DLF Spectrum

Dear Coade Members,

This is my first dynamic analysis on Water Hammer, i have a querie related to it, can u please clarify.

I would like to know which time is the the rise time.

Is it the time till the maximum water hammer pressure wave developes?

Cheers Michael

Yes. It is the time it takes for the (unbalanced) pressure wave to "traverse the curvature" of an elbow. This is the time it takes for that specific leg to go from "balanced" to "unbalanced".

Hey Richard Ay,

the problem is that the my calculated pressure wave is rising from Node 990 to 3090 and back. The Maximum of my wave pressure is at Node 990 after the reflection at Node 3090.

How do i enter this in the DLF Spectrum?

Michael,

I've modeled your piping system in PIPENET and calculated force results in 3 legs as attached images.
As it's shown rise time is about 6 sec for a force to be developed in one leg. Then load duration is about 4 sec and fall time is about 0.3 sec. So you can define Force Spectrum trapezoid for each leg as follow:

0 ms 0 N
6000 ms 1500 N
10000 ms 1500 N
10300 ms 0 N

Anyway, this hammer load is not that significant to cause any failure because valve closure time is not that fast. I hope this hepls you.

Hey Farhad,

thank you for your calculations with pipenet.

Furthermore i would like to know why do assume 1500 N. I would use the maximum or?

Regards

Michael

Michael,

It's just an estimation. Each of these load spectrum should be applied on different segments as trapezoid profiles. You may use max. force from these graphs. Or import FRC file from PIPENET to C2 and. C2 can handle it automatically from Tools>External Interfaces>PIPENET pull-down menu.

Farhad,

I will run different dynamic Analysis.

I'm doing my bachelor thesis and unfortunately i don't have pipenet, because it is too expensive.

Would it be possibble to sent me the 3 frc files?

Michael

I will sent you an email.

Richard Ay,

i have continued my work on water hammer.

I would like to know how i have to enter "my" Force-Time to the DLF Specturm.

From Node 2190 to 2150 i do consider entering this parameters.



t [ms] - Force [kN]

0 - 0
10000- 85.285
10110- 0

My closure time of the the valve is 10000 ms.

My estimated rise Time is 10000 ms and my fall time is 110 ms.

Furthermore I'm not sure if i have to use the maximum force because the duration time for this leg is about 5 ms.

Do I have to change my parameters?


I add my C II files and my Force Time graph from an Excel Data.



Cheers Michael