Page 75 - Pressure Vessel Design Manual

56 Pressure Vessel Design Manual

DERIVATION OF FLANGE MAXIMUM ALLOWABLE PRESSURE

1. Calculate Moments M, through M5 as follows: I @ Design Temperature I @ Ambient Temperature

MI = (Lesser of 1.5 Sf, or 2.5 Sfa) &I: B
f
~
Sf,hBt2
M2 =-
I .33te + 1
SfohBt2
M3 =
YA - Z(1.33te + 1)

2StoABt2g:
Mq =
f?+(l.33te + 1)g:

MMAX = Lesser of MI thru M5
1. Calculate the Maximum Allowable Moment @ Design Temperature @ Ambient Temperature

I I
2.
~MMAX( @Ambient Temperature)
&(MAX) = - Ab
hGSa
Note : If Am2>Am(MA~), then the gasket width, seating stress, or bolting is insufficient.
3. Determine the Maximum Allowable Pressure set by the Maximum Allowable Moment: (Operating Condition)
M~m(@Design Temperature)
0.785B2hD+6.28bGmh~+0.785(G2 - B')h,
4. Determine the Maximum Allowable Pressure set by Am(~~x): (Gasket Seating)
SbAm(MAX)
6.28bGm + 0.785G2

5. The Maximum Allowable Pressure = the lesser of 3. or 4.
Note that this pressure includes any static head applicable for the case under consideration.
Maximum Allowable Pressure =
MAWP is based on corroded condition at design temperature.
When MMAX is governed by Mz: Check integral type flange for new & uncorroded condition.
MAP (cold & corroded) is based on corroded condition @ ambient temperature.
MAP (new & cold) is based on new condition @ ambient temperature.