| a) |
In cases where the headers
are of such irregular form as to render impracticable
the application of a formula for the determination of
thickness, the manufacturer shall show the suitability
of the headers for the working conditions by indicating
practically the maximum internal hydraulic pressure which
a header, made to the same design and of similar material,
will withstand without permanent deformation. The maximum
working pressure for similar headers may then be determined
by the following formulae:-
| W. P. = P1
x |
Permissible
stress at working metal temperature |
Eqn.(90) |
|
F x C
|
where,
W. P. = The working pressure in lbs. Per sq. In.
P1 = The maximum internal hydraulic pressure withstood
without, permanent deformation.
F = 1.75 for wrought steel and 2 for cast steel.
C = 15500 for wrought steel of 24 tons per sq. in minimum
ultimate tensile stress.
= 16500 for wrought steel of 26 tons per sq. in minimum
ultimate tensile stress.
= 18000 for wrought steel of 28 tons per sq. in minimum
ultimate tensile stress.
= 21000 for wrought steel of 32 tons per sq. in minimum
ultimate tensile stress.
= 22000 for wrought steel of 34 tons per sq. in minimum
ultimate tensile stress.
= 15500 for wrought steel of 28 tons per sq. in minimum
ultimate tensile stress.
|
