ASTM E782-95
(Practice)Standard Practice for Exposure of Cover Materials for Solar Collectors to Natural Weathering Under Conditions Simulating Operational Mode
Standard Practice for Exposure of Cover Materials for Solar Collectors to Natural Weathering Under Conditions Simulating Operational Mode
SCOPE
1.1 This practice provides a procedure for the exposure of cover materials for flat-plate solar collectors to the natural weather environment at temperatures that are elevated to approximate operating conditions.
1.2 This practice is suitable for exposure of both glass and plastic solar collector cover materials. Provisions are made for exposure of single and double cover assemblies to accommodate the need for exposure of both inner and outer solar collector cover materials.
1.3 This practice does not apply to cover materials for evacuated collectors or photovoltaics.
1.4 The values stated in SI units are to be regarded as the standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
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Designation: E 782 – 95 An American National Standard
Standard Practice for
Exposure of Cover Materials for Solar Collectors to Natural
Weathering Under Conditions Simulating Operational Mode
This standard is issued under the fixed designation E 782; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2 This practice may be useful in comparing the perfor-
mance of different materials at one site or the performance of
1.1 This practice provides a procedure for the exposure of
the same material at different sites, or both.
cover materials for flat-plate solar collectors to the natural
3.3 Since the combination of elevated temperature and solar
weather environment at temperatures that are elevated to
radiation may cause some solar collector cover materials to
approximate operating conditions.
degrade more rapidly than either alone, a weathering box that
1.2 This practice is suitable for exposure of both glass and
elevates the temperature of the cover materials is used.
plastic solar collector cover materials. Provisions are made for
3.4 This practice is intended to assist in the evaluation of
exposure of single and double cover assemblies to accommo-
solar collector cover materials in the operational, not stagna-
date the need for exposure of both inner and outer solar
tion mode. Insufficient data exist to obtain exact correlation
collector cover materials.
between the behavior of materials exposed according to this
1.3 This practice does not apply to cover materials for
practice and actual in-service performance.
evacuated collectors or photovoltaics.
3.5 Means of evaluation of effects of weathering are pro-
1.4 The values stated in SI units are to be regarded as the
vided in Practice E 781, and in other ASTM test methods that
standard.
evaluate material properties.
1.5 This standard does not purport to address all of the
3.6 Tests of the type described in this practice may be used
safety concerns, if any, associated with its use. It is the
to evaluate the stability of solar collector cover materials when
responsibility of the user of this standard to establish appro-
exposed outdoors to the varied influences which comprise
priate safety and health practices and determine the applica-
weather. Exposure conditions are complex and changeable.
bility of regulatory limitations prior to use.
Important factors are solar radiation, temperature, moisture,
2. Referenced Documents time of year, presence of pollutants, etc. These factors vary
from site to site and should be considered in selecting locations
2.1 ASTM Standards:
for exposure. Control samples must always be used in weath-
E 781 Practice for Evaluating Absorptive Solar Receiver
ering tests for comparative analysis. Outdoor exposure for at
Materials When Exposed to Conditions Simulating Stag-
least two years is required to make evident changes, such as
nation in Solar Collectors With Cover Plates
surface degradation without the use of sophisticated analytical
E 881 Practice for Exposure of Solar Collector Cover Ma-
equipment.
terials to Natural Weathering Under Conditions Simulating
3.7 Temperature conditions attained with this box may not
Stagnation Mode
exactly duplicate those that occur under operational conditions
G 7 Practice for Atmospheric Environmental Exposure
with fluid flow. Dependent on environmental exposure condi-
Testing of Nonmetallic Materials
tions, the cover plate temperatures obtained with this box may
3. Significance and Use
be higher or lower than those obtained under operational
conditions. Additional testing under stagnation conditions,
3.1 This practice describes a weathering box test fixture and
although not covered by this practice should be conducted.
provides uniform exposure guidelines to minimize the vari-
ables encountered during outdoor exposure testing.
NOTE 1—Research has shown that exposure outdoors at sites having the
combination of high levels of humidity, solar energy, and ambient
temperature can cause more severe degradation of some polymeric cover
These test methods are under the jurisdiction of ASTM Committee E44 on
materials, (for example, microcracking and leaching of UV radiation
Solar, Geothermal, and Other Alternative Energy Sources and is the direct
screening additives) than exposure in arid climates.
responsibility of Subcommittee E44.05 on Solar Heating and Cooling Subsystems
NOTE 2—Stagnation conditions are a normal occurrence for solar
and Systems.
collectors, for example, during operation when the storage is fully
Current edition approved July 15, 1995. Published September 1995. Originally
e1
charged; when the collectors are initially installed, before system start-up;
published as E 782 – 81. Last previous edition E 782 – 86 (1991) .
Annual Book of ASTM Standards, Vol 12.02.
Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
E 782
or when the system is shut down for maintenance or seasonal consider-
ations such as heating only systems in the summer.
4. Weathering Box Test Fixture
4.1 Weathering Box Test Fixture, consisting of a box, rails,
a box top, a glazing frame, and adhesive tapes. The weathering
box test fixture should be constructed in accordance with Figs.
1-5.
4.1.1 The box and box top should be made in metal that is
suitably resistant to corrosion encountered in the exposure
environment. A weep hole should be drilled at the lower end of
the bottom of the box to provide drainage and to minimize
moisture accumulation.
NOTE 3—The box top is intended to protect the edges of the test
specimen in contact with the box from reaching excessively high
temperatures, to minimize exposure of the adhesive to sunlight, and to
minimize moisture penetration into the exposure test fixture.
4.1.2 The box interior shall be a flat black nonselective
coating having an absorptance of not less than 0.90 after
exposure. Organic absorber coatings should be heated in an
oven at 150°C (302°F) for 24 h before the test fixture is
asssembled. This should minimize outgassing, which results
from deterioration of the organic components exposed to
NOTE 1—Make: 4 per box.
elevated temperatures.
NOTE 2—Material: metal suitably corrosion-resistant for exposure. A
4.1.3 The adhesive tapes should be stable when exposed to
typical material would be 24-gage galvanized steel.
moisture and elevated temperat
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