Hi all,

one simple question: Nozzle in Cylinder
Which is the minimal distance between a nozzle weld and the circumferential weld seam of a cylinder?

I reduce the reinforcement length in the UG-37 calc. if their is a circumferential weld in this area but what is the limit?
AD 2000 has a minimal distance for the weld of the bracker reinforcement plate to the circumferential weld seam of the cylinder: lmin = Sqrt(Da * s)
[Da and s are based on the cyl.]

Many thanks

Frank

Hi Frank,

there is no minimum distance between a nozzle and a welded joint, it can even be located in the joint. UG-36(d) refers to "UW-14 Openings in or adjacent to welds". Here you will find the following in bullet point (a):


In (b) you will find the RT requirements. In UW-14(d) is the answer regarding the minimum distance if the RT requirements of (b) are not satisfied.



That´s it.
Michael

Many thanks for the fast reply.

Frank

Frank,
When a nozzle passes through a circumferential weld, the efficiency of the weld is taken to calculation of reinforcement areas (which is not so clear, when reading UG-37 first sentences under definitions). But the nozzle can pas through a shell-to-head junction. UG-45 should be based on the thicker member then.

Konrad

Konrad,
the weld efficiency is only taken into account when the nozzle is located in any other welded joint but a category B butt joint. Welds connecting two cylinders or cylinder-formed head with straight flange are cat. B joints and this means always E1 = 1 for the determination of reinforcement area A1 (independent from the efficiency of the weld).

When attaching a hemi head you´re right, this means a cat. A joint.


I do not know which sentence you refer.

Best regards
Michael

Right, B is shell course-to another one, or to elliptical head. My mistake, sorry.

I meant "For a circular opening in a cylindrical shell, the plane containing the axis of the shell is the plane of greatest loading due to pressure". Do you remember a topic about split reinforcing pad here not long ago? If the split would be cat. A- then the weld factor should be taken into account, but if it would be B- then it doesn't affect UG-37 requirements. But A and B pertain to shell, not reinf. pads. Maybe UW-3 sould be ammended with reinforcing pads.
Konrad

In my opinion this sentence is associated with Fig. UG-37 and the correction factor F, not with welding. When considering a plane not longitudinal to the vessel (along its axis), the required reinforcement area A can be reduced due to the lower loads (when using Fig. UG-37).

The greatest loadings due to pressure are in the plane containing the axis of the shell, because the circumferential stress is twice the longitudinal, therefore F=1 full A.

Michael

Michael, could you please explain me closer what benefit could be taken from fig UG-37? I understand that it depicts that stresses are smaller in different planes, but what is the use of it?

Konrad

When considering a plane not longitudinal to the vessel, you do not need the full required area A for reinforcement. E.g. for the plane in "circumferential" direction, F=0.5. This means considering this plane, A required is A/2. However, normally there is no benefit because you have to calculate the longitudinal plane along the vessel axis in any case.

With factor F you can consider that the circumferential stress is twice the longitudinal:
longitudinal stress = (p D) / (4 t)
circumferential stress = (p D) / (2 t)
(In German it´s called "Bockwurst-Formel" (sausage formula, no joke), because a sausage will always burst along its longitudinal axis.)

I think you can use it if there is an adjacent nozzle near to your nozzle which is not in the same longitudinal plane. Please note that you have to meet the requirements of UW-16(c)(1) (integral reinforcement)
Michael

Michael,
Thanks. This would mean that an opening reinforcement may be cosidered in many various planes. And this would lead to, for instance, variable width of reinforcing patch required along nozzle's circumference. And, if required width of the reinforcing pad would get 0 in a plane perpendicular to the axis, then we might need, say "8" shaped pad. It might be beneficial in rerating a vessel, when higher MAWP might be acceptable after reinforcing the nozzle-to-shell junctions. If a nozzle is flanged, a split reinforcing pad would not cause to cut the flange off in order to place the pad.

Konrad