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Active Contributor

Join Date: May 2010
Posts: 18

Minimum Flange Rating

05/17/2010 3:18 AM

Why min 300# flanes are specified for C/Vs, SDVs, Orifice flanges etc

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Guru
Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

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#1

Re: Minimum Flange rating

05/17/2010 3:25 AM

This is similar to another recent question. I'm not sure that it's even true, but for one thing, the bolting patterns for Class 150 and 300 flanges are different. If many such valves and instruments are manufactured to Class 300 dimensions, that could be what is driving this issue.

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Active Contributor

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#2
In reply to #1

Re: Minimum Flange rating

05/17/2010 9:14 AM

Can anyone throw some more light on the topic?

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Commentator

Join Date: Dec 2007
Location: texas
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#3

Re: Minimum Flange Rating

05/17/2010 9:02 PM

Hi'

Orifice flanges are required to be 300# series to accommodate the drilling and tapping for the pressure taps(1/2" pipe) some of the smaller 150# flanges are not thick enough to drill and tap without compromising the integrity of the flange.

I am not aware of 300 # flanges requirement for control valves. Our piping specs don't allow any 150# flanges smaller than 3" in hydrocarbon service because we don't like using four bolt flanges so we have to use 300# flanges for control valves in those sizes.

Thank you

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#4

Re: Minimum Flange Rating

05/17/2010 10:30 PM

HVAC uses lots of 'less than 300 class' flanged valves because (compared to mnay processes) HVAC is relatively low temperature, low pressure. Hey, if a lower class is suitable for the process conditions and it saves money . . . .

I assume that the drive to "standardize" contributes to specing one or the other.

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Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

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#5

Re: Minimum Flange Rating

05/18/2010 5:03 AM

PN16 is common in the water industry.

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Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

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#6
In reply to #2

Re: Minimum Flange rating

02/23/2022 10:45 AM

Yes. The valve and instrument manufacturers can. Telephone?

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