4 hinged expansion joints

[membername]

I have a question for experts in pipeline and expansion joint design.
We have a pipeline like this (carbon steel, 350°C) and our supplier gave us this layout.
I've never seen 4 hinged EJs in this configuration, it has 1 degree of freedom!!!
So what do you think about it?

 

[C2it]

The arrangement has a infinite number of possible positions that could be adopted. A stress analysis using software would not tell you this and would simply converge on the first deformed shape it finds.

A piping system is normally analysed as a structure. Due to the number of degrees of freedom (and it's not 1 !!), this is a mechanism.

 

[membername]

It's a four-bar linkage, so it has 1 DOF.

 

[C2it]

Four hinges have rotational freedom, two have translational freedom in two planes.

It is a mechanism. Piping systems are normally structures.

The arrangement as shown has no control over the position it may adopt. EJ's have specific rotational limits, beyond which, failure can be guaranteed.

Did you want a discussion about semantics or perhaps some useful comments aimed at avoiding a catastrophic failure ?

 

[pennpiper]

What size is this line?
What are the two dimensions from each "Anchor" to the Elbow (Change in direction)?

prognosis: Lead or Lag

 

[membername]

I wanted only your answer "It is a mechanism. Piping systems are normally structures."

Pipeline: DN250
Dimensions: about 3mx10m (I'm not involved in thi work, so I don't know exactly)