Sistemas de ar comprimido

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Compressed Air

Determine the Cost of Compressed Air
for Your Plant
Suggested Actions
• Determine the cost of
compressed air for your plant
by periodically monitoring the
compressor operating hours
and load duty cycle.
• Use a systems approach while
operating and maintaining a
compressed air system.
• Adopt a plant-wide compressed
air management policy to cutcosts and reduce waste by
eliminating inappropriate uses,
fixing leaks, and matching
system supply with demand.

Most industrial facilities need some form of compressed air, whether for running a
simple air tool or for more complicated tasks such as operation of pneumatic controls.
A recent survey by the U.S. Department of Energy showed that for a typical industrial
facility, approximately10% of the electricity consumed is for generating compressed air.
For some facilities, compressed air generation may account for 30% or more of the
electricity consumed. Compressed air is an on-site generated utility. Very often the cost of
generation is not known; however, some companies use a value of 15-30 cents per 1000
cubic feet of air.
Compressed air is one of the most expensive sourcesof energy in a plant. The overall
efficiency of a typical compressed air system can be as low as 10-15%. For example, to
operate a 1 hp air motor at 100 psig, approximately 7-8 hp of electrical power is supplied
to the air compressor.
To calculate the cost of compressed air in your facility, use the formula shown below:
Cost ($) =

(bhp) x (0.746) x (# of operating hours) x ($/kWh) x (%time) x (% full load bhp)
Motor Efficiency

Improving Compressed Air System
Performance: A Sourcebook for the
Industry, Motor Challenge and
Compressed Air Challenge,
April 1998.

where bhp—Compressor shaft horsepower (frequently higher than the motor nameplate
horsepower—check equipment specification)
Percent time—percentage of time running at this operating level
Percentfull-load bhp—bhp as percentage of full-load bhp at this operating

• Fundamentals of Compressed Air
Systems - 1 day
• Advanced Management of
Compressed Air Systems - 2 days
Offered by the Compressed Air
Challenge. Call the OIT Clearinghouse or visit the BestPractices Web
site (
for the latest schedule and

Motor efficiency—motorefficiency at this operating level

A typical manufacturing facility has a 200 hp compressor (which requires 215 bhp)
that operates for 6800 hours annually. It is fully loaded 85% of the time (motor
efficiency = 95%) and unloaded the rest of the time (25% full-load bhp and motor
efficiency = 90%). The aggregate electric rate is $0.05/kWh.
Cost when fully loaded =
(215 bhp) x(0.746) x (6800 hrs) x ($0.05/kWh) x (0.85) x (1.0)
= $48,792
Cost when partially loaded =

For additional information on
industrial energy efficiency
measures, contact the
OIT Clearinghouse at
(800) 862-2086.

(215 bhp) x (0.746) x (6800 hrs) x ($0.05/kWh) x (0.15) x (0.25)
= $2,272
Annual energy cost = $48,792 + $2,272 = $51,064


Typical Lifetime Compressed Air Costs in Perspective*
Equipment &
Installation (12%)

Electricity (76%)

* Assumptions in this example include a 75 hp compressor operated 2 shifts a day, 5 days a week
at an aggregrate electric rate of $0.05/kWh over 10 years of equipment life.

B estPractices is part of theOffice of
Industrial Technologies’ (OIT’s) Industries
of the Future strategy, which helps the
country’s most energy-intensive
industries improve their competitiveness.
BestPractices brings together the bestavailable and emerging technologies
and practices to help companies begin
improving energy efficiency, environmental
performance, and productivity right now.
BestPractices focuses on...
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