ASME B31.3, FIG 323.2.2A, Note(6)

[sks4338]

What do you mean by following sentence?
"For blind flanges and blanks, T shall be 1/4 of the flange thickness"
in ASME B31.3, FIG 323.2.2A, Note(6)

Somebody says like this.
"If you have 40mm plate, you divide it by 4 and you get
10mm. With this 10mm, you read the graph of FIG 323.2.2A."
What he mens is that you divide the thickness of plate by 4, and
apply the dividend thickness, when you read the graph.

Is that right?
If it's right, why do you have to divide the thickness of plate by 4?

 

[metengr]

I reviewed the 2004 Edition of B31.3, per Figure 323.2.2A, which deals with "Minimum Temperatures without Impact Testing for Carbon Steel materials", where T is the nominal thickness. Note (6) reads that the nominal thickness (T) for blanks or blind flanges shall be 1/4 of the flange thickness. This is self explanatory.

As far as using the ¼ factor for nominal thickness, I would guess that it reduces the effect of plane strain or conditions of restraint that would otherwise severely penalize the use of blind flanges or blanks that are usually thicker in comparison to the component wall thickness to assure joint stiffness.

 

[bvi]

Because the plate is subject to a bending stress field rather than a general membrane stress.