Flange Rating 9

[darrenyee88]

1. How do we decide the flange rating for pressure vessel? Based on the design pressure and MAWP?

2. If the flange rating is 150 psig and the hydrotest is UG-99(b) excluding the footnote 34, the hydrotest values came out higher than the flange rating of 150 psig. Will this detroy the flange?

Please answer my queries. Thanks.

Regards,
Darren

 

[pdprao]

One need to refer and understand the standard ANSI B 16.5 which defines the terms" Primary pressure" and" Primary temperature" for various Flanges ratings. ANSI B 16.5 Flange ratings are designated as Class 300 #, class 600# ,etc .
For Flange Pressure rating class 150 #,300#, 400# etc , the corresponding non-shock working pressure value permitted is 150 Psi, 300 Psi , 400 psi" etc which is known as "Primary pressure values" at "Primary temperature" . Primary temperature values are given for each Class of Flange, and material Groups.
Example: For Class 150# Flanges, of Material group 1.2 , Maximum working pressures are given bellow at different operating temperature.
-20 to 100 F --- 270 PSIG.
400F --- 180 PSIG
600F---- 150 PSIG( PRIMARY PRESSURE OF 150PSIG & PRIMARY TEMPERATURE @ 600F)
800F---- 75 PSIG

FOR Flange Class 300# and Higher class ratings ,the "Primary pressure Values" corresponds to higher" Primary temperatures" value of 850 F.
A pressure vessel design pressure and test pressure depends on process requirements and there is no manufacturing standard except design codes. Where as Flanges are manufactured to a standard ratings such as 150#,300# ,400 # etc for reasons of economy of Industrial production. One need to select the Flange rating which is very close and above the pressure vessel Design pressure&temperatures as per B 16.5 standards.

 

[darrenyee88]

Thanks all.