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In COMPRESS, you cannot directly attach
a nozzle to an ASME B16.5/B16.47 blind
flange. You must design the blind flange
as a bolted cover per UG-34, which in
turn is attached to a bolted flange as
designed per Division 1 Appendix 2. A
nozzle may then be attached to the
bolted cover.
This lengthy process is required
because: (1) the replacement area
required to reinforce the nozzle opening
is a function of the required thickness
of the blind flange. This value is
available only when the blind flange is
analyzed as a bolted cover. Analyzing as
a bolted cover per UG-34 requires that
the edge moment come from the flange
analysis. (2) The standard blind flange
pressure-temperature ratings are based
on the flange cover without holes.
A flange dimension "lookup" button is
available on the Appendix 2 flange
design dialog to import the dimensions
of standard ASME/ANSI flanges to ease
modeling the standard flange as an
Appendix 2 flange.
Note: Many standard flanges do
not meet their pressure-temperature
ratings when analyzed per Appendix 2. In
this case, COMPRESS will increase the
flange thickness as required. Therefore,
the flange may not correctly model the
actual dimensions. In these cases, you
should use the "Rating" mode (Set Mode
Options/Calculation tab) so that the
flange dimensions will not be changed.
Note: ASME B16.5 Table 7
permits a single tapped hole to be
located in the center of a blind flange
without affecting the
pressure-temperature rating. The maximum
size of tapped hole varies with the size
of the blind flange. Because ASME
Section VIII accepts standard pressure
parts as rated in the applicable
standard, Table 7 may provide an
exemption from area reinforcement for a
single concentric nozzle located within
a standard blind flange. In this case,
the nozzle should not be modeled in
COMPRESS (model the blind flange and
mating flange as standard ASME B16.5
parts and they will be accepted based on
their pressure-temperature rating).
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