Design Procedure for Flange Joint for a Cylindrical Pressure Vessel

Design Procedure for Flange Joint for a Cylindrical Pressure Vessel

a)  Design of Gasket :-

 i)Gasket inside diameter (G_i)= Do + 10

ii)G_o / G_i = ( y – pm / y – p(m+1) )^1/2

Here p is operating internal pressure

m= gasket factor

 y = gasket seating stress

Now, After calculating the ratio G_o / G_i substitute the value of G_i and calculate

iii) G_o i.e Gasket outside diameter _.

Then calculate,

iv) Mean Gasket Diameter(G)  = G_o + G_i / 2

v) Width of Gasket ( N ) = G_o - G_i / 2

       vi) Basic Gasket seating width b_o = N/2

Now,

If b_o < 6.3 then b = b_o    &

If b_o > 6.3 then b = 2.5(b_o)^1/2

Here, b is Effective gasket seating width

Also, G is calculated as :-  G_o – 2b

b) Design of Bolt :-

i)                 Bolt load under atmospheric condition is calculated as :-

         W_m1 = π b G Y_b

         ii) Bolt load under atmospheric condition is calculated as :-

                 W_m2 = π (2b) G m p + π/4 G² P

Consider the greater value from W_m1 and W_m2 for all the further calculations.

iii)           Area of bolt required at atmospheric condition:-

A _m1 = W_m1 / f_a

_Here  f_{a is allowable stress of bolt material at atmospheric condition.}

iv)           Area of bolt required at operating condition:-

A _m2 = W_m2 / f_b

_{Here  fb is allowable stress of bolt material at operating condition.}

         Consider the greater value from A_m1 and A_m2 for all the further calculations.

v)              No. of Bolts(n) = G/ 25(should be a factor of 4)

vi)           Bolt Diameter ( d_b ) = ( 4 x A_m(max) / π x n )

_vii)        Bolt circle Diameter (B) = G_o + 2 d_b

_viii)     Actual bolt spacing required( b_s ) = π x B / n

c)   Design of Flange :-

    Outside diameter of flange :-

        D_fo = B + 2 d_b

 

            Flange thickness( t_f ) = G ( P/ kf )^1/2

k = 1 / ( 0.3 +( 1.5 W_m(max) h_G/H x G ))

Hydrostatic end force (H) = π/4 G² P

Radial distance from gasket load reaction to bolt circlr (h_G)= B – G / 2