ForumB31.1 Power Piping: Y Factor in Pressure thickness formula 3A
From: Salman [1088]
Date: Thursday, July 29, 2010
Time: 2:58:29 AM
Remote Name: 202.163.127.122
Comments
My questions is based on Pressure thickness formula 3 & 3A in B31.1 referring to 2007 edition.For ferritic allow steel the y factor is 0.4 for temperatures 482 degC and it increases to about 0.7 at 538 degC and remains 0.7 for any values of temperature above.
In General Notes: b of figure: 104.1.2A [y factor table], code says
For pipe with a Do /tm ratio less than 6, the value of y for ferritic and austenitic steels designed for
temperatures of 900°F 480°C and below shall be taken as:
y d/d+Do
Question is what is d stands for in the above formula. Code mentions this small d in Nozzle re-inforcement area calculation as the dia of branch where Do is the dia of header. Calculation of thickness is independant of branch and header configuration combined i.e. We have to calculate pressure thickness/min thickness by NOT considering what branch or header configuration it is. This d must be something else or ID may be but I need the confirmation on Notes: b as of where we would take this d value from?
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