UFC 4-390-01
23 July 2003
must be used to verify the calculated system design pressure.
There are three alternative methods of verification (SCA approval
of the method chosen must be obtained prior to testing):
a)
When comparable hull geometries and identical materials
have been successfully tested to a pressure greater than
the system design pressure of the vessel to be certified,
the existing test data can be substituted for destructive
model testing of the structure under review. Any
geometric differences between the hull requiring
verification and the comparable hull for which test data
exists should be brought to the attention of the SCA.
b)
For new designs that do not fall within the parameters
described in paragraph (a) above, the calculated failure
pressure may be verified by performing destructive model
tests, either full or reduced scale. When such testing is
performed, the structural model should be large enough to
contain representative prototype geometries, material
properties, and fabrication process restraints, tolerances
and residual stresses.
c)
Nondestructive pressure testing of the actual vessel to
be put into service in accordance with applicable
requirements of the ASME will be acceptable as
verification of the calculations. All others will be non-
destructively pressure tested to 1.5 times the maximum
operating pressure. When this option is chosen, the
calculated failure pressure must be greater than 1.5 times
the maximum operating pressure by a factor of safety
sufficient to preclude damaging the structure during the
test. The SCA should approve the ratio of failure pressure
to test pressure prior to testing. Clearly, use of this
method requires that the decision be made very early in
the design process because of the profound effect on the
structural design.
For Category 3 materials, the above testing requirements may not
be appropriate or adequate. The testing used must demonstrate
the same degree of conservatism as the testing requirements for
Category 1 and 2 materials. The factor of safety and all testing
parameters should require SCA approval.
B.3.3.1 Testing Procedures/Test Instrumentation. For all
vessels, a detailed test procedure should be developed and
provided to the SCA for review and approval prior to testing.
The test should be of sufficient duration to demonstrate that the
combined stress/temperature/time loads do not produce permanent
deformation or damage in the structure. If the tested structure
is to be used in service, a complete set of instrumentation
readings should be recorded at the maximum operating pressure
(this may be accomplished during instrumented testing to 1.5
times the maximum operating pressure). The test procedure should
include a detailed strain gage plan, which specifies the number,
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