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B31.1 - Internal pressure for branch connections

B31.1 - Internal pressure for branch connections

B31.1 - Internal pressure for branch connections

(OP)
I'm trying to ind a formula that will allow me to calculate the maximum internal pipe pressure on branch connections using ASME B31.1. Does anyone have any advice on how to do this?

I found a similar equation for in sec. 904.3.2 of B31.9 ASME. This is a clean equation of what I'm looking for, but I don't think it applies to B31.1.

P = SEmSEb[Tm(Db-2Tb) + Tb^2(5 + sin α)] / SEbDm(Db – 2Tb) + 5SEmTbDb
where
Db = the O.D. of the branch pipe, in. (mm)
Dm = the O.D. of the main (run) pipe, in. (mm)
P = the maximum pressure of the joint without reinforcement, psi (kPa)
SEb = the allowable stress for the branch pipe material, psi (kPa)
SEm = the allowable stress of the main (run) pipe material, psi (kPa) (For welded pipe, Ep1.0 if the weld in the main
does not intersect the branch joint.)
Tb = the thickness of the branch less the manufacturing tolerance and less the corrosion allowance, if any, in. (mm)
Tm = the thickness of the main net of manufacturing tolerance and a corrosion allowance, in. (mm)
α = the angle between the axis of the main and the axis of the branch pipes

Does anyone know a similar equation for B31.1?

RE: B31.1 - Internal pressure for branch connections

Hwat is wrong with the formulae in ASME B31.3 Clause 104.3.1 Branch Connections
(A) This paragraph gives rules governing the design
of branch connections to sustain internal and external
pressure in cases where the axes of the branch and the
run intersect, and the angle between the axes of the
branch and of the run is between 45 deg and 90 deg,
inclusive.
Branch connections in which the smaller angle
between the axes of the branch and the run is less than
45 deg or branch connections where the axes of the
branch and the run do not intersect impose special
design and fabrication problems. The rules given herein
may be used as a guide, but sufficient additional strength
must be provided to assure safe service. Such branch
connections shall be designed to meet the requirement
of para. 104.7.

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King
http://waterhammer.hopout.com.au/

RE: B31.1 - Internal pressure for branch connections

(OP)
Stainer,

I saw ASME B31.3 Clause 104.3.1 as well, and looked through that section first. I couldn't find a neat equation for maximum allowable pressure like there was in sec. 904.3.2 of B31.9 ASME.

ASME B31.3 Clause 104.3.1 basically says that you calculate the max pressure as straight pipe, and then you have to "make up" for the material cut away by using the branch connection. The equations are all based around coming up with the necessary pipe thickness for a given design pressure.

I was hoping that someone had come across this before, and knew of a B31.1 formula that would give me maximum allowable internal pressure, where I input the following values:

Db = the O.D. of the branch pipe, in.
Dm = the O.D. of the main (run) pipe, in.
SEb = the allowable stress for the branch pipe material, psi
SEm = the allowable stress of the main (run) pipe material, psi
Tb = the thickness of the branch less the manufacturing tolerance and less the corrosion allowance, if any, in.
Tm = the thickness of the main net of manufacturing tolerance and a corrosion allowance, in.
α = the angle between the axis of the main and the axis of the branch pipes.

Thanks,
Dan

RE: B31.1 - Internal pressure for branch connections

What you see in ASME B31.1 is what you need to use. You cannot go substituting other equations. You could of course use an FEA analysis such as supplied by Paulin. You cannot cherry pick bits from different standards for convenience. A standard is a complete document and needs to be followed else you do not comply with the standard.

Do you want a simple equation so you just plug some numbers into a spreadsheet?

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King
http://waterhammer.hopout.com.au/

RE: B31.1 - Internal pressure for branch connections

(OP)
Understood on not combining the 2 standards. Yes - I'm hoping to plug numbers into a spreadsheet.

Specifically, what I'm looking for, is using B31.1, for a branch connection with a header size (spreadsheet input) and branch size (spreadsheet input), using standard pipe thicknesses and allowable stresses, what my maximum internal pressure could be. In addition, I'm looking for the maximum allowable pressure without using additional reinforcement around the weld as stated in B31.1.

Do you know of a spreadsheet like this?

RE: B31.1 - Internal pressure for branch connections

I dont use spreadsheets as they are too prone to errors. I do my calculations using Mathcad where you can see the workings.

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King
http://waterhammer.hopout.com.au/

RE: B31.1 - Internal pressure for branch connections

The B31.1 equations start with the design pressure and work out the required reinforcement. You just have used the same equations and work backwards to find the pressure where inforcement is required.

Note your tee is connection something so there will be bending stress that need to be considered. No pad has a high SIF and this means loads from attached piping are hard to design for.

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