ISO 7183:2007

INTERNATIONAL ISO
STANDARD 7183
Second edition
2007-12-15

Compressed-air dryers — Specifications
and testing
Sécheurs à air comprimé — Spécifications et essais




Reference number
ISO 7183:2007(E)
©
ISO 2007

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ISO 7183:2007(E)
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ISO 7183:2007(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 2
3 Terms and definitions. 2
4 Symbols . 4
4.1 Figure symbols . 4
4.2 Symbols and units. 4
4.3 Subscripts . 5
5 Reference conditions . 5
6 Standard rating parameters. 5
7 Performance tests. 6
7.1 Key performance parameters . 6
7.2 Pressure dew point, flow rate and outlet temperature. 6
7.3 Differential pressure drop. 8
7.4 Power consumption. 8
7.5 System air loss. 9
7.6 Dealing with in-cycle variations . 12
7.7 Noise . 13
7.8 Tests for energy saving devices . 13
7.9 Instrument accuracy. 13
8 Uncertainties . 14
9 Test report . 14
9.1 Statement. 14
9.2 Technical data . 15
Annex A (informative) Types of compressed-air dryers . 16
Annex B (informative) Report form for dryer performance. 17
Annex C (normative) Noise measurement. 18
Annex D (informative) Pressure-measuring tubes. 19
Bibliography . 21

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ISO 7183:2007(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 7183 was prepared by Technical Committee ISO/TC 118, Compressors and pneumatic tools, machines
and equipment, Subcommittee SC 4, Quality of compressed air.
This second edition of ISO 7183 revises and replaces the first edition (ISO 7183:1986), together with
ISO 7183-2:1996, which have been technically revised.
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ISO 7183:2007(E)
Introduction
The scope has been expanded to cover most current types of dryers but also to allow the use of this
International Standard and its test methods for any emerging technologies. Any new technologies can then be
incorporated at a later revision.
Exclusions to this International Standard are generally identified by reference to the definition of a dryer.
Specific exclusions have been identified, however, for absorption dryers and dryer processes involving “over-
compression” as the means of removing water from compressed air.
The process of over-compression employs the principle that water can be removed by compressing the air to
a pressure higher than the intended working pressure thereby forcing out the water from the compressed air
and then subsequently expanding the air back to the working pressure.
Absorption dryers are now considered to be of minor importance as a drying technique and are, therefore, not
considered in this International Standard.

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INTERNATIONAL STANDARD ISO 7183:2007(E)

Compressed-air dryers — Specifications and testing
1 Scope
This International Standard specifies the performance data that are necessary to state and applicable test
methods for different types of compressed air dryers. It is applicable to compressed air dryers working with an
effective (gauge) pressure of more than 50 kPa (0,5 bar), but less than or equal to 1 600 kPa (16 bar) and
include the following:
⎯ adsorption dryers;
⎯ membrane dryers;
⎯ refrigeration dryers (including drying by cooling);
⎯ or a combination of these.
NOTE A description of the principles of operation of the dryers within the Scope of this International Standard is given
in Annex A.
This International Standard identifies test methods for measuring dryer parameters that include the following:
⎯ pressure dew point;
⎯ flow rate;
⎯ pressure drop;
⎯ compressed-air loss;
⎯ power consumption;
⎯ noise emission.
This International Standard also provides partial-load tests for determining the performance of energy saving
devices or measures.
The mounting, operating and loading conditions of dryers for the measurement of noise are given in Annex C.
This International Standard is not applicable to the following types of dryers or drying processes:
⎯ absorption dryers;
⎯ drying by over-compression;
⎯ integral dryers.

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ISO 7183:2007(E)
2 Normative references
The following referenced documents are indispensable for the application of this International Standard. For
dated references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 261, ISO general purpose metric screw threads — General plan
ISO 228-1, Pipe threads where pressure-tight joints are not made on the threads — Part 1: Dimensions,
tolerances and designation
ISO 1179 (all parts), Connections for general use and fluid power — Ports and stud ends with ISO 228-1
threads with elastomeric or metal-to-metal sealing
ISO 1219-1, Fluid power systems and components — Graphic symbols and circuit diagrams — Part 1:
Graphic symbols for conventional use and data-processing applications
ISO 2602, Statistical interpretation of test results — Estimation of the mean — Confidence interval
ISO 2854, Statistical interpretation of data — Techniques of estimation and tests relating to means and
variances
ISO 3744, Acoustics — Determination of sound power levels and sound energy levels of noise sources using
1)
sound pressure — Engineering method for an essentially free field over a reflecting plane
ISO 8573-1:2001, Compressed air — Part 1: Contaminants and purity classes
ISO 8573-3, Compressed air — Part 3: Test methods for measurement of humidity
ISO 9614-2, Acoustics — Determination of sound power levels of noise sources using sound intensity —
Part 2: Measurement by scanning
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
absorption
chemical process of attracting one substance into the mass of another, so that the absorbed substance
combines with the absorbent
3.2
actual vapour pressure
partial pressure exerted by the water vapour under the actual temperature condition of the environment
3.3
adsorption
physical process in which the molecules of a gas or a vapour adhere to the surface of a solid
3.4
ambient
area surrounding the dryer under test


1) To be published. Revision of ISO 3744:1994
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ISO 7183:2007(E)
3.5
integral
equipment which is either physically integrated and/or functionally interlinked with the compressor
NOTE 1 Interlinking can be in terms of energy exchange, controls or sharing of other components.
NOTE 2 Typically, some of the performance characteristics, such as energy consumption or pressure drop, deviate
substantially from those of free-standing air-treatment equipment.
3.6
desiccant
〈adsorbent〉 substance with the ability to retain water without change of state
EXAMPLES Silica gel, activated alumina or molecular sieves.
NOTE The term excludes deliquescent substances.
3.7
dew point
temperature at which the vapour pressure of the vapour in a humid gas is equal to the saturation vapour
pressure over the pure liquid and at which condensate forms as a liquid on cooling the gas
3.7.1
pressure dew point
pdp
dew point measured at the actual pressure
3.8
dryer
device which lowers absolute moisture content of compressed air by reducing water vapour content such that
the exit relative humidity is lower than 100 %
NOTE “Separating” devices that remove only bulk water, such as a cyclone separator, are not dryers.
3.9
peak
point at which the measured parameter takes its highest, instantaneous value
3.10
permeate
compressed air and water vapour that diffuses through a membrane
NOTE The greater the selectivity of the membrane for moisture, the lower the permeate loss.
3.11
purge air flow
volume-flow of compressed air entering the dryer minus the compressed air leaving the dryer during
regeneration cycle
NOTE 1 Typically, purge air is expanded to atmospheric pressure.
NOTE 2 For membrane dryers, purge air flow is the sum of “sweep-gas” plus permeate.
3.12
regeneration
process of preparation of drying media to enable it to enter a new period of operation
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ISO 7183:2007(E)
3.13
relative humidity
ratio of the actual vapour pressure to the saturation vapour pressure over a plane liquid water surface at the
same temperature
3.14
saturation vapour pressure
partial pressure of water vapour that is in neutral equilibrium with a plane surface of pure, condensed-phase
water or ice at a given temperature
3.15
sweep gas
compressed air used in a membrane dryer to carry away moisture from the region outside the membrane
3.16
stabilization period
time taken to reach a steady state condition of an average value
3.17
test time
time taken after the stabilization period to record dryer performance
4 Symbols
4.1 Figure symbols
The symbols used in Figures 1 to 3 are in accordance with ISO 1219-1.
4.2 Symbols and units
Symbol Term SI unit Other practical units
d actual internal diameter of the tube  millimetres
l thread length  millimetres
m mass kilogram gram, milligram
P power watt megawatt, kilowatt
p pressure kilopascal bar
q flow rate cubic metres cubic metres per hour
per second cubic metres per minute
litres per second
L latent heat joules megajoules, kilojoules
n number (dimensionless)
t time second minute, hour, day
V volume cubic metre cubic decimetre, cubic centimetre,
cubic millimetre
W work joule megajoule, kilojoule, kilowatt-hour
X average of a series of measured
values, x of a parameter
i

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ISO 7183:2007(E)
4.3 Subscripts
Subscript Term
AL air loss
Av average
BL blow-down loss
sum sum
DC dryer cycle
i interval number
PF purge flow
PL purge air loss
E electrical energy
v vessel
ref reference
regn regeneration
S steam energy
s system
TOT total
5 Reference conditions
Reference conditions for volume statements shall be as given in Table 1.
Table 1 — Reference conditions
air temperature 20 °C
absolute air pressure 100 kPa [1 bar (a)]
relative water vapour pressure 0
NOTE Bar(e) is used to indicate effective pressure above atmospheric.
6 Standard rating parameters
Standard rating parameters are necessary in defining the performance of an air dryer and in comparing one
dryer with another. The standard rating parameters are given in Table 2.
The standard rating parameters are assumed to be 100 % rated flow operating at 24 hours per day and seven
days per week.
Table 2 — Standard rating parameters
a
Value
b
Quantity Unit Tolerance
c c
Option A1 Option A2 Option B
Inlet temperature °C 35 38 45 ± 2
kPa gauge
Inlet pressure 700 (7) 700 (7) 700 (7) ± 14 (0,14)
[bar(e)]
0
Inlet relative humidity % 100 100 100
−5
Cooling air inlet temperature (where applicable) °C 25 38 35 ± 3
Cooling water inlet temperature (where
°C 25 29 25 ± 3
applicable)
Ambient air temperature °C 25 38 35 ± 3
% of rated
Flow of dryer inlet 100 100 100 ± 3
flow
a
Maintain within actual gauge value.
b
The choice between options A and B is influenced by the intended geographical location of the equipment.
c
Option A1 applies to a temperate climate zone and Option A2 applies to a sub-tropical zone.
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ISO 7183:2007(E)
7 Performance tests
7.1 Key performance parameters
Data for the following key performance parameters are required for all compressed air dryers when stating or
rating product performance and for making comparisons of alternative dryers:
⎯ pressure dew point;
⎯ flow rate;
⎯ pressure drop;
⎯ power consumption;
⎯ system air loss;
⎯ outlet temperature;
⎯ noise emission.
Measurement of the inlet pressure and temperature should be done at the dryer inlet in order to avoid errors
caused by cooling or pressure drop between the measurement point and inlet whilst operating at full rated
conditions. It is the responsibility of the manufacturer to supply the required data in Annex B.
For all performance tests, the inlet air purity should be in accordance with ISO 8573-1:2001, class 4, for oil
and class 4 for particles and the humidity shall be in accordance with Table 2 of this International Standard. If
the dryer under test requires pre-filtration to operate reliably with this inlet air purity then these filters shall be
included in all tests.
7.2 Pressure dew point, flow rate and outlet temperature
Measurement of the pressure dew point should be done at the stated rated flow of the dryer using the
standard rating parameters selected from Table 2.
Measurement of the pressure dew point of the outlet air shall be in accordance with ISO 8573-3. Discharge
temperature should also be measured.
Test equipment should be arranged as shown in Figure 1 however the arrangement may vary depending on
the type of dryer being tested.
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ISO 7183:2007(E)

Key
1 conditioned compressed air supply 10 flow sensing/measuring
2 shut-off valve 11 silencer
3 inlet pressure sensing/measuring 12 ambient relative humidity sensing/measuring
4 inlet temperature sensing/measuring 13 ambient temperature sensing/measuring
5 inlet moisture content meter 14 inlet pressure measuring tube
6 dryer under test 15 outlet pressure measuring tube
7 pressure dew point sensing/measuring 16 cooling water inlet temperature sensing/measuring (if applicable)
8 outlet temperature sensing/measuring 17 cooling air inlet temperature sensing/measuring (if applicable)
9 multi-turn flow control valve
a
Details of a pressure measuring tube are given in Annex D.
b
The temperature gauges are fitted if the dryer under test has either a cooling air supply or a cooling water supply as a function of the
dryer. These would generally be features related to a refrigerant dryer.
Figure 1 — Typical test set up for pressure dew point and flow rate

It should be recognized that where filters are included for the correct operation of the dryer, then these are
included in the test set up shown in Figure 1 and the configuration of the test equipment recorded on the
performance form given in Annex B.
The rated flow rate of the dryer is the design/maximum flow rate through the dryer whilst the dryer maintains
the outlet pressure dew point at the specified level. Standard outlet pressure dew points may be selected from
the compressed air purity classes as shown in ISO 8573-1:2001, Table 3.
Conditioning of the compressed air supply to the dryer under test should be done such that the relative
humidity of the inlet air is assured to be fully saturated or at least within the tolerance of Table 2. A wide
variety of process equipment may be used to generate fully saturated air, e.g. air/water contactors, steam
injection, etc. Care should be taken in the selection and use of the inlet relative-humidity meter to ensure its
reliable and accurate operation.
Before the outlet pressure dew point measurements are taken, the dryer should be allowed a stabilization
period as recommended by the dryer manufacturer.
During this time, the pressure dew point, pdp, and flow rate should be monitored until cycle-to-cycle variations
of consecutive minima and consecutive maxima are less than 0,5 °C pdp for dryers with an average
pdp u 0 °C and shall be < 1 °C pdp with an average pdp of 0 °C.
When reporting pressure dew point, the wettest pressure dew point achieved during the test shall be recorded.
For dryers with significant pressure dew point variations during a cycle (e.g. thermal swing adsorption dryers),
the average pressure dew point may also be reported. The average pressure dew point shall be calculated in
accordance with 7.6.2. The peak and average outlet temperature are also measured.
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ISO 7183:2007(E)
7.3 Differential pressure drop
Pressure drop is the loss in total pressure between inlet and outlet of the dryer. The pressure drop is
measured at the rated flow of the dryer and the standard rating parameters selected from Table 2. Test
equipment should be arranged as shown in Figure 2. Inlet and outlet filters should be included in the pressure
drop (wet) measurement if they are part of the dryer. Stabilization should allow the filters to reach a saturated
condition.

Key
1 conditioned compressed air supply 9 silencer
2 shut-off valve 10 ambient temperature sensing/measuring
3 inlet pressure sensing/measuring 11 cooling water inlet temperature gauge (if applicable)
4 inlet temperature sensing/measuring 12 cooling air inlet temperature gauge (if applicable)
5 dryer under test 13 inlet pressure measuring tube
6 pressure drop gauge 14 outlet pressure measuring tube
7 multi-turn flow control valve 15 press drop gauge (water side)
8 flow sensing/measuring 16 flow sensing measuring (water side)
a
Details of a pressure measuring tube are given in Annex D.
b
The temperature gauges are fitted if the dryer under test has either a cooling air supply or a cooling water supply as a function of the
dryer. These are generally features related to a refrigerant dryer.
Figure 2 — Typical test set up for pressure drop measurement
7.4 Power consumption
The power consumption of the dryer is the total energy requirement of the dryer and consists of the sum total
of differing forms of energy input. For example, an adsorption dryer can use a flow of steam for heat input and
an electrical supply for fan or blower power. The report, as far as applicable, should state the power
consumption averaged over a representative number of complete operating cycles (one minimum); see 7.6.1.
7.4.1 Electrical energy
The electrical energy, W , expressed in kiloJoules, consumed by the dryer should be measured using a
E
wattmeter having an accuracy of ± 1 % of the reading, and calculated as given by Equation (1):
WP=×t (1)
EAV DC
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ISO 7183:2007(E)
where
P is the average power, calculated as given by Equation (3) over a complete dryer cycle, expressed
AV
in kilowatts;
t is time of complete dryer cycle, expressed in seconds.
DC
7.4.2 Steam energy
Collecting liquid water condensate over a complete dryer cycle and recording the inlet pressure should
measure the energy input from a steam source. The steam energy, W , expressed in kilojoules, can then be
S
calculated from Equation (2):
Wm=×L (2)
Sv
where
m is mass of steam condensate collected over one complete dryer cycle, expressed in kilograms;
L is the latent heat of vaporization of steam at the steam temperature and pressure supply conditions,
v
expressed in kilojoules per kilogram.
7.4.3 Average power requirement
The average power requirement, P , expressed in kilowatts, is then given by Equation (3):
AV
W
sum
P = (3)
AV
t
DC
where
W is sum of all energy inputs (W , W and others, where applicable), expressed in kilojoules;

sum E S
t is dryer cycle time, expressed in seconds.
DC
7.5 System air loss
Some dryers utilize compressed air diverted from the process to aid regeneration; this is normally lost from the
compressed air system. It typically consists of two components:
⎯ the blow-down loss, which consists of a volume of compressed air vented to atmosphere as part of the
pressure swing adsorption process;
⎯ the purge loss, which consists of a flow of depressurized, dried air through the off-line vessel.
In addition to the air lost by these processes, it should also be recognized that the amount of air loss through
drains can be significant.
7.5.1 Blow-down air loss for regeneration dryers
The blow-down loss occurs when a pressurized vessel of the dryer is vented to atmospheric pressure,
typically at the start of regeneration. The blow-down loss, V , expressed in cubic metres, can be calculated
BL
as given in Equation (4):
⎡⎤
pp−
()
sregn
⎢⎥
VV=× ×n (4)
BL v
⎢⎥
p
ref
⎣⎦
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ISO 7183:2007(E)
where
V is vessel volume expressed in cubic metres
v
p is system pressure expressed in bar absolute
s
p is regeneration pressure expressed in bar absolute
regn
p is reference atmospheric pressure bar absolute
ref
n is number of blow-down events for a complete dryer cycle
It is not recommended to measure the blow-down air loss but to calculate it as given in Equation (4).
NOTE The effect of the desiccant volume varies by type and has minimal effect on the volume used in calculations.
WARNING — A blow-down event, when a large volume of air is vented to atmospheric pressure during
a very short time, generates high transient flow rates and gas velocities that can damage flow meters
and create a safety hazard.
7.5.2 Purge air loss for regeneration dryers
The purge-air loss, the total volume of air diverted from the process stream and used for regeneration, is lost
from the system. Where purge air is used, the outlet flow of a dryer is lower than the inlet flow.
Measurement of the purge flow rate should be done using the arrangements shown in Figure 3. This test
should not be undertaken at the same time as the pressure dew-point measurement test, 7.2, as the addition
of backpressure to the purging flow can affect its performance.
WARNING — It is important to take care to avoid a blow-down event when measuring purge-air loss
from pressure-swing adsorption dryers, as the flow meter and purge measuring equipment can be
damaged by the rapid discharge of air and/or a safety hazard can be created.
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ISO 7183:2007(E)

Key
1 conditioned compressed air supply 8 multi turn flow control valve
2 shut-off valve 9 flow sensing/measuring
3 inlet temperature sensing/measuring 10 silencer
4 pressure measuring tube 11 ambient temperature sensing/measuring
5 inlet pressure sensing/measuring 12 cooling water inlet temperature sensing/measuring (if applicable)
6 dryer under test 13 cooling air inlet temperature sensing/measuring (if applicable)
7 purge or sweep-gas flow meter
a
The pressure measuring tube details are shown in Annex D.
b
The temperature gauges are fitted if the dryer under test has either a cooling air supply or a cooling water supply as a function of the
dryer. These are generally features related to a refrigerant dryer.
c
The purge air flow source varies among dryer types such that the figure is only an indication that a flow meter (7) is connected to the
appropriate discharge representing the purge flow.
Figure 3 — Typical test set-up for purge-air flow measurement
The purge air loss, V , expressed in cubic metres, is then calculated from Equation (5):
PL
Vq=×t (5)
PL PF PF
where
q is purge air flow rate, expressed in cubic metres per second;
PF
...