Ingangsdatum: 10-05-2005
Geldig tot en met: 08-05-2008
4.11.1 Stress corrosion test for brass nozzle parts
(see 3.11.1)
4.11.1.1 Five nozzles should
be subjected to the following aqueous ammonia test. The inlet of each nozzle should
be sealed with a nonreactive cap, e.g., plastic.
4.11.1.2 The samples are degreased and exposed for 10 days to a moist
ammonia-air mixture in a glass container of volume 0.02 ± 0.01 m3.
4.11.1.3 An aqueous ammonia solution, having a density of 0.94 g/cm3,
should be maintained in the bottom of the container, approximately 40 mm below the
bottom of the samples. A volume of aqueous ammonia solution corresponding to 0.01 ml
per cubic centimetre of the volume of the container will give approximately the
following atmospheric concentrations: 35% ammonia, 5% water vapour, and 60% air. The
inlet of each sample should be sealed with a nonreactive cap, e.g., plastic.
4.11.1.4 The moist ammonia-air mixture
should be maintained as closely as possible at atmospheric pressure, with the
temperature maintained at 34 ± 2°C. Provision should be made for venting the chamber
via a capillary tube to avoid the build-up of pressure. Specimens should be shielded
from condensate drippage.
4.11.1.5 After
exposure, rinse and dry the nozzles, and conduct a detailed examination. If a crack,
delamination or failure of any operating part is observed, the nozzle(s) should be
subjected to a leak resistance test at the rated pressure for 1 min and to the
functional test at the minimum flowing pressure (see 3.1.5).
4.11.1.6 Nozzles showing cracking, delamination or failure of
any non-operating part should not show evidence of separation of permanently
attached parts when subjected to flowing water at the rated working pressure for 30
min.
4.11.2 Stress-Corrosion Cracking of
Stainless Steel Nozzle Parts (see 3.11.1)4.11.2.1 Five samples are to be degreased
prior to being exposed to the magnesium chloride solution.
4.11.2.2 Parts used in nozzles are to be placed in a
500-millilitre flask that is fitted with a thermometer and a wet condenser
approximately 760 mm long. The flask is to be filled approximately one-half full
with a 42% by weight magnesium chloride solution, placed on a
thermostatically-controlled electrically heated mantel, and maintained at a boiling
temperature of 150 ± 1°C. The parts are to be unassembled, that is, not contained in
a nozzle assembly. The exposure is to last for 500 hours.
4.11.2.3 After the exposure period, the test samples are to
be removed from the boiling magnesium chloride solution and rinsed in deionised
water.
4.11.2.4 The test samples are then
to be examined using a microscope having a magnification of 25X for any cracking,
delamination, or other degradation as a result of the test exposure. Test samples
exhibiting degradation are to be tested as described in 4.12.5.5 or 4.12.5.6, as
applicable. Test samples not exhibiting degradation are considered acceptable
without further test.
4.11.2.5 Operating
parts exhibiting degradation are to be further tested as follows. Five new sets of
parts are to be assembled in nozzle frames made of materials that do not alter the
corrosive effects of the magnesium chloride solution on the stainless steel parts.
These test samples are to be degreased and subjected to the magnesium chloride
solution exposure specified in paragraph 4.12.5.2. Following the exposure, the test
samples should withstand, without leakage, a hydrostatic test pressure equal to the
rated working pressure for 1 minute and then be subjected to the functional test at
the minimum operating pressure in accordance with 4.5.1.
4.11.2.6 Non-operating parts exhibiting degradation are to be
further tested as follows. Five new sets of parts are to be assembled in nozzle
frames made of materials that do not alter the corrosive effects of the magnesium
chloride solution on the stainless steel parts. These test samples are to be
degreased and subjected to the magnesium chloride solution exposure specified in
paragraph 4.12.5.1. Following the exposure, the test samples should withstand a
flowing pressure equal to the rated working pressure for 30 minutes without
separation of permanently attached parts.
4.11.3 Sulphur dioxide corrosion test (see 3.11.2 and 3.14.2)4.11.3.1 Ten nozzles should be subjected
to the following sulphur dioxide corrosion test. The inlet of each sample should be
sealed with a nonreactive cap, e.g., plastic.
4.11.3.2 The test equipment should consist of a 5 litre vessel (instead
of a 5 litre vessel, other volumes up to 15 litre may be used in which case the
quantities of chemicals given below shall be increased in proportion) made of
heat-resistant glass, with a corrosion-resistant lid of such a shape as to prevent
condensate dripping on the nozzles. The vessel should be electrically heated through
the base, and provided with a cooling coil around the side walls. A temperature
sensor placed centrally 160 mm ± 20 mm above the bottom of the vessel should
regulate the heating so that the temperature inside the glass vessel is 45°C ± 3ºC.
During the test, water should flow through the cooling coil at a sufficient rate to
keep the temperature of the discharge water below 30°C. This combination of heating
and cooling should encourage condensation on the surfaces of the nozzles. The sample
nozzles should be shielded from condensate drippage.
4.11.3.3 The nozzles to be tested should be suspended in
their normal mounting position under the lid inside the vessel and subjected to a
corrosive sulphur dioxide atmosphere for 8 days. The corrosive atmosphere should be
obtained by introducing a solution made up by dissolving 20 g of sodium thiosulphate
(Na2S203H2O) crystals in 500 ml of water.
4.11.3.4 For at least six days of the 8-day exposure period, 20 ml of
dilute sulphuric acid consisting of 156 ml of normal H2SO4 (0.5 mol/litre) diluted
with 844 ml of water should be added at a constant rate. After 8 days, the nozzles
should be removed from the container and allowed to dry for 4 to 7 days at a
temperature not exceeding 35°C with a relative humidity not greater than 70%.
4.11.3.5 After the drying period, five
nozzles should be subjected to a functional test at the minimum operating pressure
in accordance with 4.5.1 and five nozzles should be subjected to the dynamic heating
test in accordance with 3.14.2.
4.11.4 Salt
spray corrosion test (see 3.11.3 and 3.14.2) [7.12.3]4.11.4.1 Nozzles intended for normal
atmospheres4.11.4.1.1 Ten nozzles should be exposed
to a salt spray within a fog chamber. The inlet of each sample should be sealed with
a nonreactive cap, e.g., plastic.
4.11.4.1.2 During the corrosive exposure, the inlet thread orifice is to
be sealed by a plastic cap after the nozzles have been filled with deionised water.
The salt solution should be a 20% by mass sodium chloride solution in distilled
water. The pH should be between 6.5 and 7.2 and the density between 1.126 g/ml and
1.157 g/ml when atomized at 35ºC. Suitable means of controlling the atmosphere in
the chamber should be provided. The specimens should be supported in their normal
operating position and exposed to the salt spray (fog) in a chamber having a volume
of at least 0.43 m3 in which the exposure zone shall be maintained at a temperature
of 35 ± 2ºC. The temperature should be recorded at least once per day, at least 7
hours apart (except weekends and holidays when the chamber normally would not be
opened). Salt solution should be supplied from a recirculating reservoir through
air-aspirating nozzles, at a pressure between 0.7 bar (0.07 MPa) and 1.7 bar (0.17
MPa). Salt solution runoff from exposed samples should be collected and should not
return to the reservoir for recirculation. The sample nozzles should be shielded
from condensate drippage.
4.11.4.1.3 Fog
should be collected from at least two points in the exposure zone to determine the
rate of application and salt concentration. The fog should be such that for each 80
cm2 of collection area, 1 m1 to 2 ml of solution should be collected per hour over a
16 hour period and the salt concentration shall be 20 ± 1% by mass.
4.11.4.1.4 The nozzles should withstand exposure to the
salt spray for a period of 10 days.
After this
period, the nozzles should be removed from the fog chamber and allowed to dry for 4
to 7 days at a temperature of 20°C to 25°C in an atmosphere having a relative
humidity not greater than 70%. Following the drying period, five nozzles should be
submitted to the functional test at the minimum operating pressure in accordance
with 4.5.1 and five nozzles should be subjected to the dynamic heating test in
accordance with 3.14.2.
4.11.4.2 Nozzles
intended for corrosive atmospheres [7.12.3.2]Five nozzles should be subjected to the tests
specified in 4.12.3.1 except that the duration of the salt spray exposure shall be
extended from 10 days to 30 days.
4.11.5
Moist air exposure test (see 3.11.4 and 3.14.2) [7.12.4]Ten nozzles should be exposed to a high
temperature-humidity atmosphere consisting of a relative humidity of 98% ± 2% and a
temperature of 95°C ± 4ºC. The nozzles are to be installed on a pipe manifold
containing de-ionized water. The entire manifold is to be placed in the high
temperature humidity enclosure for 90 days. After this period, the nozzles should be
removed from the temperature-humidity enclosure and allowed to dry for 4 to 7 days
at a temperature of 25 ± 5°C in an atmosphere having a relative humidity of not
greater than 70%. Following the drying period, five nozzles should be functionally
tested at the minimum operating pressure in accordance with 4.5.1 and five nozzles
should be subjected to the dynamic heating test in accordance with
3.14.2
1.
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1
At the manufacturer’s option, additional samples may be furnished for this test to
provide early evidence of failure. The additional samples may be removed from the
test chamber at 30-day intervals for testing.