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Optional UCS-66.1 Reductions (ASME B&PV Code, S. VIII)

Optional UCS-66.1 Reductions (ASME B&PV Code, S. VIII)

Optional UCS-66.1 Reductions (ASME B&PV Code, S. VIII)

(OP)
I'm using some software that has an option box to "take Fig. UCS-66.1 reduction" in calculating minimum design metal temperature.  Right offhand, I can't think why you wouldn't take that reduction all the time.  But in that case, why would it be optional in the software?  Am I overlooking some instance when that reduction should not be used?

RE: Optional UCS-66.1 Reductions (ASME B&PV Code, S. VIII)

JStephen, in the past there were a some design details for which Fig UCS 66.1 reductions were troublesome to calculate and support (defend), such as nozzle reinforcement and girth flanges although these have been made easier by more recent Editions / Addendas allowing ratios of MAWP's.

Customer specs may restrict this reduction, and additionaly, for a program I use often (shall remain nameless) I don't trust it.

When I do take the reduction I get out my Code book and do it myself. If there is another way, I won't normally take the reduction.

Regards,

Mike


 

RE: Optional UCS-66.1 Reductions (ASME B&PV Code, S. VIII)

The problem that I have with taking this reduction is that you pretty much have to have the vessel designed in order to quantify the stress level at which you enter the chart in the first place.

A similar situation exists with Figure 323.2.2(b) in ASME B31.3.  By the time you are in a position to satisfy the footnotes to be used in conjunction with the chart, you pretty much should already have done your flexibility analysis, which typically puts you at a stage in the design that is a bit too far down the road to start deciding if you can be A106 or A333.

Regards,

SNORGY.

RE: Optional UCS-66.1 Reductions (ASME B&PV Code, S. VIII)

The above stated, if the software or the calculation is such that the MDMT is an *output* instead of an *input*, the option to take the reduction makes a bit more sense to me.

Regards,

SNORGY.

RE: Optional UCS-66.1 Reductions (ASME B&PV Code, S. VIII)

There are some client specs that do not allow UG-20(f) exemption or UCS-66.1 reduction. They just have higher requirements on impact tests.  

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