Efficient Plant April 2019 - 18

feature | information technology
 Advantages:
» Wi-fi is easy to install and use.
» It can leverage common Bluetooth
technology.
» Mobile devices to download data are
readily available.
» Cellular connectivity or VPN tunnels
provide secure data transfer.
 Disadvantages:
» Mobile devices must be within 50 ft. of
sensors to download data.
» Wirelessly transmitting data with
Bluetooth [see comment above] quickly
drains sensor batteries.
» Wi-fi captures limited equipment data,
and battery-life limitations prohibit
full-spectrum analysis.
» Numerous teams are required to collect
data at large facilities.
» Teams typically only collect equipment
data once a month.

BOOSTED WIRELESS
Another method uses a repeater to extend the
900-MHz wireless signal as much as a mile.
The repeater eliminates the need for maintenance teams to walk throughout the facility,
saving time and labor. The receiver sends the
data to a cloud or onsite system for analysis.
As with traditional wireless, equipment sensors transmit by way of Bluetooth technology,
which can drain sensor batteries over time. To
save battery life, sensors only take a snapshot
of equipment performance every 15 minutes.
While this can include more than vibration data, it doesn't capture a full-spectrum
analysis on all assets. Personnel can, however,
collect full-spectrum analysis on assets that
trigger vibration alerts.
 Advantages:
» Sensors can transmit information as
much as a half-mile, eliminating the
need to walk within 50 ft. of the equipment to collect data.
» Boosted wireless is scalable, with
some repeaters capable of supporting

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250 sensors and some receivers capable
of supporting 300 sensors.
» Cellular connectivity or VPN tunnels
provide secure data transfer.
 Disadvantages:
» Because boosted wireless uses Bluetooth
technology, sensor-battery drain is still
a problem.

New technology
can overcome
disadvantages
of existing
networks.
» Bandwidth and battery-life limitations
prohibit full-spectrum analysis on all
assets.
» Boosted wireless can be expensive,
depending on the size of the plant and
number of repeaters and receivers
required.
» Supporting equipment requires a large
footprint.
» Receivers require a line of sight with
sensors, as obstructions can block or
weaken wireless signals.

MESH NETWORKS
Mesh networks can be tricky to explain. In
short, wi-fi and boosted wireless networks use
a single line of communication to transmit
data from a sensor to its final destination.
In a mesh network, sensors placed across a
facility serve as multiple access points, each
communicating with other sensors across the
network. If one sensor drops the signal,
another one picks it up. It's similar to a circuit:
a wireless network is like a series circuit, where
everything is wired together, and a mesh network is like a parallel circuit, where there are
multiple paths for electricity to flow.

These types of networks hold significant
potential for large facilities in that they can
create a virtual blanket of connectivity over a
plant, increase data-transfer speeds and allow
engineers to collect more of the data required
for 24/7 asset-health monitoring and predictive analytics.
The drawback of a mesh network is the
potential for "hive collapse." A collapse occurs
when a sensor fails and all of the other sensors
begin receiving the signals dumped when the
first sensor stopped transmitting. Then more
data gets transmitted to fewer sensors. As
sensors become stressed by picking up additional signals, they too, can fail. This process
continues until the volume of data is too much
for the mesh network to handle and it shuts
down.
 Advantages:
» Mesh networks support long-distance
transmission. Sensors can be placed as
far as 164 ft. from each other.
» These networks are also capable of
transmitting full-spectrum equipment
data, including vibration, temperature,
pressure, flow rates, torque, and thrust.
» Sensors automatically determine the
most reliable path to send data, which
means faster and more reliable data
transmission.
» There are no line-of-sight requirements
with equipment sensors.
» Less supporting equipment is required
compared to wi-fi and other wireless
networks, which translates as smaller
footprints and lower setup costs.
 Disadvantages:
Since mesh networks operate at 2.4 GHz,
there's potential for interference from radio
signals and other atmospheric conditions,
leading to reliability concerns.
» Installing a mesh network requires
detailed site mapping to ensure complete
facility coverage.
» As more data is transmitted, a network
can be strained, leading to hive collapse.

APRIL 2019

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Efficient Plant April 2019

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