Maintenance Technology July 2017 - 24

ENERGY EFFICIENCY

that can allow a compressor to run at
lower pressure, saving energy. If you do
upsize piping, install a large receiver
as well.

Increasing pressure adds to a compressor's
load and increases energy consumption.

Misconception: Increasing
pressure solves problems.
Marshall described what seems to
be a common low-pressure-detecting
instrument in many plants-a phone.
"If compressed-air pressure gets low," he
said, "production will call and complain,
and the compressor operators will
jack up the pressure." This may solve
production issues, but it also causes a
problem in the compressor room. That's
because, for every 2 psi of additional
compressor discharge pressure, power
input per unit of flow increases by about
1%. This manifests as higher power bills
for the same amount of compressed
air, and produces more heat inside
the compressor, which can lead to
shutdown, extra maintenance costs, and
air-dryer problems.
"Many times," Marshall said, "pressure
problems are only temporary, often
caused by production areas doing
something strange with compressed air.
They can also be caused by poorly sized
piping, connectors, and hoses at the end
use."
Another problem with extra pressure
is that all unregulated compressed-air
consumers, i.e., leaks, will use almost
1% more air for every 1 psi in extra
discharge pressure. This increases a
compressor's load, leading to more
energy consumption.

Misconception: Change filters
only if differential reads high.
Filter-pressure differential is one of the
most common and largest single pressure restrictions found in compressedair systems. According to Marshall, plant
personnel often wait to replace filters
until the differential-gauge needle (if
there is one) points to a high level (often
there are red and green indicators). Or,
they simply ignore filter replacement.
"Replacing filters based solely on
pressure differential," he explained, "is
problematic because most filters aren't

24 |

MAINTENANCE TECHNOLOGY

running at rated flow where the differential gauge is calibrated." This means
an occasional glance at a filter during
average loads won't reveal any problems.
At high flows, though, the filter may
develop excessive pressure differentials,
causing low-pressure problems in the
plant.

Misconception: Air dryers don't
improve efficiency.
Air dryers are another often-forgotten
part of compressed-air systems with
regard to energy efficiency. Marshall
stressed that it's important to choose air
dryers that turn themselves down under
light load conditions.
The choice of air dryer can save
significant extra power, especially if your
system has periods of light loading.

Misconception: Use VSD compressors anywhere, any way.
Marshall described variable-speed-drive
controlled compressors (aka VSD or

LEARN MORE

VFD compressors) as game changers
for plants. "Where VSD compressors are
applied properly," he said, "the savings
are substantially greater than with
fixed-speed units, especially for singlecompressor systems with significant
periods of light load." In fact, use of such
units can often double the savings gained
by other efficiency measures. Problems,
though, can occur when these advanced
technologies are misapplied or installed
in poor locations.
It's important to properly size and
control VSD compressors when using
them in multiple-compressor systems.
The required pressure settings are
different fixed-speed-compressor
systems. Use of VSD units in applications with high temperatures, large
amounts of ambient dust, and/or poor
power quality is not recommended.
In such cases, savings can be realized
with fixed-speed compressors, using
other types of capacity controls or with
sequencing control. MT
Ron Marshall has spent more than 22
years working with compressed-air
systems, first as an industrial systems
officer with Manitoba Hydro, and since
his retirement, as owner of a compressedair consulting company. Contact him at
ronm@mts.net.

For additional information, see:

"Who Cares About Compressed Air?"
maintenancetechnology.com/2016/08/cares-compressed-air/
"How Much Is Your Air System Really Costing?"
maintenancetechnology.com/2011/05/how-much-is-your-air-system-really-costing/
"Re-commission Your Compressed Air System"
maintenancetechnology.com/2015/12/compressed-air-challenge-re-commissionyour-system/
"Show Me the Money"
maintenancetechnology.com/2015/03/compressed-air-challenge-show-me-themoney/
"Don't Ignore Compressed Air Filters" maintenancetechnology.com/2016/05/dontignore-compressed-air-filters/

JULY 2017


http://www.maintenancetechnology.com/2016/08/cares-compressed-air/ http://www.maintenancetechnology.com/2011/05/how-much-is-your-air-system-really-costing/ http://www.maintenancetechnology.com/2015/12/compressed-air-challenge-re-commission-your-system http://www.maintenancetechnology.com/2015/03/compressed-air-challenge-show-me-the http://www.maintenancetechnology.com/2016/05/dont-ignore-compressed-air-filters

Table of Contents for the Digital Edition of Maintenance Technology July 2017

Editorial
Uptime
On The Floor
Powering Auto Production
Following The North Star
Flying Inspections
Untangle Compressed Air Misconceptions
Change Your Lubrication Mindset
HMI-Design Essentials For Today's SCADA Systems
SAP: Tips and Tricks
Cybersecurity Best Practices
Bearing Storage
Interpreting IP Code
Noisy Pumps
Move From Time- to Condition-Based Lubrication
CMMS Energizes Maintenance Efforts
Products
Ad Index
Showcase
Final Thought
Maintenance Technology July 2017 - 1
Maintenance Technology July 2017 - Cover1
Maintenance Technology July 2017 - Cover2
Maintenance Technology July 2017 - 1
Maintenance Technology July 2017 - 2
Maintenance Technology July 2017 - 3
Maintenance Technology July 2017 - Editorial
Maintenance Technology July 2017 - 5
Maintenance Technology July 2017 - Uptime
Maintenance Technology July 2017 - 7
Maintenance Technology July 2017 - On The Floor
Maintenance Technology July 2017 - 9
Maintenance Technology July 2017 - Powering Auto Production
Maintenance Technology July 2017 - 11
Maintenance Technology July 2017 - 12
Maintenance Technology July 2017 - 13
Maintenance Technology July 2017 - 14
Maintenance Technology July 2017 - Following The North Star
Maintenance Technology July 2017 - 16
Maintenance Technology July 2017 - 17
Maintenance Technology July 2017 - Flying Inspections
Maintenance Technology July 2017 - 19
Maintenance Technology July 2017 - 20
Maintenance Technology July 2017 - 21
Maintenance Technology July 2017 - Untangle Compressed Air Misconceptions
Maintenance Technology July 2017 - 23
Maintenance Technology July 2017 - 24
Maintenance Technology July 2017 - Change Your Lubrication Mindset
Maintenance Technology July 2017 - 26
Maintenance Technology July 2017 - HMI-Design Essentials For Today's SCADA Systems
Maintenance Technology July 2017 - 28
Maintenance Technology July 2017 - 29
Maintenance Technology July 2017 - SAP: Tips and Tricks
Maintenance Technology July 2017 - Cybersecurity Best Practices
Maintenance Technology July 2017 - Bearing Storage
Maintenance Technology July 2017 - Interpreting IP Code
Maintenance Technology July 2017 - Noisy Pumps
Maintenance Technology July 2017 - Move From Time- to Condition-Based Lubrication
Maintenance Technology July 2017 - 36
Maintenance Technology July 2017 - 37
Maintenance Technology July 2017 - 38
Maintenance Technology July 2017 - CMMS Energizes Maintenance Efforts
Maintenance Technology July 2017 - 40
Maintenance Technology July 2017 - 41
Maintenance Technology July 2017 - Products
Maintenance Technology July 2017 - 43
Maintenance Technology July 2017 - 44
Maintenance Technology July 2017 - 45
Maintenance Technology July 2017 - Ad Index
Maintenance Technology July 2017 - Showcase
Maintenance Technology July 2017 - Final Thought
Maintenance Technology July 2017 - Cover3
Maintenance Technology July 2017 - Cover4
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