Just so I am on the same page as you, a few questions:

• I assume you are referring to the popular nomograph by Swanson, H.S. ET AL. Design of Wye Branches for Steel Pipe. Journ. AWWA 47:6:581 (June 1995) - which only goes to 120 inch diameter pipe, correct?
• What code is your final design to follow?
• Have you tried the "Area Replacement" rules for ASME branch connections to see how onerous they are for that large of diameter?
• 
• Please confirm that you are doing a 90 degree branch connection; main run 3700 mm with the connection @ 3200 mm (slopes to 2400 mm), similar to (d) in picture, but with the conical section as pictured in (B)?
• 
• Do you REALLY need a conical section as the start of the branch?

I had a quick look at work of our copy of "Steel Penstocks, ASCE Manuals and Reports on Engineering Practice No. 79", but it seems to have grown legs and wandered off - I may track it down tomorrow, in which case I will share if it has appropriate information.

Upon a little more work:

I see that your PDV value according to "Steel Plate Engineering Data - Vol 4" is approximately 35,123 - which should be reinforced with a crotch plate(s), however, ASME B31.8 does not allow for credit for this type of reinforcement.

Xmech, thank you in advance.

Answers to your questions:

1. Yes, in Steel Plate Engineerign Data Volume 4 1998 Page 36, this is the nomograph showed.

2. The design is a pipeline for a hydraulic power plant. Client had not specified me which is specifically the code to follow. They only give me the Steel Plate Engineerign Data to follow.

3. I had tried to follow the area replacement method for ASME VIIO DIv 1, but I´m not sure if the dimensions of the pipe and the branch are allowed by that code. I will revise the code.

4. Branch Lay Out: Correct. This is exactly the situation.

5. Client specify it, in order to decrease hydraulic losses. Steel Plate Engineering Data mention it, and recommend a slope of 6° to 8°. In this case the angle is 8°.

6. I will preciate if you find something in ASCE Manual and share it.

Thank you again,

keep on contact on this issue

Regards,

Alright, I have put a call in to the search and rescue department to locate the ASCE manual, could be a couple days though because people are on vacation/good at squirreling things away.

And for your information - AWWA M11 also covers penstock design, however it is essentially the exact same information as Steel Plate Engineering 4 (both refer to the identical nomograph as well)

On a positive note - I tracked down the ASCE MOP No. 79.

On a negative note - it is somewhat lacking in this particular design detail (it does, however, extensively cover all other aspects of penstock design). It suggests using an FEA approach for this detail, and even references the AISI - Steel Plate Engineering Data, Vol 4.

If FEA is not an option for you, I would suggest using the ASME 'area replacement' rules and according to the ASCE MOP 79:

• 2/3 of the cut-out area must be replaced within 0.5√(rt); where r is the inside radius, and t is the thickness
• The limit of reinforcement normal to the longitudinal access of the penstock is 2 times the shell thickness.

I would further suggest, that instead of installing a re-pad (collar) that you make the entire shell plates (mainline and branch) thicker than required for the regular cylindrical shell and transition them down to the 'normal' thickness required at an absolute minimum distance of (rt)^1/2. For absolute confidence, I would also add the 3-plate external stiffener design loosely based on the previously discussed nomograph.

Is just my copy of Steel Plate Engineering Data (SPED) which lack of the figures 45 (e) and (f)?

Do you have this subfigures?

If you have them, please send me it.

In a previous paragraph SPED say that for D1 is over 3/4 D, figuer 45 (e) is the preferable design. But my copy don´t include it, just subfigures 45 (a), (b), (c), (d) and (g).

Section C-C is also included, but no reference to it.

Thank you.

Nope, it is not just your copy - things are definitely a little awry with Fig. 45 (1984).

I even checked in the 2nd edition (1998), which was no help, because this figure is omitted altogether.

For the assumptions that are made in the text, I'm assuming that this figures (e) and (f) are similar to figure (g) but with a plate ring, not a with formed section as indicated in figure (g).

Besides, I'm assuming that section C-C comes up from any of this missing figures.

Would you assume the same?

Thank for your collaboration and interest.

I would say that the missing 45 (e) is a 'Y' or a branch connection at an angle that has the external stiffeners as 45 (d) and 46 (f); from this quotation - "When branch outlets intersect in a manner as shown in Figure 45 (d) and (e) and wyes as shown in Figure 46 (f), three or four exterior horseshoe girders may be used, ..."

And the missing 45 (f) is very similar to 45 (g) with the ring girder type (possibly minus the internal tie rods) because of this quotation - "In the analysis of the ring girder type of reinforcement shown in Figure 45 (f) and (g), it is assumed ..."

I would say that section C-C was intended for 45 (f) for two reasons:

1. (d) has section A-A; (g) has section D-D .... so ......(e) probably should have had B-B, and (f) should have had C-C.
2. Section C-C is very similar to section D-D, which is of the ring girder type of (g)

Make sense?

I should have caught on earlier - I was even looking at it for awhile, and have had this document the whole time. That entire figure (45) is from one of the pioneering works/records/manuals for penstocks - the Bureau of Reclamation Engineering Monograph 3 [reference #9 in SPED] available @

http://www.usbr.gov/pmts/hydraulics_lab/pubs/EM/EM03.pdf

have a look at page 29 and all the missing pieces are there.

I even have the older and even more pioneering work on penstocks - "Boulder Canyon Project - Final Reports; Bulletin 5 - Penstock Analysis and Stiffener Design"; [reference #17 in SPED] but the above EM03 is more practical.

XMech,

Thanks very much for your preciate collaboration.

I have been reading a book on this issue called: "Structural Mechanics of Buried Pipes" by Raynolds King Watkings, and has a different (and interesting) evaluation of this cases.

Thank you again,

keep in touch,

ing.jferreyra@gmail.com

Buenos Aires, Argentina

I noticed that the local university library archive has a copy of the reference #15 of EM03 - "Design of Wye Branches for Steel Pipe", and probably has a copy of the previously mentioned article too.

I will be at the library this weekend and have a look and will let you know if those articles have any more insight.

I went to the library a little earlier.

That article is quite extensive and should prove to be useful (I haven't gone through it all yet).

But here it is -

(NOTE: you do not need to sign up to download. Just click on "Request Download Ticket" in the top left corner, wait a couple seconds, and then click on "Download" in the same spot)

http://ifile.it/j9q0wy5

XMech,

I finally designed the crotch plate with the lineups of the "Structural Mechanics of Buried Pipes" by Rrynold Watkings and Loren Anderson.

In chapter 18 Special Sections, you would find a very well described example of the crotch plate design for a bifurcation, guidelines that are used in the same way for any crotch plate.

If you need a digital copy of the book............

Thank you for all your collaboration,

I have been looking long for some substantial information in wye branch design.

i refer to sped 1984 and usbr monograph no.3.

Is the nomograph method sufficient or should we adopt FEA?.

I am in search for AWWA manual M11 1984/2004 Edition.

My wye branch from 2000 mm dia to 1500 m dia ,total angle between 70 deg.

internal pressure is 75 kg/cm^2.

what is the difference between a 2 plate and 3 plate reinforcement. is it one crotch plate and two circular rings !.

will u pl explain the differences in fig 46 a & b? are they with tie rods? my wye branch is not with tie rod. so which method i should follow?

thank you.

I recommend you to download de link published before in this discussion.

It is about the Swanson and others work in this issue.

It was very very helpful to me.

Regards,

J Ferreyra

Thank you, I have downloaded the paper by swanson. Ofcourse it is very usefull.

The PDV value comes to 42265 in my case. using the nomograph, i am getting depth of crotchplate dw for 3" thick as 69"(1750mm) , db= 46" (1170mm) & dt=20"(500mm).

My client has given the wye branch fabrication drg for scrutiny and he has provided only dw=1200 mm , db=800mm with 40 mm thickness,with a flange for yoke girder 450mm width and thickness 45 mm.The thickness of penstockshell at wye is 52 mm.

nomograph does not give any reduction in crotchdepths incase we provide such a flange.

Is it better to start the design with dimensions from nomograph?.SIR you have written in the earlier discussion that you have read Structural Mechanics of Buried Pipes and commented that it is good book. I have tried to get it online but only few pages are seen in the preview. can u spare me a digital copy if u have one?

thank you

susan

Susan,

I really tried the nomograph method when i did my job, and the results that i got were very unscaled, as you are telling. The nomograph method is (by my experience) useful for smallers derivations or design pressures.

I have said that the book you mention is a good one, as a reference.

Besides this, I recommend you to do the calculations and the design of your crotch plate with the appliable case of Swanson paper. This was the most useful reference that i got that time.

I´m a very missed in home nowadays, but of course as soon as I can, I will try to send you what you are asking.

Sorry, but I´m very bussy by these days.

Any other help that you need, do it by here or at my mail direction.

regards,

Javier