C412.1
General. All new
compressed air systems, and all
additions or alterations of
compressed air systems where the
total combined horsepower (hp) of the compressor(s) is 25 hp or more, shall
meet the requirements of this section. These requirements apply to the
compressors, related piping systems, and related controls that provide
compressed air and do not apply to any equipment or controls that use or
process the compressed air.
EXCEPTION:
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Medical gas compressed air systems in health care
facilities.
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C412.2
Trim compressor and storage. The compressed air system shall be
equipped with an appropriately sized trim compressor and primary storage to
provide acceptable performance across the range of the system and to avoid
control gaps. The compressed air system shall comply with 1 or 2 below:
1. The compressed air system
shall include one or more variable speed drive (VSD) compressors. For systems
with more than one compressor, the total combined capacity of the VSD
compressor(s) acting as trim compressors must be at least 1.25 times the
largest net capacity increment between combinations of
compressors. The compressed air systems hall include
primary storage of at least one gallon per actual cubic feet
per minute (acfm) of the largest trim compressor; or
2. The
compressed air system
shall include a compressor or set of compressors with total effective trim
capacity at least the size of the
largest net capacity
increment between combinations of compressors, or the size of the
smallest compressor, whichever is larger. The total effective trim capacity of
single compressor systems shall cover at least the range from 70 percent to 100
percent of rated capacity. The effective trim capacity of a compressor is the
size of the continuous operational range where the specific power of the
compressor (kW/100 acfm) is within 15 percent of the specific power at its most
efficient operating point. The total effective trim capacity of the system is
the sum of the effective trim capacity of the trim compressors. The system
shall include
primary storage of at least 2 gallons per acfm
of the largest trim compressor.
EXCEPTIONS:
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1. Alterations where the total combined added or
replaced compressor horsepower is less than the average per-compressor
horsepower of all compressors in the system.
2. Alterations where all added or replaced compressors
are variable speed drive (VSD) compressors and compressed air
systems includes primary storage of at least one
gallon per acfm of the largest trim compressor.
3. Compressed air systems that have
been preapproved as having demonstrated that the system serves
loads for which typical air demand fluctuates less than 10 percent.
4. Alterations of existing compressed air
systems that include one or more centrifugal compressors.
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C412.3
Controls.
Compressed air systems with three or more compressors and a
combined horsepower rating of more than 100 hp, shall operate with controls
that are able to choose the most energy efficient combination and loading of
compressors within the system based on the current compressed air
demand.
C412.4
Monitoring.
Compressed air systems having a
combined horsepower rating equal to or greater than 100 hp shall have an energy
and air demand monitoring system with the following minimum requirements:
1. Measurement of system pressure.
2. Measurement of amps or power of each
compressor.
3. Measurement or
determination of total airflow from compressors in cfm.
4. Data logging of pressure, power in kW,
airflow in cfm, and compressed air system specific efficiency
in kW/100 cfm at intervals of five minutes or less.
5. Maintained data storage of at least the
most recent 24 months.
6. Visual
trending display of each recorded point, load and specific
efficiency.
C412.5
Leak testing of compressed air piping.
Compressed air
system piping greater than 50 adjoining feet in length shall be
pressure tested after being isolated from the compressed air supply and
end-uses. The piping shall be pressurized to the design pressure and test
pressures shall be held for a length of time at the discretion of the local
jurisdiction, but in no case for less than 30 minutes, with no perceptible drop
in pressure.
If dial gauges are used for conducting this test, for pressure
tests less than or equal to 100 psi (689 kPa) gauges shall be incremented in
units of 1 psi (7 kPa) less, for pressure tests greater than 100 psi (689 kPa)
gauges shall be incremented in units less than 2 percent of the test pressure.
Test gauges shall have a pressure range not exceeding twice the test
pressure.
Piping less than or equal to 50 adjoining feet in length shall
be pressurized and inspected. Connections shall be tested with a noncorrosive
leak-detecting fluid or other leak-detecting methods as
preapproved by the local jurisdiction.
C412.6
Pipe sizing. Compressed
air piping greater than 50 adjoining feet in length shall be designed and
installed to minimize frictional losses in the distribution network. These
piping installations shall meet the requirements of Section C412.6.1 and either
Section C412.6.2 or C412.6.3.
C412.6.1
Service line piping. Service line piping shall have inner
diameters greater than or equal to 3/4 inch. Service line piping are pipes that
deliver compressed air from distribution piping to end uses.
C412.6.2
Piping section average
velocity. Compressor room interconnection and main header piping shall
be sized so that at coincident peak flow conditions, the average velocity in
the segment of pipe is no greater than 20 ft/sec. Compressor room
interconnection and main header piping are the pipes that deliver compressed
air from the compressor outlets to the inlet to the distribution piping. Each
segment of distribution and service piping shall be sized so that at coincident
peak flow conditions, the average velocity in the segment of pipe is no greater
than 30 ft/sec. Distribution piping are pipes that deliver compressed air from
the compressor room interconnection piping or main header piping to the service
line piping.
C412.6.3
Piping
total pressure drop. Piping shall be designed such that piping
frictional pressure loss at coincident peak loads are less than 5 percent of
operating pressure between the compressor and end use or end use
regulator.
C412.6
Compressed air system acceptance. Before an occupancy permit is
granted for a compressed air system, a certificate of
acceptance shall be submitted to the enforcement agency that certifies that the
equipment and systems meet the requirements of this code.