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Reg. 278, Reg. 279 A
End Plate subject to pressure on the concave side
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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
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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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