RE: Orifice Flange

From: <Prasad>
Date: Sat May 10 2003 - 00:49:00 EDT

Hello!

Orifice flanges (flanges with tappings for instrumentation connection) are usually bought only for sizes up to 12" (16" is mostly the upper limit). Beyond this size, the flanges are normal ones (B-16.5 or B-16.47A/B) because the tappings are not from flanges but from the connected pipes (i.e. the hub part need not be thicker to compensate for the tapping hole/holes...and hence ordinary flanges).

We may ask why are tappings from pipes and not the flanges. For this, we would need to go back to basics, to hydraulics, to bernouli's theorem, to "vena contracta" and the distance at which it is formed after the orifice, the accompanying change in velocity and drop in pressure. In fact, orifice has its demerits too, due to which other measuring alternates are used by Instrumentation at times.

Mahavir

   -----Original Message-----
   From: Sree Vardhana P.G. - [mailto:s_vardhana@yahoo.co.uk]    Sent: 10 May, 2003 1:37 AM
   To: PipingDesign@yahoogroups.com
   Subject: Re: [PipingDesign] Orifice Flange

   well ansi B16.5 shows upto 24" only for the flanges

   As per my knowledge if you wanted to have flanges    above 24" then u need to see ASME B16.47 class A which    includes MSS SP44 standards.

   if you wanted in API 605, then now it is covered in    ASME B16.47 class B for above 24" flanges.

   with regards
   sree vardhana p.g.

• virgilio balbuena <virgiliobalbuena@yahoo.com> wrote: > Friend,
  > Well ansi B16.36 show up to 24" only ..but if
  > you
  > will notice the flanges mention about 24" will be
  > the
  > same to MSS Sp 44 standard and by the way ,Do you
  > know
  > what is orifice flanges ? okay the flanges is
  > standard
  > and holes on the flanges upsteam and dowstream will
  > measure the differencial pressure and will be
  > converted to Flow.So the important part of this
  > assembly is the orifice between the flange.
  >
  > Regards,
  >
  > gil
  > --- lmathew@technip-coflexip.com wrote:
  > > Dear friends,
  > >
  > > I am a new Member.
  > >
  > > Can any body tell me is any standard for orifice
  > > flange assembly for sizes
  > > 26" and above.
  > > ( ASME B16.36 covers sizes up to 24")
  > >
  > >
  > > Regards
  > > Liju Mathew
  > >
  > >
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[Non-text portions of this message have been removed] Received on Sat May 10 00:49:00 2003