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[
EJ GUIDE ]
Internal Liner
 Internal
liners or baffles are a recommended accessory to
extend the life of many metallic expansion joints
because of their ability to protect the convolutions
from direct flow impingement, which can cause erosion
and flow-induced vibration. Internal liners should be
used when internal flow conditions exceed the
following criteria:
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Internal sleeves
shall be specified for all expansion joints,
regardless of the metal of the bellows in the
following cases. |
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Where it is
necessary to hold friction losses to a minimum
and smooth flow is desired. Where flow
velocities are high and could produce resonant
vibration of the bellows. Sleeves are
recommended when flow velocities exceed the
following values |
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Air,
Steam and other Gases
1) up
to 6-inch dia. - 4 ft/sec per inch of dia.
2) over
6-inch dia. - 25 ft/sec. |
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Water
and other Liquids
1) up
to 6-inch dia. - 1-2/3 ft/sec per inch of dia.
2) over
6-inch dia. - 10 ft/sec.
When
turbulent flow is generated within ten pipe diameters
of the expansion joint by changes in flow direction,
valves, tee or elbow sections, cyclic devices, etc.,
the actual flow velocity should be multiplied by four
prior to utilizing the criteria of the Standards of
the Expansion Joint Manufacturers Association Sections
C-3.1.2 and C-3.1.4.
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Where
there is a possibility of erosion, such as in
lines carrying catalyst or other abrasive media,
heavy gauge sleeves should be used. At no time
should the relatively thin bellows be directly
exposed to erosion.
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Where
there is reverse flow, heavy gauge sleeves may be
required.
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For
high temperature applications to decrease the
temperature of the bellows and enable the metal to
retain its higher physical properties. (To obtain
a maximum effect, the expansion joint should not
be externally insulated.)
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Internal
sleeves should not be used where high viscosity
fluids such as tars, etc., are being transmitted,
since these fluids may cause "packing
up," "coking" and
"caking" which, in turn, may cause
premature expansion joint failure. Where the fluid
is such that purging will effectively prevent the
"packing up," internal sleeves may be
used in conjunction with purge connections.
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The
standard PT&P internal liner is made of 300 Series
stainless steel. If corrosion or temperature
considerations dictate, the liner can be made of the
same material specified for the bellows.
The
liner is a longitudinally welded tube attached at one
end to the upstream end connection. The diameter of
the liner is small enough that the free, downstream
end will not interfere or contact the downstream end
connection during lateral or angular deflections. When
a standard expansion joint is selected from this
catalog with the internal liner accessory, the
expected lateral deflection should be stated so that
the liner diameter can be properly sized.
If
expected flow rates will be very high, such as at
steam safety relief valves or in turbine exhaust and
extraction steam applications, the internal liner
should be of heavier construction. Usually, the liner
material can be the same as the system pipe material,
such as carbon steel, with liner thickness' of
1/8-inch and greater depending upon flow rate and
diameter.
Internal
liners are almost always welded into the expansion
joint. However, if the Van-Stone flange end connection
is specified, the PT&P liner will have its own
flange and will be captured between the flanges at the
upstream connection into the piping.
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EJ Guide |
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= Featured Product =
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+ View larger images
Go to featured
product archives
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U.S. Bellows, Inc. Designed and Fabricated 50
Universal Expansion Joints for an Air Force Base in New Mexico
(Ref#91376-A1, EA) 11/14/2007
U.S. Bellows, Inc. fabricated 50 expansion joints from 304L
stainless steel. The expansion joints were 6" and 8" sizes. The 6"
expansion joints are 24" face to face and the 8" expansion joints
are 26" face to face. All of the expansion joints are fabricated
with liners that are also made with 304L stainless steel. The design
temperature was 200°F and the design pressure was 200 PSIG. The
expansion joints were dye-penetrant tested and hydro tested at 300
PSIG. U.S. Bellows, Inc. provides 100% customer satisfaction in
terms of quality and delivery.
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FAX: (713) 731-8640