valve that open and close continuously

Well
We had a problem with a valve that open and close very fast.

In my first calculation i get one time history analysis when the valve close. But the results was very different in comparation with the reality.(in the plant)

IN my opinion , the problem is that i have simulated only one event, what would happen if when the pressure wave come back to the valve, the valve open? Maybe resonance?

How can i simulate more events and so check the possibility of resonance?

thanks so much

Your transient event is this pressure wave that, once started by valve action, travels upstream to the source and then bounces back and forth on it's way back to equilibrium. (The is a similar event traveling downstream from the valve as well.)
Yes, the transient load continues until equilibrium is reached. This load will seen by each surface perpendicular to flow (e.g., every elbow). And there is reflection off these surfaces as well.
So, yes, you may have to run your time history simulation for a longer period to add these extra hits.
I suspect that you are using some sort of fluid transient hydraulics package to generate these loads for CAESAR II. You will have to first run that simulation longer to collect more time history for use in CAESAR II.
My guess, though, is that the first hit is most severe and later hammers are too late to sum directly with the response from the earlier hit.

Thanks Dave,

i will make other simulation with a time longer. (The distance is only 50 meters, and maybe the frecuency of the valve close and open is the same than the wave go and back. So the time to lock/open the valve is 2 times /seconds, and the time the wave come and back is aproximatly 0.5s)

Thanks.

You say 0.5s for a 50m+50m travel? If this time is equal to L/c with L=100m, that means c=200m/sec. That is a very slow speed of sound.

Sorry,

Distance = 100metres.
Tc= 0.4s
C= 200/0.4 = 500m/s

You better use AFT Impulse or Stoner (SPS) to do your hydraulic transient analysis, It should be solved by mass and momentum equations,
the transient forces are realy depended on how your pipe config and upstream pump shut off pressure, flow velocity, and your valve action time,
and your valve type( Quick open, linear or equ-percentage)

Regards,
Limin

and carbon steel pipe (0.375in WT)with water or crude oil, wave speed is about 1200-1400m/s