Chapter 18 Weld Inspection and Repair
275
Weld Integrity Inspections
Many weldments require destructive tests in
addition to nondestructive examination to verify the
weld quality. These tests may be imposed as part of
the qualifi cation test program, or an additional test
may be conducted during or after the manufacturing
cycle. The test requirements are usually a part of the
fabrication specifi cation.
Pressure Test
Pressure tests subject a vessel, tank, piping, or
tubing to internal pressure. Pressure tests can use
either air or fl uid. If a fl uid is used, the test is called a
hydrostatic test.
The test program may require a number of cycles
to be performed, simulating the use of the part in
actual service. During the test, the part will expand.
This expansion should not be restricted with tools, or
undue stresses will build within the part.
When conducting a pressure test, be alert to the
possible failure of the unit. Before beginning the test,
make sure the test procedure ensures the safety of
everyone in the testing area.
Hardness Test
Hardness tests involve pressing a test probe
into the surface of the weld. The amount of pressure
required to deform the surface of the weld metal is an
indication of the hardness of the weld or weldment. If
the weldment has been heat-treated (annealed, hard-
ened, tempered, etc.) after fabrication, the hardness
test will determine the effect of the heat treatment. A
hardness tester is shown in Figure 18-19.
Hardness test results can also be used to determine
the ultimate tensile strength of the material. The test
results can be compared with standard tables. (Refer to
the hardness conversion table included in the reference
section of this book.) Weldment designs that include
areas such as fl anges and extensions can be tested by
portable hardness testers as shown in Figure 18-20.
Weldment designs that do not have clear areas for
testing must have test bars of the same material (welds
if required) submitted with the weldment during
the heat-treating cycle. The bars are then tested on a
stationary tensile machine, as shown in Figure 18-14,
for the hardness results. Round tensile test bars are
shown in front of the tester in Figure 18-21. A fl at
tensile test bar is being tested in Figure 18-22.
Corrosion Test
Corrosion tests measure the ability of a weld to
restrict corrosion by a specifi c material. These tests
are usually performed on test weldments. The test
Figure 18-19. Rockwell hardness testing machine for
bench testing. (Mark Prosser)
Figure 18-20. Portable Rockwell hardness tester
for fl ange testing. (Qualitest International LC, www.
WorldOfTest.com, info@qualitest-inc.com)