Ordering reducing TEES across multiple schedules

[piping_design]

Hi,

Wondering what to put in the description on my isometric.

For reducing TEES, sometimes my branch schedule is different than that of the header schedule. For example, I want to order a 4"x2" reducing TEE, but my pipe spec calls for schedule for the 4" pipe is STD wall (6.02mm), and my schedule for the 2" pipe is XS (5.54mm).

When ordering the TEE, do I order a 4"x2" reducing TEE std wall? What wall thickness will the 2" branch end up being in this case? Will it be the same as the 4" section of TEE, or will it be the STD wall thickness at 2" which is 3.91mm?

I have the same question when it comes to reducers. Using the same sizes as above, if I order a 4x2 concentric reducer std wall, what is the wall thickness on the 2" end? Do I need to be more specific on the isometric and put std wall on large end and xs on small end?

Hard to put this question into words but I hope it makes sense. I could easily specify a schedule at each end, but I know the fabricator will likely just purchase a single schedule fitting and taper bore to suit, I am just trying to figure out what to put on the isometric so that it makes the most sense to the fabricator and inline with their ordering needs.

 

[XL83NL]

For the pipe specs I make for our company, we have the same issue. I have made a note for that: always take the conservative option. In real life, especially the smaller sizes you mention (which also is our typical range of applied sizes), I doubt if it will ever make a difference. For anything under say 10”, there’s often sufficient margin.
The same goes when at a certain size, a spec jumps from seamless to welded construction (or vice versa). For that the same note is mentioned; take the conservative option.
I’d go to whoever has made the spec and ask for clarification. That’s what my piping colleagues (rightfully) did to me as well.

 

[DGrayPPD]

I've worked on both sides (the fab shop and the engineering firm) and I've seen it multiple ways. The most common approach I see is to match the specs. So if the spec shows 4" STD and 2" XS, then the reducing tee would be called out with dual schedules.

The reducing fittings should always be larger NPS x smaller NPS, and the schedules will match this (larger NPS schedule first, smaller NPS schedule second).

For example: 4"x2", Red. Tee, S/STD x S/XS, BE, ASME B16.9, ASTM A234 WPB-S

Now this isn't to say that whoever procures the material will actually purchase the dual schedule fitting, but it allows the engineering firm to fall back on the client specs if questioned as to why the dual schedules were specified. When I worked in the fab shop, and we had a fitting that was dual schedule of XS & STD, our company approach was to always purchase the higher schedule and taper bore, as you mentioned.

But when making the isometrics, I'd stick with matching the specs. Because more than likely if it gets to the fab shop and someone is detailing the spools and sees an XS 4"x2" tee/reducer, and they know that the 4" should be STD, they'll probably just end up putting it on hold until they submit an RFI to clarify, and that will just slow down the whole process.

Hope this helps.

"The only limits in life are those which we impose upon ourselves."

 

[XL83NL]

Not to be pedantic, but if you’d like to get the description 100% correct, it’s A234 WPB for seamless fittings, instead of WPB-S.

 

[DGrayPPD]

XL83NL,

You're right. But the client's don't always seem to know that these days, so we've gotten to where we always still specify the weld seam with the callout. It's just a habit for me at this point. We've actually just recently changed from A234 WPB-S to A234 WPB SMLS

"The only limits in life are those which we impose upon ourselves."

 

[XL83NL]

But the client's don't always seem to know that these days, so we've gotten to where we always still specify the weld seam with the callout.

Good point