It is my understanding that orifice flanges are typically 300# rating so that there is enough flange thickness to tap into. In the
larger pipe sizes, perhaps pipe taps are used to lessen the cost of purchasing a pair of flanges (just a guess). In cold boxes, we
used to use pipe taps and welded-in orifice plates regularly to minimize the possibility of leaks and for less mass during cooldown
(I.E., no retained heat within bulky flanges).
Paul
> BS1042 describes three tapping methods for orifice plate pressure
tappings;
> D and D/2 tappings, flange tappings, corner tappings. The pipe diameter
> range is up to 1000mm.
> For flange tappings, the tap points must be nominally one inch from each
> face of the orifice plate.
>
> I would expect the reason why tapping flanges in larger sizes are not
> available is because there is very little demand for then.
>
> Orifice plates "waste" a fair amount of energy; typically 20% of the
> measured pressure differential (times flow), and much more if low flow
> accuracy is required.
>
> In larger sizes, many use venturi tubes, magflows, annubar, ultrasonic
and
> heaps of other flow measurement devices. The energy savings normally
justify
> the use of a more expensive flow measurement device.
>
> Cheers
>
> Steve McKenzie
>
>
> -----Original Message-----
> From: alwyn KAYE [mailto:altecheng@primus.ca]
> Sent: Sunday, May 11, 2003 7:05 AM
> To: PipingDesign@yahoogroups.com
> Subject: Re: [PipingDesign] Orifice Flange
>
>
> i dont understand this answer. Are you saying the orifice is in the pipe
in
> bigger sizes. This is not right. Orifice flanges have the orifice
sandwiched
> between them, I dont beleive it has anything to do with instrumentation or
> tappings in the pipe (you said ......."because
> the tappings are not from flanges but from the connected pipes").
>
> The orifice still has to be mounted into some rigid conmector whatever
size
> the flange or pipe is.
> ----- Original Message -----
> From: Prasad Mahavir/piping
> To: PipingDesign@yahoogroups.com
> Sent: Friday, May 09, 2003 10:49 PM
> Subject: RE: [PipingDesign] Orifice Flange
>
>
> 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")
Received on Sat May 10 20:42:00 2003
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