COADE training example - Clarifications needed

[PipelineDeptTME]

Hello everybody,

I am going through the SNFAIL example which was pubblished in COADE Mechanical Engineering News in June '94. Here below the link:

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

Basically is everything very clear and very logical. There are only two points I want to clarify.

1) Are they considering friction in that example? How come the pressure wave keeps reaching the maximum value at each pipe leg? I mean, after each elbow there should be some energy loss, so the peak should be less, isn't it?

2) I am doing time history analysis of a 32" Diesel pipe, 32 km lenght with expansion loops every 250 m. Because of ESD valve closure, surge pressure is generated. ESD valve takes about 30 seconds to be totally close, hence pressure peak is reached after such time. Considering a wave speed of about 1000 m/s, surge pressure along short pipe legs (<20m) will never reach high values, correct?

Thank you

 

[BigInch]

This is a dynamic response model to a given impact load, supposedly from a conservative fluid transient load generated from valve closure only. There is no fluid friction, because it is not a fluid dynamics model.

Should the fluid separate and recombine on reduced pressure, the loads calculated in this manner may be many times higher. This is not a valid method, in my opinion, to calculate fluid loads to a piping system, especially when high pressures that can vary significantly are involved and more so with high vapor pressure products (diesel is rather low.. fortunately). I would use it only to get an idea of the piping vibration response to a typical fluid transient event, but would not consider it definitive at all. You need to get a true fluid transient simulation program to see what these load could actually be.

Independent events are seldomly independent.