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CONTROL VALVE INTRODUCTION
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Valve Inspection and Testing
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Pressure Test Procedures
GENERAL
Valves designed to permit emergency or supplemental
introduction of an inject able sealant to the seat area shall
be tested with the injection system empty and not in use,
except for lubricated plug valves.
When a liquid is used as the test fluid, the valve shall
be essentially free from trapped air during the test.
Required protective coatings, such as paint, which
may mask surface defects, shall not be applied to any surface
before inspection or pressure testing. (Phosphatizing and similar
chemical conversion processes used to protect valve surfaces
are acceptable even if applied before the tests, provided
that they will not seal off porosity.)
When closure testing valves, the valve manufacturer’s
test procedure shall ensure that excessive force is not
used to close the valve. The applied force may be determined
from the appropriate figures in MSS SP-91, but in
any case shall not exceed the values published by the valve
manufacturer.
The valve shall be visually examined for leakage
after it has been fully prepared and is under full test pressure.
BACKSEAT TEST
The backseat test is required for all valves, except for
bellows seal valves, that have the backseat feature and shall
be performed by applying pressure inside the assembled
valve with the valve ends closed, the valve fully open, and the
packing gland loose or packing not installed. If the backseat
test is performed after the shell test, the packing shall be
installed and/or packing glands re-tightened after the backseat
test. The successful completion of the backseat test shall not
be construed as a recommendation by the valve manufacturer
that, while the valve is pressurized, the valve stuffing box
may be repacked or the packing may be replaced.
For valves 4 in. NPS and smaller, the backseat test
may be combined with the shell test when volumetric
devices are used to monitor leakage from the shell and backseat.
When tested by this method, the packing shall be
loose. The manufacturer shall be responsible for demonstrating
that the packing will not leak at the valve’s rated
pressure at 100°F (38°C).
SHELL TEST
Except as provided in 4.2.2, the shell test shall be made by
applying the pressure inside the assembled valve with the
valve ends closed, the valve partially open, and any packing
gland tight enough to maintain the test pressure, thereby,
except for bellows seal valves, testing the stuffing box.
LOW-PRESSURE CLOSURE TEST
The low-pressure closure test shall be performed with
the seat sealing surface interface clean and free from oil,
grease, and sealant. If necessary to prevent galling, the sealing
surfaces may be coated with a film of oil that is not
heavier than kerosene. This requirement does not apply to a
valve that uses a lubricant as its primary seal (e.g., lubricated
plug valves).
Any leakage at the seat sealing surface interface,
behind the seat ring, or through the disk on the open side of
the valve shall be detected when bubbles are observed coming
from the closure (disk, seat, and seat ring), which is either
covered with water or coated with a soap or similar solution.
As an alternative, displacement measuring devices may be
used, provided that the detectable leakage rate is equivalent to
that given in Table 5, the valve manufacturer can demonstrate
and validate that the procedure yields results equivalent to the
requirements of this standard, and the device has been accepted
by agreement between the purchaser and the manufacturer.
Bubbler testing, when used for valves larger than NPS 2, shall
only be acceptable when agreed to by the purchaser.
When volumetric devices (bubblers) are used to measure
leakage, the test duration shall not begin until flow through
the test tubing is established and stabilized. The device shall
be calibrated to yield results equivalent to the units per minute
listed in Table 5. Volumetric devices shall be calibrated with
the same test fluid and at the same temperature as used for the
production tests.
When closure testing gate, plug, and ball valves, the
valve manufacturer shall use a method of testing seat leakage
that fills and fully pressurizes the body cavity to the test pressure
between the seats and the bonnet area, as applicable,
with the test fluid. This will ensure that no seat leakage can
escape detection because of gradual filling of these volumes
during the test period.
For a valve (other than a double block-and-bleed valve or
globe valve) designed to close against pressure from either
direction, the pressure shall be applied successively to each
side of the closed valve with the other side open to the atmosphere
to check for leakage at the atmospheric side of the closure.
For a globe valve, pressure shall be applied in one
direction with the pressure applied under the disk.
For a valve designed to close against pressure from one
direction only and so marked, the pressure shall be applied on
the pressure side of the valve only. For a check valve, the
pressure shall be applied on the downstream side.
For a double block-and-bleed valve, the pressure shall be
applied successively to each side of the closure through the
valve port. Leakage into the body cavity between the seats
shall be checked through observation at a tapped opening
between the seats. Valves shall be tested with the stem in the
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DOE
Document - Std 598, valve inspection and testing, sixth edition,
Open this result
in new window book covers inspection, supplementary examination, and
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with prosthetic heart valves therefore require periodic clinical and
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EPA: Federal Register: Industry Codes and
Standards; Amended Requirements
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EPA: Federal Register: Industry Codes and
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pressure tests. The use of special equipment, examination techniques, and
evaluation of test results associated with other NDE methods such as
volumetric and surface examinations Our Standards of Inspection Open this
result in new window Advantage Inspection provides home inspections
throughout the Southeast. We also market our unique business opportunity by
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inspection practice shall be required to pass an examination as provided ...
FIXTURES AND OUTLETS: Test a representative number of Determine if pressure
relief valve is present ...
www.advantage-inspection.com/standards.html
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