Ansi Flanges Impact test

[juancito]

Acc. to Div.1, flanges made acc. to ANSI B16.5 or B16.47, are exempt of impact test until -29°F.
Questions are:
a)If for venting purposes, a 1"NPT hole is drilled in one of these flanges, is it still a flange under B16.5 / B16.47, or this slight alteration means that impact test has now to be done because the exemption is lost?
b)If I design a cover flange, identical to a say 30", 300 series, but 1/4" thicker because of the design pressure slightly over 740 psi, can I say this is an ANSI flange?
c)Which is the concept of this impact test exemption for ANSI flanges?. I ask this, because under a metalurgical point of view, I can`t see any difference between the flanges I mentioned above.
Thanks in advance

 

[1969grad]

Flanges are now under ASME and not ANSI.

From your post I assume you want to drill a hole in the rim.

I would think your situation is similar to an orifice flange which has taps drilled into the rim. You might want to consider using a standard orifice flange rather than ordering a special flange which could be expensive.

Orifice flange taps are smaller than 1" but it still might be sufficient for venting purposes. If not, you could use more than one of the taps.

Impact testing is a separate issue and depends on the material and design temperature. For example, carbon steel materials are acceptable down to -20 F but the design temperature can be extended lower with impact testing. Of couse you can select another material if you do not want to do impact testing. Otherwise, impact testing is a customer option depending on your company standards.

Drilling a hole in the face of a blind flange is another situation.

 

[bmoorthy]

A) Impact waiver stands.
If you look at it this way then there is more clear, say you weld a davit support in a manway flange, you drill extra hole in heavy flanges for jackscrew purpose etc. These operations are not considered to affect the impact waiver given to standard flange. If however the hole size is substantially large and would affect the flange strength, then it is another story. What is the limiting size of hole? Check with your AI (I am also looking for an answer)

B) No it is not ANSI Standard flange.
C) Don't know the rationale behind the waiver given to Standard flanges.