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Pipe Stress - Rotational Displacement on Anchor Support

Pipe Stress - Rotational Displacement on Anchor Support

(OP)
Dear Friends,

Can any one please share the knowledge of pipe stress Regarding the following
1)For Anchor support, include Rotational displacement input i.e., values for Rx, Ry, Rz (this was the comment i received from my client side). I hope that i will get a solution for this request

RE: Pipe Stress - Rotational Displacement on Anchor Support

Your question is not very clear.

Were you intending to define an anchor as a point with specified zero displacements ? .... meaning a restraint which prevents all translations and rotations ?

Maybe your client has noted that you defined only fixity of translations, i.e. dX=0, dY=0, dZ=0 ? This will only represent a pipe support, guide and line-stop in reality. It is not an 'anchor'.

To define a full anchor, you need to define rX=0, rY=0, rZ=0 in addition. If you are using Caesar II you need only to define the anchor point as a restraint and select 'ANC'.

RE: Pipe Stress - Rotational Displacement on Anchor Support

(OP)
HI C2IT,
Thanks for your reply, i understand that Anchor is a restraint for all translation and rotations motions. I would like to tell you the scenario of the piping system which i need help.
A 20 inch pipe connected from diesel engine exhaust (with the help of WYE manifold)to silencer nozzle which has design temperature of 500 deg.c and operating temperature 450 deg.c and its corresponding design pressure is atm, while performing pipe stress analysis of this system (with the help of CII 5.3) i provided anchor at nozzle connection of silencer and also engine exhaust and modeled rigid for silencer in order to consider thermal expansion of silencer vessel at nozzle junction. I also considered structural displacement for supports as per client requirements

What is the purpose of considering Rotational displacement (i.e., Rx, Ry, Rz )at nozzle anchor point ?

RE: Pipe Stress - Rotational Displacement on Anchor Support

Maybe your client is confused ?

If you have zero rotations and displacements at your nozzle, it is correct to model it as a full anchor 'ANC'.

However if due to thermal expansion for instnace, the nozzle has some displacements in the operation case, you must define it as a set of displacements which may look like this ....

dX =5, dY=5, dZ=0, rX=0,rY=0,rZ=0

... assuming that, as is commonly the case, there are translations due to expansion but no rotations.

To repeat, using the 'Displancements' fields, if you miss out defining a planar rotation as zero or a number, Caesar II will assume that free rotation exists in that plane.

RE: Pipe Stress - Rotational Displacement on Anchor Support

(OP)
Hi C2it,
Once again thanks for your valuable response, in my case instead of considering thermal displacement i modeled rigid of silencer vessel for thermal displacement effect of vessel nozzle.
My question is, for this case also we need to give Rx, Ry, Rz is equal to zero. And one more thing i considered structural displacements for supports do we need to provide the structural displacement in nozzle anchor point.

RE: Pipe Stress - Rotational Displacement on Anchor Support


I am not sure I can say much more about rotations ....Look at your results. If there are rotations calculated where you know they should be zero, revise your model.

If the nozzle moves due to any influence, that should be reflected in the pipe stress analysis.

Since you are clearly dealing with a large diesel engine ..... does it have flexible mounts ? Do you need to consider any movement ofthe nozzle, either shock loading of the whole engine due to start-up, throttle up, or simply vibration movement ?

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