This type of configuration is not covered by PVElite. However, you can still simulate this configuration. There are 2 important points that Design Engineer has to take care:
1: Stress ratio between the Shell/Head material & forging lip material. If this ratio is more than 1.0, then the lip thickness shall be equal to shell/head thickness multiplied by the stress ratio. However, this will open another trick that I will detail below. (Trick #1) (Trick #2)
2. The MDMT curves as well as the Impact test exemptions shall be re-examined for the lip material.
Trick #1:
Engineer has to take care that the increased lip thickness due to stress ratio is the minimum thickness for the lip. This means; if the difference in thickness between lip and shell/head goes behind the allowed difference for the butt joint (that is most likely 3 mm), then taper on lip is not acceptable because of the thickness reduction. The taper must be provided by overlapping the weld over the shell/head.
Trick #2:
Engineer has to check the MDMT and stress values case by case and not to depend on past experience. It is really dangerous. Some materials are equivalent in stress values upto certain temperature. Above this temperature differences will start to take place. And, there are materials equivalent in Div.1 but not equivalent in Div.2. SA-350 LF2 is a common example for this.
Trick #3:
The best way to avoid the above problems; Engineer to design the normal vessel as of there is no lip. Then, to model in a separate file a head with one course of shell in the lip material and to run the analysis. Lip thickness and all other code requirements shall be taken from this report. Other requirements related to the reinforcement shall be taken from the master file.
Regards,
M.Salaheldin
_________________________
Regards;
M.Salahedin
ALZAMIL HEAVY INDUSTRIES, LTD.
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