field calibrators & field management - control global
TRANSCRIPT
Field Calibrators
& Field Device
Management
eHANDBOOK
TABLE OF CONTENTSValidation in lieu of calibration 4
Adding simple checks between full verifications can raise reliability.
Calibrator communications 6
Verifying field devices involves specific demands that wireless could meet, if we let it.
Be strategic about CBM 8
Five mistakes to avoid when implementing condition-based maintenance.
Instrument specification 10
Look to the past to avoid the problems we’re seeing from trends in current practices.
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“Sometimes just OK is not OK,” says
the narrator of the cellular provid-
er’s TV commercial. The scenes
are humorous, as the befuddled customers
are confronted by lackadaisical service pro-
viders, whether a surgeon, auto repairman
or tattooist. In our discipline, we hope our
service providers have higher aspirations for
excellence. But for our ultimate end users and
the enterprise—who rely on our discipline to
provide interlocks that ensure the process
is safely parked when limits are exceeded, a
clear and unhindered view of complex and
processes to operators, and measurements
with the consistency and repeatability to sup-
port long-term forecasts for productivity and
reliability—are we exceeding “just OK?”
We read of and sometimes experience
instances where “just OK” failed. This might
mean the “squeaky wheel gets the grease” for
a spell, but it rarely results in a reconnoitering
of processes and priorities. As they read of
calamities that befall their peers and com-
petitors, corporate board members wooing
investors want assurance that their cash-pro-
ducing but complex and scary assets aren’t
going to make any headlines. Despite this,
adding positions like “instrument reliability
specialist” may be a dream, and even if we’re
authorized to create such positions, the com-
petition for competent I&C talent is intense.
How does one ensure the integrity of the I&C
system? Is there a preventive or proactive
maintenance scheme to perform and doc-
ument calibrations on a routine basis? Do
you scramble during infrequent process out-
ages to exercise instruments and interlocks,
and document any faults that would not
Validation in lieu of calibrationAdding simple checks between full verifications can improve safety and raise reliability.
By john Rezabek, Contributing Editor
eHANDBOOK: Field Calibrators & Field Device Management 4
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otherwise have been revealed? Are HAZOP
revalidations and other process hazard anal-
yses constantly identifying instances where
measurements are part of a vital “layer of pro-
tection?” Run-to-failure may be “just OK” for
fewer and fewer devices and systems.
If we’re challenged to physically validate a
measurement through calibration, i.e., apply-
ing a known, traceable standard to a device
and verifying all indications agree within toler-
ances, perhaps we can employ other features
or assumptions. For decades, designers of
safety interlocks have favored analog trans-
mitters in lieu of switches, i.e. low level in a
knock-out drum. Many such measurements
are now triplicated for fault tolerance as well
as reliability—two out of three must vote to
invoke an interlock or trip.
The old switch only needed to be accurate at
one point—the trip setting. Its downfall was
that any fault less self-revealing (such as, if the
switch was stuck), you wouldn’t know if you
didn’t test it. Now, when triplicated analog
transmitters are employed, it might suffice to
simply verify the trip point alone as opposed
to doing a five-point calibration. How import-
ant is it to know a level or a pressure within
the 1% tolerance you might enforce for cus-
tody transfer? If the trip point isn’t within
a hair’s breadth of the safe operating limit
(and why should it be), then that margin
might better dictate severity and frequency
for testing.
We have an array of flowmeters that
defy validation without using an external
meter-proving loop. One option might be to
perform a validation based on other mea-
surements. For a reboiler steam flow, an
energy balance around the tower can vali-
date it against other tower conditions, and
adequately surmise whether a flowmeter
is reading adequately. Simple relationships
between valve percent-open and flow can
identify candidates for further scrutiny—if a
flow is substantially less at the same operat-
ing point as a month ago, the procedure can
trigger an investigation or a more meticu-
lous calibration.
If we must tackle this challenge—achieving a
level of excellence that meets the expecta-
tions of our end users, without much infusion
of resources—we can explore opportunities to
exploit features of present-day systems and
measurement devices. We can exceed “just
OK” by creating some diagnostics to validate
key measurements, and examine them rou-
tinely. If you document your routine, it may be
enough to check the box for validating numer-
ous measurements, without exhaustive and
labor-intensive calibrations.
For a reboiler steam flow, an energy balance around the tower can validate it against other tower conditions, and
adequately surmise whether a flowmeter is reading adequately.
eHANDBOOK: Field Calibrators & Field Device Management 5
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With the increasing use of wired
and wireless digital communi-
cations, technicians and field
engineers are communicating with and per-
forming maintenance on field devices from
practically anywhere—and often not at the
transmitter face with screwdriver in hand to
“tweak the pots” unless necessary to force
a signal or isolate the device, as they would
when calibrating. Many practitioners believe
that because a digital transmitter is factory
calibrated for a wide signal range, and they
can configure the device anywhere within the
range, that calibration and configuration are
the same, which is certainly not the case.
Configuration refers to setting transmitter
parameters only, without any signal forcing
other than simulation of inputs, and thus
no traceability to a reference. Because they
don’t need to simulate input signals, sev-
eral configurators on the market are based
on a ruggedized, perhaps intrinsically safe
tablet or smart phone. These devices, in
addition to supporting the field protocol,
typically through a Bluetooth or USB acces-
sory/modem, also often provide WiFi- or
cellular-based Ethernet connectivity to
communicate with the enterprise mainte-
nance system and control system.
Calibration, on the other hand, is com-
paring the device under test against a
traceable reference instrument, and doc-
umenting the comparison. Therefore, to
calibrate a transmitter, the input needs to
be generated at the same time the output
is being measured. If the calibration is
done with a documenting calibrator, it will
automatically document the calibration
Calibrator communicationsVerifying field devices involves specific demands that wireless could meet, if we let it.
By By Ian Verhappen
eHANDBOOK: Field Calibrators & Field Device Management 6
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results. Fortunately, most calibrators with
digital communications at least have the
documenting capability, thus eliminat-
ing transcription errors while providing
time-stamped end-to-end traceability.
Unfortunately, some calibrators have limited
memory, and may only be capable of han-
dling as few as 20 data sets before needing
to be downloaded. On the positive side,
this will encourage technicians to download
their results every day, but the objective of
technology is to make life easier.
Another key consideration for calibrators
is their ability to isolate the input from the
output since, as we know, the simple act of
measuring something affects the measure-
ment. With calibrators, we’re both forcing
or inputting the measurement and measur-
ing the resulting output. In my experience,
running off battery is a great way to remove
one potential common-mode source of
error—the power supply, especially if it’s
an AC source. Mind you, I was using a lap-
top-based tool, so it would not have the
isolation that a properly designed industrial
instrument will, but it proves once again
that cheap and multipurpose are not quite
the same as dedicated and industrial.
The challenge with many calibrators is get-
ting the documenting information in their
memory into the main computer storage
platform. All calibrators communicate
with the calibration module that is, hope-
fully, part of or at least accessible from the
instrument maintenance system. The con-
nection between the calibrator and hosting
computer uses a wide range of technologies
from serial (tough finding computers with
this connection still) to the more common
USB interface, with the few that now support
Bluetooth about the only current wireless
option. There are also still some that require
manually pulling the SD card and installing
it in the calibration company’s standalone
proprietary software, then porting it from
there (sometimes as Excel files, though most
systems support SQL) to the enterprise’s
maintenance software for archiving and,
more important, access by QA and potential
statistical analysis and control.
Calibrators continue to get better, however,
as we can see, there’s still room to improve.
I’m confident we’ll soon see devices with
bidirectional communications directly from
the field to the quality system to support
and prompt technicians on their rounds,
while populating the central database. All
we’ll need then is the infrastructure in the
plant to make it possible; so once again we
have a Catch 22—no capable field devices
without infrastructure, and no infrastructure
because we don’t have enough capable
field devices to justify installing it.
Running off battery is a great way to remove one potential common-mode source of error —the power supply, especially if it’s an AC source.
eHANDBOOK: Field Calibrators & Field Device Management 7
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You’re likely aware of the concept
of condition based maintenance
(CBM): essentially, performing
the optimal amount of maintenance only
when required (and on your own sched-
ule). Much progress has been made on CBM
lately, including many successful program
launches. Yet, these programs are not
without risk. When considering your CBM
strategy, you should be aware of some
potential pitfalls:
Not involving everyone: When start-
ing a CBM system, a vital first step
is to ensure all key stakeholders are
involved, engaged and committed to
the plan. This may seem trivial, but sur-
prisingly, it isn’t always done for CBM
system deployments.
In one case, an engineer led a pilot pro-
gram and installed sensors that fed
predictive software, but the engineer only
gained partial commitment from the main-
tenance staff. The program struggled, and
didn’t gain much traction. This could have
been avoided if the maintenance staff
were more involved on the front end.
Likewise, integrating the CBM program
with the existing computerized mainte-
nance management system (CMMS) or
other specialized software must be con-
sidered. The closer the two can mesh,
the better. Your staff is probably com-
fortable using the CMMS to schedule and
track maintenance. CBM will enhance this
system, not necessarily replace it. Make
the integration between the two as simple
Be strategic about CBMFive mistakes to avoid when implementing condition-based maintenance.
By Bryan Christiansen, Founder and CEO, Limble CMMS
eHANDBOOK: Field Calibrators & Field Device Management 8
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as possible to ensure that your staff will
use both systems effectively.
Scoping too large: Buzzwords like smart
technology, IoT and Industry 4.0 may elicit a
variety of reactions from industry profession-
als. These reactions can vary from skepticism
to enthusiasm. However enthusiastic the
team is, it’s best to stay grounded in your
approach. A CBM program is perhaps best
viewed as a tool to help your operation. As
with any tool, it can help make things easier,
but it’s only valuable if used properly. Thus, a
broad scope implemented rapidly can quickly
becoming overwhelming and lead to a poten-
tial program failure. To fight this, start with a
pilot to learn and adjust before going all in.
Quantity over quality: An ambitious and
cost-conscious engineer may be tempted
to purchase as many low-cost sensors as
possible and place them everywhere in the
plant. This potentially introduces a new
problem of sensor administration, where
more time and effort are spent in replac-
ing cheap sensors than in using them for
improving maintenance.
Rather than multiplying sensors to gather
extra data, be more strategic in your
approach. Use quality sensors to gather the
most relevant information first. Further sen-
sors can be added as needs are identified.
No sensor management strategy: With the
potential influx of new sensors, you must
consider your sensor management strategy.
For example, how often will you check or
calibrate them? Will they feed data through
PLCs, DCS or a separate network? You will
want to find a balance between adding bur-
densome PM procedures, yet gaining value
from your new data insights.
Using wireless sensors adds more com-
plexities. A battery strategy will need to be
thought through. Consider how you’ll check
your device battery life, and at what thresh-
old you’ll respond. Who will be responsible
for this task? A good CMMS integrated with
your CBM sensors will solve a lot of these
complexities. All these questions should be
answered as part of your CBM deployment.
Security strategy not considered: The
proliferation of wireless technology allows
cost-effective and rapid deployment of
CBM. Particularly in areas with electrical
classification requirements, the cost savings
in avoiding specialized wiring are consider-
able. In the past five years, the possibilities
of electronics in manufacturing have
increased substantially.
Allowing communication between PLCs
and business LANs has great risks. The
possibility of manipulating a machine from
an external network must be eliminated.
A good understanding of proper network
architecture (DMZs, process LAN vs. busi-
ness LAN, etc.) should be a requirement of
your CBM strategy.
eHANDBOOK: Field Calibrators & Field Device Management 9
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Greg: Instruments provide the view into the
process and means of controlling it. If they’re
not telling the truth, we’re in serious trouble. If
you can’t measure it, you can’t control it.
Mike Laspisa offers his insights as to where
we are now and where we should be with
instrumentation specification based on
37-plus years working in the instrumenta-
tion and control (I&C) discipline, including
32 years as a lead I&C engineer or manu-
facturing plant staff I&C engineer. I spent
most the of the 1970s in instrument and
electrical (I&E) design and construction, and
to this day, the performance of instrumen-
tation is foremost in my mind. Mike’s goals
are very similar to mine in terms of wanting
to share our knowledge often learned the
hard way to help automation engineers do
what’s best.
Mike, what were the original intents and
methods for I&C specification from the late
1970s to the late 1980s?
Mike: Field device importance was held
in high regard. Measurement and control
device specification was a science, and
could only be learned on the job. I&C engi-
neers were considered an important asset
by both the company and the client. Instru-
ment engineers specified measurement
devices, and selected and sized control
valves, regulators and safety relief devices
using process data, process and instrument
diagrams (P&IDs), and pipe specs. A control
valve outside sales engineer would review
the engineer’s selection and discuss difficult
applications. Valve sizing calculations were
always done by the engineer doing the
valve specification.
Instrument specificationLook to the past to avoid the problems we’re seeing from trends in current practices.
By Greg Mcmillan
eHANDBOOK: Field Calibrators & Field Device Management 10
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Device selection took into account both
application requirements and device
cost. However, performance was the pri-
mary selection criteria. Process data was
analyzed by the I&C engineer for each
measurement and control application,
including control valve sizing pressure
drop, flow measurement turndown and
multiple case studies, if applicable. Accu-
racy, advanced control strategies, ratio
blending, batch addition resolution and
many other requirements were discussed
with process engineers during joint P&ID
development.
However, mass flow measurement choices
were limited (e.g., load cells, weigh belt, and
volumetric flow with pressure and tempera-
ture compensation by remote electronics or
computational module).
Greg: How would you describe our current
situation?
Mike: Project bottom line focus has led to
cost-effectiveness becoming almost more
important than performance in instru-
mentation and control device selection.
In addition, I&C device vendors are being
asked to select/size field devices more
often based solely on the data provided
on a datasheet. A reduced budget for I&C
specification work is now expected for proj-
ects and by some clients. Unfortunately, I&C
device vendors are using a younger inside
sales force that seems to rely mostly on
software for quotations without the expe-
rience to ask the right questions or quote
needed accessories.
Fast-track engineering has almost become
the standard. This sometimes leads to pre-
paring I&C device specifications without
the necessary information to specify them
completely. Also, process data is usually
provided late, and is furnished incomplete
or in partial installments. I&C engineer value
or project early involvement is questioned
by project management. Process or some-
times even project engineers think they
can make the early decisions on required
I&C devices, or assist the client in P&ID
development.
Relying on vendors to select and/or size
I&C devices has negatively impacted devel-
opment of I&C specifying engineers. This
has this led to I&C engineers not question-
ing process data and issuing incomplete
datasheets. Reduced budgets and fast-
track engineering have also compromised
the datasheet checking process. The focus
now appears to be more on checking tags
against P&IDs rather than application infor-
mation (sizing, materials of construction,
end connections/rating, pipe specs, etc.)
and the completeness of the critical pro-
cess data required to support the sizing and
selection of the device.
On the other hand, there are some bright
technology developments that have made
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I&C device applications easier (and more
forgiving), such as mass flowmeters,
smart transmitters with wide rangeability,
multivariable transmitters, radar level trans-
mitters and digital valve positioners.
Greg: I&C engineers should ask process
engineers what accuracy is required. In
my experience, the accuracy they want is
aggressive and was often not achievable
until recently.
Mike, how does this history or commentary
relate to instrument specification work at
engineering, procurement and construction
(EPC) firms?
Mike: When I was reviewing project work
before I retired, I observed a number of
specification deficiencies that included
incomplete or incorrect datasheets. Cal-
ibrated ranges didn’t always take into
account the minimum, normal and maximum
process requirements and sensor rangeabil-
ity. I’ve seen datasheets where the vendor
was to select the device size, model, trim,
etc. from limited or possibly unintentionally
skewed information (e.g., all globe valves
with 5 psi valve drop for sizing, regulators
using pilots where they weren’t required,
etc.) Some specific application requirements
(e.g., magmeters missing ground straps/
rings/ground electrodes; flow primary ele-
ment selection not compatible with process
pipe/duct; analytical probe connection
requirements not considered during spec-
ification; level measurement selection not
compatible or practical for application) were
not specified correctly. Is this a checking
issue, a philosophy issue (i.e., leave it up to
the vendor whenever possible), or a misun-
derstanding of what is required?
The interface with piping designers, includ-
ing in-line installation detail preparation,
is more after-the-fact than timely to the
piping design effort. Packaged system
instrumentation is a shared responsibility,
but process design usually is in the lead.
Historically, I&C does not get involved
with the measurement requirements, only
the hardware preferences, control system
choices, and device signal levels.
Greg: We have to be especially careful to
make sure packaged equipment suppliers
use the latest and best technology consis-
tent with plant standards.
On the other hand, there are some bright technology developments that have made I&C device applications easier
(and more forgiving), such as mass flowmeters, smart transmitters with wide rangeability, multivariable transmitters, radar
level transmitters and digital valve positioners.
eHANDBOOK: Field Calibrators & Field Device Management 12
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Mike: The package instrumentation, control
devices and control system (including the
interface with the plant control system)
must meet the equipment specification
expectations/requirements (e.g., manufac-
turer or equal, type or series, and control
system preference). There have been many
examples where the plant standards or even
preferred vendors were ignored to save
money by accepting OEM devices well after
the specification phase.
Greg: What’s needed for a much better
future in the specification of I&C devices?
Mike: Better use of appropriate instru-
mentation and control device learning
opportunities (courses, exhibitions, free
vendor/manufacturer seminars, lunch-and-
learns, asking a lot of intelligent questions
and mentoring). Provide internal or external
technical resources to discuss device-type
applications during datasheet preparation.
Develop the preferred role of vendors and
I&C engineers in selection and sizing of I&C
devices. Discuss the expectations for instru-
ment process data analysis. Determine the
critical data fields or notes for the different
I&C devices. Datasheet checking must cover
technical content as well as device checks
against P&IDs for tag and service.
In addition, see the “Instrument Data-
sheet Preparation Flowchart” for the
recommended approach to specifying
instrumentation and control devices.
Develop a standard naming convention for
instrument package workbooks, worksheets
and archiving. Discuss vessel connection
responsibilities, requirements and impact
on device specification. EPC firms need
to get I&C engineers more involved in the
packaged equipment system specification
process and bid review. Process engineers
commonly use vendors to create their pack-
age specifications, but they rarely have an
I&C engineer involved in any conversations
or meetings.
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