Estimate the thickness required for the component parts of the vessel shown in the diagram. The vessel is to operate at a pressure of $\frac{14}{b}ar($absolute$)$ and temperature of $300C.$ The material of construction will be plain carbon steel. Welds will be fully radiographed. A corrosion allowance of $2mm$ should be used.

Solution

Design pressure, take as $10$ per cent above operating pressure,

$=(14-1)1\mathrm{.}1$

$=\frac{14\mathrm{.}3}{b}ar$

$=1\mathrm{.}43\frac{N}{m}{m}^2$

Design temperature $300C.$

From Table $13\mathrm{.}2,$ typical design stress $=85\frac{N}{m}{m}^2.$

Cylindrical section

$e=\frac{1\mathrm{.}431\mathrm{.}5{10}^3}{285-1\mathrm{.}43}=12\mathrm{.}7mm$

add corrosion allowance $12\mathrm{.}7+2=14\mathrm{.}7$

say $15mm$ plate

UTAS Salalat$-$Cliteal Engineering

Domed head

$($i$)$ Try a standard dished head $($torisphere$)$:

crown radius $R_c=D_i=1\mathrm{.}5m$

knuckle radius $=6$ per cent $R_c=0\mathrm{.}09m$

A head of this size would be formed by pressing: no joints, so $J=1.$

$C_s=\frac{1}{4}(3+\sqrt[\phantom{2}]{\frac{R_c}{R_k}})=\frac{1}{4}(3+\sqrt[\phantom{2}]{\frac{1\mathrm{.}5}{0\mathrm{.}09}})=1\mathrm{.}77$

$e=\frac{1\mathrm{.}431\mathrm{.}5{10}^{3}1\mathrm{.}77}{285+1\mathrm{.}43(1\mathrm{.}77-0\mathrm{.}2)}=22\mathrm{.}0(mm{)}_{{?}_{?}}$

$($ii$)$ Try a "standard" ellipsoidal head, ratio major : minor axes $=2$:$1$

$e=\frac{1\mathrm{.}431\mathrm{.}5{10}^3}{285-0\mathrm{.}21\mathrm{.}43}$

$=12\mathrm{.}7(mm{)}_{{?}_{?}}$

So an ellipsoidal head would probably be the most economical. Take as same thickness as wall $15mm.$

Flat head

Use a full face gasket $C_p=0\mathrm{.}4$

$D_e=$ bolt circle diameter, take as approx. $1\mathrm{.}7m.$

$e=0\mathrm{.}41\mathrm{.}7{10}^3\sqrt[\phantom{2}]{\frac{1\mathrm{.}43}{85}}=88\mathrm{.}4(mm{)}_{?}$

Add corrosion allowance and round$-$off to $90mm.$

This shows the inefficiency of a flat cover. It would be better to use a flanged domed head. UTAS Salalah $-$ Chemical Engineering