Hi all;

I have to calculate a jacketed pipe as shown in the picture below
The spiders in node 10 and node 30 are modeled as restraints but in CAESAR II Application guide, in the example of jacketed pipe there is a spider modeled in each elbow.

I want to know for my case and in general I have to add a spider on each Elbow or the case of CAESAR II Application guide example is specific?

There is no spider on the elbow at node no 20 with cn120. But you may want to model as a guide with gap = (Djacket-Dcore)/2 for relative deflection between the two elbows.

Regards,

The examples in the Application's Guide are just that, "examples". These illustrations are not to be interpreted as rules or requirements.

Abdelkader,
This may be considered an unimportant side issue but I do not think your picture correctly reflects standard pipe fittings or a proper installation.

What size it the core pipe?
What kind of elbow is the core pipe (long or short radius)?

What size is the jacket pipe?
What kind of elbow is the jacket pipe (Long or short radius)?
What is the wall thickness (wall schedule)of the jacket pipe?

What is the dimension of the "Spider" piece?

What is the "Gap" dimension you are allowing between the "Spider" and the I.D. of the jacket?

One side note:

Sometime the use of the elbows will not be very easy as the pairs of elbows simply do not match as geometry.

Regards,

Jop;

the specification are little bit different cause I'm working on nuclear plant:

The core elbow is Long Radius (R = 1.5 x D) DN = 40 mm (European size)= 1.5".

The jacket elbow is short Radius (R = 1 x D)DN = 65 mm (European size)= 2.5".
thickness = 5.6 mm

Spider dimensions = length 50 and thickness 5.6 mm and for the hight it must let a gap between the spider and the inner dia of the jacket: 0.5 < j < 1 mm

In my case the two spiders are 400 mm from the elbow and I'm asking if it's really necessary to add a third spider or not.

Regards,

Abdelkader,
Just as I suspected, your drawing is not correct. It is not a major calamity but it is non the less incorrect.
I suggest that you redraw it using the correct dimensions so you and others will have the correct mental picture.

As for your other question, No I do not think you need another spacer in the elbow (node 120).

Jop,

The sketch that I post is the same that I have in my client standard specification for jacketed pipe, but if you are talking about the elbows representation, what is in the drawing is right cause the two extremity of the core elbow have to exceed the jacket pipe elbow extremity otherwise it can't be welded. this design is to resolves the fabrication issues.

Thank you both (Jop and Dan)for your answers I really appreciate your helps.

Best regards,

Abdelkader,

So, you are saying that the core elbow is actually a LONG TANGENT, Long Radius (R = 1.5 x D) DN = 40 mm (European size)= 1.5".

Is that correct?

If so, your picture is still wrong.

Jop,

You are right it's only a SKETCH to explain that the extremity of the core elbow have to exceed the jacket elbow.i will adjust it in next post.

Best regards

Jop,

You are right it's only a SKETCH to explain that the extremity of the core elbow have to exceed the jacket elbow.I will adjust it in next post.

Best regards

Indeed, normaly the jacket has short radius elbows.

regards,