Displaced Jumper

Good day to you all. If you are familiar with "Jumpers" (underwater flowlines which connect under Subsea christmas trees to Subsea Manifolds), they are designed as straight spools. The assumption is that the outlet from the wellhead and inlet to the manifold are on a straight line. Now in reality that is not the case in many instances. My question is this, in the scenario where there's an offset so that they are no longer on a straight line, how do you simulate that condition in CAESAR II? do you do that by preparing a model and then specifying a displacement or is there another way? Also there is a firm I'm working for who do not use CAESAR II and i want to recommend a stress analysis software for them; what are those parameters would I use as a basis for making recommendations for the particular software to use?

Enthusiastic stress engineer

I'm not sure (from your description) what your jumper is. However, "displacements" are probably not what you want to use. A "displacement", in simple terms, is a moved restraint. Once you specify a displacement (or a restraint), the node won't move any further, no matter what the loading.

I suspect you want to specify an "offset". There is a "checkbox" on the spreadsheet, just below the "delta dimensions". Put the focus here and press [F1] for help. See if this is what you want.

As to convincing someone to use CAESAR II, suggest they review this forum. Another good thing to do would be to ask around the industry, what program are most people using?

I'm still having problems with this "offset". Can you explain to me the simplest way possible, the meaning and application of this concept of "offset"?

Let's consider an extreme example. Say you have a 36" header with a 2" branch. Furthermore, assume the branch pipe runs for 6" to an elbow.

CAESAR II models the system using beam elements, which span between two nodes. If you simply model this intersection between two nodes, the length of the 2" line is really 24" (18 inside the header plus the actual 6). While this may be geometrically correct, it is incorrect from a stiffness point of view.

One way to avoid this error is to use offsets to correct the length of the branch element. There are examples on the use of offsets in the Technical Reference Manual.