Parr Instrument Series 4580 - Manual (Page 21)

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PERIODIC PRESSURE TESTS
Each cylinder used in a Parr stirred
reactor is tested under hydrostatic pressure
to 1.3 times its maximum rating before it is
released from the factory. For ASME U-
stamped vessels the minimum hydrostatic
test pressure is 1.3 times the rated working
pressure corrected for temperature. For CE
marked pressure vessels the minimum
hydrostatic test pressure is the higher of
1.43 times the rated working pressure at
room temperature or 1.25 times the rated
working pressure connected for
temperature. Micrometer caliper
measurements are taken during this test to
check the deflection of the walls under
pressure. Excessive deflection or failure of
the metal to resume its original dimensions
after pressure is released indicates that a
cylinder is potentially unsafe and it will be
rejected. Similar tests should be made at
regular intervals during the life of each
cylinder, and particularly whenever the user
suspects that the equipment has been over-
stressed or damaged.
Some laboratories maintain hydraulic
test facilities and make it a rule that all
pressure vessels must be tested at regular
intervals. Records are kept of deflections at
specific test pressures so that any increase
in deflection becomes a warning that the
metal has lost strength. Any cylinder that
fails to return to its original dimensions after
application of the prescribed hydrostatic test
should be discarded as unsafe for further
use.
Users who do not have pressure test
facilities can return any Parr pressure vessel
to the factory for hydrostatic testing and
overhaul. This should be done whenever
the metal shows excessive damage from
corrosion or whenever an over-pressure or
other unusual occurrence raises any safety
questions. To return a vessel for repair,
contact Parr Instrument Company for a
return authorization number. Apparatus
returned for testing and overhaul should be
shipped prepaid to Parr Instrument
Company, 211-53rd Street, Moline, Illinois
61265. An order or letter of instructions
should be mailed to the same address, as
no repair work will be started without specific
instructions and a Health & Safety
Assurance Certification form (F0042) signed
by a responsible user.