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Reg. 278, Reg. 279 A

End Plate subject to pressure on the concave side

Dished ends subjected to pressure on the concave side shall be determined by the following formula:

W. P. = 2 f ( T – C )
D K

where,

T = minimum thickness;
W. P = Maximum working pressure, Design pressure;
D = Outside diameter;
f = Permissible stress;
K = Shape factor as defined in sub-regulation (a) of regulation 277
and Figure 23D; and
C = an additive thickness equal to 0.75 mm.

The minimum head thickness should not be, however, be less than 5 mm.


Reg. 279 
STANDPIPES AND NOZZLES


(a) Standpipes and nozzles welded to shell

Where standpipes or nozzles are secured by welding, adequate compensation for the hole cut shall be provided. Compensation shall be considered adequate when the sectional area ‘X’ to be compensated measured through the axis of the shell is less than the compensating area ‘Y’ given in Figure 25-B

Sectional area X = ( dn x es )
Sectional area Y = 2 ( tn - ea ) b x fn + fn + 2 ( ta - es ) C1 ÷ C3
fs fs

where,

dn = internal diameter of the standpipe or nozzle;
ts = actual thickness of shell;
tn = actual thickness of standpipe or nozzle;
es = equivalent thickness of shell i.. e., thickness of a seamless shell of similar material unpierced by tube holes and is designed for the same conditions of pressure and temperature as the shell in question;
en = equivalent thickness of the standpipe calculated similarly as for e plus any thickness if required to withstand any external load on the standpipe or nozzle;
b = the least of the value of
             2.5 times t ;
             2.5 times tn ;

or if the length of the standpipe or nozzle outside or inside the shell is less than this value, ‘b’ shall be limited to the actual length in each case.

Cw = the aggregate cross sectional area of the fillet welds.
                                              dn
Ci = ts + 76 mm (3in.) or -----, whichever is greater;
                                               2
fs = the permissible stress for the material of the shell at the working metal temperature.
fn = the permissible stress for the material of the standpipe or nozzle at the working metal temperature.

In cases where ‘Y’ is less than ‘X’ a compensating plate shall be fitted to the shell at the standpipe and secured by fillet welds as in Figure 25-B.

The area of cross section of this compensation plate shall be governed by the ratio between the permissible stress at the working metal temperature for the material of the shell and the compensating plate.
 
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