Minimum Material Thickness 2

[PVdesigner]

Hi All
When the vessel specification calls for minimum material thickness (e.g 5/16" + Corrosion Allowance ), does it apply to minumum head thickness too? Any comments.Thanks

 

[pennpiper]

Jop: PVdesigner, How tall are you?

PVdesigner: I am 6'-1" tall

Jop: Does that include your head too?

 

[dcasto]

crack out the books. If the heads, shell or whatever will fail at the design point useing 5/16", then I'd use more wall thickness. If it only takes 1/4" on the parts, then I'd follow the letter of the spec.

 

[LSUME]

PVd
There are a few factors that need to be looked at when dealing with heads.
1. The ASME Sec VIII Div.1 calculated required thickness which is as you stated.
2. The min wall thickness called out on drawing & U1 form. This is generally the starting thickness of the head minus the forming allowance.
3. If you are dealing with heat exchangers, TEMA has a mininum wall requirement based on RCB(service) & diameter.

For example the code may require a 0.237" wall per calculations. You can order a head at 0.3125 min wall and the head manufacture may start with 0.375 aw plate. This could also be an 39" exchanger TEMA class R, which would then require the min wall to be 0.4375.