You guys dont seem to have a lot of faith in fitter/welders.
There are heaps of stab-in connections that work just fine. Lots of approved
procedures around, and are commonly used even on critical service.
Suppose you want a 1" branch line of a 12" water line, not critical service.
Using readily available fittings and complying with your requirement you
need:
1X 12" cut &prep, 1X 12"X4" reducer, 1X 4"X2.5" reducer, 1X 2.5"X1" reducer,
1X1" cut and prep, 2X12" welds, 1X4"weld, 1X2.5" weld, 1X1"weld.
This is using the standard fittings in my book; it may be possible to
eliminate a reducer or two.
For a stab in you need:
1 penetration burn (or drilled), grind & prep, 1 X 1" profiled cut and prep,
1 X 1" weld.
If there is an issue with wall thickness an olet will be required - extra
weld, larger prep.
The quantities speak for themselves as to the amount of work involved.
I think the "requirement" is intended to prohibit poor quality work and work which cannot be repaired easily. If this is the case, then the requirement needs more comprehensive wording by an experienced person.
Cheers
Steve
-----Original Message-----
From: ed engalan [mailto:edengalan@hblpipe.com]
Sent: Wednesday, May 05, 2004 8:30 AM
To: PipingDesign@yahoogroups.com
Subject: RE: [PipingDesign] Banching from pipes
I agree with you, Chris........making saddle connections is not for the faint of heart much more for the inexperienced.
But assuming that workmanshipwise everything is equal (some contractors have the expertise and the experience to do quality saddle connection), then the rest is labor and material. Try a 36" main and a 24" branch Carbon Steel assembly.
If you do a saddle connection, you have your 36" & 24" pipe (most probably in stock or readily available) and a 24" weld and 1 1/2 times fit up time than a butt weld.
If you go the fitting way, you have the cost of the 36" x 24" reduced tee and not readily available. You have (2) 36" weld and (1) 24" weld with buttweld fit-ups. The scenario just got worse if the reducing tee is not available, then you have to go to a full size tee and a 36" X 24" reducer.
Multiply these scenario umpteenth times........better yet, make the material Stainless Steel or better.....
-----Original Message-----
From: Christopher Wright [mailto:chrisw@skypoint.com]
Sent: Tuesday, May 04, 2004 11:45 AM
To: Pipingdesign
Subject: Re: [PipingDesign] Banching from pipes
>By a comparison between direct pipe to pipe connection and making use
of
>fittings or self reinforced fittings for taking branch ,it goes without
>saying that the quality and easiness of the job would be much better in
>the latter case but regarding cost the former would be cheaper.
I haven't done any real estimating for years, but it's hard to imagine
that the hand fit-up work would be enough cheaper to justify the
likelihood of poorer quality welding. I think if it were truly cheap
enough, it's because someone's taking liberties with weld quality. A
welded tee requires 3 girth welds, but they're straightforward butt
welds
with minimal fit-up.
If I understand you correctly, a 'direct pipe to pipe connection' means
a
hole manually burned in the run, and the branch hand burned and ground
to
the contour of the run. If the joint isn't fit up properly it will be a
starting point for a fatigue or corrosion failure, and if it isn't
cleaned up with no protruding edges, it'll be a mess for fluid flow. My
own opinion is that if such an operation truly is cheaper, it's because
weld quality is compromised, and that isn't really cheaper at all
Christopher Wright P.E. |"They couldn't hit an elephant at chrisw@skypoint.com | this distance" (last words of Gen. ___________________________| John Sedgwick, Spotsylvania 1864)http://www.skypoint.com/~chrisw
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