The strength of the longitudinal joint is 30 kips/ft, whereas for the girth joint it is 15 kips/ft. Calculate the maximum diameter of the cylindrical tank if the internal pressure is 120 psi. Also discuss the joint strength and diameter of tank requirement for the given conditions

 Q# The strength of the longitudinal joint is 30 kips/ft, whereas for the girth joint it is 15 kips/ft. Calculate the maximum diameter of the cylindrical tank if the internal pressure is 120 psi. Also discuss the joint strength and diameter of tank  requirement for the given conditions                                                                                                                                                 (     

solution

D= ?

 p=  120psi / 17280lbs/ft² 

 ( for lognitudinal joints)   (consider  1ft length)  

 

F= 2T

P×D×1 = 2(t×1) σ t

lets simplify it;

tangential stress

σ t = pD/2t                                                                                      δt = PD/2t                                

 

30,000lb/ft²/ t  =  17280 ×D/ 2(t)

 

After simplification;

 

D =3.472ft   or 41.667in 

 

For girth joints                                                   

 F=P

P(π/4 ×D²)  = σ l(πDt) 

σ l = pD/ 4t 

15000lb/ft /t   ⇉    17280 ×D /4(t)         (t and t are cut to each other )

 15000×4/ 17280   

 

D= 3.472ft or 41.667in  Governoring diameter ids  D=41.667in 

so in the above case  the smaller diameter is the governing diameter  because  we know that the smaller diameter will be the governring diameter .