Automatizacion Procesos Continuos

Playbook The bottom line on core automation issues for the
Oil & Gas, water/waste water and chemical industries
2014 EDITION
Ethernet, Wireless and the Mobile Workforce
PLC vs DCS
Safety: Lifecycle and Procedural Automation Approaches
Start-Ups, Upgrades & Migrations
44 13 Suggestions for Control System Migrations
48 Migrations Are Emotional Events, So Work to Minimize the Pain
49 Four Considerations for Upgrades and Migrations
52 Control System Security Tips
55 How to Avoid Mistakes with Control System Remote Access
59 SECTION THREE: SMART DEVICES & ASSET MANAGEMENT
60 The Smartest Instruments Still Need Smart Humans
66 Managing for Reliability Key to Asset Performance
68 Asset Reliability as a Performance Indicator
71 Measure First to Improve Control System Performance
75 10 Steps to Creating the Perfect HMI
78 SECTION FOUR: ADVANCES IN SAFETY
79 Intrinsic Safety: Thinking Outside the Explosion-Proof Box
8/9/2019 Automatizacion Procesos Continuos
88 12 Practical Tips for Implementing Intrinsic Safety
92 Safety: The Lifecycle Approach
97 SECTION FIVE: COMMUNICATION TRENDS
98 Wireless Trends
106 Nine Strategic Considerations for Using Wireless Technology
108 Five Practical Tips for Implementing Wireless
110 Wireless Is Evolving
114 SECTION SIX: ENERGY & THE ENVIRONMENT
115 How to Conduct an Energy Audit
125 Five Ways to Manage Energy Costs
126 Managing Emissions with Automation
129 VENDOR SELECTION RESOURCE GUIDE
Momentive Specialty Chemicals Inc.
Bayer CropScience
Michael Thibodeaux
BASF
Staubli Corporation
Juan Facundo Ferrer
Emerson Process Management
CONTRIBUTORS
Antonio Manalo
Ronald Studtmann, P.E.
Russel Treat
Dario Rossi
Automation World worked with CSIA to
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tem integrator members to bring you
much of the content in this playbook.
To become a member of CSIA, a
control system integration firm must
demonstrate experience and com-
earn CSIA Certification have passed
an independent audit of 80 criteria
covering all aspects of business per-
formance, including general management, financial management, project
management, quality management,
re-audited every three years.
its system integrator members, visit
http://www.controlsys.org
INTRODUCTION By Jeanne Schweder
Contributing Editor
Automation World
Everywhere you look, new technologies, new standards and a new generation of engineers are
transforming the control of industrial processes. Automation and information technologies are
increasing our knowledge, and changing expectations and best practices as well. These powerful
tools range from intelligent instruments to wireless communications—and everything in between.
This 2014 edition of Automation World’s Continuous Process Playbook continues our goal of providing hands-on information, automation implementation tips and best practices
specifically for the continuous process industries. It also explores some of the many trends
affecting how work gets done, from procedure automation to reliability management.
Among the many topics addressed in this playbook are implementing and migrating
control systems, intrinsic safety, asset and energy management, Ethernet and wireless
communications, automation project management and more.
As always, we thank the many industry experts and process engineers who have contributed
their experiences and expertise to this playbook. This peer-to-peer knowledge sharing is a
hallmark of what makes Automation World’s playbooks unique.
We hope you’ll find this Continuous Process Playbook to be a useful source of information now
and in the years ahead as you plan for new projects or upgrade existing production functions.
Automation World
Procedural Automation forGreater Safety and Productivity
Continuous process environments tend to be stable — until they’re not. When that happens,
the consequences can be catastrophic. Think Deepwater Horizon.
The very stability of a continuous production process often induces a false sense of security in
operators. Lack of experience with system failure or unexpected alarms can lead operators to freeze when systems suddenly cascade out of control.
Procedural automation standards originally developed for batch processes and discrete
manufacturing hold promise for helping continuous process operators deal more effectively
with sudden emergencies, as well as the more routine changes in state that can occur.
Processing’s Most Vulnerable Areas The fact is, every continuous process has non-continuous elements, such as startup, ramp-up,
emptying and filling of tanks, shutdown, emergency shutdown and clean-in-place activities. A
continuous process is really just a batch process with a very long steady state in the middle.
The ISA-88 standard has established a common terminology and a framework for writing
software to control batch production processes and procedures. ISA-95 did the same for
enterprise to manufacturing data integration. ISA-95’s “common denominator” data structure
facilitates communication between business and process
systems, so that operators and managers can make
better decisions.
implications in areas where continuous process control
is most vulnerable—process variations and disruptions.
These can result in unanticipated shutdowns that plant
operators can be ill equipped to counter because they’re
not confronted with them frequently enough to hone
their skills.
Automating procedural steps can counteract variations in operator skills and will become increasingly important
as the current generation of experienced process control
engineers retires. Defining common process procedures
can also provide additional support for employees who
are executing operations that can be more manual, as is
typical in equipment and plant startups, shutdowns and
transitions.
continued

Four IT StandardsYou Should Understand
Imagine a world without electrical standards, such as 110 V at 60 Hz, or 220 V at 50 Hz, or a
world where every phone had a different type of connection and required a different type
of switchboard. Just as these standards are critical to the basic functioning of electrical
equipment, there are also IT standards used daily to ensure optimal functioning of production
systems in the process industries.
There are four production-related IT standards of special interest to the processing industries:
• The ANSI/ISA 88 standard for batch control;
• The ANSI/ISA 95 standard for MES and ERP-to-MES communication;
• The ANSI/ISA 99 technical reports on industrial cyber security; and
• The new ANSI/ISA 106 technical report on procedure automation.
These standards and technical reports define the best practices for implementing automated
and manual control on the systems that reside above the PLC (programmable logic controller)
and DCS (distributed control system) level, and which perform the basic control that keep
production running. These four standards all share a common view of a production facility,
By Dennis Brandl Chief Consultant
S88 Builder is the first process control
system that is configured rather than
programmed. Configuration requires two
physical system and define specific tasks,
such as mixing, flow control, heating, etc.,
that the devices team up to accomplish.
Configuration is easier, more accurate and
faster than programming.
batch control tasks, S88 Builder speeds
project development by up to 90%.
S88 Builder lowers the total cost of
ownership for a batch control system by:
• Lowering initial development costs
• Reducing waste and downtime
Stop Programming Batch Tasks. Start Configuring
CONTROL AND INFORMATION SOLUTIONS FOR INDUSTRY
Learn More About the Many Cost-Saving Benefits offered by S88 Builder
www.S88Builder.com
[email protected]
compare plants within a company and across companies.
The ANSI/ISA 88 standard defines the most common and
effective method for defining control systems for batch
operations or for continuous and discrete startups and
shutdowns.
used method for exchanging information between ERP
systems, such as SAP or Oracle, and the multitude of shop
floor systems. It has also become the de facto standard for
defining MES (manufacturing execution system) and MOM(manufacturing operations management) specifications.
The ANSI/ISA 99 reports define structures and policies
for designing effective and secure networked
production facilities.
The new ISA 106 reports define the procedural control
strategy for continuous production during upsets,
switchovers, and other types of process changes.
These standards establish a commonly accepted
terminology, as well as functions and process models by
which technical professionals are trained and upon which
solution providers develop applications used in batch
and process production operations (as well as discrete
manufacturing). As such, they should be of particular
interest to those who are new to the field, and those who
seeking a refresher on the fundamentals of industrial
processes.
continued
By James R. Koelsch Contributing Writer
Automation World
Heard the News about ProcedureAutomation?
Bayer MaterialScience and Dow Chemical are on the leading edge of pending industry
standards that promise to widen the appeal of procedure automation—a system design and
programming approach known to streamline control, tighten repeatability and improve the
safety of continuous processes.
For Bill Wray, PE, spreading the good news about procedure automation is about more than
simply generating hundreds of hours of productivity at Bayer MaterialScience in Channelview,
Texas. It’s also how the Bayer engineering consultant is giving back to his profession. He found
that the benefits of borrowing from batch control to improve continuous processes were just
too great for him to keep the news to himself.
“I’d like to see more people adopt this method because it can offer real benefits in many
places where people rarely think about batch programming,” he explains. So, he joined a
small band of evangelists on the ISA-106 standards committee on Procedure Automation for
Continuous Process Operations, formed in 2010 by the International Society of Automation
(ISA, www.isa.org) in Research Triangle Park, N.C. Since joining, he has become one of the
committee’s co-chairs.
CONTINUOUS PROCESS PLAYBOOK 20 / 135
The mission of this committee was to formalize a set of closely related methods that Bayer
and other operators had developed over a few decades to accommodate change. Going by
such names as procedural control and state-based control, these methods break continuous
processes into operating states and automate the procedures for moving from one state
to another. The committee intends to develop cross-industry standards for this form of
automation, replicating the success that ISA has enjoyed in the batch industry with the ISA-88
and ISA-95 standards.
Streamlining change
Even without the standards in place yet, procedure automation is already streamlining operational changes in
continuous processes, such as the responses that a refinery
might make to accommodate a shipload of a different grade
of crude. Another example is the adjustments to a reactor to
allow it to produce a different grade of polymer. “Anything in
a plant that requires you to change the steady state and go
from Point A to Point B can be done more effectively, more
efficiently, and safer with well written code,” notes Wray.
About 13 years ago at Bayer’s Channelview facility, Wray and
his colleagues developed a form of procedure automation to
make two polyols, a triol based on glycerin and a diol based
on propylene glycol. A breakthrough in catalyst technology
had permitted them to convert a batch reactor to produce
the two polyols in a continuous mode. Because the two
continued
products are in different families, they are incompatible enough that operations must de-
inventory the system and restart to switch from one product to the other twice a month.
Engineers wrote procedural scripts for such transitional phases of the reactor as cold starts,
restarts after a trip, shutdowns, de-inventory procedures, and rate changes. “We even have
one that runs an optimizer [on the multi-constraint controller to optimize feed rates] on the
reactor,” says Wray. “At the time, though, nobody was calling it procedural automation, but
that’s what it turned out to be.”
A smooth transitionAs is often the case for users who already have experience with automating batch procedures,
developing and automating the procedures on the continuous reactor was a natural next
step for Bayer’s engineering and operations team in Channelview. “With a dozen or so years
of experience, we had developed some well-tested approaches to automating batches,” says
Wray. “We had a good, strong talent pool of people who knew how to do automation in the
style that we like to do it. It made doing the procedural control a piece of cake.”
Even so, the team found that finishing the programming took longer than it had in the past when the process was batch. Because the reactor had been running anywhere from one to four
batches a day, depending upon the product that it was making, the batch process had given
the team more opportunities to identify and debug programs. “With the continuous operation,
we get about two startups and two shutdowns a month,” says Wray. “Because the continuous
process does not exercise the code as much, it took a little longer to work out the bugs.”
continued
Despite the longer debugging period, startup was short because the team could draw upon
its experience with automating the batch process and could deploy proven techniques. For
example, the programmers wrote a script that permitted aborting a procedure if the operator
encountered a problem. After being reloaded, the script would return to the place in the
sequence where it left off.
“We also modularized the programs as much as we could to allow us to plug in changes
easily,” says Wray. “When we would run into coding errors and other problems, we tried to fix
them right away. If you write them down with the intent to fix them later, sure enough, you’ll
forget about them.”
Since going continuous about 13 years ago, the reactor has never made off-spec product and
has been more productive. Although it was the catalyst technology that had made converting
from batch to continuous processing possible, the procedure automation has allowed
Bayer to take full advantage of it. The automation, for example, expedites changeovers. “By
automating the de-inventory procedure, we cut about 12 hours off our downtime,” reports
Wray. “And 12 hours of production is quite a bit when you change over 24 times a year.”
Another benefit has been better coordination between the distributed control system (DCS)
and the safety instrumented system (SIS). “The automation communicates with the SIS, telling
it what recipe we’re making and confirming that all the values and trip settings are correct,”
says Wray. “So, it enhances safety as well.”
continued
Multiplying the benefits The ISA-106 committee hopes to multiply these kinds of benefits in continuous applications
by adapting the equipment and control modules defined in the ISA-88 batch standard. “What
the 88 standard did for batch systems was to specify a structure for organizing the different
parts of control code for flexibility and reusability,” says Dennis Brandl, president of BR&L
Consulting Inc. in Cary, N.C. (www.brlconsulting.com) and one of Wray’s fellow evangelists on
the ISA-106 committee. Before promulgation of the standard, batch control programs had a
much less uniform structure.
A similar situation exists for control systems governing continuous processes. “There really is no well-defined structure for procedures in function blocks, ladder logic, or other
programming methods that you might be using,” notes Brandl. “So, the 106 committee
is adapting the design patterns and structures in 88 for procedures used in continuous
processes.” The adaptations will account for the differences between batch and
continuous processing.
Reusing code saves time
Both users and vendors on the committee expect similar benefits from control architectures built with these models and structures. Not only should the ability to reuse modules of
code reduce the time to write, debug, validate, and install programs, but it should also cut
development and installation costs correspondingly. “People using 88 saw about a 30 percent
decrease in either the time or the cost to do their first projects,” reports Brandl. “On future
implementations, they were getting 50-70 percent savings.”
continued
Another advantage to the industry-standard structures is that programmers can develop
their code in layers and therefore separate operating procedures from the control loops that
run pumps and other basic equipment. By not having to worry about the details for running
each device, the operator can focus on just the procedure for a particular layer. At startup, for
example, the operator can concentrate on starting the reboiler, filling a column to the right
level, and bringing the system to temperature, while the software takes care of the valves,
pumps, and other devices behind the scenes.
Layered structure
The layered structure also allows nesting so that programmers can automate procedures atthe various levels within the production hierarchy, such as coordinating the various pieces
of equipment within a particular unit. Take, for example, the task of heating a reboiler to 180
degrees C. Lower-level procedures take care of opening the required steam valves and setting
the control loops necessary to do that. Then a unit procedure for the distillation column can
be built on those lower-level procedures. A plant startup procedure can also be built on top of
that unit level.
Take an incremental approach Yet another advantage of the standard structure is that programming can be done in
increments, allowing an engineering team to do the automation over time. Do some of it at
one shutdown and some more at the next one, as opposed to just automating everything at
once, which is often the case in batch operations. Automate only pieces, and use the software
to prompt the operator to do other pieces.
continued
The keys to identifying which tasks to automate and which to keep in the capable hands of
operators are risk and bang for the buck. If you have an exothermic process that requires
keeping a close eye on some variables, managing that risk might be a good place to spend
your money on automation. Other candidates are repetitive, low-level tasks, such as daily filter
flushes, that occupy an operator’s time.
Start small, work up A good approach is to start small and work your way up to progressively bigger. A good place
to start is at the bottom, equipment-module level, which includes such devices as pump
stations, heaters, coolers, and compressors. This will give operators small improvementsto work with. It will also give them a vision of what the final product will look like as more
individual items become grouped into larger control elements.
State-based control Continuous processes really operate in a series of definable states, rather than truly being
continuous. Process engineers and senior operators should discuss in the initial stages how
the process may be partitioned into states to establish state-based control. Perhaps the most
fundamental of these states are startup, shutdown and normal running.
The term “shutdown” usually describes at least two distinct states. The first is a full-
maintenance, multi-week shutdown where everything really is shut down. The other is
better described as a process interruption or a state of waiting. In this case, some parts of the
process may still be running, such as the systems for maintaining measurements, alarms or
other forms of monitoring.
Even “normal running” is rarely one process state. For example, a power-generation boiler
usually operates at three basic conditions: full, three-quarters and half. Different products,
minor product additives and changes in equipment, such as the switching of cracking
furnaces in an ethylene process, also cause changes in state. Because of variations like these,
process engineers and senior operators should include throughput conditions in their
discussions about state.
As you identify each state, create a functional specification that completely describes the
state, including alarming and visualization requirements. Once you define your states, you are
in a position to begin looking at the interactions between units.
continued
continued
Heard the Newsabout Procedure Automation?
ISA-106 TR1 Terminology Here are some of the definitions being proposed in the first of the three technical reports
being written by the ISA-106 committee as groundwork for developing standards for
Procedure Automation for Continuous Process Operations.
Automation style – a consistent approach to developing and deploying
implementation modules.
procedure and control requirements in a BPCS.
Procedure – a specification of a sequence of actions or activities with a defined
beginning and end that is intended to accomplish a specific objective.
Procedure automation – Implementation of a procedure on a programmable
mechanical, electric, or electronic system.
Procedure requirement – the definition of what is required to accomplish an objective
using a procedure.
Process state – a definable operating condition of process equipment as it progresses
from shutdown to operating and back to shutdown. Each process state represents a unique operating regime that supports the process equipment’s objectives of processing
an input into a desired output.
State-based control – a plant automation control design based upon the principle
that all process facilities operate in recognized, definable process states that represent a
variety of normal and abnormal conditions of the process.
continued

In mid-2013, the ISA-106 standards committee on Procedure Automation for Continuous
Process Operations released its first technical report. It was a milestone in the committee’s
efforts to develop a standard that applies batch manufacturing methods to improve
continuous process operations.
The work of this committee, formed in 2010, concentrates on standardizing methods—
built on the work of engineers at companies like Bayer and Dow Chemical—that break
continuous processes into operating states and automate the procedures for moving from
one state to another.
“Procedure Automation for Continuous Process Operations – Models and Terminology,”
was the committee’s first deliverable. Given the typically slow movement in standards
development, the fact that this technical report was developed in just over three years after the first meeting is impressive and underscores the industry’s interest in the
committee’s work.
Co-chairs of the ISA-106 committee are Yahya Nazer of Dow Chemical and Bill Wray of Bayer
Material Sciences, and the secretary is Charlie Green of Aramco Services. The committee’s
former co-chair is Marty King of Chevron.
First ISA technical report
technical report describes it as
providing an “overview of the benefits,
best practices, and language, including
terms and definitions, for applying
procedure automation across the
continuous process industries.
Consistent with the scope of the ISA- 106 Committee, this technical report
focuses on automated procedures that
primarily reside on systems within the
supervisory control, monitoring, and
automated process control section
1 and 2) of a production process (as
defined by ISA-95 functional level 0).
It was not the intent of the committee
to have this technical report focus on
procedure execution at the operations
management functional level (as
Seeking feedback The first ISA technical report clearly establishes the value of automating procedures for
continuous processes and provides the foundation for the reports and standards to follow.
“With strong end user representation, especially from energy and chemical companies,
coupled with representation from consultants; engineering, procurement and construction
companies; and system suppliers we had a great source of knowledge and experience to draw
upon” to create this technical report, says Dave Emerson, director of the U.S. Development
Center for Yokogawa and ISA-106 Editor. “This first technical report should generate feedback
for the committee that will be used in creating a standard.”
The committee is now working on its second technical report that addresses work processes
for automating procedures in continuous process operations. In parallel with this second
technical report, the ISA-106 committee has started work on the standard itself.
The work involved in creating this standard involves digging into sequencing concepts
that have been around a long time, but applying them to a new context. The next step
for the committee is getting feedback from industry to help guide it moving forward and encouraging more participation to ensure the standard created is reasonable to adopt.
continued

Eight Ideas for Successful DCS Implementation
Implementing a new distributed control system is one of the biggest and most
complicated projects in a process control engineer’s career. Doing one successfully requires
everything from a well-defined project document to good grounding practices. Here are
recommendations for best practices and some pitfalls to avoid.
1. Standardize. Use of standard wiring throughout the system will make it for easier
for others to understand and troubleshoot. Use standard, off-the-shelf components for ease
of stocking and reordering. If possible, have two sources for the products being used or
purchase interchangeable brands.
2. Remember the basics. It’s the little things that can trip you up. Make sure you use
proper grounding, proper grouping of signals and proper termination of electrical signals.
Make sure you understand the supplier’s grounding requirements for your DCS system. Grounding principles need to be clearly understood by all automation engineers, not just the
electrical staff. International standards can be misinterpreted. Instruments and the control
system need to be grounded separately. Double check the grounding before powering up
any DCS system to avoid any short circuits, particularly during factory acceptance or site
acceptance testing (FAT/SAT).
3. Is communication complete? While most automation suppliers have different
software versions for communicating with the system, make sure they will transmit all the
required information. Many systems only transmit the basic parameters, which means all
diagnostic features will not be available. The introduction of the “Control in Field” concept,
although not often used, has added some complications and needs to be thoroughly
examined when implementing a DCS.
4. Structuring I/O. Since today’s electronics are available with high-temperature specs
and may be G3 compliant (conforming coating), the I/O structures should be moved to the
field, reducing the rack room footprint and cabling cost. Communication links should be used over fiber optic, in a ring configuration to provide some level of redundancy, to interconnect
the field I/O structures. Extended I/O terminal blocks (three to four terminals per channel)
should also be used to allow field wiring to be connected directly, avoiding marshaling
terminal strips with the related space, additional cost, installation cost and the possibility of
poor connections.
5. Dual purpose. The purpose of DCS is twofold. Centralized human control and interface
to the plant as well as a centralized location for MIS info to the management network. DCS control should not include auto tuning of control loops other than simple on/off or start/stop
functions. These should be the function of a local dedicated controller. Use the DCS to update
the tuning parameters.
6. Good links. Distributed control systems are only as good as their communications links.
Choose a very solid and reliable link between processing units.
continued
Know Your Process
need to understand the
process clearly. Many times
the programmability of the
attitude in the engineers,
commissioning the plants. Be
sure you know the implications of controlling one way or
another. Try to understand
the interrelations among the
7. FAT is where it’s at. Make sure you do a comprehensive and detailed factory
acceptance test (FAT) before cutover. FAT involves experienced operations people interacting
with engineering to validate graphics and verify that instruments in the configuration exist
and will remain in service.
8. Use single server. Base the selection of a DCS system on its redundant capability. A
single server system is preferred. Pay attention to the hardware license for client and server
to avoid delays during a system or hard-disk crash. Care must also be taken in selecting
appropriate layered switches for communication. Make sure you properly configure trends
and history data for future analysis.
continued
Define in Detail
Successfully implementing a DCS project requires that all stakeholders (operations,
maintenance, project team, vendor, management, etc.) have a clear definition of what they
want from the system. In both upgrading and installing new DCS systems, the best tip is to
keep the end in mind. Good up-front engineering pays dividends. Automation technology can only assist us if we know what the needs are. Maintenance must know what reports and
information they really require to do their work. Operations must be completely sure how they
operate and what is the best way to do it. Don't assume anything. Write everything down that’s
actually required and all the things the technology can do. Be very specific. In the end, the
best DCS is the one that best satisfies all the important requirements in the plant. Writing and
signing this definition document should be the first step in any project.
CONTINUOUS PROCESS PL YBOOK

Teamwork Is Critical in DCS Projects
No matter how well you have planned, always leave some slack in your schedule. You may get
off to a great start, but problems invariably surface.
The fastest way to confuse a project is to have too many disjointed teams. DCS projects are
extremely complicated and all the groups have to interact. Even if you don't have anything new to share, schedule a weekly call so everyone knows what everyone else is doing.
If you’ve found a solution to a problem, one of your other team members may run into the
same issue. Instead of wasting precious time, they'll know to call you. Keep the calls short and
sweet, but make sure everyone provides a good synopsis.
If you are not a people person, make sure you get someone on your team who can talk
to people. Otherwise, people will hide their issues. Most importantly, do not shoot the messenger. If someone comes to you with an issue, handle it, but do so in a way that they will
bring you other issues. If everything is a disaster, no one is going to tell you anything until it is
too late to handle calmly (and cheaply).
As long as you have a competent team and are using a good product, you have the basis for
a successful project. A successful, on-time and on-budget installation depends on whether or
not the team works well together.
CONTINUOUS PROCESS PLAYBOOK

Using separate DCS marshaling, server and operator rooms, but
keeping the server and operator rooms close together, are some
of best practices and human factors experience to keep in mind
when implementing a DCS. Other recommendations:
• Separate grounding for each room, instrument and signal and
frame of the DCS.
• Need a good air filtering system for each room, depending on
the plant or process hazards, to protect electronics.
• Make sure proper air conditioning is available all the time.
• Don’t mix MCC and DCS marshaling panels. These panels or
rooms need to be kept separate.
• Have a dedicated UPS with the minimum required
battery backup provided separately for marshaling,
server and instruments.
• Use one communication protocol standard for electrical equipment and instruments.
• Choose a reliable communication protocol for critical loops, such as conventional
hardware instead of an OPC server or system. If the OPC server hangs or stops, it makes a
mess for controls.
• Educate everyone on the operational differences between a DCS and PLCs and where
each should be used. Most people don’t understand why you need a warm start option
for controllers with a DCS, for example.
• Use one programming approach for the entire system.
continued

PLC vs. DCS: Which Is Right for Your Operation?
Over the past decade, the functionality of different control systems has been merging.
Programmable logic controllers (PLCs) now have capabilities once found only in distributed
control systems (DCSs), while a DCS can handle many functions previously thought more
appropriate for PLCs. So what’s the difference between the two control approaches, where’s
the dividing line and are there still reasons to choose one over the other?
PLCs grew up as replacements for multiple relays and are used primarily for controlling
discrete manufacturing processes and standalone equipment. If integration with other
equipment is required, the user or his system integrator typically has to do it, connecting
human-machine interfaces (HMIs) and other control devices as needed.
The DCS, on the other hand, was developed to replace PID controllers and is found most often
in batch and continuous production processes, especially those that require advanced control measures. The vendor handles system integration, and HMIs are integral.
As users demanded more production information, PLCs gained processing power and
networking became common. PLC-based control systems began to function like a mini-
DCS. At the same time, the DCS hybridized to incorporate PLCs and PCs to control certain
By Jeanne Schweder Contributing Writer
Automation World
functions and to provide reporting services. The DCS supervises the entire process, much like
the conductor in an orchestra. Protocols, like OPC, have eased interactions between the two
control systems.
Since PLCs are less expensive and can now perform much like a DCS, wouldn’t it make sense
to convert everything to PLCs? The answer, like most things in the world of automation, is that
it depends on the needs of your application. Here are six key factors to consider:
1. Response time PLCs are fast, no doubt about it. Response times of one-tenth of a second make the PLC an
ideal controller for near real-time actions such as a safety shutdown or firing control. A DCS
takes much longer to process data, so it’s not the right solution when response times are
critical. In fact, safety systems require a separate controller.
2. Scalability A PLC can only handle a few thousand I/O points or less. It’s just not as scalable as a DCS,
which can handle many thousands of I/O points and more easily accommodate new
equipment, process enhancements and data integration. If you require advanced process control, and have a large facility or a process that’s spread out over a wide geographic area
with thousands of I/O points, a DCS makes more sense.
3. Redundancy Another problem with PLCs is redundancy. If you need power or fault tolerant I/O, don’t try to
force those requirements into a PLC-based control system. You’ll just end up raising the costs
to equal or exceed those of a DCS.
continued
4. Complexity The complex nature of many continuous production processes, such as oil and gas, water
treatment and chemical processing, continue to require the advanced process control
capabilities of the DCS. Others, such as pulp and paper, are trending toward PLC-based control.
5. Frequent process changes PLCs are best applied to a dedicated process that doesn’t change often. If your process is
complex and requires frequent adjustments or must aggregate and analyze a large amount
of data, a DCS is typically the better solution. Of course, the very flexibility of a DCS system
also makes it much more vulnerable to “meddling” by operators that can cause spuriousshutdowns.
6. Vendor support DCS vendors typically require users to employ them to provide integration services and
implement process changes.
System integrators perform similar functions for PLC-based systems. It has also become
common for PLC vendors to offer support services through their network of system integrator partners.
Process control has become increasing complex. It’s difficult for any individual to know
everything about these sophisticated systems, increasing the need for vendor support.
Manufacturers also continue to reduce factory staff and a generation of experienced process
control personnel has begun to retire. As a result, the quality of support has become a critical
factor in vendor selection.

Discussion of controllers in the continuous process industries typically centers on distributed
control systems (DCSs). However, programmable logic controllers (PLCs) play as important
a role in the process industries as they do in discrete manufacturing, particularly when it
comes to operations reliability and protection of personnel. Some of the more significant
applications for PLCs in the process industries include control of safety-instrumented systems
and control of major machinery.
Like many discrete manufacturing operations, most process operations use a variety of PLCs
from different vendors. As a result, your ability to effectively operate and manage these
disparate PLC versions has a direct impact on your plant reliability and safety.
Following is a list of the top three PLC lifecycle management concerns for the process
industries and how some of your peers are working with PLC suppliers to address those
issues, compiled from presentations delivered at The Automation Conference 2012.
1. Long plant maintenance shutdown intervals limit the opportunity to modify,
maintain and upgrade PLCs. Many process industry units, particularly in continuous process
operations, run eight years or more without shutting down. As a result, your opportunity to
do anything with the PLCs in that unit is very limited. Therefore you need to ensure that PLC
management is a key part of your unit maintenance focus.
By David Greenfield Director of Content/Editor-in-Chief
Automation World
Complete Automation Solutions
for the Process Industry
Global manufacturer of process control and factory automation solutions For more information:
Call: 1-800-463-3786 www.festo.com/us
challenges with spare parts management and training.
Because across-the-board standardization is unlikely due
to regional differences tied to support and availability, a
strategy for PLC support and training for each region should
be developed to ensure that these critical controllers are maintained in a standardized fashion.
3. Integration with main control systems
— Three aspects are critical to any plan involving the
integration of PLCs with DCSs. 1) The integration process
needs to be reliable and shareable with all other plants to
standardize the process for ease of maintenance;
2) the integration plan should be flexible for adaptability to local requirements; and 3) it must address industrial control
system security. (See “ Control System Security Tips” in this
playbook for more details on this topic.)
To better manage your PLC lifecycle, following is a set of
three requests that many top process industry operations
continued

13 Suggestions for Control System Migrations As anyone who has been involved in a control system migration will tell you, it’s never an
easy process. Whether it’s an upgrade, expansion, stepwise migration or rip-and-replace,
the bigger and more complex the project, the more fraught with tension and risk. To help
you get through the project with your sanity intact, Automation World readers share their
recommendations and suggest pitfalls to avoid:
1. Determine strategy. Your migration strategy will depend on which type of
automation you’re dealing with: scripts, workflow tools, policy-based orchestration,
configuration or control systems. The different activities that can be automated (provisioning,
maintenance, proactive incident response, production execution, etc.) and the different
degrees of automation (automating just a few actions, partial workflows or end-to-end) will
determine your strategy in terms of resources, time scale, production stops, etc.
2. Virtualize first. Automation upgrades or migrations need to be scheduled properly
in terms of system commission date to extend the warranty or for a vendor’s obsolete notice
date. The best practice is to conduct a virtualization of the new automation system. The future
of automation will need virtualized infrastructure and platforms to deal with the IT spectrum,
cyber security and better management capabilities. Virtualization has many benefits in terms
of technology, investment, maintenance and lifecycle cost.
3. Take it one step at a time. Avoid changing the entire system or manufacturer if you
are upgrading. Upgrading to the newer modules or systems of the same vendor provides a bit
more reliability, since the basic architecture remains the same.
4. Don’t experiment. While innovation is important, there is a counter-argument
for doing what you know will work. If rip-and-replace is possible (and that means you
have to stop the plant for several days, weeks, or months depending on the circumstances)
and you know that it works, that is the best choice. But if you can’t afford a shutdown, then
go for a step-by-step migration. Make sure you work with an experienced vendor
and proven technology.
5. Consider three critical migration issues. When doing a migration there
are three points to think about: how to update software and whether you have the right
conversion tools; what you need to do to avoid system failure or risk for the migration step;
what is the expected lifecycle of the new system.
6. Make no assumptions. Try to foresee every small step in a migration
implementation. Don’t assume anything. Every implementation is done to achieve some objective of the operation. The needs could range from some reporting or alarm functions to
an action initiated due to alarm. Always visit the site to understand the requirements and the
nuances completely.
7. Changing suppliers adds some complexity. The difficulty of a process
migration usually increases when you change DCS suppliers, since different brands often
don’t have similar functions. Factor that into your timeline and risk assessment when
weighing whether to switch vendors.
8. Start with data needs. First you need to understand what data the user will
require and how quickly the data is needed. That should be the starting point in developing
your migration strategy. The second priority is to determine the impact on the safety and
productivity of the plant.
9. Focus on controllers. The best strategy is to first upgrade the controllers, then
replace the I/O chassis piece-by-piece going forward. Some I/O changes could be driven by
other projects, such as a motor control center(MCC) replacement.
10. Do your homework. Do some up-front analysis to avoid creating problems
for yourself by not choosing the right migration path. For example, migrating from one
generation of processor to another one may not be a wise choice. Reviewing the instruction
sets and information available about conversions and manufacturer recommendations will give you insight into the difficulty of the conversion. If you do your homework, you might
choose a different processor to make the conversion easier.
continued
11. Technology education. It is important to educate everyone on the new
technology. Remember, it is easy to use "old" thinking instead of changing practices to take
advantage of the benefits of the new technology.
12. Decentralize. The architecture has to be critically reviewed and transformed,
keeping in view the improved performance of the local controllers. Your mantra should be to
decentralize the controls as far as possible.
13. Aging equipment. Depending on the technology you have installed, when your
equipment is more than 10 years old you will need to implement a rip-and-replace. If you are
just making some modifications you can upgrade or make an expansion only. Most of the
problems that arise during a migration are with the field equipment you have installed and
control room facilities.

Migrations Are Emotional Events, So Work to Minimize the Pain Even if the technology being used is important, the success of any control system migration
will be mainly people-related. Plan for disruption and try to minimize that.
Operators, technicians and everyone else directly touched by a migration will be upset.
Regardless of the benefits, nobody is going to like it. Just accept this. When you are explaining the new equipment, do not exaggerate or misstate anything because everyone will only
remember the thing you said it could do, but it turns out it can't.
It is mandatory to conduct an extensive upfront study to identify and clearly define the
implementation strategy and the potential consequences to production. Involve operations,
maintenance and management teams so that the suggested transition will be "blessed" by all.
Making the transition as smooth as possible will require the cooperation of all involved.
Structure your team to include both seasoned personnel who are the old-system's experts
(and know how it really works) and relatively new personnel who are competent enough to
learn, but not already ingrained with the old system. The newer people will pick up the new
system more easily, while the more-experienced people will be able to stop you from doing
something stupid.

Four Considerations for Upgrades and Migrations Regardless of whether you want to increase productivity or shorten time-to-market, attaining
success in these areas depends on the application of suitable automation technologies in a
continuous process operation. Following are the principal steps involved in assessing your
plant’s technology to gauge whether a technology upgrade or migration is in order:
1. Consider the full range of aspects that relate to your existing systems, such as:
• Risk of unplanned plant downtime and production stoppages;
• Ability to expand production or introduce new products;
• Ability to integrate with enterprise-level business software and at what cost;
• Ongoing maintenance costs;
By David Greenfield Director of Content/Editor-in-Chief
Automation World
2. In each case of upgrade or migration, return on investment plays a crucial role. A huge investment in hardware and application software is associated with
the installed process control system, as well as the accumulated know-how of the operating,
engineering, and maintenance personnel. For this reason, the prime objective of any
migration strategy should be to modernize the installed base gradually without any system
discontinuity and, if possible, without any plant downtimes or loss of production that would
negatively affect the investment return.
3. Assess the long-term security of existing investments. This assessment is important in order to
maximize the return on assets (ROA). For this reason, every
migration should include a robust lifecycle support strategy for
the new system that considers not only the availability of the
components, but also product warranties, on-site service, and
ongoing technical support.
4. Obsolescence. When deciding whether to upgrade or
migrate to a new system, there are two aspects of obsolescence to assess. In a migration, it’s important to understand the
history of the technologies supported by the company behind
the product under consideration. Does this company actively
support the long-term lifecycles of products as they are
typically employed in a process operation? Do upgrades have
significant backwards compatibility? How often are upgrades
continued
typically released for this system and what is required for installation? For upgrades, it’s
important to understand what the future outlook is for the system under consideration.
With the significant maintenance and security issues tied to process control systems, you should always consider your risk of system obsolescence and the associated costs incurred
with such a scenario versus the costs of moving to a better-supported system. The good
news is that, in the process industries, most vendors are very aware of the long-term use
of their systems by end users and thus tend to support their systems for multiple decades
rather a single decade, as is more common with office IT systems. As newer automation
technologies become core components of process control systems, be sure to talk with your
supplier about their support plan for those newer technologies.
continued

Control System Security Tips
Recognizing that the biggest security risk to your control system assets are the operators who
interface with the system on a daily basis is the most important step to successfully securing
your systems. For a thorough analysis of your risks and setup of reliable control system
security technologies and processes, consult an industrial control system security expert such
as scadahacker.com, tofinosecurity.com, or industrialdefender.com. Following are the ground-
level security steps that a continuous process facility should implement at a bare minimum:
1. Assess your systems. Compile an accurate list of all the assets in your plant: make,
model, and serial number. Where are your computers? Where are your PLCs? It’s difficult to
secure something when you don’t know it exists. This should be a high-level assessment in
which you go through your plant and figure out what is high risk and what is low risk, which is
determined by two key factors: how likely is a problem to occur? How serious is the problem?
For example, if something happened to your chlorine tank, it would be really ugly. That chip
pile, not so ugly. Get a feel for the significant risks. Where do you have to focus your effort?
The answer is going to drive your decisions and your capital allocation.
2. Document your policies and procedures. No company operates in a
vacuum. Each company will have a series of policies and procedures for things like safety
and performance, reliability, and change management. Lay those out and understand how
they impact control systems and security, and then build on that to create a set of additional
security requirements.
Automation World
3. Start training. No one is going to follow policies unless they know about them and
understand why they are necessary. All levels of employees that interact with the control
system need to understand what an attack looks like and how to respond to one. You should end up with a matrix of training for the various levels of users; it doesn't have to be onerous,
but it has to be done.
4. Understand your traffic flows. You need a diagram that shows all the things that
require intercommunication. Smart companies will have a comprehensive diagram showing
that the accounting department needs data out of this area, and maintenance needs data out
of this area, and so on.
5. Remember that SCADA security is used to control access. Access should
be segmented to specific network resources, hardware resources, and HMI. Effective security
practices should prevent access to all layers by unwanted external connections.
6. Leverage safety reports. Those responsible for safety, when they do reports and
analyses, have done a good deal of the work needed to understand the security risks.
7. Use separate networks. Though this step is becoming less and less practical, some
still advocate that the process control network be kept separate from business networks,
and also isolated from the Internet. For this approach, which may not be viable in the longer
term, utilize operating system (OS) implemented security, with active directory “domain group
security” as the preferred approach.
continued
8. Security in the operator interface should be considered broadly. With
advanced human-machine interface technologies, security can be implemented for individual
attributes. HMI should be the only accessible program, with user-specific exceptions, connected to the control operating system at a dedicated user station. All other resources for
that particular terminal should be restricted.
9. Use unique user accounts and passwords. All users should have unique user
accounts and passwords to minimize the risk of unauthorized access.
10. Provide port security. With this approach, the Ethernet MAC address connected
to the switch port allows only that MAC address to communicate on that port. If any other
MAC address tries to communicate through the port, port security will disable it. Most of the
time, network administrators configure the switch to send an SNMP trap to their network
monitoring solution that the port’s disabled for security reasons. When using port security,
you can prevent unwanted devices from accessing the network.
11. Administer antivirus protection. Use an antivirus solution that is compatible
with the installed SCADA software.
12. Open and facilitate communications between IT and process control groups. Roles need to be defined and an understanding of what each group
needs must be accomplished so true collaboration can take place to begin and continue the
process of enabling a fully functional control system with adequate security protection.
continued

How to Avoid Mistakes with Control System Remote Access As more operations aspects are tied to Ethernet networks and, therefore, are open to Internet-
based access, the potential for greater collaborative operation and a freer work environment
increases. But so do the potential for security problems. Following are some basic tips and
considerations for achieving secure and reliable remote access:
1. Map out your project from the start. When companies fail to map out their
projects thoroughly from the start, they often find themselves saddled with applications
and automation products that don’t work cohesively as a single system. Once you start
implementing various silos—be they applications or products—things get more complex.
This is typical of problems that occur when automation products are implemented hastily,
without doing proper research, planning, or analyzing current and future goals, or without
realizing that implementing remote access monitoring for a facility is just step one of many.
2. Anticipate network interactions. When people have installed devices on a
proprietary network then try to use something different (e.g., Wi-Fi or another protocol),
individual systems may conflict. Or they may just cancel each other out, so that there is
no communication whatsoever. More often you find yourself managing so many different
applications, protocols, and systems that you have more work and headaches than you
imagined possible. This issue can be avoided if you select a network that is open and allows
everything to work together.
Automation World
3. Understand users and roles. Understanding users and their roles can have
a significant impact on how the remote access strategy evolves. In most control systems
operations, the roles that may require remote access to control assets may include, but are not limited to:
• System operators and engineers for local systems;
• System operators and engineers for remote systems;
• Vendors;
• Field technicians;
• Managed service providers.
The roles of users that would require remote access to mission-critical operations can
be extensive and the assignment of specific access depending on those roles can be
continued
complicated. Map out and document all acceptable access policies and procedures related to
allowable network access and coordinate this with industrial control system security experts.
Any user access that goes beyond simple viewing of data and permits changes to system parameters should be extremely limited.
4. Know your vulnerabilities. Beginning at the remote user and following the
connection to the data or service, remote access can be compromised at any of the
following points:
• The user or system can be impersonated to fool the target system.
• The attacker can use captured or guessed credentials to impersonate the user.
• The attacker can intimidate or coerce the user to provide valid credentials, or to
perform activities at the attacker’s demand.
• The user’s access device (laptop, PDA, etc.) can be attacked, compromised, and used to
access the control system network.
• The target system can be impersonated by an attacker to fool the user and thus gain
credentials or other information from the user system.
• Communication can be listened to by third parties anywhere along the
communication chain.
• Communications can have data injected into them by an attacker.
• Communication can be hijacked after it has been initiated (does not rely on
impersonation) or intercepted during initiation (impersonating both user and target,
also known as a man-in-the-middle attack).
• Parts of a communication can be replayed to a target, even if the attacker cannot
decipher the content (also known as a replay attack).
• The target communication software listening for requests can be attacked and
potentially compromised.
• An attacker can impersonate a valid communications node and gain access to the
underlying communications medium.
• A denial-of-service attack can happen to the authentication server (e.g., radius server or RAS).
• A denial-of-service attack can happen to the outward communication device
(e.g., an outside router for remote access).
continued
Automation World
The Smartest Instruments Still Need Smart Humans Automation suppliers having been building microprocessors and digital communications
capabilities into process control instruments for more than 20 years. By 2010, process
industries had installed an estimated 69.2 million field devices, according to a study by the
ARC Advisory Group, more than 60 percent of them microprocessor-based.
Despite that massive investment in intelligent instrumentation, the promised new world
of lower maintenance costs and significantly lower risk of process failures has not yet
arrived. Blame that, say the experts, on the difficulty of changing human behavior and long-
accepted practices. Others point to a lack of sustained management support for following
best practices.
Though nearly all of the instruments shipped today have built-in intelligence, companies
continue to follow the traditional inspect and test practices they used with analog devices. The lack of links from process instruments to digital communications networks also means
workers can access little of the information available from smart field devices, and even less is
actually used as intended to improve diagnostics and process control.
The result is hundreds of thousands of man-hours wasted every year on routine and
unnecessary maintenance, and processes that are no more efficient or safer than they ever were.
instrument what you want it to do. Then you have to create a backup database to maintain
configuration accuracy over the lifecycle of the device.”
Although traditional test and inspect practices work well for production assets like pressure
vessels and piping, which typically fail slowly over decades, automation assets such as
transmitters and valves are more vulnerable and can degrade quickly. That’s where self-
diagnostics are critical and where routine predictive and preventive maintenance practices
are of less value.
“The goal is to refocus maintenance on early problem identification so that operational
issues can be quickly resolved without all the expense and risk,” Storey says. “The diagnostic
information in intelligent instruments lets you anticipate problems and be proactive. It
doesn’t reduce the failure rate, it just reduces the impact of failures.”
Storey says condition-based monitoring and maintenance practices are starting to take hold
in a number of industry segments, such as machinery and offshore oil drilling. But for most
process industries, “making better use of diagnostics is not part of the culture. People are
focused on keeping things working, not managing assets well over time. A lot of things get
deferred. While a plant may run nicely for a while, it’s actually in decline.”
Industry has been doing inspect and test for years, he notes. “Doing asset management in a
different way requires a different culture, and the tools to do it well are poorly developed and
integrated.” Standards, he adds, will finally help establish accountability for following good
practices. “It’s not an instrument, an IT or a vendor problem; it’s a management problem.
Management engagement, accountability and metrics will drive behavior change.”
continued
Wireless a catalyst The adoption of wireless has been a spur to interest in intelligent instruments. Wireless
technology has allowed intelligent devices to be more useful at a lower power budget. Once they get more digital information, users want more multi-variable data for troubleshooting
and to gain insights into their process.
On the flip side, users are often overwhelmed with all the information they can get
from their instruments, says Erik Mathiason, a member of the ISA 108 committee and an
employee of Emerson Process Management. “They don’t know what to do with it. They’re
asking suppliers for help in accessing, managing and assessing the data. They want to
know, ‘What does it all mean?’
“That’s especially true with so much of the process industry workforce retiring. The younger
people are more open to change and hungry for information because they believe it will help
them solve problems. Younger people don’t have the instincts honed by years of experience
in a plant. Data is all they have.”
Human-centered designInstrument suppliers are working to make life easier for the process industry workforce. This
includes making products that are easier to use and have device dashboards that make it
easier to see data. Suppliers are spending a lot of time and money to learn how customers
need to interact with data. Many include dashboards to display data with a similar look and
feel across multiple devices, even though the devices might do different things.
continued
This human-centered design approach owes much to the model established by the consumer
electronics industry. Its goal is to design human-technology interactions around how people
learn, think and work.
“In the past, there were fewer device types and simpler devices,” Mathiason says. “That meant
workers did the same things to the same device types many times, building expertise. Today
there are more device types, and devices themselves are more complex. In addition, devices
are more reliable, so worker-device interactions are less frequent but more varied. The result is
unfamiliar human-device interactions and more human error.”
Studies show that up to 80 percent of abnormal situations are caused by human error. With
process plants staffed with fewer and less experienced workers, the potential for both minor
problems and major catastrophes rises exponentially. Consistent navigation and operation
across multiple devices, the foundation for human-centered design, can improve the
probability that the correct actions will be taken with fewer errors.
Modular components, multiple variables
Many suppliers are re-designing their instrument lines to make products more modular. The
redesigns frequently involve electronics, software and even mechanical components such
as connectors, which facilitate simple plug-in modules, allowing replacements to be made
easily in the field. Many have adopted a common platform across all instrument lines to make
devices easier for customer to use. This means all have the same programming requirements,
software interface and approach to diagnostics.
continued
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Another trend is the development of instruments that can measure multiple variables. End
users in the oil and gas industry, for example, want multi-variable instruments that will reduce
the number of pipe penetrations the company is required to make, as well as wiring, which will save on both installation and maintenance costs.
Driving adoption Intelligent transmitters are the most widely deployed intelligent instruments today,
outnumbering analog transmitters by an estimated two to one in heavy process industries.
Also popular are positioners for control valves and flow controllers, which are used in every
industry where custody transfer is critical in controlling process input costs.
Positioners provide maintenance technicians with critical information on a valve’s activity
and can help proactively determine what a reasonable maintenance schedule should be in a
process application. Industries that have been early to appreciate the value of intelligent field
devices include oil and gas drilling, refining, chemical plants, food processing, and biotech
and pharmaceutical companies.
Automation World
Managing for Reliability Key to Asset Performance
The powerful combination of smart devices and communication networks has great potential
for helping industrial plants achieve significant gains in productivity and efficiency. But
making that happen requires companies to use the information from their production
equipment to change their asset management and maintenance practices.
Take the example of two plants, owned by the same company but located on opposite sides
of the globe. The two sites made the same products, using identical production equipment,
quality specifications and automation systems. They both spent a similar amount of time on
maintenance. Yet one plant was experiencing constant failures, shutdowns and quality issues,
while the other was performing to goals. The question was, why?
Proactive vs. reactive maintenance
An analysis by an automation supplier found the answer. The findings revealed the root cause of the disparity: the plant experiencing difficulties operated under a run-to-
failure philosophy for maintenance, spending nearly 35 percent of maintenance time on
unscheduled corrective procedures.
In contrast, the plant meeting its goals spent only eight percent of maintenance time on
unscheduled activities. More revealing, 34 percent of their maintenance time was spent on
preventive maintenance, and another 12 percent on optimizing assets. Employees at the proactive plant also received more than three times the amount of training as those working
at the reactive plant.
Unfortunately, this lack of training is not uncommon at plants with a reactive approach to
asset management. Reactive managers assume it’s less costly to fix something only when
it’s broken and they know what to fix. They see training as wasted dollars. But industry
experts will tell you this is a mistake and results in frustrated engineers who take longer to
solve a problem and are unsure of the best practices to use to make sure the problem does
not come back.
Proactive-minded users, on the other hand, have seen the benefits of this service philosophy.
They see training and certification as an investment to ensure not only that results don’t
erode, but that production and quality performance continue to improve.
continued
Finally, decisions must be made about what technologies and what data to use to determine
asset health. Some examples include when and how often to measure motor vibration
or motor stops and starts, or whether to use wireless vibration sensors or wireless mesh networks, which make it easier for companies to get data from assets in places where it’s
difficult or dangerous for humans to reach.
How work gets done Having the right people resources and assuring they have the right skills or adequate training
is another important aspect of reliability management. It’s also essential to understand
how work gets done in a plant. It takes multiple people with different skills and properly
documented work orders that provide them with an understanding of what went wrong and what tools are needed to fix a device.
Often a process needs to be improved, streamlined and documented to improve asset
reliability. You also need really good KPIs such as availability and return on asset value, and
the ability to communicate all the findings in a work management system.
Smart devices that can diagnose their own health and provide in-depth process information
are key to improving asset management. With more network or wireless connectivity, more
information has become actionable. Software lets you analyze performance and detect a
problem long before it begins, so that an operator or maintenance technician can be alerted
to take action.
Getting the right balance The combination of the speed of technology change, the growth of automated systems and
the decline in the number of plant personnel with the experience and skill set to maintain those systems is causing problems for manufacturers in all industries. One automation
supplier conservatively estimates that 75 percent of all plants are running sub-optimally.
Systems are always degrading; even valves have moving parts.
The first step in addressing the issue is to get the right balance between predictive, proactive
and reactive maintenance. There is no magic number, no strict definition for what is a good
balance. Although most people will say that keeping reactive maintenance at 20 percent
or lower is optimum, the right service schedule depends on how critical an asset is to plant
and process performance, as well as company objectives in terms of variability, cost and
equipment wear.
Condition-based maintenance that allows you to repair or replace only what’s needed, vs. trial
and error work based on historical schedules, can save a typical plant hundreds of thousands
of dollars in costs and thousands of man hours every year.
continued
Measure First to Improve Control
System Performance Most continuous process plants have lost millions of dollars from poor control system
performance, yet many plant managers and engineers are unaware of these losses. To
capture savings, you must measure and manage the performance of your control system.
Basic steps, such as measuring the
percentage of the plant running in
manual mode, are a good place to
start. A typical process plant runs
with between 20 and 30 percent of
controls in manual mode. Consider
that a typical control loop costs
$10,000 or more. A typical oil refinery
may have 3,000 control loops, with 600 to 900 in manual at any given
point, representing a lost investment
of over $6 million. And that doesn't
even count the annual process losses,
which are at least as high.FIGURE 1 – Square wave /sawtooth pattern indicates valve stiction.
Some problems, such as valve stiction, have a unique signature pattern, as shown in
Figure 1. The square wave pattern on the process measurement and sawtooth movement
of the control output are a sure sign of valve stiction. The ladder pattern in the PV/CO plot shown in Figure 2 further confirms valve stiction.
Other problems, such as oscillations and interactions between
various parts of the process, need more sophisticated analysis.
Tools such as Fourier Transforms and the resulting power spectrum
chart, shown in Figure 3, can find the cause of oscillation problems.
Process Interaction analysis, as shown in Figure 4, can also be used to pinpoint the cause of a problem that may be far
upstream in the plant.
With the problems identified and prioritized, your focus can now
turn to managing the required repairs, tuning changes and process
adjustments. This work should be managed and organized like
any project: with specific plans, assignment of responsibilities and
expected completion dates. Some repairs may need to wait until
planned shutdowns, but others can be completed on the fly.
Finally, it is important to track the effect of these improvements. A
simple before/after trend can be very useful to show the results. Whenever possible, you should
also identify the economic impact of your work, and share it with your management team.
continued
FIGURE 4 – Process interaction map pinpoints the root cause of
process problems.
If you have enough staff at your plant, each of these steps can be accomplished in-house.
Experienced software and service suppliers can also provide all or part of these activities as a
service, starting with site evaluation and progressing all the way through capture of benefits and sustaining the results.
What kind of results can you expect? That depends, of course, on your starting situation. But
it is common to see reductions in variability that lead to energy savings, production increases
and quality improvement. Because automation system improvements have a direct effect on
process results, the return on investment is typically measured in months, not years.
continued
Measure First to Improve Control System Performance
This article was adapted from content provided by George Buckbee, P.E., ExperTune
10 Steps to Creating the
Perfect HMI When developing HMI screens, realize that you are attempting to capture the essence of
the machine or process, not just posting key automation variables and control mechanisms.
Operational feedback is vital for efficient HMI screen layouts. Think of yourself as an artist,
commissioned by manufacturing operations to create the HMI screens.
1. Less is more. It’s important to keep the HMI simple and with the operator in mind. It’s
best when it’s self-explanatory and easily understood. Also, try to make the pages similar and
follow the same page layout throughout. Avoid making the display too technical. It’s normal
for engineers to try to give the customer everything, but with HMI, less really is more.
2. Right-size displays. Don’t try to save money by selecting an HMI display screen that’s
too small. It’s also important not to cram too much information onto a screen. Size the display
according to the amount of information that is most important for the operator to see. Always discuss requirements with the equipment’s operators well ahead of time, not just with their
managers. Operators usually have different needs and the success of your system depends on
their usage.
3. Design tips. A good design requires careful use of layout, color and content. If you get
it wrong, your operator misses an indication, you lose money, or worse, someone is injured.
The ”bad” screen is less than satisfactory: The layout is poor, the plant representation isn’t
logical and the screen layout makes it difficult to locate the data. Poor selection of colors,
excessive use of capitals in a serif font and repetitive use of units with all data values makes
this a really difficult screen to read—especially at a glance or from a distance. Avoid colors that could create problems for people with color blindness. Minimize the use of colors to
allow actual device state and alarms to stand out. For alarming, choose colors that contrast
with the normal process view so the operator will notice the change.
4. Plant review forum. Hold a design review with a
group of plant personnel to discuss any status notifications,
events, alerts and alarms that need to be programmed,
both from the perspective of an audio-visual action and an operations response. Step through the intended functional
system, once as the designer, once as the user and then
invite at least two levels of users who will be interfacing with
the HMI. Doing this prior to specifying equipment helps to
identify the features that users will want in the HMI station. It
also avoids surprises at point of commissioning.
5. Location, location, location. Real estate can
be prime in a busy production area. Locate the HMI in a
practical place, out of heavy traffic areas but accessible. Be
aware of near-future projects in the area. Guard the HMI
location so others don’t park or configure something else on
top of the station.
6. Back up work periodically. Backups are especially important before implementing
upgrades or changes. Software such as Norton’s Ghost Image can be invaluable to support
and maintain HMI systems.
7. Visualize the process. HMI graphics should illustrate the production process in the
plant to provide better visualization to the operators, giving them a sense of the action that’s
required. Use hardware that meets minimum requirements and keeps the number of failure
points low and assures high availability of the system.
8. Only essential data. Make control and monitoring of the process simpler by
selecting only the most essential information from the process database for the historian. This
will reduce the load on the system and keep it from stalling or failing. Don’t forget the need
for maintenance and make sure you schedule periodic backups.
9. Think about flow. It is essential to have a clear design approach to the HMI. Decide
how the display blocks naturally flow and how sections need to be grouped together for the
operator. Do not blindly follow P&I diagrams. The S88 functional hierarchy is a good place to
start. Make paper-based designs to get a feel for screens, navigation and other requirements,
and review with clients prior to designing and making electronic screens.
10. Alarm strategy. Alarming needs to have a well-articulated strategy. Alarms
must be used for conditions that require intervention and must have a clear corrective
action associated with each one. Anything else should not be an alarm.
continued
Automation World
the Explosion-Proof Box Unlike explosion-proof schemes, which aim to contain explosions inside enclosures, intrinsic
safety keeps them from ever happening at all. Consider whether it makes sense for your
production environment.
As you develop your safety plan for a hazardous production environment, you might want to
move beyond the explosion-proof methods that have been popular for so many years in the
U.S., and start thinking outside the box. Particularly for process industries, it could be time to
take a closer look at intrinsic safety (IS).
Process automation is the sweet spot for intrinsic safety. “That’s where intrinsic safety shines,”
says James Wilkinson, senior applications specialist and technical support lead for MTL
Instruments, describing analog signals from level measurement on a tank, for example, going
back to a control panel. “Process automation is intrinsic safety’s world.”
That’s because intrinsic safety makes the most sense at low energy levels, where voltages
are 24 V or less, and currents are 300 mA or less. That makes it a good fit for field instruments
such as thermocouples, RTDs, pushbuttons, simple transmitters and low-power solenoids.
For variable-frequency drives, switch gears, Coriolis meters—anything high-voltage or high-
current—explosion-proof makes more sense.
If you’re running a plant where 90 percent of it is low-voltage, low-power instrumentation,
that’s when you need to

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