Ingangsdatum: 09-05-2008
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 3.5.1).
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
4.11.1.5 or 4.11.2.6, 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 4.11.2.2. 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 4.11.2.2 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 4.11.4.1 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.