Question about ASME section I

[carthago]

.Boilers

Could someone help and give the formula wall thickness for an ellipsoidal head ( 2:1).

I was expecting something like
t =( P*L) / [ 2*S -0.2*P])

with L = 0.9*D
D= Boiler diameter corroded

.......I started doubting when I saw THE FORMULA

T = (5*P*L) /( 4*8*S)

 

[prex]

You are mixing up things.
The first formula is for a thick full hemispherical head, the second one for a dished head.
For a 2:1 ellipsoidal head the code requires the minimum thickness being the same as for a cylindrical shell with the same diameter.
You should have the code in your hands if you need to do this type of calculation or check other's calcs: for each calculation there are side rules and limits to be fulfilled.

prex

http://www.xcalcs.com

: Online tools for structural design

http://www.megamag.it

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http://www.levitans.com

: Air bearing pads

 

[carthago]

prex
thanks for this clarification.

---------------
I have the Code..the point is how to read it !!

For 2:1 ellip heads= are you refering to paragraph PG-29.6 ?
if not please specifiy which paragraph is applicable to ellip. heads



What is the exact definition of a dished head then??
is and 2:1 ellip. head not a dished head ??

 

[prex]

The paragraph is PG-29.7.
A dished head, otherwise called a torispherical head, has a central spherical portion with large radius (usually equal to shell diameter), and a torical knuckle with a small radius that connects to the shell. A 2:1 ellipsoidal has an elliptical shape (theoretically) in a diametral section and the depth is half the shell radius.

prex

http://www.xcalcs.com

: Online tools for structural design

http://www.megamag.it

: Magnetic brakes for fun rides

http://www.levitans.com

: Air bearing pads

 

[eliebl]

An ellipsoidal head can be approximated by a dished section (crown radius) that is 90% of the OD and a knuckle that is 17% of the OD. In no case can the dish radius exceed the OD of the skirt (shell) nor can the dish radius be less than 6%.

The formula in PG-29.1 is the correct one for dished heads unless they are hemispherical. Note that the divisor is 4.8 not 4*8.

EJL