While specifying reducers and reducing tees, sometimes we dont specify schedules for both the sizes. Bigger size schedule is normally specified even if small size has a different schedule.
What is the reason for that? Is there any limitation for that? How this schedule difference is taken care at fabrication stage?If you are looking for more details, kindly visit Pipe Fittings Tee Reducer.
Why don't you specify schedules ? If you don't, how could you get them purchased and used correctly ?The schedules of the fittings match those of the pipes or connecting fittings, so the fabricator has no problem.
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Weldolet or Reducing Tee
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(Mechanical)
(OP)
13 Nov 18 07:27I have been searching for this piece of information but i did not find a clear answer . Is it recommended to use a weldolet or a reducing TEE when extraction a branch connection from a main line or a header .
Some ppl are referring to "common practice " to use weldolet if the branch connection is less than or equal to 50% of the header size.
Considering Cost as well , which is more cheaper ?
(Petroleum)
13 Nov 18 12:37First, either option (RT or "Integrally reinforced branch fittings" to give them their proper name) is allowed in B 31.3 No guidance is given in any design code AFAIK.The issue is really one of welding time and weld quantity. Above about 50% branch size, the amount of welding of a IRBF is more than two butt welds of the RT.Also if you have multiple branches the heat input and loss of strength in the main line can cause bending and twisting in the header. I once had a 12" (maybe it was 10") header of thick pipe ( Sch 160) with 8 8" branches and the thing bent like a banana. Vowed not to do it again, but we had space limits and the distance between tees was quite small so people didn't want lots of welds less than 1D apart.But a lot of this is just what people are used to and if there are other factors (thickness of pipe / branch) material, spacing etc so there is no hard and fast "rule".
Remember - More details = better answers
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(Mechanical)
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13 Nov 18 13:07As LI stated, most of the time the cost comes down to the number of welds and time it takes. A general rule in my area is if the branch is:
1-2 nominal sizes below the header, use a reducing tee.
Greater than 2 nominal sizes below the header, use an IRBO fitting.
The piping specifications should also always have a branch connection table that states what the desired branch method is. I rarely see a spec that allows reducing tee's over WOL's for size differences greater than 2 NPS. But, different companies will also have different opinions on this subject as well. The service conditions will also play a factor. Commodity, pressure, temperature, material, availability, etc. are all important things to consider.
"Thinking is the hardest work there is, which is probably the reason why so few engage in it."
-Henry Ford
(Nuclear)
13 Nov 18 13:53There is a difference in the flexibility coefficients/stress intensification factors between the two types of connections when you run the pipe stress calc's for thermal expansion under B31.1 rules. Not a great difference, but a difference.
(Mechanical)
13 Nov 18 17:15My two cents .....Also consider availability.... I have always found that reducing tees are not always available in the specific schedule and sizes that I needed.Because of their geometric design, weldolets are usually more available and suitable.
MJCronin
Sr. Process Engineer
(Mechanical)
14 Nov 18 21:46If there are pipe are vibration issues consider the butt weld tee over the weldolet. All the weld around the weldolet will add a stress riser in the wall of the main line.
(Chemical)
15 Nov 18 13:29Part of the problem comes from the integrally reinforced branch fitting being designed as a one size fits all tool, with a weld bevel area to match. You get into trouble when adding 3000# sock-o-lets to sch10S pipe for instance- the fitting mfg wants you to weld out the full bevel of their fitting to avoid a stress riser at the point where the bevel meets a weld of smaller size. The resulting huge weld on a thin header pipe then turns your header into a banana.
Rule of thumb in most pipe specs for pipe branches is as noted above: 1-2 sizes down use a reducing tee- more than that size reduction switches to an integrally reinforced fitting. Some pipe specs start permitting stub-in branches at certain size ratios too, generally when the wall thickness of the line and branch are both greatly larger than that required to meet the hoop stress and the excess isn't needed for corrosion allowance.
(Mechanical)
15 Nov 18 17:34Molten,Bonney Forge (and it's army of illegal Chinese knock-offs) are all well aware of the existence of thin walled pipe and the consequential branch welding problems.BF has produced fittings (FLEXOLETS) developed specifically for this purpose....Also see this eng-tips post ..... there are many ways to skin this cat ...
MJCronin
Sr. Process Engineer
(Chemical)
16 Nov 18 14:48Looks like the catalog refers to them as LW pipets. Our past experience was that the pipets were not shelf stock at the typical suppliers so we ended up using the ordinary o-lets and making bananas out of the piping. Time to go back and re-consider this, as the list of required size ranges would be so small for us that it might make sense to just stock them ourselves.
(Chemical)
16 Nov 18 14:49Thanks for the reminder of that thread too!
(Mechanical)
19 Nov 18 13:55Another issue relates to high temperature applications, where creep damage is relevant. The weldolet has a significant failure issue at the location of 45 deg off the main centerline , and either the weld strength to be penalized due to the " weld creep strength redcution factor" or a reducing tee be used.
"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick
(Mechanical)
(OP)
21 Nov 18 06:03The conclusion is that there's no clear recommendation to use weldolet or RT but a lot of factors shall be considered i.e : size of branch compared to the main line, time, cost , thermal stresses ..etc.
i think i will add a note to the specification- as DGrayPPD mentioned :
1-2 nominal sizes below the header, use a reducing tee.
Greater than 2 nominal sizes below the header, use an IRBO fitting.
the same shall be confirmed/changed subject to the stress analysis results.
Thank You All For your comments and contribution
(Civil/Environmental)
18 Dec 18 13:44
Hello,
If a weldolet is used, how should the pipe be tapped? I'm curious about 3/4" or 1" weldolet on 2' to 8" pipes.
Thank you!
(Petroleum)
18 Dec 18 15:36See http://www.bonneyforge.com/resources/BC.pdf
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