to a high flow recirculation line, thereby reducing the injection delay to seconds.

To prevent flashing, control valves should be located so the fluid pressure in the vena contracta (that is, the narrowest opening in the flow path) does not drop below the vapor pressure of the fluid. If flashing cannot be avoided, the valve type and trim design should be selected to prevent cavitation in the valve or downstream equipment. Stan Weiner, my coauthor of the Control Talk column, recommended the flashing control valve be installed directly on an inlet nozzle near the top of a vessel so the collapsing of bubbles would occur in the vessel vapor space when cavitation could not be prevented.

Concept: Control valves do not require much in the way of straight runs and do not introduce appreciable delays within plants when they are in the same pipeline as the measurement. (Long-distance oil and gas pipelines are another story.) Valves adding flows to process equipment can cause large injection delays or bypass mixing in the equipment. Valve location on streams to equipment should not introduce excessive deadtime or noise. Valve location, type, and trim should minimize flashing and cavitation and provide safe and easy access for removal and repair. On-off valve locations should minimize the volume to the destination when flow is stopped to prevent totalization errors in charges.

Details: Control valves should be at floor level or accessible from platforms. Block, flush, and drain valves should be installed to enable them to be safely removed. Control valves should be located on the same equipment or pipeline as the measurement and downstream of flow measurements. Reagent control valves should be moved from dip tube to recirculation line injection to eliminate injection delays for pH control. On-off valves close to the point of injection should be added to provide isolation and to shut off the flow. For pH and reactor control, the volume between the on-off valve and the nozzle should be minimized by flanging the on-off valve to the nozzle or nozzle block valve for low reagent and reactant flows and high process sensitivity. Gravity flow piping is not recommended because of variable head and velocities, but if it is used, the control valve should be as close to the nozzle of the destination as possible.

Watch-outs: The location of the nozzle and dip tube entry points into a vessel must not result in the flow being injected close to an exit nozzle; thereby short circuiting inlet flow to outlet flow and bypassing the mixing in the vessel. Throttle valves should not be used as isolation valves, and isolation valves should not be used as throttle valves (see Tip #83). If an on-off valve for batch control is not close to the flowmeter, the pipeline inventory between the on-off valve and flowmeter can cause the charge to be significantly different than the batch setpoint. To minimize excess charge, the on-off valve should stroke as fast as necessary when the “close” command is given.

Exceptions: For Coriolis meters in liquid service with no possibility of flashing, the control valve can be located upstream of the flowmeter because a Coriolis meter is not sensitive to velocity profile.

Insight: Control valves can cause damage to piping from cavitation and poor control from injection delay and short circuiting.

Rule of thumb: Locate control valves to be maintainable, provide fast injection into mixing zones, and prevent flashing and cavitation.

Look for another tip next Friday.

Voting for this year’s Member’s Choice Awards is now open. The Member’s Choice Awards recognizes those individuals who have demonstrated exceptional leadership as decided by someone who knows them best — you!

There are many wonderful things about being awarded the Member’s Choice Award — peer recognition, an amazing trophy, bragging rights, and an incredible evening at a black-tie gala just to name a few. But the most unique aspect of the Member’s Choice Awards is the voting system. Unlike other ISA honors and awards, your vote will determine the honoree.

How the Voting Works

It’s simple. One person one vote every 24 hours. Yes, you have the opportunity to vote once a day, every day during the voting period for your favorite candidate.

You’ll find a list of nominees and a summary of their achievements online at:  http://www.isa.org/memberschoice.

A running tally of votes at the online voting site will let you know how your candidate fares compared to other nominees in that category. Votes will be tallied and the nominee with the most number of votes at the close of the voting period wins.

All Member’s Choice Awards winners will be honored at the 51^st ISA Honors and Awards Gala to be held 4 November 2013 at the Renaissance Nashville Hotel in downtown Nashville, Tenn., USA.

Voting for the Member’s Choice Awards will continue through 31 May 2013.

Vote now and vote often for the Member’s Choice Awards by clicking this link