road crossings for two-phase flow pipelines: when to ignore static head downhill recovery?

[Adrian48]

For our current project we have to model a two-phase oil gathering system.
The terrain is essential "flat" but the pipelines, which will be installed above ground, have several road crossings.
Is it normal when modelling a two-phase system to also ignore the static head "downhill" recovery associated with road crossings?

 

[BigInch]

What are you trying to do???
There is no downhill pressure recovery associated with road crossings.

Learn from the mistakes of others. You don't have time to make them all yourself.

 

[Adrian48]

In the simulation software you have the option to ignore the static head contribution.
I know this is normally done for downhill sections of a twophase pipeline but how about a road crossing: is it also normal (and conservative) to ignore the static head related to the (vertical downward) change in pipe elevation for the underground section of a road crossing?

 

[BigInch]

Adrian, please answer my question.
I don't know if you are trying to determine pressure loss or if you are trying to design a road crossing.
What are you trying to do???


Learn from the mistakes of others. You don't have time to make them all yourself.

 

[LittleInch]

Adrain,

Like a lot of things "it depends". It depend son exactly how flat your flat pipeline is. When modelling two phase flow, you really need to input the profile, even if it doesn't vary much, but if it is quite short then the odd one or two road crossings is not going to make an difference. However if you have say 10 or more in a pipeline then I would add it, especially if the crossings are a significant width as the hold up in these could end up being significant.

Depends how much accuracy you need or if this is a screening exercise before you go into much detail. I have no idea what the answer to any of these things are.

As for the static head bit any recovery would be eliminated by the rise on the far side of the crossing. It is usually only 2m so wouldn't make a big difference to anything unless you're running low flows in a big pipe.

Bottom line - Be as accurate as you can in your model and you'll get more accurate results. Depends then on how much time you have and how much data you have...

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[BigInch]

You must be kidding.

Learn from the mistakes of others. You don't have time to make them all yourself.