A BRIGHT FUTURE FOR WIRELESS TECHNOLOGY W

A BRIGHT FUTURE FOR WIRELESS TECHNOLOGY W
AS SEEN IN THE WINTER 2010 ISSUE OF...
A BRIGHT FUTURE FOR
WIRELESS TECHNOLOGY
W changer, especially when it comes
ireless technology is a game
to process control. Wireless lowers
implementation costs, expands access to
information and allows control in areas
previously held back by technical or economic barriers. Inevitably, approaches to
process monitoring and operations will
change when proven wireless technologies are used. In fact, wireless operations
will reinvent traditional approaches to
valve monitoring and control strategies
and offer many compelling uses for
remote and hard-to-reach locations,
which is particularly useful in the area of
automating manual valves.
The technology and the information it
provides is already used to eliminate three
common headaches: the time and effort it
takes for manual audits; the amount of
occasions in which someone is sent into
undesirable conditions; and product variances, which when reduced can improve
product quality. This article is focused not
just on the current value of wireless valves
but on what the future holds and where
this technology can make changes in the
approach to controls.
Today, manually operated valves generally are not used in control situations where
access is restricted; however, knowing the
state of those valves is important—especially after they have been used (e.g., a
clean-out valve on a chemical reactor).
Manual valves in control valve applications
are used when adjustment periods are long
(oil and gas production, transmission, etc.).
Increased position feedback information
can provide early indication that a valve is
not moving as expected or is stuck before
the situation affects the process or final
product.
Wireless will connect manual valve
feedback to an increasing number of automated controls. The result will be
improved operations and safety; one
example is adding a manual clean-out
valve to an interlock where filling the
chemical reactor will not occur unless the
1 | Valve M A G A Z I N E
Industry has a watchdog that can save costs,
provide reliability and allow more confidence that
our valves are in good health and operating at
peak capacity.The technology can also work
toward a safer work environment and provide
more information for improving processes.
BY KURTIS JENSEN
© 2010 Valve Manufacturers Association. Reprinted with permission.
valve is closed. This simple change does
three things to improve process reliability: it protects product quality, it protects
against scrap or rework, and it protects
against clean-up actions. The end result
is a more reliable process and greater
confidence that all is well.
Wireless also enables reduced
resources needed to verify a valve’s state.
Many mistakes are made in batch
processes where valves are left in the
wrong state. Therefore, increasing the
amount of valve information leads to
greater assurance, providing proof to
management that operations and safety
improvement actions are achieving
desired results. Using wireless to improve
awareness has already proven itself in the
chemical industry.
Early successes in wireless lead the
way in addressing other operational pain
points, as well. The industry-wide need
and desire to increase safety means the
percentage of manually operated blind
valves will decline while valves equipped
with feedback will increase.
ADVANTAGES OF VALVE
AUTOMATION
Manually operated valves are automated
for three primary reasons. First, moving
the valve may require too much manual
effort. Second, it may be desirable to
eliminate having personnel in dangerous
conditions such as precarious heights or
hazardous environments. Third, it might
be necessary to reduce complexity and
time needed to coordinate valve adjustments during plant operations.
Valve uses are divided into two uses or
categories: on/off or control. On/off
valves are generally used for bypass,
sampling and batching, as well as used in
series with a control valve for shutdown
or tight shutoff.
A large number of operations have
some on/off valves that are not monitored for position—they are equipped
solely with a solenoid to move the valve.
About half of these semi-automated
valves have no position feedback
because of cost or practicality of obtaining the position feedback information.
Obtaining feedback for an on/off valve
has required the use of two sets of wires,
one for open and another set for closed;
cant improvements on these old valves as
with new projects. Facilities that implement wireless feedback have the competitive advantages of operating cost reductions, improved product quality,
increased production volumes and
increased levels of safety.
ADVANTAGES OF WIRELESS
these wires are connected to simple discrete inputs at the control system.
Applications using control valves
have process feedback called “process
variables,” which include pressure, temperature, level and flow. Without a
process variable, the control loop is
called “blind.” Control loops are not
typically blind—a valve is moved and a
process variable changes. However, the
valves themselves may be blind, in
which case a command is sent to change
valve position and the process variable
is used for feedback. (No valve position
feedback is used.) These valves are
equipped solely with an I/P (current to
pneumatic) transducer, pneumatic or
electro-pneumatic positioner. Again,
position feedback can affect cost or
practicality of the operation. A single
set of wires is used for feedback (which
means less wiring expense as compared
to on/off valves), but is connected to an
analog input at the control system,
which is typically more expensive than
discrete inputs used for on/off feedback.
Until now, targeting existing valves
for improvements has been rare because
it has been a hassle and headache to
make changes to wiring infrastructure as
well as control I/O. Wireless is already
changing approaches to new projects and
installations because it eliminates wiring
and creates simplicity. But the largest
opportunity for improvement is with
valves already installed. Knowing more
about a valves’ health enables better
decisions and faster maintenance. It is
just as simple and easy to achieve signifi-
© 2010 Valve Manufacturers Association. Reprinted with permission.
In places where valve position monitoring
does not currently exist, wireless monitoring provides a way to use monitoring
technology with minimum risk.
Other compelling advantages of wireless over wired monitoring include:
䡲 Wireless is easier to install because
there are no wires. The devices can
be battery-powered and operate for
5 to 10 years in process environments. WirelessHART position
feedback devices, for example, are
very energy efficient and update
rates of 4 seconds will still provide
10 years of service without changing the power module.
䡲 Wireless devices can be implemented at 10% to 20% of the cost
of wired. An on-going cost of battery-powered devices exists; however, with life expectancies of 7 to
10 years, that burden is reduced
considerably.
䡲 Wireless instruments can be implemented in a matter of minutes and
require fewer people for the
process. Remember, battery-powered devices have no conduits or
wiring at all—they are simply
mounted to the valve. Feedback
from a manual valve has incredible
value, especially for safety. This is
why retrofitting existing valves
makes sense.
䡲 Wireless devices often require
fewer changes to drawings and
less engineering resources. Fewer
review meetings result in faster
project completions with less people involved.
䡲 Wireless can be installed in locations where wired devices cannot—in hard-to-reach locations,
areas hazardous to plant personnel or where power doesn’t exist,
running wires is not allowed or is
prohibitively expensive. These
Winter 2010 | 2
W I R E L E S S
T E C H N O L O G Y
wireless devices have features
similar to intrinsically safe (IS)
instruments and PDAs that are
already in use in these locations.
䡲 Hazardous area approvals and certifications are less complicated,
especially in locations that require
explosion-proof ratings. Because
wiring and conduits into the device
are eliminated, IS certifications
are superior; they are by their very
nature energy-limited and will not
be a source of ignition. No source
of ignition means no containment
is required as well.
䡲 Wireless devices operate on low
voltage and low current, can easily
be adapted to external power and
can eliminate battery maintenance
concerns. These power sources can
also be IS certified. Installing to
use local power is significantly less
costly than running I/O wiring back
to a control room. Another option
for power sought by some customers, especially in remote locations, is solar panels.
The speed of wireless is getting closer
to wired; monitoring devices are available with one-second update rates.
When choosing the appropriate update
rate for the device, battery life must be
considered. The transmission of data is
getting smarter through sampling the
position and only sending updates when
the valve position actually changes,
which speeds up the process and lowers
overall energy consumption.
RELIABILITY
An early concern with wireless technologies was that they were not as reliable
as wired technologies. This was because
early wireless technology was strictly
point-to-point; picture a couple of tin
cans with a string between them. If you
did not have a straight line, also called
line-of-sight, between the two devices,
the chances of solid communications
were eliminated. Also, line-of-site solutions require costly site surveys. Those
problems have been addressed.
Today’s technology—mesh networking—provides 99.9% reliability (for
WirelessHART technology). With the
advent of mesh networking, the tin can
scenario was replaced by a spider-weblike network for communication that
eliminates the need for site surveys. The
distances between instruments in a WirelessHART mesh network is 200 meters,
for example.
Every device is connected to other
devices to form this mesh, which greatly
increases the number of paths of communication as well as eliminating the
requirement that a device be within a certain distance of the gateway. If one path
fails from something such as a temporary
construction project blocking a communication path, another path is automatically used without intervention. The
result is very high reliability that in many
aspects exceeds wired I/O.
For wired, a single set of wires runs
between the input and output channel in
the cabinet room to the conduit tray to the
transmitter or valve. On the other hand,
wireless is not subject to problems such as
a broken cable from a situation such as
when a fork lift runs into a cable tray.
Understanding Wireless Standards
Wireless valve communication offers many advantages, but
can sometimes be confusing. There are many ways to set up a
system, and they are governed by different standards. How do
you choose? Here’s a brief summary.
The layout or topology of a wireless network defines which
nodes talk to which other nodes. Any wireless system has to
have both end devices (mounted on valves, actuators or sensors) and a gateway to connect to a control system or an operator display. The end devices are generally very low power battery-operated units that spend most of their time asleep to
save energy. The gateway to the rest of the world is generally
powered by the AC mains. A system in which the end devices
talk only to the gateway is called a “star” (think of the gateway as the center and the end devices as the points). Since the
end devices have fairly short transmitting range, this tends to
limit the physical size of the system.
If the end devices can hear each other and pass along any
messages they get to the next node in the system until they
reach the gateway (in other words, they can act as routers),
the system is called a “mesh.” A mesh can be much larger geographically than a star because end devices only have to be
heard by the nearest other end device, not by the gateway. In
addition, a message can take any path it must to get to its destination; if one node fails or its signal is blocked, the message
automatically finds a new route.
Some systems have what amounts to a mesh of routers,
3 | Valve M A G A Z I N E
with each router acting as the center of its own star; this is
called a “hybrid” or “star cluster” network.
Wireless systems are governed by a number of different
standards, with varying topologies and other characteristics
and with support from different groups of vendors. At the lowest level, where such things as operating frequencies and
methods of transmission are decided, most of them follow the
IEEE 802.15.4 standard. But not all do, and even those that
follow IEEE 802.15.4 aren’t necessarily compatible. There
are systems that follow ISA 100 (specifically ISA 100.11a).
There are WirelessHART systems. There are ZigBee systems.
All of them work, but not with each other.
One system that doesn’t comply with IEEE 802.15.4 is
Bluetooth. This is used a lot for things like cell phone earpieces
and laptop computer mice, but there are industrial uses for it
as well, including setting up and configuring smart valve actuators.
When considering wireless it’s important to ask a few questions: Will the wireless system connect to an existing Profibus,
Foundation fieldbus or Modbus network? Will it connect to
Ethernet? Would a mesh, star or hybrid layout be best? How
much area will it cover?
For more detail on wireless standards and topologies, take
a look at the article “Sorting out wireless standards for smart
valves and actuators” on ValveMagazine.com.
—Peter Cleaveland, Contributing Editor
© 2010 Valve Manufacturers Association. Reprinted with permission.
SAFE OPERATIONS
Security is critical to data reliability.
Wireless network standards employ security measures similar to those used for IT
(information technology) systems.
Several important elements come into
play with wireless transmission security.
The first is encryption, which is a method
of using seemingly random symbols that
surround each transmission.
With wireless transmissions, encryption keys are adjustable to match security
requirements that are designed to change
before the transmission data can be intercepted. The IT systems can set how often
these encryption keys are changed. In
addition, each transmission must be
authenticated, meaning that the sending
and receiving devices must recognize
each other. If those devices do not recognize each other, the transmission is
ignored. The data is also verified by the
receiving device.
Specific authentication and verification rules are built into each transmitter
so no foreign devices can intercept a
transmission or send bogus information
to the receiving station.
Another advantage of wireless mesh
networks is channel-hopping, which protects against frequency jamming by intentional or unintentional sources. If a channel or frequency does not work, the
devices automatically make use of 15 different frequencies without user intervention. The wireless transmitters communicate their data to a network access device,
also called a gateway. End users also may
choose to install redundant gateways to
eliminate the unlikely event that a particular gateway fails in critical applications.
Channel-hopping coupled with the multipath networks, as well as redundant gateways, provide a solid infrastructure to
move forward safely and securely with
complete wireless operations, including
critical and control applications.
USING THE DATA
The first uses with the new wireless data
will be with interlock systems. In this
case, actions will not be taken unless a
piece of equipment is in the correct
state. Referring back to our earlier
example of a manual clean-out valve
where filling the reactor will not occur
unless the valve is closed—an interlock
system would not allow the process to
move to the next stage unless the valve
is closed. Today, such action is sometimes completed manually by sending
someone to the valve and verifying its
position before transitioning the
process. Along with requiring human
resources, this can slow down a process
while automation could improve
throughput and increase consistency by
reducing the possibility of transitioning
the process without actually checking
valve position.
New information can also be stored
in repositories where it is analyzed and
used to make improvements in processes. These improvements lead to greater
confidence in operations. An example
of this would be with forensics such as
situations in which equipment state is
needed to understand what happened
just before an incident or when faulty
or out-of-specification product is produced. Added information can reveal
corrective actions that can improve
safety and reduce accidents. An example is a valve not completely closed on
a chemical reactor during a specific
phase—when a vacuum is pulled on the
reactor, air could be allowed into the
vessel, which could negatively affect
the product.
Such improved data on processes historically has been associated with highend control systems. However, it is possible to store information in generic SQL
(Structured Query Language) databases,
so that common office applications can
interface with the data easily and without
expensive control system software. More
frequently, data mining (database
queries) would result in greater awareness of the state of processing equipment.
© 2010 Valve Manufacturers Association. Reprinted with permission.
Internal and external regulations are
increasingly asking for information about
equipment health. The information gathered from wireless devices can be used
for audit purposes and may demonstrate
regulatory compliance.
A WINNING SITUATION
Automated valves can be coordinated
with simple interlock controls, such as
PLCs (programmable logic controllers),
while PID (proportional integral derivative) control can be interfaced easily
with control systems. Gateways are
generic in design—they connect the
wireless field devices’ control systems
and databases and can communicate
with many types of equipment that use
different communication languages. The
result is easy integration with whatever
control package is in use. The automated valves and control loops of the future
will leverage open standards such as
WirelessHART so designers can choose
from a variety of suppliers and replace
devices without replacing the entire network or control system.
Wireless makes valve monitoring
more feasible and encourages more
valve automation. Because of this, many
plant operations are already embracing
position monitoring and looking toward
wireless valve automation and control in
the near future. Designers of control
strategies will take advantage of wireless valves to enable greater control as
well as greater process and equipment
health awareness, all of which results in
greater confidence in operations and
processes. Designers going forward will
be well equipped to go to management
with new wireless projects armed with a
proven track record. VM
KURTIS JENSEN is an instrument product manager
at Emerson Process Management, representing
Fisher and Valve Automation Products. His
responsibilities include control accessories and
related field instrumentation. Reach Jensen at
[email protected]
Winter 2010 | 4
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