The PWHT is a function thickness, material and service. This is
quite clear in the B31 rules. Consider you need to repalce a piece
of spool that has been service for quite a period of time. Let us
say the pipe has expreinced some damage or defect and would want to
replace a section between welded joint. Cut and prep at welded joint
and reweld new pipe at same location. If thickness is under 19 mm,
the service is say steam line witth temp within the B31 range and
the matl is A106B then a pWHT is not reqd. This can be done rpvided
that the haz has passed the reqd NDT - lamellar, other defects. If
this is allowed under the rules of B31 then the 50mm rule of thumb
simply means just that - a rule of thumb (no basis, it just
speculate that the HAZ will somehow be impared). Sure its nice, but
when a situation arises then not fooliwing it will not be breaking
any Code rules.
- In PipingDesign@yahoogroups.com, "Parsons, Matthew M SUKOPPRJ
/52/01" <matthew.parsons@s...> wrote:
>
> 50mm is a good general rule for proximity of Pressure retaining
joints, however it is possible to apply a spacing of less than this
distance, but the consequences could result in PWHT. Some
inspectors will allow distance of 4x thickness of pipe or square
root of Dxt, but you should always consult your welding inspector
before breaking this 50mm golden rule.
>
> Hope this helps
>
> -----Original Message-----
> From: tomcruz55 [mailto:tomcruz55@y...]
> Sent: 26 March 2003 19:04
> To: <a href="/group/PipingDesign/post?postID=UR9f3umEWFZuSwvBQtfhUK5JGzd1BYNrx0Ix-Nip00cPX4JUTSIMJx4uJnYn7Jnak-HIgjcnSOAXEDBnNMxdx4AvSaQGNA">PipingDesign@yahoogroups.com</a>
> Subject: [PipingDesign] Re: Minimum distance between Fittings
>
>
> The HAZ width in butt weld joint is very very narrow. So what's
with
> the 50 mm pup piece? We've welded a pup piece less than this to
make
> up for the shoratge in the "short lenght" gate valve without a
> problem. As long as it pass the NDE and hydro and matl is usitable
> for service, chances are your fabricated pipe spool will be OK.
>
> For the criteria related to dimesnion of fabricated spool, ive go
> with the PFI Standard.
>
> --- In PipingDesign@yahoogroups.com, "Glenn Dillon"
> <glenn.dillon@t...> wrote:
> > Hitesh, assume these are butt weld fittings. Fitting to fitting
is
> > preferred but where not possible I work on minimum pup spool
> distance of 50
> > mm to allow for weld effected zone and weld efficiency. Haven't
> had any
> > failures yet. With steam, elbows can be highly stressed and its
> best to
> > ovoid short pipe sections and layout distribution to allow
fitting
> to
> > fitting.
> >
> > Hope these comments of some help. Best regards Glenn
> >
> > -----Original Message-----
> > From: Ashok Dani [mailto:ashokdani@t...]
> > Sent: Friday, March 22, 2002 4:29 PM
> > To: 'pipingdesign@yahoogroups.com'
> > Subject: [PipingDesign] Minimum distance between Fittings
> > Importance: High
> >
> >
> >
> > > What is the minimum distance required between Bend-Tee or Tee-
Tee
> for
> > > Steam
> > > line or as per B31.1?
> > > Thanks in advance
> > > Hitesh
> >
> >
> > _____________________________________________________
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> >
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Received on Sat Mar 29 04:44:00 2003