Ingangsdatum: 30-12-1994
4.6.1 Operating temperature test (see 3.3) [7.6]
Ten nozzles should be heated from room temperature to 20 to 22 °C below their
nominal release temperature. The rate of increase of temperature should not exceed
20 °C/min and the temperature should be maintained for 10 min. The temperature
should then be increased at a rate between 0.4 °C/min to 0.7 °C/min until the
nozzle operates.
The nominal operating temperature should be ascertained with equipment having an
accuracy of ± 0.35% of the nominal temperature rating or ± 0.25 °C, whichever is
greater.
The test should be conducted in a water bath for nozzles or separate glass bulbs
having nominal release temperatures less than or equal to 80 °C. A suitable oil
should be used for higher-rated release elements. The liquid bath should be
constructed in such a way that the temperature deviation within the test zone does
not exceed 0.5%, or 0.5°C, whichever is greater.
4.6.2 Dynamic beating test (see 3.4)
4.6.2.1 Plunge test
Tests should be conducted to determine the standard and worst case orientations
as defined in 1.4 and 1.5. Ten additional plunge tests should be performed at both
of the identified orientations. The worst case orientation should be as defined in
3.14.1. The RTI is calculated as described in 4.6.2.3 and 4.6.2.4 for each
orientation, respectively. The plunge tests are to be conducted using a brass
nozzle mount designed such that the mount or water temperature rise does not
exceed 2°C for the duration of an individual plunge test up to a response time of
55 s. (The temperature should be measured by a thermocouple heatsinked and
embedded in the mount not more than 8 mm radially outward from the root diameter
of the internal thread or by a thermocouple located in the water at the centre of
the nozzle inlet.) If the response time is greater than 55 s, then the mount or
water temperature in degrees Celsius should not increase more than 0.036 times the
response time in seconds for the duration of an individual plunge test.
The nozzle under test should have 1 to 1.5 wraps of PTFE sealant tape applied to
the nozzle threads. It should be screwed into a mount to a torque of 15 ± 3 Nm.
Each nozzle is to be mounted on a tunnel test section cover and maintained in a
conditioning chamber to allow the nozzle and cover to reach ambient temperature
for a period of not less than 30 min.
At least 25 ml of water, conditioned to ambient temperature, should be introduced
into the nozzle inlet prior to testing. A timer accurate to ± 0.01 s with suitable
measuring devices to sense the time between when the nozzle is plunged into the
tunnel and the time it operates should be utilized to obtain the response time.
A tunnel should be utilized with air flow and temperature conditions1
at the test section (nozzle location) selected from the appropriate range of
conditions shown in table 2. To minimize radiation exchange between the sensing
element and the boundaries confining the flow, the test section of the apparatus
should be designed to limit radiation effects to within ± 3% of calculated RTI
values2.
The range of permissible tunnel operating conditions is shown in table 2. The
selected operating condition should be maintained for the duration of the test
with the tolerances as specified by footnotes 4 and 5 in table 2.
4.6.2.2 Determination of conductivity factor (C) [7.6.2.2]
The conductivity factor (C) should be determined using the prolonged plunge test
(see 4.6.2.2.1) or the prolonged exposure ramp test (see 4.6.2.2.2).
4.6.2.2.1 Prolonged plunge test [7.6.2.2.1]
The prolonged plunge test is an iterative process to determine C and may require
up to twenty nozzle samples. A new nozzle sample must be used for each test in
this section even if the sample does not operate during the prolonged plunge test.
The nozzle under test should have 1 to 1.5 wraps of PTFE sealant tape applied to
the nozzle threads. It should be screwed into a mount to a torque of 15 + 3 Nm.
Each nozzle is to be mounted on a tunnel test section cover and maintained in a
conditioning chamber to allow the nozzle and cover to reach ambient temperature
for a period of not less than 30 min. At least 25 ml of water , conditioned to
ambient temperature, should be introduced into the nozzle inlet prior to testing.
A timer accurate to ± 0.01 s with suitable measuring devices to sense the time
between when the nozzle is plunged into the tunnel and the time it operates should
be utilized to obtain the response time.
The mount temperature should be maintained at 20 ± 0.5 °C for the duration of
each test. The air velocity in the tunnel test section at the nozzle location
should be maintained with ± 2% of the selected velocity. Air temperature should be
selected and maintained during the test as specified in table 3.
The range of permissible tunnel operating conditions is shown in table 3. The
selected operating condition should be maintained for the duration of the test
with the tolerances as specified in table 3.
To determine C, the nozzle is immersed in the test stream at various air
velocities for a maximum of 15 min.3. Velocities are chosen such that
actuation is bracketed between two successive test velocities. That is, two
velocities must be established such that at the lower velocity (ul)
actuation does not occur in the 15 min test interval. At the next higher velocity
(uh), actuation must occur within the 15 min time limit If the nozzle
does not operate at the highest velocity, select an air temperature from table 3
for the next higher temperature rating
Table 2 -Plunge oven test conditions
Air temperature ranges* | Velocity ranges** |
Normal temperature °C | Standard response °C | Special response °C | Fast response °C | Standard response m/s | Special response m/s | Fast response nozzle m/s |
57 to 77 | 191 to 203 | 129 to 141 | 129 to 141 | 2.4 to 2.6 | 2.4 to 2.6 | 1.65 to 1.85 |
79 to 107 | 282 to 300 | 191 to 203 | 191 to 203 | 2.4 to 2.6 | 2.4 to 2.6 | 1.65 to 1.85 |
121 to 149 | 382 to 432 | 282 to 300 | 282 to 300 | 2.4 to 2.6 | 2.4 to 2.6 | 1.65 to 1.85 |
163 to 191 | 382 to 432 | 382 to 432 | 382 to 432 | 3.4 to 3.6 | 2.4 to 2.6 | 1.65 to 1.85 |
* The selected air temperature should be known and maintained constant
within the test section throughout the test to an accuracy of ± 1
°C for the air temperature range of 129 to 141°C within the
test section and within ± 2 °C for all other air
temperatures
** The selected air velocity should be known and maintained constant
throughout the test to an accuracy of ± 0.03 m/s for velocities of 1.65 to 1.85
and 2.4 to 2.6 m/s and ± 0.04 m/s for velocities of 3.4 to 3.6 m/s
Table 3 -Plunge oven test conditions for conductivity
determination.
Nominal nozzle temperature, °C | Oven temperature, °C | Maximum variation of air temperature during
test, °C |
57 | 85 to 91 | ± 1.0 |
58 to 77 | 124 to 130 | ± 1.5 |
78 to 107 | 193 to 201 | ± 3.0 |
121 to 149 | 287 to 295 | ± 4.5 |
163 to 191 | 402 to 412 | ± 6.0 |
Test velocity selection should insure that:
(Uh/Ui)0.5 < 1.1
The test value of C is the average of the values calculated at the two velocities
using the following equation:
C = (Δ Tg/Δ Tea-1)u0.5
where
Δ Tg Actual gas (air) temperature minus the mount temperature (Tm) in °C.
Δ Tea Mean liquid bath operating temperature minus the mount temperature (Tm)
in °C.
u Actual air velocity in the test section in m/s.
The nozzle C value is determined by repeating the bracketing procedure three
times and calculating the numerical average of the three C values. This nozzle C
value is used to calculate all standard orientation RTI values for determining
compliance with 3.14.1.
4.6.2.2.2 Prolonged exposure ramp test [7.6.2.2.2]
The prolonged exposure ramp test for the determination of the parameter C should
be carried out in the test section of a wind tunnel and with the requirements for
the temperature in the nozzle mount as described for the dynamic heating test. A
preconditioning of the nozzle is not necessary.
Ten samples should be tested of each nozzle type, all nozzles positioned in
standard orientation. The nozzle should be plunged into an air stream of a
constant velocity of 1 m/s ± 10% and an air temperature at the nominal temperature
of the nozzle at the beginning of the test.
The air temperature should then be increased at a rate of 1 ± 0.25 °C/min until
the nozzle operates. The air temperature, velocity and mount temperature should be
controlled from the initiation of the rate of rise and should be measured and
recorded at nozzle operation. The C value is determined using the same equation as
in 4.6.2.2.1 as the average of the ten test values.
4.6.2.3 RTI value calculation [7.6.2.3]
The equation used to determine the RTI value is as follows:
where:
tr Response time of nozzles in seconds
u Actual air velocity in the test section of the tunnel in m/s from table
2
Δ Tea Mean liquid bath operating temperature of the nozzle minus the ambient
temperature in °C
Δ Tg Actual air temperature in the test section minus the ambient temperature
in °C
C Conductivity factor as determined in 4.6.2.2
4.6.2.4 Determination of worst case orientation RTI
The equation used to determine the RTI for the worst case orientation is as
follows:
where:
trwc Response time of the nozzles in seconds for the worst case orientation
All variables are known at this time per the equation in paragraph 4.6.2.3 except
RTIwc (Response Time Index for the worst case orientation) which can be solved
iteratively per the above equation.
In the case of fast response nozzles, if a solution for the worse case
orientation RTI is unattainable, plunge testing in the worst case orientation
should be repeated using the plunge test conditions under Special Response shown
in table 2.
1 Tunnel conditions should be selected to limit maximum anticipated
equipment error to 3%.
2 A suggested method for determining radiation effects is by
conducting comparative plunge tests on a blackened (high emissivity) metallic
test specimen and a polished (low emissivity) metallic test specimen.
3 If the value of C is determined to be less than 0.5 (m.s)0.5 a C
of 0.25 (m.s)o.5 should be assumed for calculating RTI value.