Kumar,

To put things in a very simple manner, let us consider you have a end suction-top discharge nozzle.

Give a global anchor at the pump centre, this is well defined in API 610, else you can see it on the online help screen in Caesar II, under the API 610 analysis module.Let us say this is node 10.

From node 10, you model a rigid upto the pump inlet nozzle of the same dia as the inlet pipe . Say this is node 20.Next at node 20 you model the inlet pipe flange say this is node 20-30.However number the element not as 20-30, rather number it as 21-30 and at node 21 use an anchor , with connecting node at node 20. You follow an identical pattern for the discharge side of the pump.

If you model the node and C-node in this way , you will get the correct sign of the forces and moments on the nozzle. If you switch node and C- node between nodes 20 and 21, you will get the same magnitude of forces and moments, only sign will be reversed and you can infer that physically from the behaviour of the system.

By definition, a Node and the connecting node will have same displacement in a degree of freedom if they are connected by a rigid stiffness in that degree of freedom, else if you connect them by a non rigid stiffness they wiill have relative displacement in that Dof. Sign of forces and moments on nodes and C- nodes follow the action-reaction force signs as per Newton's third law.So there is really nothing to worry about which node is C-node and which is the restraint node, so long you physically interpret the sign of the results properly.

Hope this answers your question.

A. Bhattacharya

Bechtel Corporation