| RTD Serial number: ___________
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Child Reference Test Device - Buoyancy Tracking and Verification
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To achieve repeatability in human subject
and manikin testing, the overall buoyancy and distribution of buoyancy
between the front and back of the RTD should be maintained within
a tight tolerance as specified in Table 1.
Table 1 SOLAS child RTD buoyancy
and tolerance
| Limit / Units
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Front buoyancy(1)
(2)
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Back
buoyancy(1)
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Total
buoyancy(1)
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Buoyancy
distribution(3)
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| Design / N
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63
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25
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88
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71.5% in front
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| Maximum / N
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65.4
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26.2
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91.6
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73% in front
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| Minimum / N
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60.6
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23.8
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84.4
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70% in front
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| (1)
Values at or corrected to standard temperature and pressure.
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| (2) The
left-to-right buoyancy distribution in the front inserts is to be within 1.3
N of each other.
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| (3)
Buoyancy distribution is calculated by dividing the front buoyancy by the
total buoyancy.
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The buoyancy of a new RTD may exceed the allowable tolerance
range until the normal shrinkage or compression of the foam inserts
stabilizes. Until the buoyancies of the foam inserts have stabilized,
buoyancy and distribution should be checked at regular intervals (perhaps
weekly), and then at least monthly thereafter or whenever used for
testing, whichever is longer (frequent use may require more frequent
checks). Only RTD's with buoyancies within tolerance should be used
for certification testing. A data sheet to document the buoyancy and
buoyancy distribution of the RTD is attached.
To check buoyancy tolerances, foam inserts need to be removed
from the device. Take care that all trapped air is removed when checking
buoyancy and that layers are maintained in their proper sequence when
reinstalled (considerable effort would be needed to remove entrapped
air if testing the intact device).
Adjustment of buoyancy: At the time of manufacture
the left-to-right distribution of buoyancy in the front inserts was
adjusted to be within 1.3 N of each other. To achieve this tolerance,
the layers were individually selected to achieve the cumulative insert
buoyancy. If buoyancy of a new device exceeds the upper limits, one
layer per compartment may be altered or replaced to bring the unit
into compliance. The test house may need to add make-up layers (see
figure 3) from time to time to maintain the front-to-back and side-to-side
insert tolerances. If the front buoyancy is under the minimum value,
measure the buoyancy of the right and left sides so that the proper
distribution of buoyancy (no more than a 1.3 N difference) between
the right and left front panels can be maintained.
Table 2 SOLAS child RTD insert
design buoyancies
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Combined left front
insert (13 layers)
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Combined right front
insert (13 layers)
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Combined back insert
(11 layers)
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| Design (N)
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31.5
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31.5
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25
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| S/N ____ Date:
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RTD Buoyancy Data Sheet
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| RTD
Serial number/identification: _________________
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| Date
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Left front
buoyancy
(N)
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Right front
buoyancy
(N)
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Total front
buoyancy
(N)
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Total back
buoyancy
(N)
|
Total
buoyancy
(N)
|
Buoyancy
distribution
(% in front)
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Remarks
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(1)
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(2)
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| (1) Left
and right front buoyancy need not be checked if distribution is within
tolerance.
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| (2) If the temperature and pressure at the
time of measurement is not at standard conditions, these values should be
corrected to standard temperature and pressure.
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Figure 1 Front foam insert specifications
Figure 2 Back foam insert specifications
Figure 3 Child RTD "make-up" foam insert sizes