PRESSURE TESTING OF WINDOWS.
Each window must be pressure tested at least once prior to being
accepted for service.
The pressure test must take place with the window installed in the
chamber, or a test fixture whose window seat dimensions, retaining ring, and
seals are identical to that of the chamber.
The window must be pressurized with gas or water until design
pressure is reached. The design pressure must be maintained for a minimum of
one, but no more than four hours, followed by depressurization at a maximum
rate not to exceed 650 psi (4.5 MPa) per minute.
The temperature of the pressurizing medium during the test must be
the design temperature for which the window is rated with a tolerance of
+0/-5 deg. F. Brief deviations from the above temperature tolerances are
allowed not exceeding +/- 10 deg. F and lasting less than 10 minutes.
Windows that leak during the pressure tests must be removed, fitted
out with new seals, and retested. If, during the retest, the leakage
continues, efforts will be made to complete the test by stopping the leak
with a temporary seal. The inability of seals to operate properly during the
test must be noted in the test report, submitted at the conclusion of the
pressure test to the chamber manufacturer/user.
At conclusion of the pressure test, the windows must be visually
inspected for presence of crazing, cracks or permanent deformation. This
examination may be performed without removal of the window from the chamber.
Presence of crazing, cracks or permanent deformation visible with
unaided eye (except for that necessary to correct for 20/20 vision) must be
cause of rejection of the windows and must be so noted on the test report.
A hydrostatic or pneumatic test in excess of design pressure may be
substituted for the mandatory test of c. and d. During the hydrostatic or
pneumatic test the pressure must be maintained for a minimum of one, but no
more than four hours, The test pressure must not exceed 1.6 x design pressure
or 20,000 psi, whichever is the lesser value. The temperature of
pressurizing medium during the test must be at least 25 deg. F lower than the
design temperature to prevent permanent deformation of windows tested above
design pressure. All he other requirements of the mandatory pressure test
spelled out in e., f., and g. must be retained.
ANSI/ASME PVHO 1, requires extensive recorded documentation for
acrylic windows in manned chambers. Special forms must be completed for the
material properties, the fabrication procedures and the test methods for each
window. These forms are contained in the PVHO Code. The Navy's diving
safety program requires the same documentation for system certification.