input WATER HAMMER in static model

Hello again,

Please, find attached an example of a piping system. Considering water hammer effect because the valve at node 60.
I want to analize in a static model the pressure effect in my piping system. I consider that the wave return to the pipe and I have to introduce a force in each change of direction. I introduce the force "F" till no more restraint in the same dirección (the force F at node 50 is compensated by the restraint Rx at node 35, the force F at node 40 is compensated by the restraint Ry at node 35 and the force F at node 30 is compensated by the restraint Rz at node 35).

Do you think that is it a correct way to analize the water hammer in a static analysis?


Thanks in advance.

Could anyone tell me if consider this method as correct to analyze the water hammer in the piping system?

If not, how do you analyze the water hammer in a static model in CII?

Analyzing a dynamic event in a psuedo-static manner involves a number of assumptions:

1) You're assuming the actual response of the system is dominated by a single degree of freedom. If this isn't true for your system, your results are "less than accurate". Unfortunately you won't know this unless you perform a dynamic analysis.

2) You'll be assuming a DLF (dynamic load factor) of 2, which is hopefully not too conservative. Again, you won't know this unless you perform a dynamic analysis.

3) You'll have to "walk" that force around your system. In any given load case, you only want the hammer force acting on one node.

Jorge MB,


I recently read the following newsletter with an example of time history analysis (steam hammer due to sudden valve closure). It could be helpful even if you decide to perform a quasi static analysis.

http://www.coade.com/Uploads/mechanical-engineering-news/jun94.pdf

Also, if you have a pressure wave traveling upstream, I would expect the direction of the loads to be +X load @ node 60, -Y load @ node 50, +Z load @ node 40 and so on. Someone please correct me if I'm wrong at this point.